EA039286B1 - Method for producing metal ingot - Google Patents

Abstract

The problem of the invention is to provide a method for producing a metal ingot, which makes it possible to inhibit impurities contained in molten metal in a hearth from being mixed into the ingot. The solution is a method for producing a metal ingot by using an electron-beam melting furnace having an electron gun and a hearth that accumulates a molten metal of a metal raw material, wherein the metal raw material is supplied to the position on a supply line disposed along a second side wall of the hearth that accumulates the molten metal of the metal raw material. A first electron beam is radiated along a first irradiation line that is disposed along the supply line and is closer to a central part of the hearth relative to the supply line on the surface of the molten metal. By this means, a surface temperature (T2) of the molten metal at the first irradiation line is made higher than an average surface temperature (T0) of the entire surface of the molten metal in the hearth, and in an outer layer of the molten metal, a first molten metal flow is formed from the first irradiation line toward the supply line.

Description

The field of technology to which the invention belongs

The present invention relates to a method for producing a metal ingot in which a metal raw material is melted using an electron beam melting process.

State of the art

Ingot of commercially pure titanium or titanium alloy, etc. produced by melting titanium raw materials such as titanium sponge or waste. Examples of methods for melting metal raw materials (hereinafter simply raw materials) such as titanium raw materials include a vacuum arc remelting process, a plasma arc melting process, and an electron beam melting process. In the electron beam melting process, a raw material is melted by directing an electron beam onto a solid raw material in an electron beam melting furnace (hereinafter also referred to as an EB furnace). In order to prevent scattering of electron beam energy, the melting of raw materials by electron beam irradiation in an EL furnace is performed in a vacuum chamber. Molten titanium (hereinafter also referred to as molten metal), which is a molten raw material, is refined in a furnace bath and then solidified in a mold to form a titanium ingot. According to the electron beam melting process, since the irradiation position of the electron beam, which is the heat source, can be precisely controlled by electromagnetic force, heat can also be sufficiently supplied to the molten metal near the mold. Therefore, it is possible to produce an ingot without degrading its surface quality.

An EL furnace typically includes a raw material supply portion that supplies raw materials such as a titanium sponge, one or a plurality of electron guns for melting the supplied raw material, a bath (for example, a water-cooled copper bath, a crucible) for accumulating the molten raw material, and a mold for forming ingot by cooling the molten titanium poured into it from the bath. EL furnaces are roughly classified into two types according to differences in bath configurations. Specifically, for example, an EL furnace 1A which includes a melting bath 31 and a cleaning bath 33 as illustrated in FIG. 1 and an EL furnace 1B that only includes a cleaning bath 30 as illustrated in FIG. 2 are two different types of EL furnace.

EL furnace 1A illustrated in FIG. 1 includes a raw material supply portion 10, electron guns 20a to 20e, a melting bath 31 and a cleaning bath 33, and a casting mold 40. The solid raw material 5 that is introduced into the melting bath 31 from the raw material supply portion 10 is irradiated by the electron guns 20a and 20b to thereby melt the raw material 5 and obtain molten metal 5c. The molten raw material (molten metal 5c) in the melting bath 31 flows into a purification bath 33 which communicates with the melting bath 31. In the purification bath 33, the temperature of the molten metal 5c is maintained or increased by irradiating the molten metal 5c with electron guns 20c and 20d. Through this, impurities contained in the molten metal 5c are removed and the like, and the molten metal 5c is purified. Thereafter, the purified molten metal 5c flows into the mold 40 from the spout portion 33a provided at the end portion of the purification bath 33 . The molten metal 5c solidifies in the mold 40, thereby producing an ingot 50. A bath consisting of a melting bath 31 and a cleaning bath 33, as shown in FIG. 1 is also referred to as a long bath.

On the other hand, the EL furnace 1B shown in FIG. 2 includes raw material supply portions 10A and 10B, electron guns 2OA-2OD, a cleaning bath 30, and a mold 40. A bath that only consists of a cleaning bath 30 is also referred to as a short bath, in contrast to the long bath shown in FIG. . 1. In the EL furnace 1B, which uses a short bath, the solid raw material 5, which is placed on the raw material supply portions 10A and 10B, is melted by electron beams that are emitted from the electron guns 20A and 20B, and the molten raw material 5 is dripped into the molten metal 5c, located in the cleaning bath 30, from the raw material supply parts 10A and 10B. Thus, the melt bath 31 illustrated in FIG. 1 can be removed from the EL furnace 1B illustrated in FIG. 2. In addition, in the cleaning bath 30, the temperature of the molten metal 5c is maintained or increased by irradiating electron beams from the electron gun 20C over a wide range over the entire surface of the molten metal 5c. Through this, impurities contained in the molten metal 5c are removed and the like, and thus the molten metal 5c is purified. Thereafter, the purified molten metal 5c flows into the mold 40 from the spout portion 36 provided at the end portion of the purification bath 30, and an ingot 50 is produced.

In the case of producing an ingot using a bath and a mold through an electron beam melting process as described above, if impurities enter the ingot, they will cause cracks in the ingot. Therefore, there is a need to develop an electron beam melting technology that can ensure that impurities do not enter the molten metal that flows into the mold from the bath. The impurities originate mainly from the feedstock and are classified into two types, namely HDI (high density inclusions, HRP) and LDI (low density inclusions, GNP). GDP is, for example, an impurity in which tungsten is the main component, and the density of GDP is greater than that of molten titanium. On the other hand, GNP is an impurity in which nitrided titanium and the like are the main component. The internal part of the GNP is in a porous state, and therefore the density of the GNP is less than the density of the melt

- 1 039286 flax titanium.

On the inner surface of the water-cooled copper bath, a hardened layer is formed, which is molten titanium, solidified from contact with the bath surface. This cured layer is known as the scull. Among the aforementioned impurities, since the HPFs have a high relative density, they are deposited in the molten metal (molten titanium) in the bath and adhere to the surface of the scull, and thereby are trapped, and therefore the probability of the HPFs entering the ingot becomes low. On the other hand, since the density of the GNP is less than the density of the molten titanium, the main part of the GNP floats to the surface of the molten metal inside the bath. While the GNP float to the surface of the molten metal, nitrogen diffuses into the molten metal and dissolves in it. In the case of using the long tub shown in FIG. 1, since the residence time of the molten metal in the long bath can be increased, it becomes easier to cause impurities such as GNP to dissolve in the molten metal compared to the case of using a short bath. On the other hand, in the case of using a short bath, as shown in FIG. 2, since the residence time of the molten metal in a short bath is shorter compared to a long bath, the probability that impurities will not be dissolved in the molten metal is high compared to using a long bath. In addition, in the case of GNPs that have a high nitrogen content, since their dissolution temperature is high, the probability that the GNPs are dissolved in the molten metal during the residence time in normal operation is extremely low.

Therefore, for example, Patent Document 1 discloses a titanium metal electron beam melting method in which the surface of the molten metal in the bath is scanned with an electron beam in a direction opposite to the direction in which the molten metal flows into the mold, and the average temperature of the molten metal in a region adjacent with an outlet for molten metal in the bath, maintained equal to or higher than the melting point of impurities. According to the technique disclosed in Patent Document 1, by scanning the electron beam in a zigzag manner in the opposite direction of the molten metal flow, an attempt is made to push back impurities that float on the surface of the molten metal so that they do not enter the mold.

List of Prior Art Documents Patent Documents

Patent Document 1: JP 2004232066A.

non-patent document

Non-Patent Document 1: Tao Meng, Factors influencing the fluid flow and heat transfer in electron beam melting of Ti-6A1-4V, (2009).

The essence of the invention

Technical problem

However, according to the method disclosed in the above-mentioned Patent Document 1, since the electron beam is scanned in the opposite direction of the molten metal flow, there is a possibility that impurities further downstream of the molten metal from the electron beam irradiation position will enter the mold. . In addition, further downstream of the molten metal from the electron beam irradiation position, the molten metal flow accelerates towards the mold, and thus the residence time of the molten metal in the bath is reduced, and there is a possibility that the impurity removal rate will decrease. In addition, when impurities are present further downstream of the molten metal from the electron beam irradiation position, the risk of them entering the mold with the molten metal stream is increased. For these reasons, there is a possibility that the impurities contained in the molten metal inside the bath, in particular the GNP floating on the surface of the molten metal 5c, will flow into the mold from the bath and end up in the ingot which is formed in the mold. Therefore, there is a need for a method for producing a metal ingot, which, by preventing impurities such as GNR from flowing out of the bath into the mold, can prevent impurities from entering the ingot.

The object of the present invention, which has been made in view of the above problem, is to provide a new and improved method for producing a metal ingot, which can inhibit the ingress of impurities contained in the molten metal in the furnace bath into the ingot.

Solution

In order to solve the above problem, according to one aspect of the present invention, there is provided a method for producing a metal ingot by using an electron beam furnace having an electron gun capable of controlling an electron beam irradiation position and a bath that accumulates molten metal from a metal raw material, the metal ingot contains a total of 50 wt.% or more of at least one metallic element selected from the group consisting of titanium, tantalum, niobium, vanadium, molybdenum and zirconium, and

- 2 039286 among the plurality of side walls of the bath, which accumulates molten metal from metal raw materials, the first side wall is a side wall provided with a spout part for flowing molten metal from the bath into the mold, and the second side wall is at least one of the side walls , different from the first side wall;

the metal raw material is fed to a position on the supply line, which is located along the inner surface of the second side wall on the surface of the molten metal;

the first electron beam is emitted along the first irradiation line located along the supply line and located closer to the Central part of the bath relative to the supply line on the surface of the molten metal; and emitting the first electron beam along the first irradiation line increases the surface temperature (T2) of the molten metal in the first irradiation line above the average surface temperature (T0) of the entire surface of the molten metal in the bath, and forms in the outer layer of the molten metal the first molten metal flowing from the first irradiation line to the supply line.

The configuration can be made such that the temperature gradient AT/L represented by the following formula (A) is -2.70 (L/mm) or more:

AT/L=(t2-T1)/L(A) where T1: surface temperature (K) of molten metal in the supply line;

T2: surface temperature (K) of the molten metal in the first irradiation line;

L: distance (mm) between the first irradiation line and the supply line on the surface of the molten metal.

The configuration can be made such that the aforementioned AT/L gradient is 0.00 (K/mm) or more, and the first molten metal flow that flows from the first irradiation line through the supply line to the inner surface of the second side wall is formed in the outer layer molten metal.

The configuration can be made such that the raw metal melts in the raw material supply part and the molten metal raw material drips from the raw material supply part to a position in the bath molten metal supply line.

The configuration can be made such that on the surface of the molten metal, both ends of the first irradiation line are located on the outside in the direction of passage of the supply line relative to both ends of the supply line.

The configuration can be made such that a second molten metal stream towards the spout part is formed in the ribbon-like region between the supply line and the first irradiation line, and the second electron beam is irradiated as a spot onto the second molten metal stream.

The configuration can be made such that the second electron beam is emitted as a spot onto the second molten metal stream at the position of the irradiation spot, which is located at the end portion of the ribbon-like region on the side of the spout portion.

The configuration can be made such that the third electron beam is emitted along the second irradiation line, located so that it blocks part of the spout on the surface of the molten metal, and both ends of the second irradiation line are located in close proximity to the first side wall.

The metal raw material may contain 50% by weight or more of elemental titanium.

Useful effects of the invention

According to the present invention described above, impurities contained in the molten metal in the furnace bath can be inhibited from entering the ingot.

Brief description of the drawings

Fig. 1 is a schematic diagram illustrating an electron beam furnace that includes a long bath.

Fig. 2 is a schematic diagram illustrating an electron beam furnace that includes a short bath.

Fig. 3 is a schematic diagram illustrating an electron beam furnace (short bath) which carries out the method for producing a metal ingot according to the first embodiment of the present invention.

Fig. 4 is a plan view illustrating one example of an irradiation line and supply lines in a bath according to the first embodiment of the present invention.

Fig. 5 is a plan view illustrating one example of molten metal streams that are formed by the metal ingot production method according to the first embodiment of the present invention.

Fig. 6A is a longitudinal section showing a state of molten metal flow when an electron beam is not emitted along an irradiation line as a comparative example for the first embodiment of the present invention.

Fig. 6B is a plan view illustrating a state of molten metal flow.

- 3 039286 when the electron beam is not emitted along the irradiation line, as a comparative example for the first embodiment of the present invention.

Fig. 7 is a longitudinal section illustrating a state of molten metal flow when an electron beam is emitted along an irradiation line according to the method for producing a metal ingot of the first embodiment of the present invention.

Fig. 8 is a plan view illustrating another example of molten metal streams that are formed by the metal ingot production method according to the first embodiment of the present invention.

Fig. 9 is a plan view of the bath illustrating another example of molten metal streams that are formed by the metal ingot production method according to the first embodiment of the present invention.

Fig. 10 is a plan view of the bath that illustrates one example of a molten metal flow generated by a metal ingot production method according to a modification of the first embodiment of the present invention.

Fig. 11 is a plan view of the bath that illustrates one example of a molten metal flow generated by a metal ingot production method according to a modification of the first embodiment of the present invention.

Fig. 12 is a plan view illustrating one example of molten metal streams that are formed by the metal ingot production method according to the second embodiment of the present invention.

Fig. 13 is a plan view of the bath that illustrates one example of a molten metal flow generated by a metal ingot production method according to a modification of the second embodiment of the present invention.

Fig. 14 is a plan view of the bath that illustrates one example of a molten metal flow generated by a metal ingot production method according to a modification of the second embodiment of the present invention.

Fig. 15 is a plan view illustrating one example of molten metal streams that are formed by the metal ingot production method according to the third embodiment of the present invention.

Fig. 16 is a plan view of the bath that illustrates one example of a molten metal flow generated by a metal ingot production method according to a modification of the third embodiment of the present invention.

Fig. 17 is a plan view showing the state of the bath according to Comparative Examples 1 and 2.

Fig. 18 is a flow line diagram illustrating the flow of molten metal according to Example 1.

Fig. 19 is an explanatory drawing illustrating a simulation result according to Example 1.

Fig. 20 is an explanatory drawing illustrating a simulation result according to Example 2.

Fig. 21 is an explanatory drawing illustrating a simulation result according to Example 3.

Fig. 22 is an explanatory drawing illustrating a simulation result according to Example 4.

Fig. 23 is an explanatory drawing illustrating a simulation result according to Example 5.

Fig. 24 is an explanatory drawing illustrating a simulation result according to Example 6.

Fig. 25 is an explanatory drawing illustrating a simulation result according to Example 7.

Fig. 26 is an explanatory drawing illustrating a simulation result according to Comparative Example 1.

Fig. 27 is an explanatory drawing illustrating a simulation result according to Example 8.

Fig. 28 is an explanatory drawing illustrating a simulation result according to Example 9.

Fig. 29 is an explanatory drawing illustrating a simulation result according to Example 10.

Fig. 30 is an explanatory drawing illustrating a simulation result according to Example 11.

Fig. 31 is an explanatory drawing illustrating a simulation result according to Example 12.

- 4 039286

Fig. 32 is an explanatory drawing illustrating a simulation result according to Comparative Example 2.

Description of Embodiments

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. It should be noted that in the present description and the accompanying drawings, constituent members having essentially the same functional configuration are denoted by the same reference symbols, and their repeated description is omitted.

1. First Embodiment.

First, a method for producing a metal ingot according to the first embodiment of the present invention will be described.

1.1. Configuration of an electron beam melting furnace.

First with reference to FIG. 3, the configuration of the electron beam furnace for carrying out the metal ingot production method according to the present embodiment will be described. Fig. 3 is a schematic diagram illustrating the configuration of an electron beam furnace 1 (hereinafter referred to as an EB furnace 1) according to the present embodiment.

As shown in FIG. 3, the EL furnace 1 includes a pair of raw material supply portions 10A and 10B (hereinafter referred to generally as raw material supply portion 10), a plurality of electron guns 20A to 20E (hereinafter collectively referred to as electron guns 20), a cleaning bath 30, and a foundry form 40. Thus, the EL furnace 1 according to the present embodiment includes only one cleaning bath 30 as a bath, and the bath structure in question is referred to as a short bath. It should be noted that although the method for producing a metal ingot of the present invention can be preferably applied to the short bath EV furnace 1 as shown in FIG. 3, the metal ingot production method of the present invention is also applicable to the EL furnace 1A, which has a long bath as shown in FIG. 1.

The purification bath 30 (hereinafter referred to as bath 30) is a device for purifying molten metal 5c from metal raw material 5 (hereinafter referred to as raw material 5) and simultaneously accumulating molten metal 5c to thereby remove impurities contained in the molten metal 5c. The bath 30 according to the present embodiment is, for example, a water-cooled copper bath having a rectangular shape. A spout part 36 is provided in a side wall at the end of one side in the longitudinal direction (Y direction) of the vat 30. The spout part 36 is an outlet for flowing molten metal 5c from the vat 30 into the mold 40.

The mold 40 is a device for cooling and solidifying the molten metal 5c from the raw material 5 to thereby produce a metal ingot 50 (for example, a titanium ingot or a titanium alloy ingot). The mold 40, for example, is a water-cooled copper mold having a rectangular tubular shape. The mold 40 is positioned under the spout 36 of the tub 30 and cools the molten metal 5c pouring into it from the tub 30 above the mold 40. As a result, the molten metal 5c within the mold 40 gradually solidifies towards the bottom of the mold 40 and a solid ingot 50 is formed.

The raw material supply part 10 is a device for supplying the raw material 5 to the bath 30. The raw material 5 is, for example, titanium raw material such as titanium sponge or waste. In the present embodiment, for example, as illustrated in FIG. 3, a pair of feed portions 10A and 10B are provided above a pair of long side walls of the tub 30. The solid feed 5 supplied from outside is placed in the feed portions 10A and 10B, and electron beams from the electron guns 20A and 20B are emitted onto the feed 5.

Thus, in the present embodiment, to supply the raw material 5 to the bath 30, the solid raw material 5 is melted by emitting electron beams on the raw material 5 in the raw material supply portion 10, and the molten raw material 5 (molten metal) drips into the molten metal 5c in the bath 30 from the inner edges parts 10 supply of raw materials. In other words, the raw material 5 is fed into the bath 30 by first pre-melting the raw material 5 outside the bath 30 and then allowing the molten metal to drip into the molten metal 5c in the bath 30. supply of raw materials to the surface of the molten metal 5c in the bath 30, correspond to the supply lines 26, which will be described later (see Fig. 4).

It should be noted that the method for supplying the raw material 5 is not limited to the dripping described in the above example. For example, the solid raw material 5 can be directly introduced, as it is, into the molten metal 5c in the bath 30 from the raw material supply portion 10.

The introduced solid raw material 5 is then melted into the high temperature molten metal 5c, and thereby added to the molten metal 5c. In this case, the introduction lines, which are the positions at which the solid raw material 5 is introduced into the molten metal 5c in the bath 30, respectively

- 5 039286 feed lines 26, which will be described later (see Fig. 4).

To carry out the electron beam melting process, the electron guns 20 emit electron beams on the raw material 5 or the molten metal 5c. As shown in FIG. 3, the EL furnace 1 according to the present embodiment includes, for example, electron guns 20A and 20B for melting the solid raw material 5 that has been supplied to the raw material supply portion 10, the electron gun 20C for maintaining the temperature of the molten metal 5c in the bath 30 , an electron gun 20D for heating molten metal 5c at the top inside the mold 40, and an electron gun 20E for preventing impurities from flowing out of the bath 30. Each of the electron guns 20A to 20E is capable of controlling the electron beam irradiation position. Therefore, electron guns 20C and 20E are capable of projecting electron beams to desired positions on the surface of molten metal 5c in bath 30.

The electron guns 20A and 20B emit electron beams on the solid raw material 5 placed on the raw material supply portion 10 to thereby heat and melt the raw material 5. The electron gun 20C heats the molten metal 5c and maintains the molten metal 5c at a predetermined temperature by emitting an electron beam in a wide range onto the surface of the molten metal 5c in the bath 30. The electron gun 20D emits an electron beam onto the surface of the molten metal 5c in the mold 40 to thereby heat the molten metal 5c at its top and maintain the molten metal 5c at the top while predetermined temperature so that the molten metal 5c at the top of the mold 40 does not solidify. The electron gun 20E emits an electron beam in a focused manner along the irradiation line 25 (see FIG. 4) on the surface of the molten metal 5c in the bath 30 in order to prevent impurities from flowing out of the bath 30 into the mold 40.

Thus, the present embodiment is characterized in that it prevents impurities from escaping by, for example, emitting (emission lines) an electron beam in a focused manner along the irradiation line 25 on the surface of the molten metal 5c using the electron gun 20E. This characteristic will be described in detail later. It should be noted that in the EL furnace 1 according to the present embodiment, the electron gun 20E for the emission line shown in FIG. 3 is provided separately from other 2OA-2OD electron guns. Due to this, when other electron guns 20A to 20D are used to melt the raw material 5 and maintain the temperature of the molten metal 5c, the linear irradiation of the electron gun 20E can be continued at the same time, and therefore the decrease in the surface temperature of the molten metal 5c at the irradiation line position can be prevented. However, the present invention is not limited to this example. For example, the electron beam can be emitted along the irradiation line 25 using one or more of the existing electron guns 20A and 20B for melting raw materials or electron guns 20C and 20D for maintaining the temperature of the molten metal, without additional installation of the electron gun 20E for linear irradiation. Due to this, the number of electron guns installed in the EL furnace 1 can be reduced, the equipment cost can be reduced, and the existing electron guns can be used efficiently.

1.2. Scheme of a method for the production of a metal ingot.

Next, with reference to FIG. 3-5, a flowchart of a method for producing a metal ingot according to the present embodiment will be described. Fig. 4 is a plan view illustrating one example of an irradiation line 25 and a supply line 26 in a bath 30 according to the present embodiment. Fig. 5 is a plan view illustrating one example of a molten metal flow that is formed according to the metal ingot production method of the present embodiment. It should be noted that the top views of tub 30 in FIG. 4 and FIG. 5 correspond to the bath 30 of the EL furnace 1 shown in FIG. 3.

The problem solved by the method for producing a metal ingot according to the present embodiment is to prevent impurities from entering the ingot 50 when it is produced from commercially pure titanium or a titanium alloy, or the like. by inhibiting the flow of impurities contained in the molten metal (molten metal 5c) from the solid raw material into the mold 40 from the bath 30. According to the metal ingot production method of the present embodiment, specifically, titanium raw material as a metal raw material is taken as an object, and the metal ingot production method solves the problem of preventing the occurrence of a situation in which the GNR, which, among all the impurities contained in the titanium raw material, has a density less than that of the molten titanium metal (molten titanium) enters the titanium or titanium alloy ingot 50. It should be noted that, as used herein, the term titanium or titanium alloy refers to a metal containing 50% by mass or more of titanium as an element.

In order to solve the above problem, in the method for producing a metal ingot according to the present embodiment, as illustrated in FIG. 4, raw material 5 is fed into molten metal 5c within bath 30 at positions along supply lines 26 that are adjacent to side walls 37A and 37B on the long sides of bath 30. In addition, the electron beam

- 6 039286 is emitted in a focused manner along the irradiation lines 25, which are adjacent to the supply lines 26 on the surface of the molten metal 5c, which accumulates in the bath 30.

The supply lines 26 (corresponding to the supply line of the present invention) are imaginary lines representing the positions at which the raw material 5 is supplied from the outside of the bath 30 to the molten metal 5c in the bath 30. The supply lines 26 are located on the surface of the molten metal 5c at positions along the respective inner surfaces of the side walls. 37A and 37B of tub 30.

In the present embodiment, the molten raw material 5 drips into the bath 30 from the inner edge portions of the raw material supply portion 10 located at the top of the side walls 37A and 37B on the long sides of the bath 30, as illustrated in FIG. 3. Therefore, the respective supply lines 26 are located on the surface of the molten metal 5c in the bath 30 under the inner edge portions of the raw material supply portion 10, and are in the form of lines along the inner surface of the respective side walls 37A and 37B. It should be noted that while the supply lines 26 are in the form of lines extending along the inner surfaces of the side walls 37A, 37B, and 37C of the tub 30, the supply lines 26 need not be strictly linear, and may, for example, be in the form of a dotted line, a dotted line, a curved shape, a wavy line shape, a zigzag shape, a double line shape, a ribbon shape, a polygonal line shape, and the like.

The irradiation line 25 (corresponding to the first irradiation line of the present invention) is an imaginary line that is a path of positions at which an electron beam (corresponding to the first electron beam of the present invention) is emitted in a focused manner onto the surface of the molten metal 5c in the bath 30. The irradiation line 25 is arranged along line 26 feed raw materials 5 on the surface of the molten metal 5c. As long as the irradiation line 25 is in the form of a line along the feed line 26, the irradiation line 25 need not be strictly straight, and may, for example, be in the form of a dotted line, a dotted line, a curvilinear form, a wavy line form, a zigzag form, a double line form. , ribbon shape, polygonal line shape, and the like.

The location of the irradiation line 25 and the supply line 26 will now be described in more detail. As illustrated in FIG. 4, the rectangular tub 30 according to the present embodiment has four side walls 37A, 37B, 37C, and 37D (hereinafter, may be collectively referred to as side wall(s) 37). The pair of side walls 37A and 37B that face each other in the X direction constitute a pair of long sides of the tub 30 and are parallel to the longitudinal direction (Y direction) of the tub 30. In addition, the pair of side walls 37C and 37D that face each other in in the Y direction make up a pair of short sides of tub 30 and are parallel to the width direction (X direction) of tub 30.

A spout part 36 for flowing molten metal 5c from the pool 30 into the mold 40 is provided in a side wall 37D which is one of the short sides. On the other hand, the spout portion 36 is not provided in the three side walls 37A, 37B, and 37C, which are side walls different from the side wall 37D. Therefore, the side wall 37D corresponds to the first side wall in which the spout portion is provided, and the side walls 37A, 37B, and 37C correspond to the second side wall(s) in which the spout portion 36 is not provided.

In the example illustrated in FIG. 4, two linear supply lines 26, 26, which are parallel to each other, are located on the surface of the molten metal 5c in the bath 30. In addition, two straight lines of irradiation 25, 25, which are parallel to each other, are located on the inside ( closer to the central part in the width direction (X direction) of the tub 30) of the feed lines 26, 26. The supply lines 26, 26 are located along the inner surfaces of the two side walls 37A and 37B (second side walls) among the four side walls of the tub 30, at positions closer to the central part in the width direction (X direction) of the tub 30, which are separated by a predetermined distance L1 from the respective internal surfaces. The irradiation lines 25, 25 are located along the supply lines 26, 26 at positions closer to the central part in the bath 30 width direction, which are separated by a predetermined distance L from the respective supply lines 26, 26.

In the present embodiment, a special temperature gradient is formed on the surface of the molten metal 5c in the bath 30 by emitting an electron beam in a focused manner along the irradiation line 25 on the surface of the molten metal 5c as mentioned above, and thereby controlling the flow of the molten metal 5c. Next, the temperature distribution on the surface of the molten metal 5c in the bath 30 will be described.

Generally, in the electron beam melting process, in order to prevent the molten metal 5c from solidifying in the bath 30, the electron beam is evenly irradiated, for example, by the electron gun 20C, to the heat-holding irradiation region 23, which occupies a wide surface area of the molten metal 5c, to thereby maintain the temperature. of the molten metal 5c in the bath 30. By performing such heat-holding electron beam emission, all of the molten metal 5c accumulated in the bath 30 is heated, and the average surface temperature T0 (hereinafter

- 7 039286 referred to as the surface temperature of the molten metal T0) of the entire surface of the molten metal 5c is maintained at a predetermined level. The surface temperature of the molten metal T0 is, for example, in the range from 1923 K (melting point of the titanium alloy) to 2323 K, and preferably is in the range from 1973 to 2273 K.

In the present embodiment, electron beams are emitted onto the solid raw material 5 at the aforementioned raw material supply portion 10 by the electron guns 20A and 20B to melt the raw material 5, and the high temperature molten metal flows down to the positions of the molten metal supply lines 26 5c in the bath 30, to thereby supply the raw material 5 to the bath 30. Therefore, among all the molten metal 5c in the bath 30, impurities such as GNP contained in the raw material 5 are mainly present near the supply lines 26 . In addition, since the high temperature molten metal is supplied continuously or intermittently to the supply lines 26, a high temperature region (see region S1 in FIGS. 6 and 7) having a surface temperature T1 higher than the aforementioned molten metal surface temperature T0 is formed near the lines 26 submissions. The surface temperature T1 (hereinafter referred to as the raw material supply temperature T1) of the molten metal 5c in the supply lines 26 is approximately the same as the temperature of the molten metal which drips from the raw material supply portion 10 into the bath 30, and is higher than the aforementioned temperature. surface of the molten metal Т0 (Т1>Т0). The feed temperature T1 is, for example, within the range 1923-2423 K and preferably within the range 1973-2373 K.

In addition, according to the production method of the metal ingot of the present embodiment, apart from emitting the above-mentioned heat holding electron beam to the heat holding irradiation area 23 of the molten metal 5c, the electron beam is emitted in a focused manner by the electron gun 20E to the surface of the molten metal 5c along line 25 irradiation. Specifically, the irradiation position of the electron beam emitted from the electron gun 20E moves along the irradiation line 25 on the surface of the molten metal 5c. Due to such concentrated electron beam emission along the irradiation line 25, a high temperature region (see region S2 in FIG. 7) is formed near it, having a surface temperature T2 higher than the above-mentioned molten metal surface temperature T0. The surface temperature T2 (hereinafter referred to as the irradiation line temperature T2) of the molten metal 5c in the irradiation line 25 is higher than the above-mentioned molten metal surface temperature T0 (T2>T0). In addition, in order to suppress the leakage of impurities more reliably, the irradiation line temperature T2 is preferably higher than the above-mentioned feed temperature T1 (T2>T1>T0). The temperature of the irradiation line T2 is, for example, within the range of 1923 to 2473 K, and preferably is within the range of 1973-2423 K.

Thus, according to the metal ingot production method of the present embodiment, by emitting an electron beam in a focused manner along the irradiation line 25 on the surface of the molten metal 5c, a high temperature region of the molten metal 5c is also formed near the irradiation line 25, not only near the supply lines 26. Due to this, as illustrated in FIG. 5, in the outer molten metal layer 5c, a molten metal stream 61 (corresponding to the first molten metal stream of the present invention) can be forcibly formed from the irradiation line 25 to the supply lines 26. In particular, the generated molten metal stream 61 can be constantly maintained by maintaining the temperature of the molten metal 5c above the temperature T0 at arbitrary positions of the irradiation line 25 .

By means of the molten metal flow 61, the flow of impurities such as GNR, which are present in large quantities near the supply lines 26, can be controlled, and the flow of impurities to the spout part 36 can be prevented. In particular, by means of the molten metal stream 61, impurities such as HLR that float on the surface of the molten metal 5c in the regions near the supply lines 26 are moved to the side walls 37A and 37B of the bath 30, and thus impurities such as HLR can be be captured by the scull 7 formed on the inner surfaces of the side walls 37A and 37B. In addition, by emitting an electron beam along the irradiation lines 25 to increase the temperature of the irradiation line T2, it is possible to accelerate the dissolution of nitrided titanium, etc., which is the main component of the GNR, floating in the molten metal 5c near the irradiation line 25.

Thus, in the method for producing a metal ingot according to the present embodiment, electron beams are emitted along the irradiation lines 25, 25, which are closer to the central part (inside) of the pool 30 relative to the supply lines 26, 26. By this, a high-temperature region of molten metal 5c is formed near each irradiation line 25, and by means of the molten metal flow 61 from the high-temperature regions, impurities such as GNR that are present near the supply lines 26 begin to flow towards the side walls 37A and 37B, preventing, thus moving the impurities to the sock portion 36 . Therefore, the leakage of impurities from the bath 30 into the mold 40 can be prevented.

- 8 039286

1.3. Molten metal flow generated by linear radiation.

Next, the flow of molten metal 5c inside the bath 30 generated by the linear emission of the electron beam will be described in detail with reference to FIG. 5-7. Fig. 6A and 6B are a longitudinal section and a top view of the bath, respectively, which illustrate the state of the molten metal flow 5c when no electron beam is emitted along the irradiation lines 25, as a comparative example of the present embodiment. Fig. 7 is a longitudinal section of the bath that illustrates the state of the molten metal flow 5c when the electron beam is emitted along the irradiation lines 25 according to the metal ingot production method of the present embodiment.

As described above, in the present embodiment, the raw material supply portions 10A and 10B are located above the side walls 37A and 37B on the long sides of the tub 30, respectively, and electron beams are emitted by the electron guns 20A and 20B onto the solid raw material 5 on the raw material supply portions 10A and 10B, to thereby melt the raw material 5. The molten raw material 5 drips onto the positions of the molten metal supply lines 26, 26 5c in the bath 30 of the raw material supply portions 10A and 10B. Thus, in the present embodiment, the raw material 5 is supplied to the bath 30 by dropping the molten metal of the raw material 5 onto the molten metal 5c in the bath 30. In this regard, the supply lines 26 according to the present embodiment correspond to imaginary lines (drip lines) that represent are positions in which the molten metal of the raw material 5 drips onto the surface of the molten metal 5c.

The molten metal 5c that accumulates in the bath 30 is cleaned while in the bath 30 and then flows out of the spout portion 36 into the mold 40. As illustrated in FIG. 5, at the central portion in the width direction (X direction) in the bath 30, the molten metal flow 60, which flows along the longitudinal direction (Y direction) of the bath 30, is formed from the vicinity of the side wall 37C, which is one of the short sides, and flows to the part 36 drain sock. Through this flow of molten metal 60, the molten metal 5c that accumulates inside the bath 30 flows out of the spout portion 36 into the mold 40.

In addition, as illustrated in FIG. 5-7, a solidified layer (called scull 7) of molten metal 5c is formed on the inner surface of the side walls 37 and on the surface of the bottom of the bath 30. By accumulating the molten metal 5c in the bath 30, it is possible to remove the impurities contained in the molten metal 5c by using the skull 7 etc. Impurities are categorized into HPS (not shown), which have a high relative density compared to molten metal 5c, and HPS 8, which have a low relative density compared to molten metal 5c. HPFs that have a high relative density settle in the molten metal 5c and adhere to the scull 7 that is formed on the surface of the bottom of the tub 30, and hence the probability of the HPFs flowing into the mold 40 from the spout portion 36 becomes low. On the other hand, a large part of the VNP 8, which have a low relative density, floats on the surface of the molten metal 5c and flows with the flow in the outer layer of the molten metal 5c. Therefore, it is preferable to control the flow of the outer layer of molten metal 5c so that the EOR 8 floating in the molten metal 5c of the bath 30 does not flow from the spout portion 36 into the mold 40.

Therefore, in the method for producing a metal ingot according to the present embodiment, the electron beams are emitted in a focused manner along the irradiation lines 25, 25, which are on the inside of the supply lines 26, 26 on the surface of the molten metal 5c in the bath 30. Due to this, the Marangoni convection is created by a temperature gradient on the surface of the molten metal 5c, and as illustrated in FIG. 5 and 7, the outer molten metal flow 5c (first molten metal stream 61) to the supply lines 26 from the irradiation line 25 is formed in the outer molten metal 5c. Due to this, the RNP 8, which are present in large quantities near the supply lines 26, begin to flow to the side walls 37A and 37B of the bath 30 adjacent to the supply lines 26, and are caught by the scull 7 formed on the inner surface of the side walls 37A and 37B. This principle is described in more detail below.

When a temperature gradient occurs in the outer layer of the fluid, there is also a surface tension gradient in the fluid that causes convection to form in the fluid. Such convection in a fluid medium is called Marangoni convection. When the fluid is molten titanium or molten titanium alloy, Marangoni convection is a flow from a high temperature region to a low temperature region of the fluid. The reason for this is that the surface tension of the molten titanium and the molten titanium alloy decreases as the temperature rises.

Here, as a comparative example of the present embodiment, as illustrated in FIG. 6A, the case will be considered in which the electron beam is not irradiated to the irradiation line 25 and the temperature of the molten metal (feed temperature of raw material T1) which drips onto the supply line 26 is higher than the surface temperature T0 of the molten metal which has already accumulated in bath 30. In this case, the area S1 near the lines 26 of the supply, which drips

- 9 039286 molten raw material 5 (molten metal) is a high temperature area in which the temperature is higher than the temperature of the molten metal 5c in other areas. Therefore, as illustrated in FIG. 6A, since the molten metal 5c in the area S1 flows from the respective supply line 26 both towards the central part in the width direction (X direction) of the bath 30 and towards the side wall 37B, the molten metal flows 62 and 63 are formed in the outer layer. molten metal 5s.

Thus, as illustrated in FIG. 6A and 6B , the VNP 8 contained in the molten metal that drips onto the supply line 26 moves with the molten metal flow 62 towards the center portion in the width direction (X direction) of the bath 30, and also moves with the molten metal flow 63 towards the side wall 37B. baths 30. As illustrated in FIG. 6B, the molten metal streams 62, 62 that flow toward the center of the pool 30 from each of the left and right supply lines 26, 26 collide at the center in the width direction of the pool 30, thereby forming a stream of molten metal 60 toward the spout portion 36. along the longitudinal direction (Y-direction) of the pool 30. As a result, the EORs 8 that float in the molten metal 5c also move with the molten metal flow 60 to the spout part 36 and flow out of the spout part 36 into the mold 40. Therefore, in order to In order to ensure that impurities such as RNR 8 do not flow from the spout portion 36 into the mold 40, it is preferable to control the flow of the outer layer of molten metal 5c so that the RNR 8 that are present near the supply lines 26 do not move with the flow 62 molten metal shown in Fig. 6A and 6B and flowed towards the central part in the width direction of the bath 30.

Therefore, in the present embodiment, as illustrated in FIG. 5 and 7, the electron beam is emitted in a focused manner along the irradiation lines 25, which are located closer to the central part of the bath 30 relative to the supply lines 26. This increases the surface temperature T2 of the molten metal 5c in the area S2 near each irradiation line 25 and creates a surface temperature gradient of the molten metal 5c in the ribbon-like area S3 between each irradiation line 25 and the corresponding supply line 26 . As a result, Marangoni convection in the molten metal 5c (first molten metal stream 61) occurs in the outer layer of molten metal 5c from the irradiation lines 25 to the inner surface of the side walls 37A and 37B. By means of the molten metal stream 61, the HLRs 8, which float on the surface of the molten metal 5c near the supply lines 26, are forcibly carried away to the side walls 37A and 37B, and their advance towards the spout part 36 can be prevented. Accordingly, in the areas between the irradiation lines 25 and the side walls 37A and 37B, the RNPs 8 contained in the molten metal that has dripped onto the positions of the supply lines 26 move along with the respective molten metal streams 61, flow towards the side walls 37A and 37B, and adhere to the skull 7 formed on the inner surfaces of the side walls 37A and 37B, and thus are captured.

The molten metal flow 5c generated by the linear radiation mentioned above will now be described in more detail. Fig. 5 and 7 illustrate the flow of molten metal 5c when the surface temperature T2 of the molten metal 5c in the irradiation line 25 (irradiation line temperature T2) is higher than the surface temperature T1 of the molten metal 5c in the supply line 26 (raw material supply temperature T1) .

As described above, when the molten metal 5c is molten titanium, the Marangoni convection is a flow from the high temperature region to the low temperature region of the molten metal 5c. When the electron beam is emitted in a focused manner along the irradiation line 25, the region S2 near the irradiation line 25 to which the electron beam is irradiated heats up and becomes a high temperature region. Correspondingly, the Marangoni convection arises from the region S2 to the region of low temperature around the region S2. As a result, as illustrated in FIG. 7, in the outer molten metal layer 5c, a molten metal flow 64 is formed from the irradiation line 25 to the center in the width direction of the bath 30, and a molten metal flow 61 is formed from the irradiation line 25 to the side wall 37B through the supply line 26. On the other hand, in the deep layer of molten metal 5c, a flow of molten metal 65 is formed towards the central part of the bath 30 from the side wall 37B at the end part in the width direction (X direction) of the bath 30.

In this case, it is preferable that in the outer layer of the molten metal 5c, the temperature distribution is formed such that the temperature of the irradiation line T2 is higher than the feed temperature of the raw material T1, and the surface temperature of the molten metal 5c gradually decreases from the irradiation line 25 to the supply line 26. By implementing such a temperature distribution as illustrated in FIG. 7, in the outer layer of molten metal 5c, no molten metal flow from the supply lines 26 to the central part of the bath 30 is formed (corresponding to the molten metal flow 62 in FIGS. 6A and 6B), and the molten metal flow 61 from the irradiation line 25 to the supply line 26 may cross the supply line 26 and reach the inner surface of the side wall 37B.

As a result, as illustrated in FIG. 7, GNP 8, which stagnate near line 26 along

- 10 039286 dachas, are carried away to the side wall 37B from the area S1 near the supply line 26 by the molten metal stream 61, and therefore the VNP 8 do not flow to the central part of the bath 30. It should be noted that the VNP 8, which are contained in the molten metal dripping onto the line 26 supply are temporarily distributed to both sides in the width direction (X direction) from the supply line 26 due to the impact effect on the surface of the molten metal 5c when the molten metal drips onto the molten metal 5c. However, thereafter, the VNR 8 is forcibly carried away to the side wall 37B from the region S1 near the supply line 26 by the aforementioned molten metal stream 61 .

In most cases, the distance L1 between the supply line 26 onto which the raw material 5 drips and the side wall 37B is small. Therefore, if the HLRs 8, which float near the supply line 26, are moved towards the side wall 37B of the bath 30 by the molten metal stream 61, the HLRs 8 readily adhere to the ledge 7 that is formed on the inner surface of the side wall 37B. Accordingly, by forming the molten metal stream 61 in the outer layer of the molten metal 5c by means of linear electron beam emission, the HLRs 8 that float in the area S1 near the supply line 26 can be effectively captured by the ledge 7 on the inner surface of the side wall 37B, and thereby removed from the molten metal 5s.

In addition, the source of contamination of the EORs 8 that float in the molten metal 5c in the bath 30 is the molten metal that drips into the bath 30 from the outside, and at least one part of the EORs 8 contained in the molten metal that drips on the supply line 26, dissolves in the molten metal 5c or adheres to the scull 7 while inside the bath 30. Therefore, it is believed that almost no GNR 8 floats in the molten metal 5c in areas that differ from the vicinity of the supply lines 26. Accordingly, as illustrated in FIG. 7, in the region S2 near the irradiation line 25 to which the electron beam is irradiated in a focused manner, there are almost no floating RTRs 8, and the RTRs 8 are not contained in the flow of molten metal 64 from the region S2 towards the central part in the width direction of the bath 30. As illustrated in fig. 5, the molten metal flow 64 in the X direction changes direction at the central portion in the width direction of the bath 30 and becomes the molten metal flow 60 in the Y direction towards the spout portion 36, and the molten metal flow 60 also does not contain the EOR 8. Therefore, there is no problem even if the molten metal stream 60 is discharged from the spout portion 36 into the mold 40 in the state as it is.

1.4. The location of the irradiation line.

Next, the location of the irradiation line 25 along which the electron beam is emitted in a focused manner will be described in detail.

According to the production method of the metal ingot of the present embodiment, as illustrated in FIG. 4, the electron beams are emitted in a focused manner on the irradiation lines 25, 25, which are located closer to the central part in the width direction (X direction) of the bath 30 relative to the supply lines 26, 26. The supply lines 26 are imaginary lines representing the positions at which the molten metal of the raw material 5 drips into the molten metal 5c in the bath 30. The irradiation line 25 is an imaginary line that corresponds to the travel path of the electron beam that is emitted by the linear irradiation electron gun 20E.

From the point of view of reliably preventing impurities from escaping by linear irradiation, it is preferable that the supply lines 26, 26 have a rectilinear shape and are substantially parallel to the inner surface of the side walls 37A and 37B, which are a pair of long sides of the tub 30. In addition, each line 25 irradiation preferably has a rectilinear shape and is essentially parallel to each line 26 supply.

Here, the term essentially parallel not only refers to the case where the respective two objects are strictly parallel (the angular difference is 0°), but also includes all cases in which the angular difference between the respective two objects does not exceed some predetermined angle. As a specific example, if the angular difference between the supply lines 26 and the inner surfaces of the side walls 37A and 37B of the tub 30 is not more than 6°, the effect of the present invention is obtained. However, this does not apply when the feed lines 26 are too close to the side walls 37A and 37B, in particular when the feed lines 26 are about 5 mm or less away from the side walls 37A and 37B, and thus, there is a difficulty in supplying molten metal. In addition, with regard to the irradiation lines 25, the effect of the present invention can be obtained if their angular difference with the corresponding feed lines 26 does not exceed 4°. However, this does not apply when the corresponding irradiation line 25 is too close to the corresponding supply line 26, in particular, when the irradiation line 25 is about 5 mm or less away from the supply line 26, and thus occurs difficulty for the formation of the stream 61 of molten metal, which will be described later.

In the method for producing a metal ingot according to the present embodiment, as illustrated in FIG. 5, due to the emission of electron beams by a focused image

- 11 039286 ZOM along the lines 25 irradiation creates a Marangoni convection (flow 61 of molten metal) from the lines 25 irradiation to the lines 26 supply. The molten metal streams 62 from each of the supply lines 26 to the central part of the bath 30 are driven back to the side walls 37A and 37B of the bath 30 by the molten metal stream 61. In this case, it is preferable to properly arrange the location of the supply lines 26 and the irradiation lines 25 so that the flows 62 of molten metal from the supply lines 26 to the central part of the bath 30 do not pass through the irradiation lines 25 and flow to the central part of the bath 30.

Therefore, in the present embodiment, as illustrated in FIG. 4, the supply lines 26 are rectilinear and substantially parallel to the inner surface of the side walls 37A and 37B on the long side of the bath 30, and the irradiation lines 25 are rectilinear and substantially parallel to the supply lines 26. Due to this, regardless of the position in the longitudinal direction (Y direction) of the tub 30, the distance L1 between the inner surface of the side wall 37A or 37B and the corresponding supply line 26 is approximately constant, and the distance L between each irradiation line 25 and the corresponding supply line 26 is approximately constant. Accordingly, the flows 61 of molten metal in the X direction from the irradiation lines 25 to the supply lines 26 are formed approximately equally in the longitudinal direction (Y direction) of the bath 30. Therefore, the flows 62 of molten metal from the supply lines 26 to the central part of the bath 30 can be uniformly controlled by the flows 61 of molten metal through the entire area in the Y direction of the feed lines 26 . Therefore, the occurrence of a situation in which the molten metal streams 62 cross the irradiation lines 25 and flow towards the center portion in the width direction (X direction) of the pool 30 can be more reliably prevented.

Next, the distance L between each irradiation line 25 and the corresponding supply line 26 will be described. As illustrated in FIG. 5, in the space between the supply line 26 and the central part in the bath 30 width direction, the irradiation line 25 is located at a position which is separated from the supply line 26 by a predetermined distance L. In most cases, the distance L is determined by the feed temperature of the raw material T1 and the emission conditions of the electron beam, is emitted along the irradiation line 25 or the like, and for example, the distance L is preferably within the range of 5-35 mm. In this way, the RNPs 8 that stagnate near the supply lines 26 are favorably carried to the side walls 37A and 37B by the molten metal stream 61 from the irradiation line 25 and can thereby be captured by the skull 7.

If the distance L is less than 5 mm, the irradiation line 25 will be too close to the supply line 26, and the high temperature region S2 and the high temperature region S1 illustrated in FIG. 7 will overlap each other. Therefore, there will be a possibility that it will become difficult to form a stream of molten metal 61 from the irradiation line 25 to the supply line 26 and that the IRR 8 from the vicinity of the supply line 26 will flow to the spout portion 36 . On the other hand, if the distance L is more than 35 mm, then the flow 61 of molten metal from the irradiation line 25 to the supply line 26 will weaken before it reaches the supply line 26 . Therefore, it will become difficult to cause the HLR 8 from the vicinity of each supply line 26 to flow towards the side walls 37A and 37B, and it will be likely that in the ribbon-like region S3 between the irradiation line 25 and the supply line 26, the HLR 8 will flow towards the drain sock portion 36. Accordingly, in order to suitably push back the molten metal stream 62 by the molten metal stream 61, it is preferable that the distance L is within the range of 5-35 mm.

In addition, as illustrated in FIG. 4 and 5, it is preferable that the irradiation lines 25 are longer than the supply lines 26 and that the two ends of each irradiation line 25 are located on the outside in the direction of passage of the corresponding supply line 26 relative to the two ends of the supply line 26 respectively (in the example illustrated in the drawings, on the outside in the longitudinal direction (Y direction) of the tub 30). Due to this, since each irradiation line 25 covers the corresponding line 26 with a margin in the Y direction, the molten metal stream 62 that flows in the X direction from each supply line 26 can be suppressed so that the molten metal stream 62 does not bypass two end in the Y direction of the corresponding irradiation line 25 and flow towards the central part of the tub 30.

1.5. Electron beam settings for linear irradiation.

Next, the settings of the electron beam for linear irradiation (the first electron beam) which is emitted in a focused manner along the above-mentioned irradiation line 25 will be described.

In order to push back the molten metal stream 62 from the supply lines 26 (see FIGS. 6A and 6B) to the side wall 37B of the bath 30 by means of the molten metal stream 61 from the irradiation line 25 (see FIG. 7), as mentioned above, it is preferable to appropriately set the irradiation conditions such as the amount of heat transferred, the scanning speed, and the heat flux distribution of the electron beam for linear irradiation.

The amount of heat transferred (W) of the electron beam is a parameter that affects the temperature increase of the molten metal 5c in the irradiation line 25, as well as the flow rate

- 12 039286 Marangoni convection (flow 61 of molten metal), which is formed due to the considered increase in temperature. If the amount of electron beam heat transfer is small, the molten metal stream 61 which overcomes the molten metal stream 62 from the supply lines 26 cannot be formed. Accordingly, the larger the electron beam heat transfer amount, the better, and, for example, the heat transfer amount may be in the range of 0.15-0.60 MW.

The scanning speed (m/s) of the electron beam is a parameter that affects the speed of the aforementioned molten metal flow 61 . When the electron beam is emitted along the irradiation line 25, the irradiation line 25 on the surface of the molten metal 5c is repeatedly scanned by the electron beam emitted from the electron gun 20E. If the scanning speed of the electron beam is then low, then the irradiation line 25 will have places that are not irradiated by the electron beam for a long time. At these locations, the surface temperature of the molten metal 5c will rapidly decrease and the flow rate 61 of molten metal that occurs at these locations will also decrease. In such a case, it will be difficult to suppress the molten metal flow 62 from the supply lines 26 by the molten metal flow 61, and the possibility that the molten metal flow 62 will pass through the irradiation line 25 will increase. Therefore, the scanning speed of the electron beam is preferably as high as possible, and is, for example, within the range of 1.0-20.0 m/s.

The distribution of the heat flux generated by the electron beam on the surface of the molten metal 5c is a parameter that affects the amount of heat transferred to the molten metal 5c by the electron beam. The heat flux distribution corresponds to the size of the electron beam aperture. The smaller the aperture of the electron beam, the greater the degree of steepness of the distribution of the heat flux transmitted to the molten metal 5c. The heat flux distribution on the surface of the molten metal 5c, for example, is described by the following formula (1) (see, for example, Non-Patent Document 1). The following formula (1) shows that the heat flux decreases exponentially according to the distance from the electron beam spot.

Expression 1:

q(t, x, y) - q ₀ exp (x-x _o ) ² + (y-y _o ) ²

2σ ² (1) ίί qdxdy = Q

J Jail surface (2) where (x, y) represents the position of the molten metal surface, (x ₀ ,y ₀ ) represents the electron beam spot, and σ represents the standard deviation of the heat flux distribution. In addition, as illustrated in the above formula (2), the amount of heat transfer Q from the electron gun is equal to the total sum of the heat flow q over the entire surface of the molten metal 5c inside the bath 30. With regard to these parameters, for example, by modeling the heat flow and t .p., their values can be determined and set so as to create streams 62 of molten metal that flow from the supply lines 26 to the central part of the bath 30 to flow to the side walls 37A and 37B of the bath 30 due to Marangoni convection, which is created by radiation electron beam along the lines 25 exposure.

However, if the velocity of the molten metal streams 61 from the irradiation lines 25 to the supply lines 26 is greater than the velocity of the molten metal streams 62 from the supply lines 26 to the center portion of the bath 30, the molten metal streams 61 may more reliably stop the molten metal streams 62 and may push back flows 62 of molten metal back to the inner surfaces of the side walls 37A and 37B of the bath 30.

Therefore, it is advantageous to set the electron beam emission conditions for linear irradiation such that, as illustrated in FIG. 7, the temperature (irradiation line temperature T2) of the high temperature region S2 near the irradiation line 25 became higher than the temperature (raw material supply temperature T1) of the high temperature region S1 near the supply line 26. Due to this, the temperature difference between the temperature of the irradiation line T2 and the surface temperature of the molten metal T0 can be made larger than the temperature difference between the temperature of the raw material supply T1 and the surface temperature of the molten metal T0, and therefore the flow 61 of molten metal from the irradiation line 25 to the line 26 feed can be reinforced.

It should be noted that the aforementioned radiation conditions, such as the amount of heat transferred, the scanning speed, and the heat flux distribution of the electron beam for linear irradiation, are limited by the characteristics of the equipment that emits the electron beam. Accordingly, when setting the electron beam emission conditions, it is advantageous to make the amount of heat transfer as large as possible, the scanning speed to be as high as possible, and the heat flux distribution to be as narrow as possible (i.e., to make the aperture of the electron beam as small as possible) within the performance range of the equipment. In addition, the emission of the electron beam through the irradiation line 25 can

- 13 039286 can be performed by a single electron gun or a plurality of electron guns. In addition, the electron gun 20E exclusively for linear irradiation (see FIG. 3) can be used as the electron gun for the linear irradiation described here, or alternatively, electron guns designed for other purposes, such as electron guns 20A and 20B for melting raw materials or electron guns 20C and 20D for maintaining the temperature of the molten metal (see Fig. 3).

1.6. Temperature gradient AT/L.

Next, the effect that the temperature gradient AT/L between the irradiation lines 25 and the supply lines 26 has on the flow of molten metal 5c in the bath 30 will be described with reference to FIG. 5, 8 and 9.

The strength of the aforementioned molten metal flow 61 flowing from each irradiation line 25 to the respective supply line 26 varies depending on the temperature gradient AT/L between the irradiation line 25 and the corresponding supply line 26. Here, the temperature gradient AT/L (K/mm) is represented by the following formula (A).

AT/L=(T2-T1)/L(A) where T1: surface temperature of the molten metal 5c on the supply line 26 (feed temperature of the raw material) (K);

T2: surface temperature of the molten metal 5c on the irradiation line 25 (linear irradiation temperature) (K);

L: distance between the irradiation line 25 and the supply line 26 on the surface of the molten metal 5c (mm).

The temperature gradient AT/L is preferably -2.70 (K/mm) or more (AT/L>-2.70 K/mm), and more preferably 0.00 (K/mm) or more (AT/L> 0.00K/mm). Thus, the molten metal stream 61 that flows from the irradiation line 25 to the supply line 26 can be suitably formed. Therefore, in the ribbon-like region S3 between the irradiation line 25 and the supply line 26, the flow of impurities such as the GNR 8 floating near the supply lines 26 to the spout portion 36 can be prevented from flowing, and the amount of impurities flowing from the spout portion 36 can be advantageously suppressed. The reason for this is detailed below.

(1) The case where AT/L>0.00.

First, the case where the temperature gradient AT/L is 0.00 (K/mm) or more will be described with reference to FIG. 5. In this case, the temperature of the irradiation line T2 increases to a temperature that is equal to or higher than the feed temperature T1 (T2>T1>T0) and AT/L also increases sufficiently.

Accordingly, as illustrated in FIG. 5, in the ribbon-like regions S3 between the irradiation lines 25 and the supply lines 26, the molten metal streams 61 that flow from the irradiation lines 25 to the supply lines 26 predominate over the molten metal streams 62 that flow from the supply lines 26 to the irradiation lines 25 (see Fig. Fig. 6A and Fig. 6B). Therefore, the molten metal streams 61 that flow from the irradiation lines 25 and cross the supply lines 26 to flow to the inner surfaces of the side walls 37A and 37B can be suitably formed. Accordingly, by means of the molten metal streams 61, it is possible to make the HPR 8 in the vicinity of the supply lines 26 suitably flow towards the side walls 37A and 37B and be reliably caught by the scull 7 on the inner surfaces of the side walls 37A and 37B, and thereby be removed from the molten metal 5c (see Fig. Fig. 7). Therefore, if AT/L>0.00 K/mm, since impurities such as GNP 8 can be suitably prevented from flowing out of the spout portion 36, the amount of impurities flowing from the spout portion 36 can be greatly reduced, for example, up to 0.1% or less, as compared to the case where no electron beams are emitted along the irradiation lines 25 . In this case, the amount of outflowing impurities is a value obtained by counting the mass amount of impurities contained in the molten metal 5c that flows out of the spout portion 36 per unit time.

(2) The case where -2.70<T/L<0.00.

Next, the case where the temperature gradient AT/L is -2.70 (K/mm) or more and less than 0.00 (K/mm) will be described with reference to FIG. 8. In this case, although the temperature of the irradiation line T2 is increased to a temperature that is higher than the surface temperature of the molten metal T0 (T2>T0), the temperature of the irradiation line T2 is lower than the feed temperature of the raw material T1, and AT/L also less than zero.

Accordingly, as illustrated in FIG. 8, in the ribbon-like regions S3 between the irradiation lines 25 and the supply lines 26, the molten metal streams 62 that flow from the supply lines 26 to the irradiation lines 25 and the molten metal streams 61 that flow from the irradiation lines 25 to the supply lines 26 become equal to each other. friend. Therefore, in the ribbon-like regions S3, in some cases, a stream 66 of molten metal is formed, which flows in the Y direction to the spout portion 36. However, since the molten metal streams 62 from supply lines 26 may be

- 14 039286 suppressed by the streams 61 of molten metal from the lines 25 of the irradiation, it is possible to prevent the situation when the streams 62 of molten metal cross the lines 25 of the irradiation and flow towards the central part in the direction of the width of the bath 30. VNP 8, which were prevented from entering the central part, move along with flow 66 of molten metal through the ribbon-like region S3 and gradually move towards the part 36 of the drain sock. Because the ribbon-like region S3 is located between the supply line 26 at temperature T1 and the irradiation line 25 at temperature T2, the temperature in the ribbon-like region S3 is higher than T0. Therefore, some of the GNP 8 dissolve during their stay in the ribbon-like region S3. Therefore, if AT/L>-2.70 K/mm, since impurities such as GNP 8 can be prevented from flowing out of the spout portion 36, the amount of impurities flowing from the spout portion 36 can be reduced, for example, to 1%. or less than when no electron beams are emitted along the irradiation lines 25 .

(3) The case where AT/L<-2.70.

Next, the case where the temperature gradient AT/L is less than -2.70 (K/mm) will be described with reference to FIG. 9. In this case, the temperature of the irradiation line T2 becomes lower than the feed temperature T1 (T1>T2>T0), and AT/L also becomes a negative value. Therefore, with respect to the molten metal streams 61 that flow from the irradiation lines 25 to the supply lines 26, depending on the irradiation positions (positions in the Y direction) of the electron beams with respect to the irradiation lines 25, positions may occur at which the molten metal streams 61 are formed, and positions in which molten metal streams 61 are not formed.

In particular, as illustrated in FIG. 9, in each of the ribbon-like regions S3 between the irradiation lines 25 and the supply lines 26, both a molten metal stream 61 that flows from the irradiation line 25 to the supply line 26 and a molten metal stream 62 that flows from the supply line 26 to the supply line 25 are formed. irradiation. In addition, depending on the position of the electron beam irradiation with respect to the irradiation line 25, the region S31 in which the molten metal flow 61 and the molten metal flow 62 are equal to each other and the region S32 in which the molten metal flow 62 prevails over the molten metal flow 61 are mixed. together. Thus, although the molten metal flow 61 and the molten metal flow 62 become equal in the region S31 in which the temperature of the irradiation line T2 is high, since the region S31 is close to the irradiation position of the electron beam that travels along the irradiation line 25, in the region S32, in which the temperature of the irradiation line T2 decreases due to being away from the electron beam irradiation position, sometimes the molten metal stream 61 is not generated with sufficient force.

Therefore, there is a possibility that in the ribbon-like region S3 between the irradiation line 25 and the supply line 26, a molten metal stream 66 will be formed that flows to the spout portion 36, and a molten metal stream 67 will be formed that flows from the supply line 26 through the line 25 of irradiation towards the central part in the direction of the width of the bath 30. Therefore, there is a risk that the VNR 8, moving along with the molten metal stream 66 or the molten metal stream 67 and located in the vicinity of the supply lines 26, will flow out of the spout portion 36.

However, even when AT/L<-2.70, the molten metal flow 62 from the supply line 26 can be suppressed to some extent by the molten metal flow 61 from the irradiation line 25. Therefore, the VNP 8 that has been prevented from entering the center portion in the bath 30 width direction by the molten metal flow 61 gradually dissolves while they are in the ribbon-like region S3. Therefore, since the movement of impurities, such as VNR 8 in the vicinity of the supply lines 26, to the spout portion 36 can be prevented to some extent, the amount of impurities flowing from the spout portion 36 can be reduced, for example, to 5% or less, according to compared with the case in which the electron beams are not emitted along the irradiation lines 25 .

Therefore, in order to form a suitable molten metal stream 61 by linear irradiation and reduce the amount of outflowing impurities, the preferred temperature gradient AT/L is -2.70 (K/mm) or more, and more preferably 0.00 (K/mm )or more. It is sufficient to appropriately set the electron beam emission conditions for linear irradiation (for example, the amount of heat transferred, the scanning speed and the heat flux distribution of the electron beam), the temperatures T0, T1 and T2 of the molten metal 5c, or the arrangement of the irradiation lines 25 and supply lines 26, or the distances L and L1, etc. so that a temperature gradient AT/L is obtained that is in an appropriate suitable range of numerical values.

It should be noted that the larger the value of the temperature gradient AT/L, the better in terms of suppressing the amount of outflowing impurities. However, the value of the temperature gradient AT/L is limited from above by the characteristics of the equipment emitting the electron beam. Due to such limitations in terms of equipment performance, for example, the upper limit value of the temperature gradient AT/L is preferably 64.0 (K/mm) or less, and more preferably 10.0 (K/mm) or less.

- 15 039286

1.7. Modification.

Next, one modification of the above-described first embodiment will be described. An example has been described above in which, as illustrated in FIG. 4, a pair of irradiation lines 25, 25 are arranged parallel to the side walls 37A and 37B in the longitudinal direction (Y direction) of the tub 30, as well as to the supply lines 26, 26. However, the present invention is not limited to this example. It suffices that the irradiation lines 25 and the supply lines 26 are located along an arbitrary one or more side walls 37A, 37B and 37C (second side walls) that are different from the side wall 37D (first side wall) in which the spout portion 36 is provided. , and the irradiation line 25, as well as the number and direction of the irradiation lines 25, and the like. are not limited to the example illustrated in FIG. 4.

For example, as illustrated in FIG. 10, in some cases the raw material 5 is fed into the bath 30 along a single straight supply line 26 which is substantially parallel to the side wall 37C which is on one short side of the bath 30. In this case it is sufficient to position the irradiation line 25 in a position along the supply line 26 closer to the central part in the longitudinal direction (Y direction) of the tub 30 relative to this feed line 26 . If a molten metal stream 61 is formed that flows from the irradiation line 25 to the side wall 37C on the short side, impurities near the supply line 26 may be captured by the skull 7 on the inner surface of the side wall 37C and thereby removed from the molten metal 5c.

In addition, as illustrated in FIG. 11, there are also cases where one supply line 26 having an inverted C-shape is located along the side walls 37A and 37B on a pair of long sides and one side wall 37C on the short side, and the raw material 5 is fed into the bath 30 along this line 26 filing. In this case, it is sufficient to arrange a single irradiation line 25 having an inverted C-shape along the aforementioned supply line 26 closer to the central part in the longitudinal direction (Y direction) and the width direction (X direction) of the tub 30 relative to this supply line 26. If a stream 61 of molten metal is formed that flows from the irradiation line 25 to the side walls 37A and 37B on the long sides and the side wall 37C on the short side, impurities near the supply line 26 may be trapped by the skull 7 on the inner surfaces of the side walls 37A, 37B and 37C. and thereby removed from the molten metal 5c.

In addition, although not shown in the drawings, for example, there are also cases where the side walls of the bath have a curved shape, such as elliptical or oval. In such a case, the supply line 26 and the irradiation line 25, which have a curved shape, may be located along the curved side walls of the tub.

1.8. Summary.

The method for producing a metal ingot according to the first embodiment of the present invention has been described above. According to the present embodiment, the irradiation lines 25 are arranged along the supply lines 26 at positions closer to the central part in the width direction of the bath 30 with respect to the supply lines 26, and the electron beams are emitted in a focused manner along these irradiation lines 25. Due to this, as illustrated in FIG. 5, 8, 9, and the like, a high temperature region can be formed near each irradiation line 25, and a molten metal stream 61 can be formed that flows from the irradiation line 25 to the corresponding supply line 26. Accordingly, the diffusion of impurities, such as GNP 8, which float on the surface of the molten metal 5c near the supply lines 26, can be prevented by the molten metal stream 61. In this way, impurities can be prevented from flowing out of the downcomer portion 36 of the tub 30 into the mold 40 and entering the ingot 50.

In addition to this, as illustrated in FIG. 5, if at AT/L>0.00, molten metal streams 61 are formed, which flow from the irradiation lines 25, crossing the respective supply lines 26, to the side walls 37A and 37B of the bath 30, the aforementioned impurities begin to flow to the side walls 37A and 37B of the bath. 30 and can adhere to the scull 7 on the inner surfaces of the side walls 37A and 37B. In this way, impurities can be more reliably prevented from flowing out of the downcomer portion 36 of the tub 30 into the mold 40 and entering the ingot 50.

In addition, when AT/L>-2.70, as illustrated in FIG. 8, the molten metal streams 62 from the supply lines 26 can be suppressed by the molten metal streams 61 from the irradiation lines 25. Therefore, a situation can be prevented in which impurities, such as the GNP 8, which float on the surface of the molten metal 5c near the supply lines 26, move along with the molten metal flow 62, crossing the irradiation lines 25, towards the center portion in the width direction of the bath 30 Therefore, since the impurities such as the GNP 8 can be retained in the ribbon-like region S3 having a high temperature and thereby dissolved, the leakage of the impurities from the spout portion 36 can be suitably prevented.

Moreover, according to the metal ingot production method of the present embodiment, since there is no need to change the shape of the existing bath 30, this method can be easily carried out and special maintenance is also not required.

- 16 039286

In the conventional production methods for titanium or titanium alloy ingot, it is common to remove impurities by holding the molten metal for a long time in the bath, thereby dissolving the HRP in the molten metal, while causing the HRP to adhere to the scull formed on the bottom surface of the bath. Therefore, a long bath has traditionally been used to thereby ensure sufficient residence time of the molten metal in the bath. However, according to the present embodiment, since the impurities can be suitably removed even when the residence time of the molten metal in the bath is relatively short, it is possible to use a short bath. Accordingly, by using a short bath in the EL furnace 1, the production cost of the EL furnace 1 can be reduced. In addition, if a short bath is used, the yield of ingot 50 can be improved even without reusing the skull 7 that remains in the bath.

2. Second embodiment.

Next, a method for producing a metal ingot according to the second embodiment of the present invention will be described.

2.1. Scheme of the method for the production of a metal ingot.

First, an outline of a metal ingot production method according to the second embodiment will be described with reference to FIG. 12. FIG. 12 is a plan view illustrating one example of molten metal streams that are formed by the metal ingot production method according to the second embodiment.

As illustrated in FIG. 12, a feature of the method for producing a metal ingot according to the second embodiment is that, in order to further reduce the amount of impurities flowing out of the pool 30, in addition to emitting (linear emission) of an electron beam along the irradiation lines 25 according to the first embodiment that has been described above, , the impurity dissolving electron beam (corresponding to the second electron beam of the present invention) is emitted as a spot onto the molten metal stream 66 (corresponding to the second molten metal stream of the present invention) which flows through the ribbon-like region S3 between the irradiation line 25 and the corresponding supply line 26.

In the second embodiment, also by emitting an electron beam along the above-mentioned irradiation lines 25, a high temperature region S2 is formed near each irradiation line 25, and molten metal streams 61 are formed that flow from each irradiation line 25 to the corresponding supply line 26. This controls the flow of the molten metal 5c between the irradiation lines 25 and the side walls 37 of the tub 30, and contaminants such as GNR 8 that float near the supply lines 26 are restricted so that they do not flow to the spout portion 36. In addition, also in the second embodiment, if the molten metal streams 61 are generated from the irradiation lines 25 to the side walls 37A and 37B, the VLRs 8 that are near the supply lines 26 can be captured by the scull 7 that is formed on the inner surfaces of the side walls. walls 37 of the bath 30 and thus can be removed from the molten metal 5c.

With regard to this point, in the aforementioned first embodiment, as has been described with reference to FIG. 5, when the temperature gradient AT/L between the irradiation line 25 and the supply line 26 is large enough (for example, when AT/L>0.00), the molten metal streams 61 that flow from of the irradiation lines 25 to the supply lines 26, pass through the supply lines 26 and reach the side walls 37A and 37B. Due to these strong streams 61 of molten metal, the RNR 8, which floats near the supply lines 26, begins to flow towards the inner surfaces of the side walls 37A and 37B, thereby allowing the ledge 7, which is formed on the inner surfaces, to capture the RNR 8. In this way, leakage can be prevented. impurities, such as GNP 8, from the part 36 of the drain sock.

However, as described with reference to FIG. 8 and 9, when the temperature gradient AT/L is small (for example, when AT/L<0.00), the molten metal streams 61 that flow from the irradiation lines 25 to the supply lines 26 are relatively weak, and therefore, it is difficult for the molten metal streams 61 to push back the molten metal streams 62 that flow from the supply lines 26 to the irradiation lines 25. For this reason, as illustrated in FIG. 8, molten metal streams 66 that flow in the Y direction to the spout part 36 are formed in the ribbon-like regions S3 between the irradiation lines 25 and the supply lines 26. In this case, there is a risk that impurities, such as GNR 8, which move along with the streams of molten metal 66 and flow to the spout part 36, will flow from the spout part 36 into the mold 40.

Therefore, in the second embodiment, as illustrated in FIG. 12, the electron beam is irradiated in a focused manner to the irradiation spots 27 which are located in the ribbon-like regions S3 between the irradiation lines 25 and the supply lines 26 (spot irradiation). As a result, the electron beam is radiated in a dotted manner onto the molten metal streams 66 which flow through the ribbon-like regions S3 towards the spout portion 36 . Accordingly, the surface temperature of the molten metal 5c locally increases at the positions of the irradiation spots 27, and the impurities

- 17 039286 such as GNP 8, which are contained in the streams 66 of the molten metal, can be dissolved in the molten metal 5c and thereby removed. Therefore, leakage of impurities such as GNP 8 from the spout portion 36 to the mold 40 can be more reliably prevented.

2.2. Irradiation spot temperature.

GNP 8, consisting of titanium nitride and the like, and the melting point of titanium nitride is higher than the melting point of commercially pure titanium. Therefore, in the case where the surface temperature of the molten metal T0 is relatively low, even if the titanium which is the main component of the molten metal 5c is melted, the titanium nitride which is the component of the GNP 8 does not dissolve and remains in the form of hard granules. Therefore, in the above-mentioned irradiation spots 27, the electron beam is emitted in a focused manner in order to increase the surface temperature T3 of the molten metal 5c in the corresponding irradiation spot 27 (hereinafter referred to as the irradiation spot temperature T3) by a large margin relative to the surface temperature of the molten metal T0. By this, the temperature of the irradiation spot T3, for example, can be made higher than the melting point of titanium nitride, and thus titanium nitride can be dissolved in the molten metal 5c to cause nitrogen to diffuse and thereby convert titanium nitride to titanium. Accordingly, the RNP 8 contained in the molten metal streams 66 that pass through the irradiation spots 27 can be reliably dissolved in the molten metal 5c, and thereby removed. It should be noted that the melting point of titanium nitride varies depending on the nitrogen concentration. For example, when the nitrogen concentration is in the range of 1.23-4 wt%, the melting point of titanium nitride is 2300 K.

In this case, the irradiation spot temperature T3 is, for example, in the range of 2300-3500 K and preferably in the range of 2400-2700 K. Preferably, the irradiation spot temperature T3 is higher than the aforementioned feed temperature T1 and the irradiation line temperature T2 and T3>T2). Due to this, even in the case where the RNP 8 do not dissolve and remain in a solid state, when the raw material 5 is melted in the raw material supply portion 10 (raw material supply temperature T1) and when linear irradiation is performed (irradiation line temperature T2), since the RNP 8 can be heated at the T3 irradiation spot temperature, which is a higher temperature, the GNP 8 can be more reliably dissolved.

2.3. The position of the irradiation spot.

First, the position of the respective irradiation spots 27 in the Y direction will be described. As illustrated in FIG. 12, within the ribbon-like region S3 between the irradiation line 25 and the supply line 26, the irradiation spot 27 is preferably located at or near the end on the side of the spout portion 36. The stream 66 of molten metal that flows through the ribbon-like region S3 to the spout portion 36 flows out of the ribbon-like region S3 from the end portion of the ribbon-like region S3 on the side of the spout portion 36 . Therefore, the VNP 8 contained in the stream 66 of molten metal that flows through the ribbon-like region S3, pass through the end portion of the ribbon-like region S3 from the part 36 of the drain sock. Therefore, it is preferable to arrange the irradiation spot 27 on the end portion of the ribbon-like region S3 on the side of the spout part 36, and to emit an electron beam in a focused manner to this irradiation spot 27. Due to this, all or most of the VNP 8, which move along with the stream 66 of molten metal, which flows through the ribbon-like region S3 to the part 36 of the drain sock, can be more reliably dissolved and removed at the position of the spot 27 of irradiation.

Next, the position of the respective irradiation spots 27 in the X direction will be described. The irradiation spot 27 is located between the irradiation line 25 and the supply line 26 . The distance L2 between the irradiation spot 27 and the supply line 26 is suitably set according to the feed temperature of the raw material T1, the temperature of the irradiation line T2, and the radiation conditions for linear irradiation and spot irradiation, and the like, and the distance L2 is preferably about half the distance L between line 25 irradiation and line 26 supply. Due to this, since the irradiation spot 27 can be suitably located at the position of the molten metal stream 66 that flows through the ribbon-like region S3 between the irradiation line 25 and the supply line 26, the RNP 8 contained in the molten metal stream 66 can be effectively dissolved and removed.

It should be noted that in the example illustrated in FIG. 12, in each of the ribbon-like regions S3, only one irradiation spot 27 is located on the end part on the side of the spout part 36, and the electron beam is pointwise irradiated onto the molten metal stream 66 at one place. However, the present invention is not limited to this example, and the electron beam can be pointwise emitted at arbitrary positions through which impurities such as GNP 8 pass on the surface of the molten metal 5c. For example, a plurality of irradiation spots 27 may be located at positions that are separated from each other in the ribbon-like region S3, and the electron beam may be pointwise irradiated onto the molten metal stream 66 at a plurality of locations. In addition, as long as the position in question is the position at which point irradiation of the molten metal stream 66 inside the ribbon-like region S3 can be performed, the electron beam can be point irradiated

- 18 039286 start at any position in the ribbon-like region S3 (for example, in the central part in the Y direction, or in the previous position or in the subsequent position in the Y direction of the central part). In addition to this, the electron beam can also be pointwise irradiated onto the molten metal flow that flows to the spout portion 36 outside the ribbon-like region S3 and not only in the ribbon-like region S3, and the electron beam can also be pointwise irradiated at a location that is located around parts 36 of the drain sock.

2.4. Electron beam settings for the irradiation spot.

In the second embodiment, as described above, the flow path of the EPR 8 (molten metal flow 66) is formed in the ribbon-like region S3 between the irradiation line 25 and the corresponding supply line 26, the irradiation spot 27 is positioned to cut off this flow path, and the electron beam is emitted in a focused manner onto the irradiation spot 27 . By thus maintaining the temperature of the irradiation spot T3 in the irradiation spot 27 at a high level, the RNP 8 can be more reliably dissolved in the molten metal stream 66 that flows to the spout portion 36 . In the case where the molten metal 5c is molten titanium, if the temperature of the irradiation spot T3 as measured by a beam thermometer is maintained at 2400 K or higher, for example, the HNP 8 contained in the molten titanium can be reliably dissolved.

It should be noted that if the temperature of the irradiation spot T3 can be maintained within a predetermined temperature range, the electron beam for spot irradiation that dissolves impurities such as HLR 8 can be emitted continuously or intermittently to the irradiation spot 27. In addition, the radiation conditions, such as the amount of heat transferred, the scanning speed, and the heat flux distribution of the electron beam, for spot irradiation are limited by the characteristics of the equipment that emits the electron beam. Accordingly, when setting the electron beam emission conditions, it is preferable to make the amount of heat transferred by the electron beam as large as possible, the scanning speed to be as high as possible, and the heat flow distribution to be as narrow as possible (i.e., to make the aperture of the electron beam as small as possible) within the performance range of the equipment.

Moreover, the emission of the electron beam at the irradiation spots 27 may be performed using a single electron gun or using a plurality of electron guns. In addition, preferably, the aforementioned linear irradiation electron gun 20E (see FIG. 3) also serves as a spot irradiation electron gun. By this, the number of electron guns installed in the EL furnace 1 can be reduced, the equipment cost can be reduced, and the electron guns already installed can be used efficiently. However, the present invention is not limited to this example, and as the electron gun for spot irradiation, an electron gun dedicated exclusively to spot irradiation (not shown) or, alternatively, an electron gun dedicated to other purposes such as a 20A or 20B electron gun can be used. for melting raw materials or an electron gun 20C or 20D for maintaining the temperature of the molten metal (see Fig. 3), can also be used for spot irradiation.

2.5. Modification.

Next, one modification of the above-described second embodiment will be described. An example has been described above in which, as illustrated in FIG. 12, the two ribbon-like regions S3, S3 are arranged substantially parallel to the side walls 37A and 37B in the longitudinal direction (Y direction) of the tub 30. However, the present invention is not limited to this example. The ribbon-like region S3 may be disposed along any one or more side walls 37A, 37B, and 37C (second side walls) other than the side wall 37D (first side wall) in which the spout portion 36 is provided, and the number, direction, shape, and etc. The provided ribbon-like regions S3 are not limited to the example illustrated in FIG. 12.

For example, as illustrated in FIG. 13, the single feed line 26 having a rectilinear shape and the single irradiation line 25 may be arranged substantially parallel to the side wall 37C on one of the short sides of the tub 30, and the ribbon-like region S3 substantially parallel to the side wall 37C on the short side may be located between the supply line 26 and the irradiation line 25. In this case, it is sufficient to arrange two irradiation spots 27, 27 at the two end portions in the X direction of the ribbon-like region S3 and emit electron beams in a focused manner at the positions of these two irradiation spots 27, 27 onto the molten metal streams 66, 66 that flow through the inside of the ribbon-like area S3 in the X direction. Due to this, since the HLR 8 contained in the streams 66, 66 of the molten metal can be dissolved, it is possible to prevent the HLR 8 from bypassing the irradiation line 25 from two ends in the X direction and flowing towards the spout part 36 of the spout.

In addition, as illustrated in FIG. 14, the supply line 26 and the irradiation line 25, each having an inverted C-shape, may be arranged along the side walls 37A and 37B on a pair of long sides and a side wall 37C which is on one of the short sides, and a ribbon-like region S3. , having an inverted C-shape, can be located between

- 19 039286 supply line 26 and irradiation line 25. In this case, it is sufficient to arrange two irradiation spots 27, 27 on the two end parts of the inverted C-shaped ribbon-like region S3 on the side of the spout portion 36, and to emit electron beams in a focused manner at the positions of these two irradiation spots 27, 27 to streams 66 , 66 of molten metal that flow through the inside of the ribbon-like region S3 to the spout portion 36 . By this, since the HLR 8 contained in the molten metal streams 66, 66 can be dissolved, the HLR 8 can be prevented from passing through the two end portions of the inverted C-shaped ribbon-like region S3 and flowing towards the spout portion 36.

2.6. Summary.

The method for producing a metal ingot according to the second embodiment of the present invention has been described above. According to the second embodiment, the following effects are obtained in addition to the above-mentioned effects of the first embodiment.

According to the second embodiment, when the molten metal stream 66 that flows to the spout portion 36 is formed in the ribbon-like region S3 between the irradiation line 25 and the supply line 26, an electron beam for dissolving impurities is irradiated in a focused manner onto the molten metal stream 66 in the spot 27 irradiation, which is located on one or both end parts of the ribbon-like area S3. In this way, before impurities such as HLR 8, which are contained in the molten metal stream 66, reach the spout portion 36 from the ribbon-like region S3, these impurities can be dissolved in the high temperature irradiation spot 27 and thereby removed from the molten metal. Therefore, leakage of impurities such as GNP 8 from the spout portion 36 to the mold 40 can be more reliably prevented.

In the above first embodiment, in the case where the temperature of the irradiation line T2 is lower than the feed temperature of the raw material T1, or in the case where the temperature gradient AT/L between the supply line 26 and the irradiation line 25 is less than 0.00 of due to equipment characteristics or other limitations, there is a possibility that the molten metal stream 66 that flows to the spout part 36 will be formed in the ribbon-like region S3, and that the impurities that move with the molten metal stream 66 will flow to the part 36 drain sock. Even so, in the metal ingot production method according to the second embodiment, impurities can be more reliably prevented from flowing out to the spout portion 36, and therefore the metal ingot production method according to the second embodiment is particularly useful.

3. Third embodiment.

Next, a method for producing a metal ingot according to the third embodiment of the present invention will be described.

3.1. Scheme of the method for the production of a metal ingot.

First, a flow chart of a metal ingot production method according to the third embodiment will be described with reference to FIG. 15. FIG. 15 is a plan view illustrating one example of molten metal flows that are formed by the metal ingot production method according to the third embodiment.

As illustrated in FIG. 15, a feature of the method for producing a metal ingot according to the third embodiment is that, in order to further reduce the amount of impurities flowing out of the bath 30, in addition to emitting (linear emission) an electron beam along the irradiation lines 25 (corresponding to the first irradiation line of the present invention) according to In the first embodiment described above, an electron beam (corresponding to the third electron beam of the present invention) is emitted along an irradiation line 28 (corresponding to the second irradiation line of the present invention) which is positioned to block the spout portion 36.

In the third embodiment, also by emitting an electron beam along the above-mentioned irradiation lines 25, a high temperature region S2 is formed near each irradiation line 25, and molten metal streams 61 are formed that flow from each irradiation line 25 to the corresponding supply line 26. This controls the flow of the molten metal 5c between the irradiation lines 25 and the side walls 37 of the tub 30, and contaminants such as GNR 8 that float near the supply lines 26 are restricted so that they do not flow to the spout portion 36. In addition, also in the third embodiment, if the molten metal streams 61 can be formed from the irradiation lines 25 to the side walls 37A and 37B, the VLRs 8 that are near the supply lines 26 can be captured by the scull 7 that is formed on the inner surfaces of the side walls 37 of the tub 30 and thus can be removed from the molten metal.

However, as described with reference to FIG. 8 and 9, when the temperature gradient AT/L is small (for example, when AT/L<0.00, especially when AT/L<-2.70), the molten metal streams 61 which flow from the irradiation lines 25 to the supply lines 26, are relatively

- 20 039286 extremely weak, and therefore the streams 61 of molten metal cannot push back the streams of molten metal 62 that flow from the supply lines 26 to the irradiation lines 25. For this reason, in some cases, the molten metal streams 66 that flow in the Y direction to the spout part 36 are formed in the ribbon-like regions S3 between the irradiation lines 25 and the supply lines 26 (see FIG. 8), and the molten metal streams 67 from the lines 26 feeds cross the irradiation lines 25 and flow towards the central part of the tub 30 (see FIG. 9). In this case, there is a risk that the VNR 8, which travels with the molten metal streams 66 or together with the molten metal streams 67 and the molten metal stream 60, will flow towards the spout part 36 and will flow out of the spout part 36 into the mold. 40.

Therefore, in the third embodiment, as illustrated in FIG. 15, the irradiation line 28 is positioned to block the spout portion 36 on the surface of the molten metal 5c in the bath 30, and the electron beam is emitted in a focused manner along the irradiation line 28 (the second irradiation line). Due to this, the surface temperature of the molten metal 5c locally increases along the irradiation line 28, and a high temperature region is formed near the irradiation line 28. As a result, a molten metal stream 68 that flows in a direction opposite to the spout part 36 from the vicinity of the irradiation line 28 is formed in the outer layer of molten metal 5c in the region around the spout part 36 . The molten metal stream 68 prevents molten metal streams 66 or molten metal stream 60 that contain impurities such as GNR 8 from flowing into spout portion 36 and can be pushed back. Since the molten metal 5c, which is pushed back, will be in the bath 30 for a long time, the nitrogen contained in impurities such as GNP 8 contained in the subject molten metal 5c diffuses into the molten metal 5c over time and dissolves, thereby removing most impurities from molten metal 5c.

Therefore, in the third embodiment, compared with the aforementioned first embodiment, it is possible to more reliably prevent impurities such as GNR 8 from flowing out of the spout portion 36 into the mold 40.

3.2. The position of the irradiation line and the temperature of the irradiation line.

The irradiation line 28 is an imaginary line that is a sequence of positions at which an electron beam is radiated in a focused manner onto the surface of the molten metal 5c in the bath 30. The irradiation line 28 is positioned on the surface of the molten metal 5c so as to surround the spout portion 36. The two ends of the irradiation line 28 are located near the inner surface of the side wall 37D (first side wall) of the tub 30. As used herein, the term neighborhood means that the distance between the two ends of the irradiation line 28 and the inner surface of the side wall 37 does not exceed 5 mm. By positioning both ends of the irradiation line 28 near the side wall 37D, the occurrence of a situation in which impurities pass through the gaps between the two ends of the irradiation line 28 and the side wall 37D and flow to the spout portion 36 can be suitably prevented.

It should be noted that although in the example illustrated in FIG. 15, the irradiation line 28 has a V-shape, if the irradiation line 28 has a linear shape and is positioned so as to surround the spout part 36, the irradiation line 28 may be, for example, an arc shape, an elliptical shape, another curvilinear shape, an inverted C- shape, U shape, wavy line shape, zigzag shape, double line shape, ribbon shape, and the like.

By emitting an electron beam in a focused manner along the above-mentioned irradiation line 28, a high temperature region having a surface temperature T4 that is higher than the above-mentioned molten metal surface temperature T0 is formed near the irradiation line 28 on the surface of the molten metal 5c. Preferably, the surface temperature T4 (hereinafter referred to as the second irradiation line temperature T4) of the molten metal 5c in the irradiation line 28 is higher than the above-mentioned molten metal surface temperature T0 (T4>T0), and is higher than the above-mentioned raw material supply temperature T1 ( T4>T1>T0). The temperature of the second irradiation line T4 is, for example, within the range of 1923 to 2473 K, and preferably is within the range of 1973-2423 K.

3.3. Electron beam settings for the second linear irradiation.

In the third embodiment, as illustrated in FIG. 15, by emitting the electron beam in a focused manner along the irradiation line 28 which surrounds the spout part 36, a stream of molten metal is formed which flows from the irradiation line 28 away from the spout part 36. The area around the spout part 36 is protected by the molten metal stream 68 so that the molten metal stream containing impurities such as GNP 8 does not flow into the spout part 36 . If the irradiation temperature of the second line T4 can be maintained within a predetermined range, the electron beam for irradiating the second line may be emitted continuously or discontinuously along the irradiation line 28. In addition, radiation conditions such as the amount of heat transferred, the scanning speed, and the distribution of the heat flux of the electron beam for irradiating the second line are limited by the characteristics of the equipment,

- 21 039286 which emits an electron beam. Accordingly, when setting the electron beam emission conditions, it is preferable to make the amount of heat transferred by the electron beam as large as possible, the scanning speed to be as high as possible, and the heat flow distribution to be as narrow as possible (i.e., to make the aperture of the electron beam as small as possible) within the performance range of the equipment.

In addition, the emission of the electron beam along the irradiation line 28 (the second irradiation line) can be performed using a single electron gun or using a plurality of electron guns. In addition, preferably the aforementioned linear irradiation electron gun 20E (see FIG. 3) also serves as the second line irradiation electron gun. By this, the number of electron guns installed in the EL furnace 1 can be reduced, the equipment cost can be reduced, and the electron guns already installed can be used effectively. However, the present invention is not limited to this example, and the above-mentioned point irradiation electron gun (not shown) can be used as the second line irradiation electron gun, or alternatively, an electron gun for other purposes such as a 20A or 20B melting electron gun. raw materials or electron gun 20C or 20D to maintain the temperature of the molten metal (see Fig. 3), can also be used to irradiate the second line.

3.4. Modification.

Next, with reference to FIG. 16, one modification of the above third embodiment will be described. Fig. 16 is a plan view illustrating one example of molten metal streams formed by the metal ingot production method according to one modification of the third embodiment.

The metal ingot production method according to this modification is an example in which point radiation according to the above-mentioned second embodiment (see FIG. 12 and the like) is further applied to the metal ingot production method according to the third embodiment illustrated in FIG. . 15. As illustrated in FIG. 16, according to this modification, the irradiation of the irradiation line 25 (the first embodiment), the irradiation of the irradiation spot 27 (the second embodiment), and the irradiation of the second irradiation line 28 (the third embodiment) are combined. In this case, the location of each of the irradiation line 25, the irradiation spot 27, and the irradiation line 28 is adjusted so that the irradiation line 25, the irradiation spot 27, and the irradiation line 28 do not interfere with each other.

By thus combining the irradiation line 25, the irradiation spot 27, and the irradiation line 28, even if impurities such as GNP 8 are not completely removed by the linear emission according to the first embodiment and the point emission according to the second embodiment, and some impurities move along with the flow of molten metal to the spout part 36, eventually the contaminants in question can be prevented from entering the spout part 36 on the irradiation line 28, which is located near the spout part 36. Therefore, leakage of impurities from the spout portion 36 into the mold 40 can be prevented even more reliably.

Examples

Next, examples of the present invention will be described. The following examples are just specific examples to test the effects of the present invention, and the present invention is not limited to the following examples.

(1) Examples of linear irradiation.

First, with references to Table. 1 and FIG. 18-26, examples will be described in which simulation was performed to test the effect of GNP removal by linear irradiation according to the first embodiment of the present invention, which was described above.

With regard to the present examples, the flow of molten metal inside the bath 30 was simulated for the case in which titanium alloy was used as the raw material 5, for example, and an electron beam was emitted along the irradiation line 25 to the molten titanium alloy metal 5c, which was accumulated in a short bath, shown in FIG. 3. The distribution of temperatures of the molten metal 5c in the bath 30, the behavior of the GNR and the amount of GNR flowing out of the bath 30 were established.

Simulation conditions and evaluation results of the present examples are shown in Table 1. 1.

- 22 039286

Table 1. Simulation conditions and evaluation results of examples of linear irradiation

No. Illustration Linear irradiation Spot irradiation Surface temperature of molten metal TO [TO] Raw material supply temperature Т1 [TO] Irradiation line temperature Т2 [TO] Irradiation spot temperature [TO] Temperature difference ΔΤ (=T2-T1) [TO] Electron beam output Q2 for linear irradiation [MW] Electron beam output Q3 for spot irradiation [MW] Distance L between irradiation line and supply line [mm] Temperature gradient ΔΤ/L [K/mm] Estimating the effect of GNP removal Example 1 Fig. 19 present absent 2093 2173 2177 - 4 0.4 - thirty 0.13 A Example 2 Fig. 20 present absent 2093 2173 2174 - 1 0.4 - 35 0.03 A Example 3 Fig. 21 present absent 2087 2173 2197 - 24 0.4 - 5 4.80 A Example 4 Fig. 22 present absent 2096 2173 2170 - -3 0.4 - 40 -0.08 IN Example 5 Fig. 23 present absent 2166 2373 2298 — -75 0.4 — thirty -2.50 IN Example 6 Fig. 24 present absent 2165 2373 2300 - -73 0.4 - 20 -3.65 WITH Example 7 Fig. 25 present absent 2157 2373 2300 - -73 0.4 - 10 -7.30 WITH Comparative Example 1 Fig. 26 absent absent 2065 2173 - - - - - - - D

In the simulations of examples 1-7 shown in table. 1 as illustrated in FIG. 4, two straight-shaped feed lines 26, 26 were arranged parallel to the side walls 37A and 37B, and two straight-shaped irradiation lines 25, 25 were parallel to the feed lines 26. When the molten titanium alloy was dripped at the raw material supply temperature T1 along the supply lines 26, 26, the heat holding electron beam was emitted to the molten metal heat holding irradiation area 23 5s inside the bath 30 (heat holding radiation) to maintain the surface temperature of the molten metal 5s equal to the surface temperature of the molten metal T0, and the electron beam for linear irradiation was emitted in a focused manner along the irradiation lines 25, 25 (linear irradiation).

On the other hand, as Comparative Example 1, as illustrated in FIG. 17, similar simulation was also performed for the case in which the heat-holding electron beam was irradiated to the irradiation area 23 to hold the heat of the molten metal 5c inside the bath 30, but in which no linear irradiation along the irradiation lines 25, 25 was performed. It should be noted that in the simulations of examples 1-7 and comparative example 1 shown in table. 1, point emission of the electron beam to the irradiation spot 27 was not performed.

Used in Examples 1 to 7 and Comparative Example 1, the different temperatures T0, T1, and T2, the electron beam output Q2 for linear irradiation, the distance L between the irradiation line 25 and the supply line 26, the temperature gradient AT/L, and the like. shown in the above table. 1.

For each simulation, a transient was calculated, since the flow and temperature of the molten metal 5c change at each time point depending on the emission of the electron beam. The modeling was carried out on the basis of the assumptions that the GNP is titanium nitride, the grain size of titanium nitride is 3.5 mm, and the density of titanium nitride is 10% less than the density of the molten metal 5c. In addition, in Examples 1 to 7 and Comparative Example 1, an electron beam was emitted in a focused manner along each of the irradiation lines 25, 25 by scanning the electron beam from one end to the other end of each of the irradiation lines 25, 25 using one electron gun for linear irradiation. . Although the temperature of the irradiation line T2 fluctuated in time and space, the average value of the temperature of the irradiation line T2 was equal to that shown in Table. 1.

As illustrated in Table. 1, in Examples 1 to 7 and Comparative Example 1, the GNP removal effect was evaluated on a four-point scale (from A to D). The amount of GNP per unit time (g/min) flowing out of the bath 30 in the respective Examples 1 to 7 was evaluated based on the following evaluation criteria, taking the amount of GNP per unit time (g/min) flowing out of the bath 30 in Comparative Example 1 as a reference value ( 100%).

A: GNP leakage is less than 0.1% or not detectable.

B: The resulting amount of GNP is 0.1% or more and less than 1%.

C: The resulting amount of GNP is 1% or more and less than 5%.

D: The resulting amount of GNP is 100% (reference value).

Next, the simulation results and estimation of the resulting GNP amount for Examples 1 to 7 and Comparative Example 1 will be described. FIG. 18 is a flow line diagram illustrating the flow of molten metal 5c in Example 1. FIG. 19-25 show simulation results for Examples 1-7, respectively, and FIG. 26 shows the simulation result for Comparative Example 1.

Fig. 19 to 25 show the temperature distribution on the surface of the molten metal 5c in the bath 30 and the behavior of the HLR that flow through the surface of the molten metal 5c when the electron beam irradiation position for linear irradiation that is scanned along the irradiation line 25 was at six representative positions. In the temperature distribution diagrams on the left side of the above-mentioned FIGS. 19-25, the high temperature region marked with a circle indicates the position of the electron beam irradiation relative to the irradiation line 25 at a given time, the two upper and lower ribbon-like high temperature portions indicate the two supply lines 26, 26, and the low temperature portion near the inner surface bath indicates the part in which

- 23 039286 a swarm 7 is formed. In addition, in the flow diagrams on the right side in FIG. 19-25, flow lines having a non-linear shape indicate the flow path of the GNP.

In Example 1, as illustrated in FIG. 18 and 19, a high temperature region was formed along the irradiation lines 25 on the inside of the supply lines 26, and molten metal streams 61 were formed, which passed through the supply lines 26 from the irradiation lines 25 and flowed to the side walls 37A and 37B of the bath 30. Therefore, as illustrated in FIG. 19, all of the EOR in the vicinity of the supply lines 26 moved with the molten metal streams 61 and flowed towards the side walls 37A and 37B, and there were no flow lines extending from the spout portion 36 towards the mold 40. Thus, it was found that that the RRR within the tub 30 was trapped by the ledge 7 on the side walls 37A and 37B, and the RNR did not flow out of the spout portion 36 into the mold 40. As a result, in Example 1, the amount of RNR escaping was extremely low, less than 0.1%, and, thus, the GNP removal effect was rated as A.

Similarly, in example 2 shown in FIG. 20 and in example 3 shown in FIG. 21, it was also found that all of the EPR in the vicinity of the supply lines 26 was entrained towards the side walls 37A and 37B by the molten metal streams 61 from the irradiation lines 25 and were trapped by the skull 7, which prevented the EPR from flowing out of the spout portion 36 into the mold 40. As a result, in Examples 2 and 3, the GNP effluent was also extremely low, less than 0.1% of the GNP effluent in Comparative Example 1, and thus the GNP removal effect was rated as A.

It is believed that the reason for this is the following. In each of the above examples 1 to 3, the temperature of the irradiation line T2 was higher than the feed temperature of the raw material T1, and the temperature gradient AT/L between the supply lines 26 and the irradiation lines 25 was large, 0.00 K/mm or more. Therefore, it is believed that since strong flows 61 of molten metal from the irradiation lines 25 could be generated, which cross the supply lines 26 and flow to the side walls 37A and 37B, the GNR was appropriately controlled so that they did not flow to the drain sock portion 36, and thus the GNR was reliably prevented from flowing into the mold 40.

Further, in Example 4 and Example 5, as illustrated in FIG. 22 and 23, although it was possible to prevent the SNR near the supply lines 26 from intersecting the irradiation lines 25 and flowing closer to the central part in the width direction (X direction) of the bath 30, some of the HPR flowed in the longitudinal direction (Y direction) of the bath 30 through ribbon-like regions S3 between supply lines 26 and irradiation lines 25 . Therefore, in Examples 4 and 5, compared with Comparative Example 1, although the outflow of RNP from the spout part 36 could be largely prevented, a small amount of RNP still leaked out from the spout portion 36. As a result, in Examples 4 and 5, the GNP effluent was in the range of 0.1% to less than 1% of the GNP effluent in Comparative Example 1, and thus the GNP removal effect was evaluated as B.

It is believed that the reason for this is the following. In Examples 4 and 5, the irradiation line temperature T2 was lower than the feed temperature T1, and the temperature gradient AT/L ranged from -2.70 K/mm to less than 0.00 K/mm, which was less than the temperature gradient AT/L in the above examples 1-3. Therefore, in examples 4 and 5, the molten metal flows 61 from the irradiation lines 25 to the supply lines 26, which are illustrated in FIG. 8 could not suppress the molten metal flows 62 from the supply lines 26 to the irradiation lines 25, and the molten metal flows 66 in the Y direction were generated in the ribbon-like regions S3 between the supply lines 26 and the irradiation lines 25. Therefore, it is believed that some of the GNP moved along with the streams 66 of molten metal and flowed to the part 36 of the drain sock.

In addition, according to the results of comparing the above-mentioned examples 1-3 with examples 4 and 5, it can be said that the effect of preventing GNP leakage due to irradiation is excellent in examples 1-3 (T2>T1, AT/L A0.00) compared with examples 4 and 5 (T2<T1, -2.70<AT/L<0.00).

Further, in Example 6 and Example 7, as illustrated in FIG. 24 and 25, the flow of the RNP near the supply lines 26 to the central part in the width direction (X direction) of the bath 30 may be prevented to some extent by areas of high temperature near the irradiation lines 25. However, some RNP flowed from the supply lines 26 through the irradiation lines 25 to the central portion in the width direction (X direction) of the tub 30, and then flowed in the Y direction to the spout portion 36 from the central portion, and some RNP flowed from the spout portion 36 sock. As a result, in Examples 6 and 7, the GNP effluent was in the range of 1% to less than 5% of the GNP effluent in Comparative Example 1, and thus the GNP removal effect was evaluated as C.

It is believed that the reason for this is the following. In Examples 6 and 7, the irradiation line temperature T2 was lower than the feed temperature T1, and the temperature gradient AT/L was less than -2.70 K/mm, which was even smaller than the temperature gradient AT/L in the above examples 4 and 5. Therefore, in examples 6 and 7, in the part of the area illustrated in FIG. 9, molten metal flows 62 from supply lines 26 to irradiation lines 25 dominated molten metal flows 61 from irradiation lines 25 to supply lines 26. Therefore, it is believed that the formation

- 24 039286 flows 67 of molten metal from the supply lines 26, which crossed the irradiation lines 25, and a certain amount of VNP flowed to the central part of the bath 30.

In addition, according to the results of comparing Examples 1-5 with Examples 6 and 7, it can be said that the effect of preventing GNP leakage due to irradiation is excellent in Examples 1-5 (ΔT/L>-2.70) compared with Examples 6 and 7 (AT/L<-2.70).

In contrast, in Comparative Example 1, as illustrated in FIG. 17, no electron beam was emitted along the irradiation lines 25. Therefore, as illustrated in FIG. 26 , the EGR flowed freely from the high temperature regions at the supply lines 26 to the central part of the bath 30 and was carried along by the molten metal flow 60 in the central part of the bath 30, and a large amount of the EGR flowed from the spout part 36 into the mold 40. The result of comparative example 1, in which no GNP removal effect was obtained according to the present invention was rated as D and was used as a reference for other examples.

The simulation results for Examples 1-7 and Comparative Example 1 have been described above. According to these results, it can be said that it has been confirmed that by performing linear emission of the electron beam in a focused manner along the irradiation lines 25 as described in Examples 1 to 7, the flow of RNPs that are near the supply lines 26 is limited, and it can be prevented from entering RNR to the spout portion 36, and thus the amount of RNR flowing from the spout portion 36 can be reduced to less than 5% of that in Comparative Example 1. In particular, it can be said that it was confirmed that with from the point of view of preventing the expiration of GNP due to linear irradiation and increasing the effect of removing GNP, examples 4 and 5 (-2.70<ΔT/L<0.00) are preferred, and examples 1-3 (AT/L>0.00) are even more preferable.

(2) Examples of linear irradiation and spot irradiation.

Further with references to tab. 2 and FIG. 27 to 32, examples will be described in which simulation was performed to test the GNP removal effect by the combination of linear irradiation and point irradiation according to the second embodiment of the present invention, which was described above.

With regard to the present examples, the flow of molten metal inside the bath 30 was simulated for the case in which titanium alloy was used as the raw material 5, for example, and to the titanium alloy molten metal 5c that was accumulated in the short bath shown in FIG. 3, the electron beam was emitted along the irradiation lines 25, and the electron beam was irradiated onto the irradiation spots 27. The temperature distribution of the molten metal 5 s in the bath 30, the behavior of the WOR and the amount of WOR flowing from the bath 30 were established.

Simulation conditions and evaluation results for the present examples are shown in Table 1. 2.

Table 2. Simulation conditions and evaluation results for examples of linear irradiation and point irradiation

No. Illustration Linear irradiation Spot irradiation Surface temperature of the melted metal TO [TO] Raw material supply temperature T1 [TO] Tsmpsrate ra irradiation line T2 [TO] Spot temperature [TO] Temperature difference ΔΤ (= T2- T1) [TO] Output Q2 electron beam for linear irradiation [MW] Electron beam output Q3 for spot irradiation [MW] Distances with L between the irradiation line and the supply line [mm] Temperature gradient AT/L [K/mm] Estimate of the removal effect' GNP Example 8 Fig. 27 present present 2160 2373 2307 2432 -66 0.4 0.1 25 -2.64 A Example 9 Fig. 28 present present 2172 2373 2263 2432 -By 0.4 0.1 80 -1.38 A Example 10 Fig. 29 present present 2176 2373 2362 2432 -eleven 0.4 0.1 140 -0.08 A Example 11 Fig. thirty present present 2089 2173 2187 2432 14 0.4 0.1 20 0.70 A Example 12 Fig. 31 present present 2153 2373 2301 2432 -72 0.4 0.1 20 -3.60 WITH Comparative Example 2 Fig. 32 absent absent 2159 2373 - - - - - - - D

In the simulations of examples 8-12 shown in table. 2 as illustrated in FIG. 12, two feed lines 26, 26 having a rectilinear shape were arranged parallel to the side walls 37A and 37B, two irradiation lines 25, 25 having a rectilinear shape were arranged parallel to the feed lines 26, and irradiation spots 27, 27 were located at the end parts of the ribbon-like areas S3, S3 on the side of the spout part 36 between the two pairs of the irradiation line 25 and the supply line 26 . When the molten titanium alloy was dripped at the raw material supply temperature T1 along the supply lines 26, 26, the heat-holding electron beam was emitted to the heat-holding irradiation region 23 of the molten metal 5s inside the bath 30 (heat-holding radiation) to maintain the surface temperature of the molten metal 5 with the same molten metal surface temperature T0, and the linear irradiation electron beam was emitted in a focused manner along the irradiation lines 25, 25 (linear irradiation), and the spot electron beam was irradiated in a focused manner onto the irradiation spots 27, 27 (spot irradiation).

- 25 039286

On the other hand, as Comparative Example 2, as illustrated in FIG. 17, a similar simulation was also performed for the case in which irradiation of the molten metal 5c was performed for heat retention, but linear irradiation along the irradiation lines 25, 25 and spot irradiation of the irradiation spots 27, 27 were not performed.

Different temperatures T0, T1, T2, and T3 used in Examples 8 to 12 and Comparative Example 2, electron beam output Q2 for linear irradiation, electron beam output Q3 for spot irradiation, distance L between irradiation line 25 and supply line 26, temperature gradient AT /L etc. shown in the above table. 2. Other conditions were the same as in the above examples 1-7. In addition, with regard to the criteria for evaluating the effect of GNP removal (on a four-point scale from A to D), the evaluation criteria were made the same as in the above examples 1-7, except that, as a reference value (100%) instead of Comparative Example 1, Comparative Example 2 was adopted.

Next, the simulation results and estimation of the resulting amount of GNP for Examples 8-12 and Comparative Example 2 will be described. FIG. 27-31 show the simulation results for Examples 8-12, respectively, and FIG. 32 shows the simulation result for Comparative Example 2. Note that in the temperature distribution diagrams on the left side of FIG. 27-31, the two high temperature spots which are on the right end side of the supply lines 26, 26 mean the above-mentioned irradiation spots 27, 27.

In example 8, as illustrated in FIG. 27, although it was possible to prevent the SNR near the supply lines 26 from intersecting the irradiation lines 25 and flowing out closer to the central part in the width direction (X direction) of the bath 30, some of the HPR flowed in the longitudinal direction (Y direction) of the bath 30 through the ribbon-like regions. S3 between the supply lines 26 and the irradiation lines 25. However, it has been found that since the electron beam was emitted in a focused manner to the irradiation spot 27 at the end portion of each ribbon-like region S3 (on the right in the figure) from the spout part 36 side, as illustrated in the flow line diagram on the right in FIG. 27, the RNR does not pass beyond the position of the irradiation spot 27 and flows to the spout portion 36, and thus the RNR from the spout portion 36 to the mold 40 can be prevented from flowing out. than 0.1% of the outflowing amount of GNP in Comparative Example 2, and thus the GNP removal effect was rated as A.

Similarly, in Example 9 and Example 10, as illustrated in the flow line diagram on the right in FIG. 28 and 29, it was also found that the RNP did not extend beyond the position of the irradiation spot 27 at the right end of the ribbon-like regions S3 and did not flow to the drainer portion 36. As a result, in Example 9 and Example 10, the GNP effluent was also low, less than 0.1% of the GNP effluent in Comparative Example 2, and thus the GNP removal effect was rated as A.

It is believed that the reason for this is the following. In Examples 8-10, since the temperature gradient AT/L ranged from -2.70 K/mm to less than 0.00 K/mm, the molten metal flows 61 from the irradiation lines 25 to the supply lines 26, which are illustrated in FIG. . 8 could not suppress the molten metal flows 62 from the supply lines 26 to the irradiation lines 25, and the molten metal flows 66 in the Y direction were formed in the ribbon-like regions S3 between the supply lines 26 and the irradiation lines 25. In this regard, it is considered that in the case where spot irradiation is not performed, as in the above examples 4 and 5, a certain amount of RNP is entrained in the molten metal streams 61 illustrated in FIG. 8 and flows to the spout portion 36. However, in Examples 8-10, as illustrated in FIG. 12, the electron beam was irradiated to the irradiation spots 27 located at the end portion of the molten metal flow 66 of each ribbon-like region S3 from the spout part 36 side, and a high temperature region was formed in which the temperature was equal to the temperature of the irradiation spot T3, that is, higher than T1. Therefore, it is believed that at the positions of the irradiation spots 27, the titanium nitride in the RNP contained in the molten metal streams 66 was dissolved in the molten metal 5c by heat, thereby removing the RNR.

Further, in Example 11, as illustrated in FIG. 30, it was found that all of the EPR in the vicinity of the supply lines 26 was entrained towards the side walls 37A and 37B by the molten metal streams 61 from the irradiation lines 25 and were trapped by the skull 7, which prevented the EPR from flowing out of the spout portion 36 into the mold 40. As a result, Example 11, the GNP effluent was low, less than 0.1% of the GNP effluent in Comparative Example 2, and thus the GNP removal effect was rated as A.

It is believed that the reason for this is the following. In the above example 11, the temperature of the irradiation line T2 was higher than the feed temperature of the raw material T1, and the temperature gradient AT/L between the supply lines 26 and the irradiation lines 25 was +0.70 K/mm, which was substantially greater than 0.00 K/mm, which is the aforementioned threshold value. Therefore, it is considered that since strong flows 61 of molten metal from the irradiation lines 25 could be formed

- 26 039286 lines that cross the supply lines 26 and flow to the side walls 37A and 37B, the ROP is suitably controlled so that they do not flow to the spout portion 36, and thus the ROP is reliably prevented from flowing into the mold 40. Accordingly, with respect to Example 11, it is believed that even if the spot irradiation was not performed, the leakage of the GNR could be properly prevented.

Further, in Example 12, as illustrated in FIG. 31, the flow of the RNR near the supply lines 26 towards the central part in the width direction (X direction) of the bath 30 may be prevented to some extent by the regions of high temperature near the irradiation lines 25. However, some RNP flowed from the supply lines 26 through the irradiation lines 25 to the central portion in the width direction (X direction) of the tub 30, and then flowed in the Y direction to the spout portion 36 from the central portion, and some RNP flowed from the spout portion 36 sock. As a result, in Example 12, the effluent amount of GNP was in the range of 1% to less than 5% of the effluent amount of GNP in Comparative Example 2, and thus the GNP removal effect was evaluated as C.

It is believed that the reason for this is the following. In Example 12, the irradiation line temperature T2 was lower than the feed temperature T1 and the temperature gradient AT/L was -3.60 K/mm, which was less than the above threshold of -2.70 K/mm. Therefore, in Example 12, in the part of the area illustrated in FIG. 9, molten metal flows 62 from supply lines 26 to irradiation lines 25 dominated molten metal flows 61 from irradiation lines 25 to supply lines 26. Therefore, it is believed that streams 67 of molten metal were formed from the supply lines 26 that crossed the irradiation lines 25, and some of the EOR flowed to the central part of the bath 30.

In contrast, in Comparative Example 2, as illustrated in FIG. 17, no electron beam was emitted along the irradiation lines 25. Therefore, as illustrated in FIG. 32, the HPR flowed freely from the high temperature areas at the supply lines 26 to the central part of the bath 30 and was carried along by the molten metal flow 60 in the central part of the bath 30, and a large amount of the HPR flowed from the spout part 36 into the mold 40. The result of comparative example 2, in which no GNP removal effect was obtained according to the present invention was rated as D and was used as a reference for other examples.

The simulation results for Examples 8-12 and Comparative Example 2 have been described above. According to these results, it can be said that it was confirmed that when performing point electron beam irradiation in a focused manner on the irradiation spots 27 as described in Examples 8 to 12, the WLR contained in the molten metal stream 66 that flows in the Y direction in the ribbon-like regions S3 are dissolved, and it is possible to prevent the RNP from flowing to the spout portion 36, and thus the amount of RNP flowing from the spout portion 36 can be reduced to less than 5% of that in Comparative Example 1. Specifically, it can be said , which was confirmed that in Examples 8 to 10, since the value of AT/L is in the range of -2.70 K/mm to less than 0.00 K/mm, in the case that the molten metal stream 66 that flows in the Y direction toward the spout portion 36, is formed in the ribbon-like region S3 (see Fig. 9), effectively perform electron beam emission in a focused manner onto the irradiation spot 27 .

While the preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, the present invention is not limited to the examples described above. Obviously, a person skilled in the art will be able to develop various examples of changes and modifications within the technical idea described in the attached claims, and it should be understood that such examples will naturally belong to the technical scope of the present invention.

The above have mainly given examples of producing a titanium ingot 50 using a bath 30 and a mold 40, in which the metal raw material 5 that is the melting object of the metal ingot production method of the present embodiments is, for example, a titanium or titanium alloy raw material. However, the method for producing a metal ingot of the present invention is also applicable to those cases in which a metal raw material other than a titanium raw material is melted and an ingot is produced from the corresponding metal raw material. In particular, the method for producing a metal ingot of the present invention is also applicable to the case of producing an active metal ingot with a high melting point, in which the ingot can be produced using an electron gun capable of controlling an electron beam irradiation position and an electron beam furnace having a bath that accumulates molten metal from metallic raw materials such as tantalum, niobium, vanadium, molybdenum or zirconium. In other words, the present invention can be particularly effectively applied to the case of producing an ingot containing the respective mentioned elements in a total amount of 50 mass% or more.

- 27 039286

Reference designation list:

- electron-beam melting furnace (EL-furnace);

- metal raw materials;

c - molten metal;

- garnisage;

- GNP;

10A, 10B - part of the supply of raw materials;

20A, 20B - electron gun for melting raw materials;

20C, 20D - electron gun for maintaining the temperature of the molten metal;

20E - electron gun for linear irradiation;

- irradiation area for heat preservation;

- the first line of irradiation;

- supply line;

- irradiation spot;

- the second line of irradiation;

- cleaning bath;

- part of the drain sock;

37A, 37B, 37C - second side wall;

D - first side wall;

- casting shape;

- ingot;

, 62, 63, 64, 65, 66, 67, 68 - molten metal flow;

S3 - ribbon-like area.

Claims (9)

1. A method for producing a metal ingot containing a total of 50 wt.% or more of at least one metal element selected from the group consisting of titanium, tantalum, niobium, vanadium, molybdenum and zirconium, by using an electron beam furnace having an electronic a gun capable of controlling an electron beam irradiation position; and a bath that accumulates molten metal from the metal raw material, wherein among the plurality of side walls of the bath that accumulates molten metal from the metal raw material, the first side wall is a side wall provided with a spout part for flowing out molten metal from the bath into the mold, and the second side wall is at least one of the side walls other than the first side wall; the metal raw material is fed to a supply line which is located along the inner surface of the second side wall on the surface of the molten metal; the first electron beam is emitted along the first irradiation line, and the first irradiation line has a linear shape passing along the supply line, is located along the supply line and is closer to the central part of the bath relative to the supply line on the surface of the molten metal, while the first irradiation provides heating of the metal surface in a narrow region at said irradiation line; and by emitting the first electron beam along the first irradiation line, the surface temperature (T2) of the molten metal on the first irradiation line is increased above the average surface temperature (T0) of the entire surface of the molten metal in the bath, and a stream of molten metal flowing from the first irradiation line is formed in the outer layer of the molten metal. to the supply line. 2. The method for producing a metal ingot according to claim 1, wherein the temperature gradient AT/L represented by the following formula (A) is -2.70 (K/mm) or more: AT/L=(T2-T1)/L (A) where T1: surface temperature (K) of molten metal in the supply line, T2: surface temperature (K) of the molten metal in the first irradiation line, L: distance (mm) between the first irradiation line and the supply line on the surface of the molten metal. 3. The metal ingot production method according to claim 2, wherein the AT/L value is 0.00 (K/mm) or more, and the molten metal flow that flows from the first irradiation line through the supply line to the inner surface of the second side wall, formed in the outer layer of molten metal. 4. The metal ingot manufacturing method according to claim 2, wherein the AT/L value is less than 0.00 (K/mm), and the second molten metal flow towards the downspout part is formed in the ribbon-like region between the supply line and the first irradiation line, and a second electron beam is emitted as a spot onto the second stream of molten metal. - 28 039286 5. The method for producing a metal ingot according to claim 4, wherein the second electron beam is pointwise emitted onto the second molten metal stream at the position of the irradiation spot, which is located on the end part of the ribbon-like region, on the side of the drain nose part between the supply line and the first irradiation line. 6. A method for producing a metal ingot according to any one of claims 1 to 5, wherein the metal raw material is melted in the raw material supply part and the molten metal raw material drips from the raw material supply part to a position in the bath molten metal supply line. 7. A method for producing a metal ingot according to any one of claims 1 to 6, wherein both ends of the first irradiation line are arranged on the surface of the molten metal to protrude beyond the ends of the supply line in the direction of passage of the supply line. 8. A method for producing a metal ingot according to any one of claims 1 to 7, wherein the third electron beam is emitted along a second irradiation line disposed to separate a portion of the spout on the surface of the molten metal from the supply line, and both ends of the second line exposures were located in the immediate vicinity of the first side wall. 9. A method for producing a metal ingot according to any one of claims 1 to 8, wherein the metal raw material contains 50% by weight or more of elemental titanium.