JPH08176810A - Production of aluminum-high melting point metal alloy ingot and target material - Google Patents

Abstract

PURPOSE: To produce an alloy ingot of uniform composition at the time of producing the Al-high m.p. metal alloy ingot by fusion casting by avoiding the weight segregation due to the settling of a heavy intermetallic compd. crystallized in solidification and suppressing an increase in impurities resulting from the contaminant from a melting crucible. CONSTITUTION: An Al-high-m.p. metal alloy ingot consisting essentially of Al and contg. >=0.1 atomic % high-m.p. metallic element is produced by fusion casting. In this case, a melting crucible formed of the refractory consisting essentially of aluminum oxide and contg. <=10wt.% silicon as an impurity is used in the melting stage, and the molten metal injecting rate to a casting mold is controlled to 1.0kg (molten metal weight)/sec in the casting stage. Consequently, a target having a desired characteristics is obtained from the ingot.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel method for producing an Al-high melting point metal alloy ingot, which is a raw material for a functional material such as a sputtering target material, by a melt casting method, and a method thereof. The present invention relates to the target material obtained by any method.

[0002]

2. Description of the Related Art Usually, an Al alloy is added with Mg, Si, etc. as main alloying components, but these alloying components have a specific gravity almost equal to that of Al and cause segregation of components during melting or solidification. It's not that there aren't any problems, but it's practically adequate. Further, as a general melting and casting method of an Al alloy, gas heating furnace melting-DC (direct chill) continuous casting is known, which is a state established as a mass production technique.

In contrast to the above Al alloys, the Al-high melting point metal alloys which are the object of the present invention have hardly been used as general alloy materials, and their melting and casting methods have been established. Not in a state. This is because in the alloys of this type, as is clear from the state diagrams (FIGS. 2 and 3) shown later,
At the time of solidification, an intermetallic compound of Al-high melting point metal is crystallized as a primary crystal, and since the specific gravity of this intermetallic compound is remarkably larger than that of molten Al, they precipitate during solidification and cause extreme segregation, Furthermore, it is considered that this may cause cracks during processing in the subsequent process.

By the way, in recent years, the above Al-refractory metal alloys have been receiving attention as a sputtering target material (see, for example, JP-A-4-99171 and JP-A-4).
-17670, JP-A-4-26757, JP-A-4-26757
(28096, etc.), in order to cope with this, it is necessary to establish a melting method that suppresses contamination due to reaction with the refractory material and the atmosphere during melting, and a casting method that hardly causes component segregation during solidification. However, the current general melting and casting method applied to Al alloys avoids the problem of weight segregation due to the precipitation of heavy intermetallic compounds that occur during solidification of Al-refractory metal-based alloys, High alloy S
It is difficult to manufacture without being affected by contamination such as i.

As a method for producing a sputtering target material, a powder metallurgy method in which powder metal is produced by sintering is known in addition to the above-described melting and casting method. Generally, powder metallurgy is used. The Al alloy target material manufactured by the method has a problem that the oxygen concentration as an impurity tends to be high. From these reasons as well, there is an urgent need to establish a melt casting method for Al-high melting point metal alloys.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of these circumstances, and its purpose is to provide Al-
When manufacturing refractory metal alloys by melting casting method, avoid the problem of weight segregation due to sedimentation of heavy intermetallic compounds that crystallize during solidification, and suppress increase of impurity components due to contamination from melting crucible. By establishing a melt casting method for producing a clean ingot with homogeneous alloy components, the ingot obtained by this method is intended to obtain a target material having desired characteristics. .

[0007]

Means for Solving the Problems The present invention capable of achieving the above-mentioned object means that the main component is Al and the refractory metal element is 0.0
In producing an Al-refractory metal alloy ingot containing 5 atomic% or more by a melting and casting method, in the melting step, a refractory material containing aluminum oxide as a main component and containing silicon as an impurity in an amount of 10% by weight or less is used. An Al-high melting point metal-based alloy ingot having the gist of using a melting crucible and forming an ingot at a casting rate of 1.0 kg (molten metal weight) / second or less in a casting process Is a manufacturing method.

In the above-mentioned manufacturing method, the refractory metal element means IVa, Va, VIa, VIIa, VIII,
One or more elements selected from the group consisting of Ib group transition elements, Sc, Y, and lanthanoid series rare earth elements.

As a more specific structure of the above-mentioned manufacturing method, a molten metal outlet provided at a proper position on the upper edge of the melting crucible and a molten metal receiving portion provided at a proper position on the upper edge of the mold are connected via a transfer member. An example is a configuration in which the melted crucible and the mold are connected and tilted together with the melt transfer member to inject the melt into the mold from the tapping portion via the melt transfer member.

In the above manufacturing method, (a) the atmosphere during melting and casting is set to an inert gas atmosphere or a vacuum / reduced pressure atmosphere, and (b) the molten metal in the melting crucible is passed through a porous refractory material. It is also effective to perform the casting after injecting an inert gas, or to apply the circulating degassing method to the molten metal in the melting crucible (c) before casting. Further, in the above-mentioned manufacturing method, it is more effective to perform casting while maintaining the temperature of the molten metal in the melting crucible at (liquidus temperature + 50 ° C.) or higher.

On the other hand, by molding the ingots obtained by the above various methods by hot working and cold working, a good quality Al-high melting point metal-based alloy target material can be obtained.

[0012]

The refractory metal element in the Al-refractory metal alloy targeted by the present invention is, as described above, IVa of the periodic table.
(Ti, Zr, Hf), Va (V, Nb, Ta), VIa
(Cr, Mo, W), VIIa (Mn, Tc, Re), VI
II (Fe, Co, Ni, Ru, Rh, Pd, Os, I
r, Pt), a transition element such as Ib group (Cu, Ag, Au), Sc, Y and one or more elements selected from the group consisting of lanthanoid series rare earth elements. All of these elements have a higher melting point than Al (for example, Ce, which is the lowest melting point rare earth element, has 798 ° C., Ti has 1670 ° C., and V has 1902 ° C.) and has a large specific gravity.

Therefore, in the case of forming a molten bath of Al-refractory metal alloy, in order to completely dissolve the refractory metal element added as an alloy component, the temperature is considerably higher than that of a usual Al alloy. Need to rise to. In the temperature range of about 600 to 800 ° C., which is adopted for general Al alloys, when a refractory metal element such as Ta is used as an alloy component, the specific gravity may be larger than that of Al, so that the alloy component Is sunk into the bottom of the crucible,
Complete dissolution in the bath becomes difficult. Empirically,
It is understood that when the Ta concentration is high, a bath temperature of 1200 ° C. or higher is required to form a homogeneous molten alloy (the liquidus temperature is about 9 at Al-1 at% Ta).
00 ° C., about 1100 ° C. for Al-2 at% Ta).

When the molten Al alloy is held at the high temperature as described above, since the Al alloy is a very active metal, a reaction occurs with the refractory material forming the crucible. Under such circumstances, if a mullite (alumina-silica) melting crucible that is widely used is used, SiO ₂ and Al in the crucible
A reaction as shown in the following formula (1) occurs between the alloy bath and Al
There is a problem that Si is melted in the alloy bath, and alumina produced is caught in the molten metal, so that the concentrations of Si and O which are impurity components become extremely high. 4Al + 3 (SiO ₂ ) → 3Si + 2 (Al ₂ O ₃ ) ... (1)

Most Al alloys containing the above-mentioned various refractory metal elements as alloy components in an amount of 0.05 atomic% or more,
For example, FIG. 2 (a binary phase diagram of Al and Ti) and FIG.
As shown in (Al-V binary system phase diagram), A
One of the characteristics is that the intermetallic compound of l-high melting point metal is crystallized, and the specific gravity of this intermetallic compound is significantly larger than that of molten Al. In addition, since the solubility of the refractory metal element in the molten Al is small, it becomes a situation where these intermetallic compounds are scattered in the molten Al during solidification,
If the method of solidifying the molten alloy over a long period of time like the ordinary casting method is adopted, the crystallized intermetallic compound will settle down due to the difference in specific gravity, and the refractory metal will segregate under the ingot (weight segregation). ) It becomes the ingot.

By the way, the content of the refractory metal element in the functional material such as the sputtering target material is about 0.5 to 5.0 atom% in most cases, but it is partially low (0.05 atom%). However, the content of the refractory metal element in the Al-refractory metal alloy targeted by the present invention is set to 0.05 atomic% or more. The melting point (liquidus temperature) of such an alloy is often much higher than that of a normal Al alloy. For example, when Ti or Ta is contained, the liquidus temperature far exceeds 1000 ° C. There are many. Therefore, in order to form a molten alloy having a completely uniform composition, an ordinary Al melting crucible having a melting temperature of about 800 ° C. or lower cannot sufficiently cope with the problem. The melting method is preferably an induction melting method which has a high stirring effect on the molten alloy bath. Further, in melting the alloy targeted by the present invention, a bath temperature of about 800 to 1600 ° C. is often necessary for homogenizing the alloy components, although it depends on the alloy composition.

Under these circumstances, the present inventor examined from various angles. As a result, in the melting step, a melting crucible made of a refractory material containing aluminum oxide as a main component and containing silicon as an impurity in an amount of 10% by weight or less is used, and in the casting step, the rate of pouring the molten metal into the mold is increased. The present invention has been completed by finding that the above object can be achieved satisfactorily by adopting a structure that forms an ingot at 1.0 kg (molten metal weight) / second or less.

When the molten Al alloy is held at a high temperature, the content of Si or O in the molten metal increases when a crucible material containing a large amount of silica component is used. Si as an impurity component in the crucible
The lower the concentration, the better, and if it is 2 to 3% by weight, it will not cause a big problem. Further, when the component specifications are loose or the melting point of the alloy is relatively low, a Si content of up to about 10% by weight is practically usable, but 10% by weight
Above that, pickup of Si and O that cannot be ignored occurred. Therefore, in the present invention, in the dissolution step,
It is necessary to use a melting crucible mainly made of aluminum oxide and made of a refractory having a content of silicon as an impurity of 10% by weight or less.

On the other hand, when a molten alloy heated above the liquidus temperature is poured into the mold in a short time as in the usual casting method,
In many compositions of Al-refractory metal alloys, an intermetallic compound of Al and a refractory metal element that is an alloy component is crystallized as a primary crystal in a molten alloy cooled by a mold, and in many cases, this crystal Due to the flow of the molten alloy injected into the mold, the product is separated from the mold wall and released into the molten alloy.
Since the specific gravity of this intermetallic compound is remarkably higher than that of the molten Al alloy, it will settle below the ingot and cause segregation by weight.

As a means for avoiding the segregation of alloy components, the molten metal is gradually poured into the mold from the crucible and at the same time solidification is advanced, and the ingot is grown from the bottom side toward the upper part of the mold, By constantly injecting new molten metal into the upper surface of the ingot, a steep temperature gradient is formed in the height direction of the ingot, and the temperature range between the liquidus line and the solidus line is narrowed, It is considered effective to reduce the region where the intermetallic compound precipitates. Hereinafter, such a method is referred to as a "lamination solidification method" for convenience of description.

The present inventors have studied a specific method for achieving the layered solidification method. As a result, as shown in FIG. 1, the tapping portion 2 provided at a proper position on the upper edge of the melting crucible 1
And a molten metal receiving portion 8 provided at an appropriate position on the upper edge of the mold 3 are connected via a molten metal transfer member 5, and the melting crucible 1 and the mold 3 are connected together with the molten metal transfer member 5 to the upper end portion of the molten metal transfer member 5. By tilting [direction of arrow A in FIG. 1 (2)] as a support shaft,
It has been found that a configuration in which the molten metal 4 is injected from the tapping portion 2 into the mold via the transfer member 5 is effective. In the figure, 5 is a mold stand, 6 is a telescopic mechanism, 7 is an ingot, and 9 is a heating coil. 1 (1) shows before casting, FIG. 1 (2) shows during casting, and FIG. 1 (3) shows after casting. The expansion / contraction mechanism 6 is used to make the mold substantially horizontal with the floor surface after the completion of casting. In the configuration shown in FIG. 1, the angle θ formed by the welding crucible 1 and the mold 3 is initially 90 °.
As described above, the flow of molten metal is improved [Fig. 1 (1)], and then the angle is gradually changed in accordance with the tilting of the melting crucible 1 and the mold 3 so that the angle θ finally becomes 90 °. [Figure 1
(3)] has been done.

It is important that the molten metal be poured into the mold gently so that the flow of the molten metal will not be greatly disturbed and the oxide film will not be involved. In order to achieve the layered solidification and quiet pouring of the molten metal, it is necessary to control the pouring speed of the molten metal to 1.0 kg (molten metal weight) / second or less in the casting process. For example, when a molten metal of 10 kg is cast for about 5 seconds as is the case with normal heavy weight casting (injection rate: 2 kg / sec), segregation in which the alloy component is concentrated is observed in the center and bottom of the ingot.

According to the experiments conducted by the inventors of the present invention, it was found that it is necessary to cast a molten metal of 10 kg in a time of at least 10 seconds. The preferable range of this injection rate is 2 kg of molten metal of 10 kg.
It is to inject over 0 seconds (injection rate: 0.5
kg / sec or less). That is, from the pouring time of the usual weight segregation method when producing ingots of the same scale, at least 1.5 to
It is effective to pour the molten metal more than twice as long.

In the system shown in FIG. 1, the molten metal receiving portion 8 of the mold is attached so as to be connected to the molten metal discharge portion 2 of the melting furnace (melting crucible 1), so that the mold 3 is tilted together with the tilting of the melting crucible 1. By tilting, the molten metal in the melting crucible 1 can be injected into the mold 3 very naturally. Further, at this time, it is important that the molten metal outlet portion 2 and the molten metal receiving portion 8 are connected as smoothly as possible. That is, if there is a large step at this connecting portion, the flow of molten metal there will be significantly disturbed, and as a result, the oxide film formed on the surface will be caught in the mold.

In the casting method as shown in FIG. 1, since the casting can be performed while the melting crucible 1 is heated, it is possible to easily perform the molten metal injection (injection over time) at a low speed. You can The control of the casting speed can be easily achieved by adjusting the tilting speed of the melting crucible 1.

By the way, in adopting the method as shown in FIG. 1, the material used for the mold 3 is steel material, cast iron, pure copper, copper alloy, carbon / graphite material, ceramics, breathable refractory material according to the purpose. Etc. can be used, but in order to increase the cooling rate of the ingot to keep the metal bath region of the ingot at the time of solidification small, a mold made of metal or carbon / graphite material is preferable. . Further, the internal shape of the mold 3 used at this time (that is, the shape of the ingot) is not particularly limited, and may be appropriately selected according to the purpose such as a cylindrical shape, a plate shape, or a thin plate shape. Furthermore, it is effective to apply a coating agent to the inner wall of the mold in order to prevent the reaction between the molten metal and the mold. At this time, an appropriate coating agent should be selected in consideration of prevention of Si contamination from the coating agent. It is effective to select.

As a casting method for rotating a mold, the Darville method is known (for example, "melt casting / casting",
Metal Engineering Course 5, Processing I, p. 245, published by Asakura Shoten). In this method, as shown in FIG. 4, after the molten metal 4 is once injected into the pool 10 kept warm from the melting furnace [FIG.
(1)], the mold material 11 is slowly rotated to melt 4
Gently pour the water from the basin 10 into the mold 12 [Fig.
(2) → FIG. 4 (3)], which is a method of manufacturing a sound ingot 13 in the mold part 12 [FIG. 4 (4)], and is particularly applied to ingot production of various copper alloys. The above-described method shown in FIG. 1 uses a mechanism common to this method in that the crucible is rotated (tilted), but the mold is connected to the melting furnace to play the role of the basin 10 in the derbil method. The characteristic is that the crucible itself is fulfilled. Therefore, there is an advantage that the temperature of the mold and the crucible during casting can be easily controlled.

Regarding the casting temperature, as long as the molten metal in the crucible is in a fluid state, there is no problem in casting itself, and if necessary, the temperature may be set slightly lower than the liquidus temperature to crystallize in the molten metal. Casting is possible even when the intermetallic compound is suspended. However, from the viewpoint of improving the surface properties of the ingot, it is rather preferable to cast at a relatively high temperature. From this point of view, the casting temperature is preferably (liquidus temperature + 50 ° C.) or higher.

In carrying out the present invention, a melting crucible having a larger capacity than that of the mold is used, and the structure of the melting crucible is such that the mold can be easily connected to the melting crucible so that a large amount of molten metal is produced at one time. It is also possible to manufacture a plurality of ingots by melting once by repeating the steps of mounting → casting → removing the mold / ingot a plurality of times. It is also possible to manufacture a plurality of ingots at the same time by dispensing the tap hole in one casting operation.

The atmosphere during melting / casting may be an air atmosphere, but alloys such as the alloy targeted by the present invention, which have a particularly high melting point and require a high temperature for melting, and rare earth elements and the like. When an active element is contained as an alloy component, an inert atmosphere or a vacuum / reduced pressure atmosphere is preferable. By setting such an atmosphere, it is possible to avoid problems such as loss due to oxidation of alloy components and abnormal heat generation due to a rapid reaction between Al and atmospheric oxygen.

On the other hand, when the hydrogen content in the molten metal becomes high,
There are many gas hole defects in the ingot. To prevent this,
Dehydrogenation of molten metal is effective. Particularly, in the case of the alloy targeted by the present invention, since the melting temperature is high, hydrogen absorption is likely to occur. Also, since the temperature of the molten metal is high, it is often difficult to perform degassing treatment with a flux that is used for ordinary Al melting. The present inventors have also examined a specific method for achieving such dehydrogenation. For example, by blowing an inert gas such as argon through an alumina-based porous refractory material, hydrogen pickup of the molten metal is performed. It turns out that it becomes possible to suppress. In addition, for the molten metal in the melting crucible, a conventional degassing method, that is, by immersing the vacuum container in the molten metal in the crucible and continuously sucking and circulating the molten metal in the vacuum container, Performing a method of degassing is also effective from the viewpoint of dehydrogenation.

The ingot obtained by the above method is
Since the primary crystal intermetallic compounds are dispersed as fine crystallized substances, Al-Fe system and Al-Mn, which were difficult to hot work (roll or forge) in the ingot cast by the conventional method, were difficult. Relatively high Fe and Mn concentrations such as those of the system (about 2 atom%)
Even alloys can be hot worked. In addition, the material that has been subjected to hot working can be slightly cold worked. The material processed in this way has fewer defects (smiling hole-shaped defects) than the ingot at the time of manufacture, and by using this, a very sound target material for sputtering can be realized. Of.

[0033]

EXAMPLES Examples will be shown below. However, the present invention is not limited by the following examples, and it is needless to say that appropriate modifications can be made within a range that can be fit to the purpose of the preceding and following description. Yes, all of them are included in the technical scope of the present invention.

Example 1 An ingot of Al-2 atomic% Ta-2 atomic% Si material was produced according to the method of the present invention. The melting / casting conditions at this time are as follows. (Melting conditions) Melting method: Induction melting method Crucible: Al ₂ O ₃ system (impurity amount; SiO ₂ <3% by weight, inner diameter; 230 mm) Melting weight: 10 kg Molten metal temperature: 1350 ° C. (maximum temperature) Atmosphere: Ar gas atmosphere Dehydrogenation: Ar gas blown through a porous plug (2 liters / min) (casting conditions) Mold: copper [ingot size; 250 ^W x 450 ^h x 2]
5 ^t (mm)] Casting temperature: 1350 ° C. (liquidus temperature: 1250 ° C.) Casting time: 40 seconds (casting speed: 0.1 kg / sec) Number of ingots: 2 pieces (2 pieces in one casting Create ingot)

After the upper part of the obtained ingot was cut off, the surface of the ingot was rolled without care, and 240 ^W × 800 ^l × 1
It was a rolled piece of 0 ^t (mm). When the segregation of Ta, which is an alloy component in this rolled piece, was investigated, it was 2.0 ± 0.
Within the range of 2 atomic%, and the segregation of Si component is 2.0.
Within the range of ± 0.1 (atomic%), the impurity components are Fe <0.01 wt%, Si <0.001 wt%, Cu <0.002 wt%, C <0.005 wt. %,
O <0.01% by weight was satisfied. This result indicates that the method of the present invention could easily produce a highly clean ingot with less segregation of components.

Example 2 A sputtering target of Al-2 atomic% Ti material was used.
It was prepared according to the method of the present invention. The melting / casting conditions at this time are as follows. (Dissolution conditions) Dissolution method: Induction dissolution method (maximum dissolution amount; 30 kg) Crucible: Al ₂ O ₃ system (impurity amount; SiO ₂ <3 wt%, inner diameter; 230 mm) Dissolution weight: 8.5 kg Melt temperature: 1300 ° C (Maximum temperature) Atmosphere: Ar gas atmosphere (Casting conditions) Mold: Copper [Ingot size; 250 ^W x 450 ^h x 3
0 ^t (mm)] Casting temperature: 1100 ° C. (liquidus temperature: 900 ° C.) Casting speed: 0.2 kg / sec (casting time: 40 sec)

A target material was prepared from the obtained ingot. The component segregation of Ti, which is an alloy component of this target material, is within the range of 2.5 ± 0.3 (atomic%), and the impurity components are Fe <0.01 wt% and Si <0.
001% by weight, Cu <0.002% by weight, C <0.00
5% by weight and O <0.01% by weight were satisfied. This result indicates that the target material with less impurities and segregation could be easily manufactured by the method of the present invention.

[0038]

The present invention is constructed as described above, and a melt casting method for producing a clean ingot having a uniform alloy composition can be established, and the ingot obtained by this method has desired characteristics. A target material is obtained.

[Brief description of drawings]

FIG. 1 is a schematic diagram for explaining a method of the present invention.

FIG. 2 is a phase diagram of a binary system of Al and Ti.

FIG. 3 is a binary system phase diagram of Al and V.

FIG. 4 is a schematic diagram for explaining the derbil method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Melting crucible 2 Molten metal part 3 Mold 4 Molten metal 5 Transfer member 6 Expansion / contraction mechanism 7 Ingot 8 Molten metal receiver

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Reference number in the agency FI Technical indication location F27B 14/02 F27D 1/00 N (72) Inventor Hoyuki Koga Wakihama-cho, Chuo-ku, Kobe-shi, Hyogo 1-3-18 Kobe Steel, Ltd. Kobe Head Office (72) Inventor Kenichi Takeda 1-3-18 Wakihama-cho, Chuo-ku, Kobe City, Hyogo Prefecture Kobe Steel Co., Ltd. Kobe Head Office

Claims (8)

[Claims] 1. In producing an Al-refractory metal alloy ingot containing Al as a main component and a refractory metal element in an amount of 0.05 atomic% or more by a melt casting method, aluminum oxide is mainly contained in a melting step. Using a melting crucible made of a refractory having a content of silicon as impurities of 10% by weight or less, and casting at a casting rate of 1.0 kg (molten metal weight) / sec or less in the casting process. A method for producing an Al-refractory metal alloy ingot, which comprises forming an ingot. 2. The refractory metal element is IV of the periodic table.
a, Va, VIa, VIIa, VIII, Ib group transition elements, S
The method according to claim 1, wherein the production method is one or more elements selected from the group consisting of c, Y and lanthanoid series rare earth elements. 3. A molten metal outlet provided at an appropriate position on the upper edge of the melting crucible and a molten metal receiving portion provided at an appropriate position on the upper edge of the mold are connected via a transfer member to form the melting crucible and the mold. The molten metal is injected into the mold from the tapping portion through the molten metal transfer member by tilting together with the molten metal transfer member.
The manufacturing method described in. 4. The manufacturing method according to claim 1, wherein the atmosphere during the melt casting is an inert gas atmosphere or a vacuum / reduced pressure atmosphere. 5. The production method according to claim 1, wherein the molten metal in the melting crucible is blown with an inert gas through a porous filter and then cast. 6. The manufacturing method according to claim 1, wherein the molten metal in the melting crucible is cast after applying a circulating degassing method. 7. The manufacturing method according to claim 1, wherein casting is performed while maintaining the temperature of the molten metal in the melting crucible at (liquidus temperature + 50 ° C.) or higher. 8. A target material, which is formed by hot working and cold working the ingot obtained by the method according to claim 1.