JPH11199315A - Refractory for blowing inert gas in melted metal and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a refractory having excellent gas permeation stability and high tolerance by forming a gas-permeable tissue comprising silica, chromia and alumina in specific amounts, respectively, and binding portions used as aggregates with a component having a high melting point of specific temperature or higher. SOLUTION: This refractory for blowing an inert gas has a gas-permeable tissue comprising a refractory material containing 1-5 wt.% of silica, 1-5 wt.% of chromia and 90-98 wt.% of alumina, wherein portions used as aggregates are bound with a component having a high melting point of >=1,800 deg.C. The pore diameter distribution of the refractory has a <=75 μm pore diameter rate of 25-50%. The refractory is produced by adding a binder such as a phosphoric acid compound to a mixture containing corundum, chromium oxide, silica, mullite, etc., in a prescribed particle size and in a mixing ratio, kneading the mixture together with water, press-molding the kneaded product, and subsequently sintering the molded product at 1,800-1,860 deg.C. The formed refractory has gas-permeable tissues 21, 22 in which aggregates 29 are bound through a high melting point component having a melting point of >=1,800 deg.C and further in which gas-permeable pores are formed from spaces 31 among the aggregates 29.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to blowing an inert gas, such as a nitrogen gas or an argon gas, into a molten metal and blowing the inert gas into a molten metal such as a porous plug used for stirring the molten metal. The present invention relates to a refractory for use and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, in a refining process of molten steel, a refractory for blowing an inert gas having air permeability is disposed on a wall surface or a bottom surface of a molten steel pot or a tundish, and the refractory is introduced into the molten steel through the refractory material. A method is employed in which the molten steel is stirred by blowing active gas to adjust the temperature of the molten steel or to make the molten steel components uniform. However, in these breathable refractories, metal and slag infiltrate into the pores of the breathable tissue when no inert gas is passed. For this reason, even if a high back pressure is applied to the refractory when the ventilation of the inert gas is required, poor ventilation of the inert gas and misfire of the inert gas occur. Then, in order to prevent such poor ventilation or misfiring, after using the refractory, oxygen gas is blown to the infiltration layer through which the metal or slag has penetrated to dissolve and remove the metal or slag. It becomes necessary. At the time of this oxygen cleaning, high heat is generated, so that the refractory itself is melted or damaged, and the number of times the refractory is used is reduced, which causes a rise in the cost of the refractory. In addition, since replacement work of refractories occurs frequently, many high-temperature heavy-bar work has been required.

The infiltration and heat of the metal and slag
The purpose of this study was to reduce spalling damage caused by spalling due to impact.
For example, Japanese Patent Publication No. 7-74091 discloses
Is 3 to 96 weight of raw material consisting of zirconia mullite
% And an alumina-silica-based raw material of 97 to 4% by weight
Using a gas injection refractory consisting of
I have. In addition, it is resistant to blowing inert gas such as porous plugs.
Breathable porous bricks (porous
When manufacturing bricks, aggregates such as alumina are mainly used.
Used to give moldability to this
Chromia (Cr) to improve corrosion and corrosion resistance_TwoO_Three)etc
Is added to provide infiltration resistance and spall resistance
Mullite (3Al_TwoO_Three・ 2SiO_Two)
Silica (SiO _Two) Is used as raw material
It has been.

[0004]

However, the refractory for gas injection disclosed in Japanese Patent Publication No. 7-74091 has the following problems. Since the range of the pore size distribution (pore size distribution) in the gas-permeable structure is wide and the average pore size is large, the amount of slag, metal, and the like infiltrated during casting for a long time increases.
For this reason, the durability is reduced due to factors such as peeling of the infiltration layer during oxygen cleaning of the infiltration layer. Since the fire resistance of the aggregate-bonded portion made of zirconia, mullite or the like is low, this portion is easily worn when blowing inert gas or washing with oxygen. Since the pore size distribution of the permeable tissue is not strictly controlled, the variation in the ratio of pores (pores) of 75 μm or less is particularly large, and the influence of the thermal shock at the time of injecting the inert gas and at the time of oxygen washing is reduced. It is susceptible to damage such as cracks. Since the flow path of the supplied inert gas is not formed uniformly, there is a disadvantage that the air permeability becomes unstable and troubles such as poor gas blowing easily occur.

Further, in the above-mentioned conventional method for producing a refractory for blowing an inert gas, 1600 to 175
In order to sinter at a relatively low sintering temperature in the range of 0 ° C., it is necessary to lower the melting point of the connective structure connecting the aggregates to improve the sinterability of the base material obtained by kneading and molding the raw materials. There is. For this reason, there was a problem that the mechanical strength and corrosion resistance of the bonding structure obtained by sintering became low, and the amount of wear of the refractory for blowing an inert gas to molten steel and slag increased. In addition, since the refractory for blowing an inert gas formed by a bonding structure having a low melting point generally easily oversinters and easily forms isolated pores, communication that contributes to air permeability in spite of its porosity. Since the number of pores is small and the variation in pore size distribution is large, there is a disadvantage that poor ventilation is likely to occur. The present invention has been made in view of such circumstances, and has as its object to provide a refractory for blowing an inert gas into a molten metal having excellent ventilation stability and high durability, and a method for producing the same. .

[0006]

According to the present invention, there is provided a semiconductor device comprising:
The refractory for blowing an inert gas into the molten metal described above contains silica and chromia in an amount of 1 to 5 wt% and 1 to 5 wt%, respectively.
And the alumina content is 90-98 wt%. If the alumina content is less than 90% by weight, the corrosion resistance is greatly reduced, and the melting point is lowered, so that a breathable structure having sufficient permeability cannot be obtained. On the other hand, if the alumina content exceeds 98% by weight, the spalling resistance is remarkably reduced, and the durability is deteriorated due to crack generation due to thermal shock at the time of oxygen washing or the like, which is not preferable. If the contents of silica and chromia are each less than 1 wt%, the amount of melt required for firing becomes insufficient, and the mechanical strength and spalling resistance of the refractory for injecting inert gas obtained by firing. In addition to lowering the chromia content, sufficient corrosion resistance cannot be maintained due to insufficient chromia content. On the other hand, if the content of silica and chromia exceeds 5% by weight, the melting point of the connective tissue that binds the aggregates is reduced, and adverse effects such as variations in air permeability are caused.

The refractory for injecting an inert gas into a molten metal according to the present invention is characterized in that silica and chromia are 1 to 5 respectively.
It has a gas-permeable structure mainly composed of alumina containing 1% to 5% by weight of alumina and a portion of the gas-permeable structure serving as an aggregate is bonded by a high melting point component of 1800 ° C. or more. If the content of silica and chromia in the refractory for injecting inert gas is less than 1% by weight, respectively, the amount of melt required for sintering is insufficient, and the refractory for injecting inert gas obtained by sintering is insufficient. The mechanical strength, spalling resistance and the like are reduced, and sufficient corrosion resistance cannot be maintained due to the shortage of chromia content. Further, when the content of silica and chromia exceeds 5 wt%, it becomes a factor to lower the melting point of the connective tissue in the breathable tissue,
It is not preferable because it causes adverse effects such as variations in air permeability. If the melting point of the high melting point component that binds the aggregate of the refractory for injecting inert gas is lower than 1800 ° C., the heat resistance and mechanical strength of the bonded portion are undesirably reduced. Here, although the upper limit of the melting point of the high melting point component is not particularly specified, it is clear that the highest melting temperature in the alumina-silica-chromia system is the upper limit.

A refractory for blowing an inert gas into a molten metal according to claim 3 is the refractory for blowing an inert gas into a molten metal according to claim 1 or 2, wherein In the pore size distribution of the refractory, the proportion of pores of 75 μm or less is 25 to 50%. When the ratio of pores having a diameter of 75 μm or less is lower than 25% (volume percent), the ability to alleviate distortion due to thermal stress decreases, and spalling occurs in the breathable structure of the refractory for injecting inert gas, resulting in damage. It is not preferable because it becomes easy to perform. Conversely, if the ratio of the pores exceeds 50%, the mechanical strength sharply decreases and the amount of metal or slag infiltration increases.

According to a fourth aspect of the present invention, there is provided a method for producing a refractory for injecting an inert gas into a molten metal, comprising forming a refractory material containing alumina, silica and chromia from 1800 to 1860.
Firing at a temperature of ° C. When calcined at a temperature lower than 1800 ° C., it is difficult to produce a gas-permeable structure of a refractory for injecting inert gas, which forms a gas-permeable structure having sufficient mechanical strength and an appropriate pore size distribution. become. Conversely 18
When firing at a temperature exceeding 60 ° C., the densification of the entire structure proceeds, so that a predetermined amount of air permeability cannot be maintained and the spall resistance is also reduced.

According to a fifth aspect of the present invention, there is provided a method for producing a refractory for injecting an inert gas into a molten metal. The content of the silica and the chromia therein is 1 to 5 wt% and 1 to 5 wt%, respectively. The content of silica and chromia in the refractory material is 1wt each
%, The amount of melt required for firing is insufficient, and the mechanical strength and spalling resistance of the breathable structure of the refractory for injecting inert gas obtained by firing are reduced. In addition, sufficient corrosion resistance cannot be maintained due to insufficient chromia content. On the other hand, when the content of the silica and the chromia exceeds 5% by weight, it becomes a factor of lowering the melting point of the connective tissue in the air-permeable tissue, and the air permeability varies.

The method for producing a refractory for blowing an inert gas into a molten metal according to claim 6 is the method for producing a refractory for blowing an inert gas into a molten metal according to claim 4 or 5. Corundum and silica are used as a part of the material of the refractory material. The method for producing a refractory for blowing an inert gas into a molten metal according to claim 7 is a method for producing a refractory for blowing an inert gas into a molten metal according to claim 6,
The corundum has a spherical shape. By making the shape of the corundum in the refractory material spherical, variation in the pore size distribution can be suppressed, and a predetermined airflow can be maintained.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described with reference to the accompanying drawings to provide an understanding of the present invention. FIG. 1 is an explanatory view of a continuous casting facility for applying a refractory for injecting an inert gas into a molten metal according to one embodiment of the present invention, and FIGS. FIG. 3 is a side sectional view of a porous plug and a tundish porous plug, and FIG. 3 is a conceptual explanatory view of a ventilation tissue.

First, a continuous casting facility 10 for applying a refractory for blowing an inert gas into a molten metal according to an embodiment of the present invention will be described. As shown in FIG. 1, a continuous casting facility 10 is a molten steel pot 12 that holds a molten steel 11 that is an example of a molten metal, and a molten steel that is an example of an inert gas injection refractory disposed at the bottom of the molten steel pot 12. Porous plug for pot 1
6, a long nozzle 19, a tundish 13 disposed below the molten steel pot 12, and a tundish porous plug 17 which is an example of an inert gas injection refractory disposed at the bottom of the tundish 13. A dipping nozzle 14 attached to the bottom of the tundish 13 and a continuous casting mold 15 into which the molten steel 11 discharged from the dipping nozzle 14 is injected. A cylindrical long nozzle 19 made of alumina carbon or the like is disposed at the bottom of the molten steel pot 12, and the molten steel 11 is supplied to the tundish 13 via the long nozzle 19. In addition, an inert gas such as argon gas or nitrogen gas is supplied into the molten steel 11 from the molten steel pot porous plug 16 at a necessary time such as during continuous casting, and the components and temperature of the molten steel 11 held in the molten steel pot 12 are adjusted. It can be made uniform. The tundish 13 is a container lined with a refractory such as alumina silica, and the surface thereof is coated with a magnesia coating material. The tundish 13 is formed by blowing an inert gas such as argon into the molten steel 11 from a porous plug 17 for tundish. The components and temperature of the molten steel 11 to be held are made uniform. The immersion nozzle 14
It is a generally tubular refractory mainly composed of alumina carbon or the like, and is configured to inject molten steel 11 into a continuous casting mold 15 from a discharge hole 20 provided at a lower portion. Then, a porous brick 18 which is an example of a refractory for injecting an inert gas is placed on one of the tubular inner wall surfaces formed by the outflow holes of the upper nozzle, the sliding nozzle, the lower nozzle, and the immersion nozzle 14 (not shown). Arranged as necessary, and an inert gas can be blown from here.

FIGS. 2A and 2B are side sectional views of the molten steel pot porous plug 16 and the tundish porous plug 17 disposed in the molten steel pot 12 and the tundish 13, respectively. Note that the two types of porous plugs shown in FIGS. 2A and 2B can be exchanged for a molten steel pot and a tundish, respectively, and that only one type of porous plug is used. Can also.
Further, continuous casting can be performed without providing any one of the porous plugs for the molten steel pot and the tundish. As shown in FIG. 2 (a), the molten steel pot porous plug 16 having a substantially truncated cone shape holds a nozzle body made of a refractory portion, and a metal case 26 for sealing an inert gas. A precast sleeve 27 which is a refractory which is disposed on the inner surface side of the metal case 26 and is formed by casting a castable; a gas permeable structure 21 of an inert gas blowing refractory provided with a gas pool 25 at the bottom;
An inert gas introduction pipe attached to the bottom of the metal case; On the other hand, as shown in FIG. 2B, the porous plug 17 for tundish is divided and arranged in two stages of an upper permeable tissue 23 and a lower permeable tissue 24 in which the portion of the permeable tissue 22 has a truncated cone shape. The other structure is the same as the structure of the porous plug 16 for molten steel pot. Thus, in the porous plug 17 for tundish, the air permeable tissue 2
Since the upper gas-permeable surface 23 of the porous plug 17 for tundish is worn out and separated from the lower gas-permeable structure 24 because the 2 is divided into two stages, the area and the shape of the gas discharge surface are dramatically increased. Change. After discharging the molten steel 11 and the like in the tundish 13,
By discharging the gas from the introduction pipe 28, the discharge surface is cooled more than the surrounding precast sleeve 27a. The state of the remaining thickness of the porous plug 17 for tundish at that time can be easily grasped by inspection. The upper permeable tissue 23 and the lower permeable tissue 24 do not need to have the same composition, and the permeable tissue of the present invention is applied only to the upper permeable tissue 23 in which infiltration resistance and the like are particularly problematic. May be.

The precast sleeves 27, 27a are formed by kneading a refractory castable containing a hydraulic component such as alumina cement and mainly composed of alumina siliceous with water, pouring them into a mold and curing them. I do. As another method, the air-permeable tissues 21 and 22 formed and processed in advance are arranged in a metal case 26, and the kneaded material is poured between the air-permeable tissues 21 and 22 and the metal case 26 to be cured, and the mold is formed. It is also possible to form the precast sleeves 27, 27a without using. Then, if necessary, through a mortar or the like, the metal case 26
And precast sleeves 27, 27a and breathable tissue 2
After joining the metal case 1 and the metal case 26, the bottom of the metal case 26 is welded to the introduction pipe 28, and the metal case 26, the precast sleeves 27 and 27a, and the air-permeable structures 21 and 22 are integrated into a molten steel pot. Porous plug 16
In addition, the tundish porous plug 17 can be configured.

Hereinafter, a method for producing the breathable tissues 21 and 22 will be described. First, an inorganic or organic binder such as a phosphate compound and a phenol resin is added to a mixture containing main raw materials such as corundum, chromium oxide, silica, and mullite having a predetermined particle size and a compounding ratio, and the mixture is mixed with water. Knead with. The corundum shape used here is, for example, a spherical shape having a diameter of 1.0 to 1.5 mm, so that the size of air-permeable pores (voids) formed between the respective spherical particles, By maintaining the distribution of pores in an appropriate range, the air-permeable tissues 21 and 22 having a small amount of infiltration layer and a small variation in air permeability can be obtained. FIG. 3 is a conceptual diagram of such air-permeable tissues 21 and 22;
9 are joined by a high melting point component 30 having a melting point of 1800 ° C. or more, and air gaps 31 between the aggregates 29 form air-permeable pores. Here, the particle size of each of the main raw materials and the mixing ratio thereof are 1.0% in the air-permeable structures 21 and 22 after the high-temperature firing treatment at 1800 to 1860 ° C.
It is configured such that the melting point of the joint portion connecting the aggregates 29 having a particle size of about 1.5 mm is 1800 ° C. or more. Specifically, various test proportions, and a number of test compacts having a combination of particle sizes are prepared, and the test compacts are fired at a firing temperature of 1800 to 1860 ° C., and the structure is subjected to an optical microscope, or Electron beam micro analyzer (E
By analyzing using a method such as PMA), the chemical composition of the binding portion can be determined, and the melting point corresponding to the chemical composition can be estimated using an equilibrium diagram or the like.

Next, the obtained kneaded material is supplied into a mold of a press molding machine, and is subjected to pressure molding, whereby a base material for the air-permeable tissues 21 and 22 can be obtained. Then, the base is oxidized or reduced in an atmosphere of 1800 to 18
Sintering is performed at a temperature in the range of 90 ° C. for a predetermined period of time, for example, 1 to 10 hours, and sintered bodies of the permeable structures 21 and 22 are obtained. Such a fired body is subjected to processing such as cutting or grinding as necessary, and finished in a predetermined shape such as a truncated cone, a truncated pyramid, or a quadrangular prism, and finally a desired ventilation property and a bonding state. Can be obtained.

Subsequently, the refractory for injecting an inert gas into the molten metal according to the embodiment of the present invention is used in the continuous casting equipment 1.
The casting method applied to No. 0 will be described. First, 163 from a converter (not shown) having a molten steel capacity of 350 tons is added to the molten steel pot 12.
Inject molten steel 11 at 0 to 1660 ° C. At this time, the molten steel outflow hole of the sliding nozzle (not shown) provided in the molten steel pot 12 is kept closed, and the molten steel 11 is stirred by blowing argon gas from the molten steel pot porous plug 16 provided at the bottom of the molten steel pot 12. I do. At this time, the back pressure (pressure) of the argon gas supplied from the introduction pipe 28 was 4.0 kgf / cm ² , the supply rate of the argon gas was 400 to 1200 NL / min, and the blowing time of the argon gas was per heat. 15-20 minutes. Then, after filling the molten steel 11 into the molten steel pot 12, the molten steel pot 12 is transported to a position above the tundish 13 as shown in FIG. Attach to the bottom following the sliding nozzle. Next, the molten steel outflow hole of the sliding nozzle is opened, and the molten steel 11 is injected into the tundish 13. Then, when the molten steel 11 in the tundish 13 reaches a predetermined level, the molten steel 11 is fed into the continuous casting mold 1 through the immersion nozzle 14.
5 to start continuous casting. During this time, if necessary, argon gas can be blown into the molten steel 11 passing through the tundish 13 or the immersion nozzle 14 via the tundish porous plug 17 and / or the porous brick 18. In this way, when the molten steel 11 held in the molten steel pot 12 is exhausted, the molten steel pot 12 is replaced with another standby molten steel pot 12, whereby continuous casting, that is, continuous casting is performed.

The operation from receiving the molten steel in the ladle 12 to receiving the next steel is called one heat. The next steel receiving operation is performed while checking the air permeability and the remaining thickness of the molten steel pot porous plug 16 before receiving the steel. When checking the air permeability and the remaining thickness, if necessary, oxygen gas is blown from the inner surface side of the molten steel pot 12 to the gas discharge surface of the porous plug 16 for the molten steel pot, so that the metal or slag adhering thereto is adhered. Are melted and removed, safety and the like are checked, and when the remaining thickness is small, this is discarded and replaced with a new molten steel pot porous plug 16. Thus, the number of reuses of the molten steel pot porous plug is a measure of durability. In addition, as the thickness of the infiltration layer is smaller and the oxygen cleaning time is shorter, the degree of damage given to the molten steel pot porous plug can be reduced, and as a result, the durability can be improved.

Here, the examples shown in Table 1 show the specifications of the refractory for blowing an inert gas having the air permeable structure 21 and the results of using the continuous casting. In the examples, the proportion and the particle size of the refractory raw materials including corundum, silica, mullite, chromium oxide and the like were adjusted to obtain alumina (Al ₂ O ₃ ), silica (SiO ₂ ), chromia (Cr ₂ O ₃ ) was 93.0 wt.
%, 4.0 wt%, and 3.0 wt%. Thus, the contents of silica and chromia are each 1 to
In the case where a composition having a range of 5 wt% and a range of 1 to 5 wt% and an alumina content of a range of 90 to 98 wt% is kneaded and molded, and then calcined, the infiltration of metal and slag during use is suppressed. A highly resistant refractory structure is obtained, and since it has a high melting point, air-permeable pores are secured. In the present embodiment, the molded body containing such a refractory material is placed in a normal firing temperature range (1600-1.
By firing at a firing temperature of 1840 ° C. higher than 750 ° C.), an air-permeable structure 21 is obtained. The melting point of the aggregate-bonded portion in the obtained permeable tissue 21 is 1820 ° C., the ratio of pores having a size of 75 μm or less in the pore size distribution is 30%, and the permeability of the permeable tissue 21 is 1.8 cm ³ / cmH ₂ O.・ Cm ²・ s
ec.

[0021]

[Table 1]

The results of use in Table 1 are obtained by applying a number of molten steel pot porous plugs 16 having the same air-permeable structure 21 to obtain respective data, and displaying the average value. During this time, the frequency of gas blowing misfires was 0%, the number of reuse times was 5, the oxygen cleaning time per time was 3 minutes, and the thickness of the slag infiltration layer after use was 2.0 mm. This is because the raw materials used contain few components that have a low melting point, and the firing temperature during production is set to a specific high temperature range, so that the heat resistance of the connective structure between the aggregates is increased and the pore size distribution is increased. Is controlled to be within an appropriate range, and the ventilation stability, the slag infiltration resistance, and the metal infiltration resistance are improved. Incidentally, when the refractories for blowing inert gas shown in the conventional example of Table 1 were used under the same conditions, the frequency of the gas blowing misfire trouble was 1%, and the number of reusing times was 3.5 times, and the number of times of reusing was 3.5 times. The oxygen cleaning time is 5 minutes, and the thickness of the slag infiltration layer after use is 5.0.
mm, which is a very poor result as compared with the embodiment.

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, description has been made mainly of an example in which an inert gas injection refractory is applied to a molten steel pot porous plug of a molten steel pot used for continuous casting.
The refractory for blowing an inert gas of the present invention is not limited to the case of the molten steel pot or the continuous casting, and can be applied to the case where the inert gas is blown into the molten steel to perform a decarburizing treatment or the like.

[0024]

In the refractory for blowing an inert gas into a molten metal according to the first and third aspects of the present invention, the contents of silica, chromia and alumina are set to specific ratios. It is possible to provide a refractory for blowing an inert gas, which has excellent resistance to infiltration of metal and slag during use and has excellent ventilation stability. The refractory for injecting an inert gas into a molten metal according to the second and third aspects has a gas-permeable structure mainly composed of alumina containing specific amounts of silica and chromia, respectively. Therefore, resistance to infiltration of metal and slag during use can be maintained. Furthermore, the portion that becomes the refractory aggregate is 1
Because it is bound by a high melting point component of 800 ° C or more,
The air permeability can be stably maintained at a predetermined level, and the durability can be improved. In particular, in the refractory for injecting an inert gas into a molten metal according to claim 3, since the pore size distribution of the refractory for injecting the inert gas is in a specific range, the refractory for injecting the inert gas into the molten metal. The operation can be stably performed without variation in the ventilation characteristics of the inert gas blown into the air.

According to a fourth aspect of the present invention, there is provided a method for producing a refractory for injecting an inert gas into a molten metal.
Since it is fired at a temperature of 0 to 1860 ° C., it is possible to obtain a breathable structure in which the aggregates are bonded with a high melting point component, and it is possible to produce a breathable structure of a highly durable refractory for blowing an inert gas. . In particular, in the method for producing a refractory for injecting an inert gas into a molten metal according to claim 5, since the content of silica and chromia in the refractory material is in a specific range, an appropriate ventilation rate is maintained. In addition to obtaining a permeable structure, a permeable structure of a refractory for injecting an inert gas with excellent resistance to infiltration into a structure such as metal or slag can be produced. In the method for producing a refractory for blowing an inert gas into a molten metal according to claims 6 and 7, since corundum and silica are used as a part of the raw material of the refractory material, corundum having excellent corrosion resistance is used as an aggregate. Thus, a breathable structure of a highly durable refractory for blowing inert gas can be produced. In the method for producing a refractory for injecting an inert gas into a molten metal according to claim 7, since the corundum has a spherical shape, the breathable structure of the refractory for injecting an inert gas with little variation in permeability is provided. Can be easily manufactured.

[Brief description of the drawings]

FIG. 1 is an explanatory view of a continuous casting facility for applying a refractory for blowing an inert gas into a molten metal according to an embodiment of the present invention.

FIGS. 2A and 2B are side sectional views of a porous plug for a molten steel pot and a porous plug for a tundish, respectively.

FIG. 3 is a conceptual explanatory view of a breathable tissue.

[Explanation of symbols]

Reference Signs List 10 continuous casting equipment 11 molten steel (molten metal) 12 molten steel pot 13 tundish 14 immersion nozzle 15 continuous casting mold 16 porous plug for molten steel pot (refractory for blowing inert gas) 17 porous plug for tundish (inert gas blowing) 18 porous brick (refractory for blowing inert gas) 19 long nozzle 20 discharge hole 21 air-permeable tissue 22 air-permeable tissue 23 upper air-permeable tissue 24 lower air-permeable tissue 25 gas pool 26 metal case 27 precast Sleeve 27a Precast sleeve 28 Inlet tube 29 Aggregate 30 High melting point component 31 Void

Claims (7)

[Claims] 1. Silica and chromia are each 1-5 watts
t%, 1-5 wt%, alumina content 90-9
A refractory for blowing inert gas into molten metal, characterized in that the content is 8 wt%. 2. Silica and chromia are each contained in an amount of 1 to 5 watts.
It has a gas-permeable structure mainly composed of alumina containing 1% to 5% by weight of t%, and a portion of the gas-permeable structure serving as an aggregate is bonded by a high melting point component of 1800 ° C. or more. Refractory for blowing inert gas into molten metal. 3. In the pore size distribution of the refractory for injecting inert gas, the ratio of pores of 75 μm or less is 25 to 50.
%. The refractory for blowing an inert gas into a molten metal according to claim 1 or 2. 4. A method for producing a refractory for blowing an inert gas into a molten metal, comprising forming a refractory material containing alumina, silica, and chromia, followed by firing at a temperature of 1800 to 1860 ° C. 5. The content of the silica and the chromia in the refractory material is 1 to 5 wt% and 1 to 5 wt%, respectively.
The method for producing a refractory for blowing an inert gas into a molten metal according to claim 4, wherein the content is wt%. 6. The method for producing a refractory for blowing an inert gas into a molten metal according to claim 4, wherein corundum and silica are used as a part of the material of the refractory material. 7. The method according to claim 6, wherein the corundum has a spherical shape.