JPH09108795A - Continuous casting method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a continuous casting method for producing a clean steel, etc., having less defect by restraining the generation of inclusion and the involving of the air during the continuous casting. SOLUTION: In the continuous casting method for executing a flow rate control of molten steel 11 by vertically driving a stopper 15 fitted to a molten steel flowing inlet 14 at the upper part of an immersion nozzle 13, on the inner surface of the immersion nozzle 13 corresponding to at least below a meniscus surface 18 of the molten steel in a continuous casting mold 17, a non-carbon refractory composition 20 having 0.1-10wt.% silica content is arranged. Further, inert gas is blown into the molten steel 11 through a gas spouting hole 21 arranged in the inner surface side of the immersion nozzle 13.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a continuous casting method for producing clean steel with less defects by reducing nonmetallic inclusions, powder inclusions and pinholes in steel.

[0002]

2. Description of the Related Art In a continuous casting method, when a molten steel is poured from a tundish into a continuous casting mold, an alumina graphite dipping nozzle having excellent spalling resistance is arranged to prevent oxidation of the molten steel during casting. Then, casting is performed. Explaining this in detail with reference to FIG. 4, the molten steel 51 held in the tundish 50 has a flow rate of the molten steel 51 and an upper nozzle 52 having a gas introduction pipe 59 for blowing gas into the molten steel and introducing the molten steel 51. Two sliding nozzle plates 53, 54 to be controlled, a lower nozzle 56 connecting the sliding nozzle plates 53, 54 and the immersion nozzle 55, and an immersion nozzle 55 having a gas introduction pipe 60 for blowing gas into the molten steel. The discharge holes 5 provided in the lower portion of the immersion nozzle 55 are sequentially passed through.
It is designed to be injected into the continuous casting mold 58 from No. 7. However, such an immersion nozzle 55 has a tendency that during operation, inclusions adhere to the inner hole surface to close the nozzle hole. As measures against this nozzle clogging, for example, Japanese Patent Laid-Open No. 62-62
No. 130754 discloses a method in which argon gas or the like is discharged from the inner surface of the immersion nozzle to destroy the boundary layer adhered to the inner surface of the immersion nozzle to prevent inclusions from adhering to the inner surface of the immersion nozzle. Japanese Patent No. 118949 employs a method of forcibly stirring molten steel by electromagnetic force, a method of moving the immersion nozzle itself in a mold in a horizontal direction, and the like. In addition, the method of blowing the argon gas has an advantage that it helps improve the quality of the steel because the inclusions in the continuous casting mold are also floated when the blown argon gas floats.

[0003]

However, in the tundish 50 having the structure shown in FIG. 4, the upper nozzle 52, the sliding nozzles 53, 54, the lower nozzle 56, and the dipping nozzle 55 are connected to each other between refractory materials. Since there are 4 joints in the joint, even if each joint is sealed with mortar or a sealing material, the sealing is not perfect, and the molten steel inevitably comes from the joints with the sliding operation of the sliding nozzle plates 53 and 54. Air enters the inside and becomes a factor that deteriorates the quality in the steel. Further, in the method of blowing the argon gas described in JP-A-62-130754, a large amount of inert gas is required to remove the air bubbles due to the entrainment of air as described above,
There was a problem that the basic unit increased. Furthermore, in the method for stirring molten steel by electromagnetic force described in Japanese Patent Laid-Open No. 3-118949, it is difficult to effectively remove the boundary layer in the molten steel adhering to the inner surface of the immersion nozzle, and it is possible to partially remove the boundary layer more than necessary. There is a drawback that a molten steel flow is generated and the durability of the immersion nozzle body is reduced.

Further, in the conventional immersion nozzle 55 made of alumina graphite, since the carbon content is present on the contact surface with the molten steel 51, the carbon content in the immersion nozzle 55 is picked up in the molten steel and the immersion nozzle is The silica content in 55 is reduced by the carbon content to become SiO gas, CO gas or oxygen, which oxidizes aluminum or the like in the molten steel to produce non-metallic inclusions such as alumina. Furthermore, the inner surface of the immersion nozzle 55, which serves as the contact surface for molten steel, becomes highly uneven due to the disappearance of silica or carbon. Therefore, during operation, inclusions in the molten steel gradually adhere to the inner hole of the immersion nozzle 55 and This may cause casting troubles such as clogging of the discharge hole and hindering the flow rate control of the molten steel 51. Further, when argon gas is blown to the extent that the nozzle clogging can be suppressed, the continuous casting mold 58
There was a problem that the interface between the powder and the molten steel was disturbed when the argon gas floated inside, causing the inclusion of powder inclusions into the molten steel, which remained in the molten steel. .

The present invention has been made in view of such circumstances, and is a continuous casting for producing clean steel or the like with few defects by suppressing the inclusion formation of inclusions or metal and air entrainment during the continuous casting. The purpose is to provide a method.

[0006]

According to the present invention, there is provided a semiconductor device comprising:
The continuous casting method described above, when injecting molten steel into a continuous casting mold through a dipping nozzle provided at the bottom of a tundish that holds the molten steel, moves a stopper that fits into the molten steel inlet above the dipping nozzle up and down. Is a continuous casting method in which the flow rate of molten steel is controlled by driving to the inner surface of the immersion nozzle corresponding to at least the molten steel meniscus surface in the continuous casting mold, and the silica content is 0.1 to 1.0 wt%. A non-carbon refractory composition is arranged, and an inert gas is blown into the molten steel through a gas discharge part arranged on the inner hole surface side of the immersion nozzle.

The continuous casting method according to claim 2 is the method according to claim 1.
In the continuous casting method described above, the gas discharge part disposed in the immersion nozzle is provided at a position that is equal to or higher than the molten steel meniscus surface of the continuous casting mold, and the discharge amount of the inert gas is 0.5.
˜2.0 N liter / ton-molten steel. The continuous casting method according to claim 3 is the continuous casting method according to claim 1 or 2, wherein the non-carbon refractory composition has a thickness of 3 to 10 mm. The continuous casting method according to claim 4 is the continuous casting method according to any one of claims 1 to 3, wherein the surface temperature of the immersion nozzle is set to 11
After preheating to 00 ° C to 1300 ° C, injection of molten steel into the continuous casting mold is started. A continuous casting method according to a fifth aspect is the continuous casting method according to any one of the first to fourth aspects, wherein the bottom portion of the immersion nozzle is formed in a screwed structure.

The molten steel meniscus surface refers to the position of the molten steel surface in the continuous casting mold. The non-carbon refractory composition includes, for example, components such as silica, alumina, zirconia, calcia, magnesia, chromia, silicon nitride, metal powder and the like, or components in which a plurality of them are combined, and carbon such as graphite, carbon and organic polymer. The composition refers to a composition that does not substantially contain a carbon source. Silica content is 0.1
If it is less than wt%, it is difficult to select a high-purity material as a raw material, and it cannot be put to practical use in terms of industrial production cost. On the other hand, if it exceeds 1.0 wt%, the mechanical strength and the like of the refractory composition is lowered, the wear due to the flow of molten steel becomes remarkable, and the adverse effect of non-metallic inclusions caused by the reduction of silica increases. It is not preferable.

The discharge amount of the inert gas, that is, the volume of the inert gas blown per ton of molten steel to be treated in the standard state (temperature: 0 ° C., pressure: 1 atm) is 0.5 N.
When it is smaller than liter / ton-molten steel, the amount of alumina-based inclusions precipitated in the boundary layer rapidly increases because the boundary layer on the inner surface of the immersion nozzle is stabilized without being broken or separated. Further, when it exceeds 2.0 N liter / ton-molten steel, the inert gas discharged from the discharge hole of the dipping nozzle coalesces into large bubbles when floating, so that the molten steel meniscus surface in the continuous casting mold is disturbed and the molten steel meniscus is disturbed. The powder floating on the surface is entrained and the amount of powder inclusions in the molten steel increases. Thickness of non-carbon refractory composition is 3m
If it is less than m, the durability is not sufficient and continuous casting for a long time cannot be supported. Further, it becomes difficult to apply a thin non-carbon refractory composition to the inner hole surface of the dipping nozzle. Further, even if the non-carbon refractory composition is arranged to have a thickness of more than 10 mm, it is not preferable because it is wasted without being worn after the end of the continuous casting and is wasted, and the resistance of the immersion nozzle to thermal shock is weakened. If the surface temperature of the preheating immersion nozzle is lower than 1100 ° C., the thickness of the molten steel solidified layer that adheres when continuous casting is started becomes large, which promotes nozzle clogging. If the preheating temperature is higher than 1300 ° C, oxidation of the immersion nozzle is promoted during preheating, and characteristics such as mechanical strength and erosion resistance deteriorate.

[0010]

In the continuous casting method according to claims 1 to 5,
Since the stopper that fits into the molten steel inlet at the top of the immersion nozzle is driven up and down to control the flow rate of the molten steel, there should be joints such as refractory surfaces between the molten steel inlet and the discharge hole of the immersion nozzle. Instead, the air from the outside can be completely shut off. Furthermore, since the non-carbon refractory composition having a silica content of 0.1 to 1.0 wt% is arranged on the inner surface of the immersion nozzle corresponding to at least the molten steel meniscus surface or less in the continuous casting mold, carbon is contained in the molten steel. Does not migrate, and defects such as pinholes are less likely to occur in the steel. In addition, the amount of SiO gas and oxygen produced when silica is reduced by carbon in the refractory can be minimized. Therefore, while suppressing the generation of non-metallic inclusions in the molten steel, carbon or silica is less likely to desorb or disappear from the contact surface with the molten steel, so that the smoothness of the surface of the non-carbon refractory composition is maintained. It becomes difficult for the inclusions to adhere. Further, since the inert gas is blown into the molten steel through the gas discharge portion provided on the inner surface side of the immersion nozzle, it is possible to suppress the adhesion of alumina inclusions to the inner surface of the immersion nozzle.

Particularly, in the continuous casting method according to the second aspect, the gas discharge portion arranged in the immersion nozzle is provided at a position higher than the molten steel meniscus surface of the continuous casting mold, and the discharge amount of the inert gas is 0. 0.5-2.0 N liter / ton
-Because it is set within the range of molten steel, it depends on the amount of alumina inclusions adhering to the inner surface of the immersion nozzle and the floating of the inert gas in the continuous casting mold in the area where the temperature drop is greater than the molten steel meniscus surface. By adjusting both the amount of powder inclusion and the optimum range, it is possible to cast steel with few defects such as pinholes.

In the continuous casting method according to claim 3,
Since the thickness of the non-carbon refractory composition is 3 to 10 mm, it is easy to apply the non-carbon refractory composition lined on the inner surface of the immersion nozzle, and good corrosion resistance without impairing the thermal shock resistance of the immersion nozzle, The molten steel contact surface having both surface smoothness can be maintained. Claim 4
In the continuous casting method described above, after preheating the surface temperature of the immersion nozzle to 1100 ° C to 1300 ° C, since the injection of the molten steel into the continuous casting mold is started, the molten steel introduced into the immersion nozzle after the injection is started is It is not excessively cooled and solidified molten steel rarely narrows the inner hole of the immersion nozzle. In the continuous casting method according to claim 5, since the bottom portion of the immersion nozzle is formed into a screwed structure, the screw portion can be removed to easily perform the lining construction of the non-carbon refractory composition on the inner surface of the immersion nozzle, Since the nozzle is divided into small parts by the screwed structure, the thermal stress generated by the thermal shock is dispersed by the screwed structure, and the resistance of the immersion nozzle itself to the thermal shock can be increased.

[0013]

Therefore, in the continuous casting method according to claims 1 to 5, alumina-based inclusions, powder-based inclusions,
It is possible to exert a synergistic effect by taking various measures against various defects of the continuous cast piece and nozzle clogging due to air bubbles and the like caused by air wrapping. That is, while completely shutting off the air from the outside, carbon further migrates into the molten steel from the immersion nozzle, or silica forms the inner surface of the immersion nozzle with a refractory composition in which silica is not reduced by the carbon, It is possible to effectively prevent nozzle clogging due to precipitation of non-metallic inclusions in the immersion nozzle, and cast steel with few defects such as non-metallic inclusions and pinholes.

Particularly, in the continuous casting method according to the second aspect, the amount of the inert gas blown into the molten steel from the gas discharge part can be adjusted to the optimum range, and the basic unit of the inert gas can be minimized. Steel with few defects such as alumina-based inclusions, powder-based inclusions or pinholes can be cast at low cost.

In the continuous casting method according to claim 3,
Since the molten steel contact surface having both good corrosion resistance and surface smoothness is maintained, the generation of non-metallic inclusions and nozzle clogging can be further suppressed. In the continuous casting method according to the fourth aspect, since the inner hole of the immersion nozzle is less likely to be narrowed by the solidified molten steel, it is possible to further reduce the occurrence of nozzle blockage during the continuous casting operation. Claim 5
In the continuous casting method described, while facilitating the lining construction on the inner surface of the immersion nozzle of the non-carbon refractory composition,
Since the resistance of the immersion nozzle itself to thermal shock can be increased, it is possible to manufacture an immersion nozzle with less nozzle clogging at low cost, and it is possible to reduce problems such as breakage of the immersion nozzle during casting.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Next, referring to the attached drawings, an embodiment in which the present invention is embodied will be described to provide an understanding of the present invention. 1 is a schematic explanatory view of a continuous casting facility to which a continuous casting method according to an embodiment of the present invention is applied, FIG. 2 is a diagram showing a relationship between a refractory surface temperature immediately after preheating and a metal adhesion thickness, and FIG. 3 is It is a figure which shows the relationship between argon blowing amount and inclusion content index.

First, a continuous casting facility to which the continuous casting method according to the embodiment of the present invention is applied will be described. FIG.
As shown in FIG. 1, the continuous casting facility 10 is arranged so as to face the tundish 12 that holds the molten steel 11, the integral immersion nozzle 13 provided at the bottom of the tundish 12, and the molten steel inlet 14 of the immersion nozzle 13. The stopper 15 for controlling the injection amount of the molten steel 11 and the discharge hole 1 of the immersion nozzle 13
The continuous casting mold 17 into which the molten steel 11 discharged through 9 is poured. It should be noted that the integral type immersion nozzle 13 is different from a molten steel injecting device configured to have a plurality of members such as an upper nozzle, a sliding nozzle plate, a lower nozzle, etc. Is a refractory member whose flow rate is controlled by directly opening and closing the molten steel inflow port 14 of the immersion nozzle 13.

The immersion nozzle 13 has a total length of about 1000 m.
m, an outer diameter of about 100 mm, and an inner diameter of about 50 mm is a substantially tubular refractory material mainly composed of a substantially alumina carbonaceous material, the bottom portion of which is sealed by a bottom plug 23 having a screw-in structure, and a bottom side surface of the refractory material. Two ejection holes 19 each having a substantially oval shape of 60 × 40 mm or a substantially rectangular shape of about 60 × 60 mm are provided so as to face each other. The immersion nozzle 13 is provided on the outer periphery of the immersion nozzle main body 13a so as to contact the powder 24 floating on the molten steel meniscus surface 18, the immersion nozzle main body 13a, and mainly below the molten steel meniscus surface 18. It has a protective layer 20 having a thickness of 8 mm and formed of a non-carbon refractory composition provided around the discharge hole 19. As shown in Table 1, the components of the immersion nozzle body 13a are alumina: 57 wt%, silica: 18 wt%, silicon carbide: 5 wt%, carbon: 20
It is a refractory material containing alumina carbonaceous matter of wt% composition as a main component, and as the non-carbon refractory composition, use each of compositions having substantially no carbon as shown in A to D of Table 1. You can For the powder line portion 25, a zirconia carbon refractory composition having excellent erosion resistance against the powder 24 is used.

[0019]

[Table 1]

The immersion nozzle main body 13a is prepared by placing a predetermined mixture of alumina carbon material in a rubber mold having a rod-shaped mold therein, and subjecting this to a hydrostatic pressing to form a cylindrical cylinder with a substantially bottom. It can be manufactured by molding, processing and firing in a reducing atmosphere. Then, the protective layer 20 made of the non-carbon refractory compositions A to D can be formed by, for example, a casting method of an amorphous refractory as shown below. That is, first, the bottom of the immersion nozzle body 13a is processed by a lathe or the like to be opened by forming the bottomed cylindrical shape or firing, and then the threaded portion is formed to have the same composition as the immersion nozzle body 13a. The bottom plug 23 provided with a screw part can be attached and detached. Next, the immersion nozzle body 1
With the bottom plug 23 of 3a removed, the immersion nozzle body 1
3a, the bottom of a mold (not shown) for forming the protective layer 20 around the discharge hole 19, and the gap between the immersion nozzle body 13a and the mold by inserting from the discharge hole 19 For example, a void having a width of 8 mm is formed. Then, castable non-refractory materials such as castables made of the non-carbon refractory compositions A to D are respectively poured into the voids to cure the cast refractories, the mold is removed, and finally the non-carbon refractory compositions A to D are removed. Immersion nozzle 13 having protective layers 20 of desired non-carbon refractory compositions A to D, respectively, by screwing and fixing a bottom plug 23 having a protective layer 20 consisting of the inside to the bottom of immersion nozzle body 13a.
Can be obtained.

Further, in the immersion nozzle body 13a, a gas discharge portion 21 for discharging an argon gas, which is an example of an inert gas, toward the molten steel 11 in the nozzle hole is located above the molten steel meniscus surface 18. It is located in a position.
The gas discharge portion 21 has a width of 0.5 to 1.
It is a 5 mm slit (void), and the immersion nozzle body 1
It is adapted to be connected to an argon gas introduction pipe 22 arranged on the outer periphery of 3a. Then, a predetermined amount of argon gas is supplied from an argon gas supply device (not shown) to the gas discharge portion 21 via the argon gas introduction pipe 22, and the inner surface of the immersion nozzle main body 13 a corresponding to the position of the gas discharge portion 21 is filled with argon. Gas is being blown in. At this time, the portion of the immersion nozzle main body 13a which becomes the flow path of the argon gas has a shape, distribution state of pores in the refractory tissue,
And a material having a predetermined air permeability by controlling the bulk specific gravity and the like.

The stopper 15 has a total length of about 1000 m.
m is a columnar structure having an outer diameter of about 80 mm, and is a structure composed of a core metal (not shown) and a refractory material arranged on the outer periphery thereof.
The stopper 15 is a molten steel inflow port 1 above the immersion nozzle 13.
4, the molten steel inflow port 14 of the immersion nozzle 13 which is arranged to face
And a stopper sleeve 16 that protects a cored bar (not shown) that supports the stopper head 15a from the molten steel 11. The composition of the stopper head 15a and the stopper sleeve 16 is shown in Table 1.
As shown in FIG. 5, the stopper head 15a is made of a refractory material containing 3 wt% of zirconia as a main component. Use a material with enhanced properties such as properties. With the above-described configuration, the distance between the stopper head 15a and the molten steel inflow port 14 can be adjusted by a stopper drive mechanism (not shown) to inject the molten steel 11 into the continuous casting mold 17 at a predetermined injection amount or stop the injection. it can. If necessary, an inert gas such as argon gas can be blown into the molten steel from the tip of the stopper head 15a.

The continuous casting mold 17 solidifies the molten steel 11 to have a long side of 800 to 2000 mm and a short side of 200 to 300 m.
It is a mold for obtaining a slab having a rectangular cross section of m. In the continuous casting, in order to prevent the oxidation of the molten steel surface by blocking the contact between the molten steel 11 on the molten steel meniscus surface 18 and the air, and to secure the lubricity between the continuous casting mold 17 and the molten steel solidified shell, S
Powder 2 containing iO ₂ , CaO, Na ₂ O, etc. as main components
4 is floated on the molten steel meniscus surface 18 and used.

Subsequently, the continuous casting facility 10 described above is used.
The continuous casting method using is described. First, prior to continuous casting, the circumference of the immersion nozzle 13 arranged in the tundish 12 is surrounded by an iron plate or the like not shown, and the surrounded immersion nozzle 13 is heated by using a gas burner or the like not shown to The surface temperature is set to about 1150 ° C. Then, the molten steel inlet 14 of the immersion nozzle 13
In the state where the stopper head 15a is tightly fitted to and the molten steel inflow port 14 is closed, the injection of the molten steel 11 into the tundish 12 is started through the long nozzle provided at the bottom of the ladle (not shown). Then, when the molten steel 11 poured into the tundish 12 reaches a predetermined level, the stopper head 15a is slightly raised by a stopper driving device (not shown) to form a gap between the molten steel inlet 14 and the stopper head 15a. The molten steel 11 in the tundish 12 by the preheated immersion nozzle 1
3 into the continuous casting mold 17.

At this time, since the immersion nozzle 13 is preheated to the proper range of 1150 ° C., the molten steel 11 is not cooled in the immersion nozzle 13 at the start of casting and solidified on the inner surface of the immersion nozzle 13. The adhesion thickness of the molten steel (metal) was almost zero. FIG. 2 is a diagram showing the relationship between the surface temperature of the immersion nozzle 13 and the metal adhesion thickness, which shows that the metal adhesion thickness increases when the preheating temperature is 1100 ° C. or lower. Also,
Since the immersion nozzle main body 13a has a composition containing carbon (carbon, graphite, etc.), when the preheating temperature exceeds 1300 ° C., the surface of the immersion nozzle main body 13a is significantly oxidized, and the structure becomes brittle. Oxidation products and the like that fall off from the structure mix in the molten steel and become the cause of inclusions. In addition,
The metal adhesion thickness shown in FIG. 2 is the thickness of the metal adhered to the inner hole surface of the immersion nozzle 13 after cutting the casting under the same casting conditions and cutting the immersion nozzles 13 used at the different preheating temperatures. Are individually measured.

Further, during continuous casting, about 1400 ton per one dipping nozzle 13 while blowing argon gas from the gas discharge portion 21 of the dipping nozzle 13 at a ratio of 1.0 N liter / ton-molten steel within an appropriate range.
The amount of molten steel 11 was cast. In addition, by blowing a minimum amount of argon gas through the stopper head 15a and / or the immersion nozzle 13 around the fitting portion between the molten steel inflow port 14 and the stopper head 15a of the integrated immersion nozzle 13, the stopper 15 can be used. It is also possible to stabilize the control of the molten steel flow rate. During this period, the stirring phenomenon such as the foaming of the powder 24 in the continuous casting mold 17 was small, and the trouble such as the nozzle clogging was small. Then, after the casting is completed, the obtained slab is cut, and the number of inclusions per certain area is counted using an optical microscope, a scanning electron microscope or the like, and the inclusion content index is measured. Was about 0.1 and powder inclusions were about 0.25, which were extremely low rates. Since this is the minimum amount of argon gas required to remove the boundary layer adhering to the inner hole surface of the immersion nozzle 13, collision coalescence of bubbles is suppressed, and the interposition that occurs by adhering to the enlarged bubbles is caused. It is based on the reduction of quality defects such as accumulation of objects and pinholes. In the above calculation of the inclusion content index, the count value of the slab obtained under the casting conditions in the configuration of the conventional example as shown in FIG. 3 is the reference value (1.0).
Used as

In FIG. 3, casting conditions other than the argon blowing amount were all set to be the same, and slabs having different argon blowing amounts were manufactured, and the inclusion content index of each slab was set to that of an alumina system, The results obtained by measuring the powder type and the powder type are shown. As shown in the figure, the powder-based inclusions (symbol: ●) due to the powder 24 in the continuous casting mold 17 increase with the increase of the amount of blown-in argon, but conversely the alumina-based inclusions deposited on the refractory surface. It can be seen that the non-metallic inclusions mainly consisting of the substances (symbol: ◯) decrease with the increase of the argon blowing amount. Therefore, both of the alumina-based inclusions and the powder-based inclusions are relatively small, 0.5 to 2.0 N liter /
It is desirable to set the amount of argon gas blown in the range of ton-molten steel.

Table 2 shows the results of experiments conducted to select the refractory composition used for the protective layer 20 of the immersion nozzle 13. Here, five types of refractory compositions (magnesia, zirconia, alumina, calcia, mullite) to be selected in advance were fixed in the tundish 12 so as not to float, and the tundish 12 was used under predetermined conditions. The results obtained by taking out the refractory composition after casting and analyzing and evaluating the surface of the refractory composition by microscopic observation and the like are shown. However, in the table, the evaluation symbol ◯ means good, Δ means good, and × means bad. As shown in the table, mullite (3Al ₂ O ₃ ·.
In the case of 2SiO ₂ ), silica is reduced by the carbon content in the molten steel and unevenness is formed on the contact surface with the molten steel to increase the surface roughness, so that the inclusions in the molten steel are trapped and the inclusions are trapped. Was adhered thickly, but with other non-carbon refractory compositions containing no silica source, such a phenomenon was small and good. It has been confirmed that magnesia and zirconia are poor in thermal expansion characteristics, and therefore, they are materials easily cracked by thermal shock, and that magnesia and calcia are easily digested by moisture in the air.

[0029]

[Table 2]

The embodiment of the present invention has been described above.
The present invention is not limited to such an embodiment, and all changes in conditions that do not depart from the gist are within the scope of the present invention. For example, in the present embodiment, an example in which the protective layer 20 made of the non-carbon refractory compositions A to D is arranged at a position below the molten steel meniscus surface 18 has been shown, but the non-carbon refractory compositions A to D are shown. It is also applicable to an integral type immersion nozzle in which the protective layer 20 consisting of is arranged so as to include the entire inner surface of the immersion nozzle or a part thereof above the molten steel meniscus surface 18.

[Brief description of the drawings]

FIG. 1 is a schematic explanatory diagram of continuous casting equipment to which a continuous casting method according to an embodiment of the present invention is applied.

FIG. 2 is a diagram showing a relationship between a refractory surface temperature immediately after preheating and a metal adhesion thickness.

FIG. 3 is a diagram showing a relationship between an argon blowing amount and an inclusion content index.

FIG. 4 is a schematic explanatory view of a continuous casting facility according to a conventional example.

[Explanation of symbols]

10 Continuous Casting Equipment 11 Molten Steel 12 Tundish 13 Immersion Nozzle 13a Immersion Nozzle Main Body 14 Molten Steel Inlet 15 Stopper 15a Stopper Head 16 Stopper Sleeve 17 Continuous Casting Mold 18 Molten Steel Meniscus Surface 19 Discharge Hole 20 Protective Layer 21 Gas Discharge Section 22 Argon Gas Introduction Tube 23 Bottom plug 24 Powder 25 Powder line part

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location B22D 11/18 B22D 11/18 K 41/50 520 41/50 520 41/54 41/54 41 / 58 41/58 (72) Inventor Shoichi Sakaguchi 1-1 Hibahata-cho, Tobata-ku, Kitakyushu, Fukuoka Prefecture New Nippon Steel Corporation Yawata Works

Claims (5)

[Claims] 1. When a molten steel is poured into a continuous casting mold through a dipping nozzle provided at the bottom of a tundish holding the molten steel, a stopper fitted to the molten steel inflow port above the dipping nozzle is driven up and down. It is a continuous casting method for controlling the flow rate of molten steel, wherein the silica content is 0.1 or more on the inner surface of the immersion nozzle corresponding to at least the molten steel meniscus surface in the continuous casting mold.
~ 1.0 wt% non-carbon refractory composition is arranged, and an inert gas is blown into the molten steel through a gas discharge part arranged on the inner hole surface side of the immersion nozzle. . 2. The gas discharge part disposed in the immersion nozzle is provided at a position above the molten steel meniscus surface of the continuous casting mold, and the discharge amount of the inert gas is 0.5 to 2.0 N liter / ton-. It is molten steel, The continuous casting method of Claim 1 characterized by the above-mentioned. 3. The non-carbon refractory composition has a thickness of 3 to
It is 10 mm, The continuous casting method of Claim 1 or 2 characterized by the above-mentioned. 4. The surface temperature of the immersion nozzle is 1100 ° C.
The method of continuous casting according to any one of claims 1 to 3, wherein the molten steel is injected into the continuous casting mold after preheating to -1300 ° C. 5. The continuous casting method according to claim 1, wherein the bottom of the immersion nozzle is formed in a screwed structure.