WO2009072216A1

WO2009072216A1 - Immersion nozzle and method of continuous casting

Info

Publication number: WO2009072216A1
Application number: PCT/JP2007/073899
Authority: WO
Inventors: Satoru Ito; Shinichi Fukunaga; Masaharu Sato; Taijiro Matsui; Mineo Niitsuma; Tomohide Takeuchi
Original assignee: Nippon Steel Corporation
Priority date: 2007-12-05
Filing date: 2007-12-05
Publication date: 2009-06-11
Also published as: KR20100080938A; BRPI0722253A2; CN101883647B; CN101883647A

Abstract

An immersion nozzle that attains an enhancement of durability; and a method of continuous casting including the step of preheating the immersion nozzle. The immersion nozzle is one for use in a method of continuous casting for molten metal, characterized in that the immersion nozzle at at least its area of outer circumferential part brought into contact with slag consists of a refractory containing 70 mass% or more ZrO2 and 30 mass% or less FC (free carbon), or a refractory composed of 70 mass% or more ZrO2, 20 mass% or less FC (free carbon) and 10 mass% or less the balance containing a ZrO2 stabilizer, and that the immersion nozzle is preheated by high-frequency induction heating.

Description

Description Immersion nozzle and continuous fabrication method Technical Field

The present invention relates to an immersion nozzle used in a continuous production method for molten metal, and a continuous production method including a preheating step for preheating the immersion nozzle. Background art

Conventionally, there has been known a continuous forging method in which molten metal is continuously cooled and solidified to form pieces of a predetermined shape. In this continuous forging method, a mold (water-cooled) is formed from a tundish through an immersion nozzle. A forging process is performed in which molten metal is injected into the mold.

The immersion nozzle is attached to the bottom of the tundish and is configured to discharge the molten metal in the evening dish into the mold from the discharge port at the lower end of the nozzle. This immersion nozzle is used in a state where the lower end side is immersed in the molten metal in the mold, thereby preventing the injected molten metal from scattering and preventing the injected molten metal from contacting the atmosphere. Oxidation is suppressed. Moreover, since the immersion nozzle can be injected in a rectified state, impurities such as slag and non-metallic inclusions floating in the molten metal are prevented from being caught in the molten metal. As a result, the quality of the chips can be improved and the stability of the operation can be secured.

Such an immersion nozzle is generally formed of Al ₂ O 3 —SiO ₂ to C (carbon) refractory or Al ₂ O 3 C refractory. These A 1 ₂ O 3 - C refractories containing steel immersion nozzle, A 1 ₂ O 3 is superior in corrosion resistance to the refractory and the molten metal, C inclusions (slag It is currently most widely used in continuous casting of molten metal because it is difficult to wet with the component), has low expansion, and has good thermal conductivity.

Here, during the continuous casting of molten metal, slag, which has a low basicity and is highly erodible, called mold powder floats on the surface of the molten steel in the mold. This mold powder generally contains C a 0, S i 0 ₂ , C a F ₂ , N a ₂ 0, C, and its basicity is about 1, so Al ₂ O 3 and S i Refractories containing O ₂ will be severely damaged. For this reason, the conventional refractory containing Al ₂ 03 1 C has a large melting loss in the outer periphery of the immersion nozzle that contacts the mold powder (hereinafter referred to as the powder line part) and cannot be used for a long time. There was a problem.

In order to deal with this problem, conventionally, a powder line part of a submerged nozzle using a ZrO ₂ —C quality refractory is known, for example, in Japanese Laid-Open Patent Publication No. 1 1-3 0 2 0 7 3 Yes.

Z r O ₂ — C-quality refractory has a combination of excellent corrosion resistance against mold powder of Z r 0 ₂ and the thermal shock resistance of C. This Z r 0 ₂ — Use of C-quality refractories in the powder line can improve the durability of the immersion nozzle.

Such Z r 〇 ₂ - In C refractories in, in order to improve the corrosion resistance, by reducing the amount of C, it is effective to increase the amount of Z R_〇 ₂ . However, increasing the Z r 〇 ₂ causes a decrease in thermal shock resistance, cracking and breakage problems during use occurs. On the other hand, to improve the thermal shock resistance, it is effective to increase the amount of C and reduce the amount of ZrO ₂ , but the corrosion resistance is reduced.

In this way, Z r 0 ₂ It is necessary to optimize the amount of C and C. Above JP 1 1 one 3 0 2 0 7 No. 3 described in Japanese configuration, Z r O ₂ in the amount 7 0-9 5 mass%, and 5-3 0% by weight the amount of C This optimization is aimed at.

By the way, in the forging process, when the temperature of the immersion nozzle is low, the immersion nozzle is cracked or clogged when starting the injection of the molten metal, or the slag does not float sufficiently on the molten metal. Problems such as quality deterioration may occur. Therefore, by preheating the immersion nozzle, it is conceivable to reduce the temperature difference that occurs in the immersion nozzle when the injection of molten metal is started, thereby preventing the occurrence of the above problems.

As such a preheating method, for example, a combustion gas is blown by a burner 100 as shown in FIG.

In addition, for example, Japanese Laid-Open Patent Publication No. 10-1118876 proposes a method in which the outer periphery of the immersion nozzle is surrounded by an electric heater and heated by heat transfer / radiation.

However, after preheating a soaking nozzle using a ZrO ₂ —C quality refractory material in the powder line part as described in the above-mentioned Japanese Patent Application Laid-Open No. 11 1300 073, the forging process is performed. When implemented, Zr 0 ₂ — C quality refractory is a high thermal expansion material, so there are the following problems (A) and (B).

(A) When preheating is performed using a burner 1 100 as shown in Fig. 5, a burner 1 0 0 is inserted from the upper end of the nozzle, and combustion gas is blown into the inside from the discharge hole on the lower end side. Exhaust. For this reason, it is difficult to uniformly heat the entire nozzle, and stress cracking or the like occurs due to the difference in thermal expansion of Z r 0 ₂ due to this temperature difference.

Also, in the case of preheating with a burner, the time required for preheating is long. In addition, due to the oxidizing atmosphere generated from the combustion gas, the C component in the refractory of Zr ○ 2 _C quality disappears as C ○ gas or CO ₂ gas due to oxidation. For this reason, a large-diameter pore is formed in the Zr 0 ₂ -C refractory, making it easier for the mold powder to erode in the pore and promoting the melting damage due to the mold powder. There is.

(B) In the case of preheating using the d-heater described in Japanese Patent Application Laid-Open No. 10-1 1 8 7 46, the loss of the c component can be prevented, but the nozzle is heated by heat transfer / radiation. Partly reaches 1400 ° C, but it is still difficult to heat the whole evenly o

The present invention provides an immersion nozzle capable of improving durability, and

To provide a continuous forging method including a preheating process for preheating the sludge

Disclosure of the invention

The present invention has been devised based on the knowledge that high-frequency induction heating is preferably used to uniformly heat the immersion nozzle. The gist of the present invention is as follows. It is.

(1) An immersion nozzle according to the present invention is an immersion nozzle used in a method for continuously producing molten metal, and at least a portion in contact with the slag on the outer periphery is Zr 0 ₂ : 70% by mass or more And refractory material including FC (free carbon) 30 mass% or less, and preheated by high frequency induction heating

More preferably, Z r 0 ₂ is 80 mass% or more, and the FC is 20 mass% or less.

Here, if the amount of Z r O ₂ is 7 less than 0 wt%, and, when the amount of FC is 3 greater than 0% by mass, no sufficient corrosion resistance can not be obtained for mode one Rudopauda scratch. Such an immersion nozzle is formed, for example, by kneading various inorganic fine powders with a binder such as phenol resin into a predetermined shape by the CIP method, etc., and then reducing and firing this. Is done. ZrO ₂ having a crystal grain size of about several m to 2 mm is used. In addition, FC usually includes, for example, carbon remaining after the binder is baked in addition to additive graphite such as scale graphite, electrode scrap, anthracite, and earth graphite.

According to the present invention, since FC exists in the refractory, the FC can be selectively heated by high-frequency induction heating, as shown in FIG. 5 and the above-mentioned Japanese Patent Application Laid-Open No. 10 1 1 8 7 46. Compared to the case where the immersion nozzle is preheated by such a conventional heating method, the immersion nozzle can be preheated uniformly.

For this reason, when the injection of molten metal is started in the forging process, the thermal shock received by the immersion nozzle by the molten metal can be mitigated, and problems such as cracking can be prevented. In particular, since the nozzle can be preheated uniformly, even if the blending amount of FC with excellent thermal shock resistance is reduced to 20% by mass or less, problems such as cracks do not occur. This makes Z r O

_Since the blending ratio of ₂ can be further increased, the rate of erosion caused by slag can be reduced.

Also, with high frequency induction heating, preheating can be completed in a short time without using combustion gas as in the past, so there is little disappearance of FC in the refractory and the rate of slag erosion can be reduced. Accordingly, the durability of the immersion nozzle can be improved.

(2) The immersion nozzle according to the present invention can be realized as the following configuration in addition to the immersion nozzle described in (1) above. That is, the immersion nozzle according to the present invention is an immersion nozzle that is used in a method for continuously forming molten metal, and at least the portion that contacts the slag in the outer peripheral portion is Zr 0 ₂ : 70 mass% or more. , FC (free carbon): 20% by mass It is formed of a refractory material including the following, and the remaining 10% by mass or less including the stabilizing material of Zr 0 ₂ and is preheated by high frequency induction heating.

According to the invention of (2), the same effect as the invention of the above (1) can be obtained. In addition, the Z r 〇 ₂ can be fixed to the refractory in tissue in a stable state by the addition of the stabilizing material, it is possible to prevent the Z R_〇 ₂ grains from falling off in the slag. Thereby, it can suppress that the part which contacts slag melts | dissolves by slag. Therefore, the durability of the immersion nozzle can be further improved.

(3) immersion nozzle according to the present invention, in the immersion nozzle according to the above (2), stabilizing Kazai includes C A_〇, M G_〇 and Y ₂ O least for either one also of 3 It is preferable.

Here, if the amount of Z R_〇 ₂ 7 lower than 0 wt%, if the sum of the amount of FC Contact and balance 3 higher than 0 mass%, sufficient corrosion resistance to mold powder one I can't get it.

(4) The continuous forging method according to the present invention includes a preheating step of preheating the immersion nozzle according to any one of the above (1) to (3) by high-frequency induction heating, and the immersion immersed in the preheating step. And a forging step of injecting molten metal from the tundish into the mold through a nozzle.

According to the invention of (4), the effects described in any of (1) to (3) above can be achieved. Therefore, the durability of the immersion nozzle can be improved. Brief Description of Drawings

FIG. 1 shows a schematic configuration of a continuous forging machine according to an embodiment of the present invention. 2 is a side sectional view showing the immersion nozzle according to the embodiment of FIG. 1. FIG. 3 is a combination of ZrO ₂ and FC of refractory used in the powder line portion of the immersion nozzle in the embodiment of FIG. It is the figure which showed quantity. FIG. 4 is a side sectional view showing the preheating device with the immersion nozzle in the embodiment of FIG.

FIG. 5 is a side sectional view showing a state in which the immersion nozzle is preheated by a heating method using a conventional burner. BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[Schematic configuration of continuous forging machine]

Figure 1 shows the schematic configuration of the continuous forging machine in this embodiment. In FIG. 1, 1 is a continuous forging machine, and this continuous forging machine 1 continuously cools and solidifies molten steel to form a steel ingot of a predetermined shape. Such a continuous forging machine 1 includes a ladle 2, a long nozzle 3, a tundish 4, a plurality of immersion nozzles 5, and a plurality of molds 6. In FIG. 1, only one immersion nozzle 5 and one mold 6 are shown.

The ladle 2 is a heat-resistant container into which molten steel is first introduced in continuous forging, and has an inlet 21 at the bottom.

The long nozzle 3 is attached to the inlet 2 1 of the ladle 2 and is configured to discharge the molten steel stored in the ladle 2 into the tundish 4 from the nozzle lower end opening 3 1. .

The tundish 4 is a heat-resistant container that is disposed below the long nozzle 3 and stores molten steel injected from the ladle 2 through the long nozzle 3. This tundish 4 is compatible with each mold 6 on the bottom. A plurality of inlets 41 are formed, and a flow rate adjuster (not shown) for adjusting the flow rate of the molten steel flowing out from the inlet 41 is provided inside the inlet 41. By such a tundish 4, the molten steel from the ladle 2 is rectified, and the molten steel is distributed to each mold 6 by a predetermined amount.

The immersion nozzle 5 is specifically described later, and is attached to the lower part of the injection port 41 in the tundish 4, and the molten steel in the tundish 4 is injected into the mold 6 through this nozzle.

The mold 6 is a water-cooled vertical mold provided below the immersion nozzle 5. The mold 6 has a predetermined cross-sectional shape, and molten steel from the tundish 4 is continuously injected into the mold 6 through the immersion nozzle 5. With such a mold 6, the molten steel in the mold 6 is cooled, and a solidified shell is formed and grown from the inner peripheral surface side in the mold 6 to form solidified steel.

Further, below the mold 6, there are provided a roller apron and a drawing roll for continuously drawing the steel formed in the mold 6 downward from the lower opening in the mold 6. (Not shown) Further, on the downstream side of the drawing roll, the steel that has been continuously drawn from the inside of the mold 6 by being drawn by the drawing roll is cut into a predetermined length dimension (not shown) ) Is provided. By cutting the steel with this cutting machine, a steel ingot having a predetermined shape such as a plate shape or a rod shape is formed.

[Structure of immersion nozzle]

Next, the configuration of the immersion nozzle 5 will be described with reference to FIGS. FIG. 2 is a side sectional view showing the immersion nozzle according to the present embodiment. Fig. 3 shows the blending amounts of refractory Zr 0 ₂ and FC used in the powder line part of the immersion nozzle. In FIG. 2, the immersion nozzle 5 includes a nozzle body 5 1 and a holder 5 2 that is attached to the lower part of the inlet 4 1 and holds the upper end of the nozzle body 5 1. The immersion nozzle 5 is used after being preheated by high frequency induction heating in a preheating process described later.

The nozzle body 51 is formed in a substantially cylindrical shape, and is provided with a bottom surface 51 11 that closes its lower end. In the vicinity of the bottom surface portion 5 11 of the side surface portion of the nozzle body 51, a pair of discharge ports 5 1 2 are provided so as to face each other. With such a nozzle body 51, the molten steel flowing from the upper end opening of the nozzle body 51 is discharged into the mold 6 through the pair of discharge ports 5 12.

The nozzle body 5 1 is used with its lower end side immersed in molten steel in the mold 6. Here, the two-dot chain line in Fig. 2 shows the slag line S. When the nozzle body 51 is immersed in the molten steel, it contacts the mold powder below the slag line S on the outer peripheral surface of the nozzle body 51 (powder thickness is about 10 mm). Furthermore, the lower side of the mold powder is immersed in the molten steel. In the case of preheating failure, cracks may occur on the upper side of the powder line S. Such a nozzle body 51 has a powder line part 5 1 3 above the discharge port 5 1 2 on the outer peripheral part. The other parts have a two-layer structure made of different refractories.

The refractory that forms the powder line part 5 1 3, as shown in area A and area B in Fig. 3, is Zr 0 ₂ : 70 mass% or more, and FC (free carbon): 30 mass % Or less. Also, the refractory forming the powder line part 5 1 3 is composed of Zr 0 ₂ : 70 mass% or more, graphite containing FC: 20 mass% or less, as shown by region A in FIG. r〇 10% by mass of balance including stabilizing material that stabilizes ₂ The following may be comprised.

Z R_〇 ₂ upper limit of the content is not particularly defined, 1 0 0 is less than mass% may also FC (free carbon> lower limit of the content is also not particularly defined, 0 mass Further, the lower limit of the balance including the stabilizing material is not particularly specified, and may be more than 0 mass%.

Parts other than the powder line part 5 1 3 in the nozzle body 5 1 are formed of a refractory material such as A 1 ₂ 0 3 S i O 2 1 C or A 1 ₂ O 3 1 C, for example. Note that the refractory material used in parts other than the powder line section 5 1 3 is not limited to this, and is a material that can provide excellent fire resistance and low melt wettability to the molten steel flowing through the nozzle body 5 1. Any of them can be adopted.

[Configuration of preheating device]

Next, a preheating device for preheating the immersion nozzle 5 having the above-described configuration will be described with reference to FIG. FIG. 4 is a side sectional view showing the preheating device with the immersion nozzle attached.

In FIG. 4, 7 is a preheating device, and this preheating device 7 preheats the immersion nozzle 5 by high frequency induction heating. Such a preheating device 7 includes a heat-resistant container 7 1, an outer coil 7 2, an inner coil 7 3, and an induced current applying device (not shown).

The outer coil 72 is an induction heating coil confiscated inside the heat-resistant container 71, and is configured to be able to accommodate from the lower end of the nozzle body 51 to the upper part of the middle part on the inner peripheral side of the coil. .

The inner coil 7 3 is an induction heating coil similar to the outer coil 7 2, and is configured to be inserted inside from the upper opening of the nozzle body 5 1. The induction current application device includes the outer coil 7 2 and the inner coil 7 2. 7 3 each This is a device that applies a high-frequency induced current.

[Continuous fabrication method]

The continuous forging method according to this embodiment will be described using an example in which the continuous forging machine 1 and the preheating device 7 configured as described above are used.

The continuous forging method of the present embodiment includes a preheating step, a forging step, a drawing step, and a steel ingot forming step.

In the preheating process, a preheating device 7 shown in FIG. 4 is used to preheat the immersion nozzle 5 by high frequency induction. Specifically, first, the preheating device 7 is set with respect to the immersion nozzle 5 removed from the tundish 4. In this set state, the nozzle body 51 is accommodated in the outer coil 72, and the inner coil 73 is inserted into the inside from the upper opening of the nozzle body 51. Then, an induced current is applied to the outer coil 72 and the inner coil 73 by an induced current application device. As a result, a high-density eddy current is generated in the vicinity of FC included in the nozzle body 51, generating large Joule heat, and the entire nozzle body 51 is heated uniformly.

By this high frequency induction heating, the temperature of the nozzle body 5 1 reaches 100 ° C. or more in a heating time of about 0.5 to 2 hours, for example. For example, when the nozzle body 5 1 is heated to 1 100 ° C or higher, and when heated with a burner 1 0 0 (see Fig. 5) as in the past, a maximum of 5 0 0 ° (~ 6 Although a temperature difference of 0 ° C occurs, high-frequency induction heating can only produce a maximum temperature difference of about 300 ° C between each part.

In addition, according to high frequency induction heating, preheating is completed in a short time without using combustion gas as in the conventional case, so that C in the powder line portion 5 1 3 is not easily lost, and pores in the refractory are not easily lost. Expansion is prevented. In the forging process, molten steel is forged using the continuous forging machine 1 shown in Fig. 1. First, dip the immersion nozzle 5 preheated in the preheating process. After installing in the inlet 4 1 of the 4th, introduce molten steel into the ladle 2. This molten steel flows from the ladle 2 into the tundish 4 through the long nozzle 3 and is rectified in the tundish 4. After that, the rectified molten steel is injected into the mold 6 through the immersion nozzle 5 while adjusting the outflow amount with a flow rate adjuster (illustrated), and a constant molten metal level is maintained in the mold 6. .

In this forging process, when the injection of molten steel is started, the nozzle body 5 1 is uniformly preheated in the preheating process, so the thermal shock received by the immersion nozzle 5 from the molten steel is alleviated, and there is no problem such as cracking. Occurrence can be prevented. And since the powder line part 5 1 3 is formed of a refractory material containing Z r 0 ₂ and FC in the above range, it has high corrosion resistance against the mold powder, and according to the mold powder. Melting damage can be suppressed. Also, since the pores in the powder line part 5 1 3 are not enlarged due to preheating in the preheating process, the mold powder erodes inside the pores and prevents crystal grains in the refractory from falling into the mold powder. it can. Therefore, the durability of the immersion nozzle 5 can be improved.

In the drawing process, the steel that has been cooled and solidified in the mold 6 is continuously drawn downward by means of a roller apron (not shown) and a drawing port.

In the steel ingot forming step, the steel drawn by the drawing roll is cut into a predetermined length by a cutting machine to continuously form pieces having a predetermined shape.

In the preheating process, the long nozzle 3 and the tundish 4 are preheated in addition to the immersion nozzle 5. In the preheating process, preheating was performed without the immersion nozzle 5 being attached to the tundish 4, but preheating was performed with the immersion nozzle 5 being attached to the tundish 4. May be.

Example

An example for confirming the effect of the above-described embodiment will be described.

[Experimental sample]

• Immersion nozzles: A plurality of immersion nozzles similar to the immersion nozzle 5 of the above embodiment shown in FIG. 2 were prepared.

• Nozzle dimensions: The nozzle body 51 has a maximum outer diameter of φ140 mm, an inner diameter of φ80 mm, and a length of 700 mm.

, Refractory composition: The composition of the refractory forming each powder line part 5 1 3 includes the composition shown in each plot in Fig. 3, including those shown in Table 1 below.

• Forming method: After kneading refractory aggregate and scaly graphite together with a binder, pour the kneaded material (yes earth) into a nozzle-shaped rubber mold. If different materials are to be poured, insert a rubber mold so that it does not get mixed. Then, it is hardened by applying a high pressure (50 to 10 OMPa) with a wet CIP molding method. After taking out the molded product from the frame, firing is performed at a high temperature of 100 0 ^ or more in a reducing atmosphere. After cooling, it is processed to the required dimensions, applied with antioxidants, and then used in actual equipment.

table 1

[Preheating by high frequency induction heating]

• Preheating target: Examples 1 to 6

'Preheater: Same as preheater 7 shown in Fig.4. Use an outer coil 7 2 with a diameter of 200 mm and a length of 500 mm, and an inner coil 7 3 with a diameter of 70 mm and a length of 300 mm. did.

'Inductive current: The outer coil 7 2 was applied with an induction current having a frequency of 30 kHz, a current of 20 A, and a power of 15 kW. An inductive current having a frequency of 37 kHz, a current of 200 A, and a power of 12 kW was applied to the inner coil 73.

• Preheating time: 40 minutes

[Preheating by burner heating]

• Preheating target: Comparative examples 1 and 2

'Preheater: Preheated using the burner 1 0 0 shown in Fig. 5. In FIG. 5, with the immersion nozzle 5 housed in the heat-resistant container 10 1, a burner 1 0 0 is inserted into the inside from the upper end opening of the immersion nozzle 5 and sprayed with combustion gas.

• Combustion gas: C O G (Coke-oven Gas)

• Air ratio: 1.2

• Preheating time: 90 minutes

[Forging experiment]

• Experiment subjects: Examples 1 to 6 and Comparative Examples 1 and 2

• Continuous forging machine: The same one as the continuous forging machine 1 of the above embodiment shown in Fig. 1 was used (8 charges).

• Forging method: Same as the forging process in the above embodiment. Specifically, after each submerged nozzle 5 is preheated alone, it is attached to each tundish 4, and forging starts 5 minutes after the end of preheating. It was.

• Steel type: Low carbon steel (carbon concentration 0.06 mass%)

• Mold powder basicity: 1.0

• Operating hours: Total 3 60 minutes

〔Experimental result〕

Table 1 also shows the results of the forging experiment (melting rate index, trouble occurrence index) for the immersion nozzles 5 of Examples 1 to 6 and Comparative Examples 1 and 2.

• Melting rate index: Example 1 when the rate of erosion of Comparative Example 1 (the amount of erosion of the powder line part 5 1 3 due to forging was divided by the operating time) was 1 0 0 The melting rate for ˜6 and Comparative Example 2 is indexed.

• Trouble occurrence index: Trouble occurrence for Example 1 when the trouble occurrence rate for Comparative Example 1 (ratio between the number of times of forging and the number of occurrences of defects such as breakage or cracking) is 100 The rate is an index.

[Knowledge 1: About the effect of high frequency induction heating]

As shown in Table 1, the composition of Example 1 and Comparative Example 1 are the same in the powder line part 5 1 3 (Zr 0 ₂ : FC: C a O = 75: 20: 5). Example 2 and Comparative Example 2 have the same composition of the powder line part 5 1 3 (Zr 0 ₂ : FC: C a 0 = 8 2: 1 3: 5). Examples 1 and 2 differ in that the preheating method is high frequency induction heating (IH), and comparative examples 1 and 2 are heating by a burner.

In the results shown in Table 1, when the erosion rate index is compared, Example 1 is 10% lower than Comparative Example 1, and Example 2 is about 9.5 compared to Comparative Example. % Is low. This is different from the case of preheating with a high frequency induction heating, unlike the case of preheating with a burner. This is presumably because the preheating is completed in a short time without using the soot, and the loss of C in the powder line part 5 1 3 is prevented.

In addition, in the results of Table 1, when the trouble occurrence index is compared, Example 1 is 85% lower than Comparative Example 1. This is presumably because each part of the nozzle body 51 was preheated more uniformly when preheated by high frequency induction heating than when preheated by a burner. As a result, it was found that it was difficult for the mold powder to melt and the frequency of occurrence of defects such as cracks at the start of fabrication could be significantly reduced. In other words, it was found that the durability of the immersion nozzle 5 can be improved.

[Knowledge 2: Mixing ratio of ZrO2 and FC]

As shown in Table 1, when Examples 1 to << 3, 6 are compared with each other, the powder line part 5 1 3 contains about 5% of CaO, and Z r

The blending amount of O ₂ is 75% by mass (Example 1), 82% by mass (Example 2).

), 88% by mass (Example 3) and 70% by mass (Example 6), with Example 3 being the highest <and Example 6 being the lowest. For this, the blending amount of F C is 20% by mass (Example 1), 13% by mass (Example 2),

8 mass% (Example 3) and 26 mass% (Example 6). Example 3 is the lowest and Example 6 is the highest.

And in the results of Table 1, when comparing the erosion rate index, Example 1 is about 5% lower than Example 6, Example 2 is about 9% lower than Example 6, and Example 3 is The value is about 13% lower than Example 6. This is thought to be due to an increase in the corrosion resistance of the powder line portion 5 1 3 to the mold powder due to an increase in the proportion of Zr 0 ₂ with excellent corrosion resistance.

In these Examples 1 to 3 and 6, at the start of molten steel injection Almost no cracks occurred, and all of them exhibited good thermal shock resistance. This is thought to be due to the fact that the blending amount of FC having excellent thermal shock resistance was sufficient and the nozzle body 51 was heated uniformly by high frequency induction heating.

Although not shown in Table 1, and if the amount of Z r 〇 ₂ 7 lower than 0 wt%, if the amount of FC is 3 greater than 0% by mass, compounding of Z r O 2 The amount was not sufficient and sufficient corrosion resistance to the mold powder could not be obtained.

From the above, by the amount of Z R_〇 ₂ and 7 0 wt% or more, to obtain a sufficient corrosion resistance to model one field powder, further, to the 8 0 wt% or more amount of Z r 〇 ₂ It has been found that the corrosion resistance can be further improved.

Further, it was found that the high thermal shock resistance of the powder line portion 5 13 can be obtained by setting the blending amount of FC to 30% by mass or less. Furthermore, it was found that the good thermal shock resistance of the powder line portion 5 13 can be maintained even when the blending amount of FC is 20% by mass or less.

[Knowledge 3: Effect of adding stabilizers]

As shown in Table 1, when Examples 3 and 4 and Example 5 are compared, the amount of Z r 0 ₂ contained in the powder line part 5 1 3 is 8 8 mass% (Example 3), 86 mass% (Example 4) and 85 mass% (Example 5). In addition, Examples 3 and 4 contain 4% Ca 0 and Mg O as stabilizers, respectively, and Example 5 does not contain any stabilizer.

And in the results of Table 1, when the erosion rate index is compared, Example 3 is about 5% lower than Example 5, and Example 4 is about 7% lower than Example 5. % Is low. This is because the addition of the stabilizer makes it difficult for ZrO and crystal grains to fall out of the refractory structure. PT / JP2007 / 073899 This is probably because of the problem.

In addition, even when the balance containing the stabilizing material is more than 10% by mass, the effect is exerted, but the proportion of ZrO ₂ is relatively small and sufficient corrosion resistance to the mold powder is obtained. Since it becomes difficult to obtain, it is preferably 10% by mass or less.

Although not shown in Table 1, the same result was obtained when Υ ₂ Ο 3 was added as a stabilizer.

From the above, it was found that by adding 10% by mass or less of the stabilizing material, the melting rate of the powder line portion 5 13 can be reduced.

It should be noted that the present invention is not limited to the above-described embodiments, and modifications, improvements and the like within the scope that can achieve the object of the present invention are included in the present invention. For example, the composition of the powder line portion 5 13 is not limited to the composition of Examples 1 to 6, and any composition that falls within the region A in FIG. 3 and the basket is included in the present invention. Industrial applicability

According to the present invention, when FC is present in the refractory, the FC can be selectively heated by high-frequency induction heating, and the immersion nozzle can be preheated uniformly. For this reason, after preheating, it is possible to prevent the occurrence of defects such as cracks in the submerged nozzle at the start of forging, and it is possible to suppress melting damage due to slag in the portion that contacts the slag during the forging process. Therefore, the durability of the immersion nozzle can be improved.

Claims

1. An immersion nozzle used in the continuous metal casting method, where at least the part in contact with the slag on the outer periphery is Zr 0 ₂ : 70% by mass or more, FC (free force one bond) A submerged nozzle characterized in that it is formed of a refractory composed of 30% by mass or less and is preheated by high frequency induction heating.

2. It is an immersion nozzle used in the continuous casting method of molten metal, and at least the part in contact with the slag on the outer circumference is Zr 0 ₂ : 70% by mass or more, FC (free force one bond): 20 mass% or less, Z r 0 ₂

An immersion nozzle, characterized in that it is formed of a refractory material including the remaining 10% by mass or less including a stabilizing material, and is preheated by high-frequency induction heating.

3. In the immersion nozzle according to claim 2, wherein the stabilizing Kazai the immersion nozzle, characterized in that it comprises a C a O, least any one also of M g O and Y ₂ Omicron 3.

4. A preheating step of preheating the immersion nozzle according to any one of claims 1 to 3 by high frequency induction heating, and a molten metal from the evening dish to the mold via the immersion nozzle preheated in the preheating step. A continuous forging method, comprising: a forging step for pouring.