JPH10297978A - Porous refractory for gas blowing and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the porous refractory having excellent spalling resistance and excellent corrosion resistance by compounding an inorganic refractory raw material, a carbon raw material, one or more kinds of raw materials selected from Si, Al, silicon carbide and boron carbide, and a thermosetting resin, granulating the composition into spherical granules, calcining the granules, further adding the fine powder of an inorganic refractory raw material, Si, Al, etc., to the calcined granules, kneading the mixture, molding the product, drying the molded product, and subsequently calcining the dried product in a reducing atmosphere. SOLUTION: The inorganic refractory raw material includes alumina, and the carbon raw material includes a pitch. The spherical granules produced by the first granulation treatment have a composition comprising 1-10 wt.% of one or more kinds of raw materials selected from Si, Al, silicon carbide and boron carbide, 5-30 wt.% of carbon, and the remainder of an inorganic refractory raw material, and have a particle diameter of 3-0.3 mm. In the second compounding treatment, the spherical granules of inorganic refractory raw material-carbon raw material are added in an amount of 97-80 wt.%. The calcination temperature in the first and second calcination treatments is about 1000 deg.C. The obtained refractory can surely and stably supply a gas to prevent the generation of non-opened pores.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a porous refractory for blowing gas and a method for producing the same.

[0002]

2. Description of the Related Art A porous refractory for gas injection is mounted on the upper plate hole of a slide gate plate provided at the bottom of a molten metal discharge container such as a tundish. By blowing an inert gas such as an argon gas into the molten steel through the porous refractory, the molten steel is stirred to prevent solidification and prevent troubles of non-opening.

In the initial stage of transferring molten steel from a ladle to a tundish in the continuous casting process, pouring from the tundish is not performed until the molten steel has accumulated to a predetermined level. At this time, the molten steel in the slide gate upper plate hole set in the tundish solidifies, which may cause a trouble of non-opening. The same applies to the case where the slide gate plate is closed for some reason in operation.

[0004] In order to prevent such a problem of non-opening due to solidification of molten steel, an inert gas such as argon is blown from the upper plate hole diameter portion. As a gas injection method, a method of injecting gas from a porous refractory attached to the upper plate hole diameter portion, and a method of laser processing a dense refractory such as alumina / carbon by laser processing to a diameter of 0.1 to 1.0 mm.
There is a method in which a through hole is made and gas is blown from there.
A method using a porous refractory is described in, for example, Japanese Patent Publication No. 49-210.
16. A method using a refractory having a through hole is disclosed in, for example, Japanese Patent Publication No. 63-52999.

[0005]

The material of the porous refractory is generally high alumina. A fine powder of silica, alumina, clay, chromium oxide or the like is mixed with alumina aggregate particles, and an organic binder is added. After kneading, molding, and drying, it is manufactured by firing at a high temperature of 1500 ° C. or more in an air atmosphere.

However, the porous refractory produced in this manner has a low strength due to a small number of contact points between particles, and has a high coefficient of thermal expansion due to a high alumina material, and has a problem in spall resistance. For this reason, cracks were generated by the thermal shock at the time of receiving the steel, and molten steel penetrated therefrom, which sometimes led to poor gas blowing.

In addition, since it is a porous body, there is also a problem that molten steel easily infiltrates and causes a problem in gas blowing operation.
In order to suppress such infiltration of molten steel, the addition of chromium oxide is effective. However, when a large amount of chromium oxide is added, there is a problem in disposal of used products.

The dense refractory having the through holes is generally made of high alumina or alumina carbon. For example, in the case of an alumina-carbon refractory, pitch, graphite, alumina fine powder, silicon, etc. are first added to alumina particles, a thermosetting resin is added, kneading, molding, drying, and firing in a reducing atmosphere to obtain a dense Obtain refractory. Further, if necessary, a tar pitch is impregnated, heat treatment is performed, and a through hole of about 40 to 60 is formed by a laser processing machine.

However, while gas is supplied to the entire surface of the porous refractory within the hole diameter, a dead zone in which gas is not supplied to the through-hole type refractory is formed between the through-holes.
Therefore, there were cases where the molten steel solidified and the hole diameter portion was blocked.
Further, there is a problem that the laser processing apparatus itself is considerably expensive, the processing cost per unit is high, and the cost is higher than that of the porous refractory.

[0010] In order to solve the problems of the prior art, it has excellent spall resistance and corrosion resistance, can stably supply gas, and can reliably prevent the generation of non-opening. It is an object of the present invention to provide a porous gas refractory for gas injection and a method for producing the same.

[0011]

The first invention of the present application is directed to an inorganic refractory raw material such as alumina, a carbon raw material such as pitch, and at least one raw material selected from silicon, aluminum, silicon carbide and boron carbide. And adding a thermosetting resin to the mixture, granulating the mixture into a spherical or nearly spherical shape, and firing this in a reducing atmosphere to form aggregates of spherical particles,
Fine powder of an inorganic refractory raw material such as alumina and at least one or more raw materials selected from silicon, aluminum, silicon carbide and boron carbide are added to the spherical particle aggregate, and a thermosetting resin is further added and kneaded. A method for producing a porous refractory for gas injection, comprising forming, drying, and firing in a reducing atmosphere.

The second invention of the present application is directed to a spherical particle aggregate comprising an inorganic refractory raw material such as alumina, a carbon raw material such as pitch, and at least one raw material selected from silicon, aluminum, silicon carbide and boron carbide. And a fine powder of an inorganic refractory raw material such as alumina, and at least one or more raw materials selected from silicon, aluminum, silicon carbide and boron carbide. The subject is the gist.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The method for producing a porous refractory for gas injection according to the present invention is selected from an inorganic refractory raw material such as alumina, a carbon raw material such as pitch, silicon, aluminum, silicon carbide and boron carbide. At least one or more raw materials are mixed, a thermosetting resin is added thereto, and the mixture is granulated into a spherical shape or a shape close to a spherical shape, which is fired in a reducing atmosphere to obtain an aggregate of spherical particles. Fine powder of an inorganic refractory raw material such as alumina and at least one or more raw materials selected from silicon, aluminum, silicon carbide, and boron carbide are added to the material, and a thermosetting resin is further added, and kneading, molding, and drying are performed. Thereafter, firing in a reducing atmosphere is characterized.

The present inventors have conducted intensive studies to improve the spall resistance of a porous refractory without adding chromium oxide, which is difficult to dispose, and as a result, the inorganic refractory raw material and carbon material as described above were used. It has been found that it is effective to use spherical particles granulated into a spherical shape or a shape close to a spherical shape as an aggregate.

By using such an aggregate, it is possible to produce a porous refractory for gas injection which is excellent in spall resistance, can supply a stable gas, and has no disposal problem.

The reason why spherical particles obtained by granulating a composition mainly composed of an inorganic refractory raw material and a carbon raw material are used as the aggregate is as follows. In other words, by using inorganic refractory raw materials and carbonaceous spherical particles as aggregates, it is possible to obtain a high thermal conductivity and a low coefficient of thermal expansion as compared with conventional alumina aggregate porous refractories, and to achieve a high spall resistance. Can be improved. In addition, since the aggregate is spherical particles of a carbon-containing refractory, the aggregate is hardly wet by molten steel and slag, so that infiltration of molten steel can be suppressed.

The reason for granulating the inorganic refractory raw material / carbonaceous particles into a spherical shape or a shape close to a spherical shape is as follows. It is well known that when non-spherical particles, such as massive fused alumina particles, which have conventionally been used in porous refractories, are used, the distribution width of pore diameters becomes wide. That is, the filling is likely to be non-uniform, and fine pores that hardly contribute to gas blowing are formed from relatively large pores that easily infiltrate the molten steel. On the other hand, when spherical particles are used, the particles can be more uniformly filled, so that the particles can be more uniformly filled and the distribution width of the pore diameter can be narrowed. Therefore, coarse pores are not formed and both suppression of infiltration of molten steel and securing of gas flow can be realized.

The spherical or nearly spherical inorganic refractory raw material and carbonaceous spherical particles used in the present invention can be produced, for example, as follows. A predetermined amount of commercially available sintered alumina, soil graphite, and silicon fine powder are blended, and an appropriate amount of phenol resin is added to the mixture, and the mixture is granulated to a predetermined particle size in a spherical or nearly spherical shape using a rolling granulator. After drying, firing is performed in a reducing atmosphere to obtain alumina-carbonaceous spherical particles.

The inorganic refractory raw material and carbonaceous spherical particles having a spherical shape or a shape close to a spherical shape are made of carbon raw material 5 to 30.
wt%, at least one or more raw materials selected from silicon, aluminum, silicon carbide, and boron carbide in an amount of 1 to 10 wt%, and the balance can be formed of an inorganic refractory raw material such as alumina.

The carbon raw material has the effect of improving the spall resistance by lowering the coefficient of thermal expansion and increasing the thermal conductivity and improving the wet resistance to molten steel and slag.
0 wt% is preferred. If the added amount of the carbon material is less than 5 wt%, the effect of improving the spall resistance is not sufficient, and if it exceeds 30 wt%, the corrosion resistance as spherical particles decreases. From such a viewpoint, the more preferable addition amount of the carbon raw material is 10 to 20 wt%.

Fine powder raw materials such as silicon and aluminum have an effect of improving the strength of inorganic refractory raw materials and carbonaceous spherical particles and preventing deterioration in properties such as strength due to oxidation, and the addition amount thereof is preferably 1 to 10% by weight. These fine powder raw materials are 1wt
%, The particle strength is low and there is a problem in moldability.
If it exceeds 0 wt%, the corrosion resistance as spherical particles will be reduced. From such a viewpoint, the addition amount of the fine powder material such as silicon and aluminum is more preferably 3 to 8 wt%.

The particle size of the fine powder raw material is preferably finer from the viewpoint of dispersibility and reactivity in order to surely obtain the preferable characteristics as described above, and is desirably set to 74 μm or less.
More preferably, it is 44 μm or less.

The inorganic refractory raw material used is not particularly limited, and may be alumina, magnesium, zirconia, mullite,
Spinel, alumina / zirconia, zirconia / mullite, etc. can be used. These raw materials can be selected in an appropriate amount according to the use conditions such as the type of steel and the required corrosion resistance or spall resistance.

The particle diameter of the inorganic refractory raw material / carbon spherical particles is preferably 3 to 0.3 mm, more preferably 1.0 to 0.5 mm. If the particle size is less than 0.3 mm, the pore diameter becomes small and it is difficult to secure a required gas flow rate.If it exceeds 3 mm, the pores formed by filling the particles become large and the effect of suppressing molten steel infiltration becomes low, Further, the number of contact points between the particles is reduced, and the strength as a product is reduced.

The addition amount of the inorganic refractory raw material and carbonaceous spherical particles is preferably 97 to 80 wt%, more preferably 85 to 95 wt%. If the content exceeds 97 wt%, the fine powder portion is small, and sufficient strength as a product cannot be obtained.
If it is less than t%, the amount of fine powder increases, and it becomes impossible to secure a necessary gas flow rate.

The porous refractory for gas injection according to the present invention comprises an inorganic refractory raw material such as alumina, a carbon raw material such as pitch, and at least one raw material selected from silicon, aluminum, silicon carbide and boron carbide. Characterized in that it is obtained by mixing fine powder of an inorganic refractory raw material such as alumina and at least one or more raw materials selected from silicon, aluminum, silicon carbide and boron carbide. .

[0027]

EXAMPLES The present invention will now be described in detail with reference to Examples, but the Examples are intended to facilitate or promote the practice of the present invention, and do not limit the present invention.

Alumina fine powder, pitch, soil graphite, silicon, aluminum, and silicon carbide were blended at the ratios shown in Tables 1 to 3, and an appropriate amount of phenol resin was added thereto. Thus, a granulated product was obtained. This was dried at 200 ° C., baked at a temperature of 1000 ° C. in a reducing atmosphere, and then classified to a predetermined particle size to obtain alumina-carbon spherical particles.

[0029] The spherical particles thus obtained are used as aggregates, to which inorganic refractory raw materials, silicon and aluminum are added, phenol resin is further added, kneaded and molded in a wet pan, and dried at 200 ° C. 1000 under reducing atmosphere
Calcination was carried out at ℃ to obtain a porous refractory.

From the porous refractory, a diameter 50 × height 50
A test piece having a shape of mm was cut out, and apparent porosity, compressive strength, and air permeability were measured.

Similarly, a test piece having a shape of 25 × 130 mm was cut out and subjected to a spalling test and an erosion test. That is, 10r is contained in the molten steel melted in the induction furnace.
After being immersed for a predetermined time while rotating at pm, the sample was cut and the state of crack generation, the amount of corrosion, and the amount of infiltration of molten steel and slag were compared.

In addition, as an actual machine test, a porous refractory manufactured in a ring shape was attached to the upper plate hole diameter portion, and it was set on a 30-ton tundish, and the plate was closed during initial opening and during operation. The state of opening when opened was examined.

Hereinafter, these results will be examined.

First, with reference to Table 1, the physical properties and the actual machine test depending on the composition of the alumina-carbonaceous spherical particles used as the aggregate of the porous refractory are compared. Examples 1 to 5 are included in the scope of the present invention, Comparative Examples 1 and 2 use carbon materials outside the scope of the present invention, and Comparative Examples 3 and 4 use amounts of raw materials such as silicon and aluminum. It is outside the scope of the present invention.

As a result of the actual machine test, Examples 1 to 5 were able to open holes without any problem even after the SG plate was once closed at the time of initial opening and casting.

On the other hand, in Comparative Example 1, cracks were generated in the porous refractory due to the thermal shock at the time of receiving the steel, and molten steel penetrated therefrom so that gas could not be blown out. became. This can be presumed to be due to insufficient spall resistance.

In Comparative Examples 2 and 4, there was no problem with the initial opening, but the use was stopped halfway due to large melt damage and a problem in controlling the flow rate of molten steel. This can be presumed to be due to the poor corrosion resistance of the porous refractory.

In Comparative Example 3, since the particle strength was low and the spherical particles were crushed at the time of molding, a product as designed could not be obtained.

Next, with reference to Table 2, the physical properties of the porous refractory due to the difference in the diameter of the spherical particles of alumina and carbonaceous materials and the results of actual machine tests will be examined. Examples 6 and 7 are included in the scope of the present invention, and Comparative Examples 5 and 6 are outside the scope of the present invention.

In Examples 6 and 7, good results were obtained, whereas in Comparative Example 5, the gas flow did not reach the standard, so that no actual machine test was performed.

In Comparative Example 6, gas infiltration was not possible when the SG plate was once opened because the infiltration of the molten steel was large, and the molten steel solidified inside the hole diameter and became unopened.

Finally, with reference to Table 3, the physical properties of the porous refractory due to the difference in the amount of the alumina-carbon spherical particles added thereto and the results of the actual machine test will be examined. Example 8-
10 is included in the category of the present invention, and Comparative Examples 7 and 8 are out of the scope of the present invention.

While good results were obtained in Examples 8 to 10, Comparative Example 7 had low spall resistance due to insufficient strength, and cracks were generated in the porous refractory due to thermal shock.
From there, the molten steel entered and gas blowing became impossible, and the molten steel solidified inside the hole diameter to form unopened holes.

In Comparative Example 8, since the gas flow rate did not reach the standard, the actual machine test was not completed.

[0045]

The porous refractory for gas injection according to the present invention has both excellent spall resistance and corrosion resistance. By stably supplying the gas, it is possible to reliably prevent the generation of unopened holes and to reduce chromium oxide. Since it is not included, there is no problem of disposal.

Although the embodiment has been described with respect to the ring-shaped refractory for gas injection mounted on the upper plate, the refractory of the present invention can be applied to a porous portion of a porous upper nozzle or the like.

[Table 1]

[Table 2]

[Table 3]

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Isao Watanabe 1st Minamito, Ogakie-cho, Kariya-shi, Aichi Pref. Toshiba Cellular Co., Ltd. Lamix Corporation Kariya Factory

Claims (5)

[Claims] An inorganic refractory raw material such as alumina, a carbon raw material such as pitch, and at least one or more raw materials selected from silicon, aluminum, silicon carbide and boron carbide are blended with a thermosetting raw material. A resin is added and granulated into a spherical shape or a shape close to a spherical shape, which is baked in a reducing atmosphere to obtain an aggregate of spherical particles.The fine particles of an inorganic refractory raw material such as alumina, silicon, At least one or more raw materials selected from aluminum, silicon carbide, and boron carbide are added, and a thermosetting resin is further added, kneaded, molded, dried, and then fired in a reducing atmosphere. How to make refractories. 2. The method according to claim 1, wherein the spherical particles formed into a spherical shape or a shape close to a spherical shape include at least one raw material selected from silicon, aluminum, silicon carbide and boron carbide in an amount of 1 to 10 wt.
2. The method for producing a porous refractory for gas injection according to claim 1, wherein the composition has a composition comprising 5% by weight of carbon, 5 to 30% by weight of carbon, and the balance being an inorganic refractory raw material. 3. The porous refractory for gas injection according to claim 1, wherein the spherical particles formed into a spherical shape or a shape close to a spherical shape have a particle diameter of 3 to 0.3 mm. Production method. 4. The gas injection device according to claim 1, wherein an addition amount of the spherical particles formed into a spherical shape or a shape close to a spherical shape is 97 to 80 wt%. Manufacturing method of porous refractory. 5. A spherical particle aggregate comprising an inorganic refractory raw material such as alumina, a carbon raw material such as pitch, and at least one raw material selected from silicon, aluminum, silicon carbide and boron carbide. A porous refractory for gas injection, characterized by mixing fine powder of an inorganic refractory raw material such as alumina and at least one or more raw materials selected from silicon, aluminum, silicon carbide and boron carbide.