JPH08157252A - Refractory for molten iron preliminary treating vessel - Google Patents

Abstract

PURPOSE: To obtain a high durable brick coping with a severe service condition of the brick for molten iron preliminary treating vessel and having more excellent anti-spalling property, which the brick must have, than the conventional. CONSTITUTION: This brick has preferably thickness of 0.2-2mm and ratio of length or width to thickness of 2-50, contains 3-70wt.% plate-like alumina based fire resisting aggregate and a carbonaceous raw material, silicon carbide, an alumina based fire resisting material and an anti-oxidant are added in the remainder. Then, the improvement of anti-spalling property is attained without decreasing the corrosion resistance and the durability is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a refractory brick used in a processing container for pretreatment of hot metal.

[0002]

2. Description of the Related Art In recent years, with the upgrading of steel, pretreatment such as desiliconization, dephosphorization, and desulfurization of hot metal has been carried out.

[0003] The hot metal ladle and the mixing pig car are assumed to serve not only as a container for carrying hot metal from the blast furnace to the converter but also as a pre-refining container for desiliconization, dephosphorization, desulfurization, etc. of the hot metal. Has become. Refractory for lining as such a pre-refining vessel has spalling resistance, corrosion resistance,
In addition, Al ₂ O ₃ is well balanced in oxidation resistance.
-SiC-C quality unfired bricks are mainly used.

However, recently, in order to improve refining efficiency, the basicity of slag varies widely from 1.0 to 3.0, and slag with strong erosion has come to be adopted, and the operating conditions are more severe. It has become.

Under such a background, although the corrosion resistance of the lining of the hot metal pretreatment container has been improved, on the other hand, the deterioration of the spalling resistance is unavoidable and the cracking and peeling due to the spalling are unavoidable. Therefore, the service life is decreasing.

In order to improve the spalling resistance, one of the methods conventionally used is as follows.
There are approaches from the chemical composition of refractory raw materials. That is, the sponge resistance is improved by increasing the thermal conductivity of the refractory by blending the carbon source or by reducing the thermal stress by increasing the blending amount of the raw material having low thermal expansion and suppressing thermal stress. However, changing the chemical composition of the refractory material for such a hot metal pretreatment container is significantly restricted in the fire resistance of the refractory brick, and is subject to the essence of the refractory brick, which is an increase in erosion due to the refining slag. In many cases, the field of application thereof is severely restricted and cannot be put to practical use.

On the other hand, in place of such a chemical composition of the refractory raw material, by applying a raw material having a specified shape, physical concentration of thermal stress is physically prevented, and spalling resistance is improved by dispersing the thermal stress. An attempt has been made to do so. For example, JP-A-1-305849 and JP-A-54-13.
Japanese Patent No. 0608 discloses the blending of fibrous raw materials such as carbon fibers and metal fibers. Also,
JP-B-58-49514, JP-B-59-3076
No. 2, etc., describes blending a rod-shaped or columnar refractory raw material having a diameter of 2 to 8 mm.

In the case of carbon fiber, however, the fibrous raw material is poor in dispersibility and has a low adhesive strength with the matrix portion, so that the density of the brick tends to decrease. In addition, since the metal fiber melts at a high temperature, there is a limit to the performance of a refractory used at a high temperature. Furthermore, columnar or rod-shaped refractory raw materials tend to break during kneading or forming, which is the manufacturing process of bricks, and the length tends to be shortened.
As described above, a material having a certain thickness is required, and in order to exert the shape effect for improving the spalling resistance, a condition of several tens of millimeters is required. If the above condition is satisfied, the kneading property and moldability of the refractory material will be deteriorated, so that the spalling resistance cannot be improved as planned and the practicality is poor.

[0009]

SUMMARY OF THE INVENTION It is an object of the present invention, without impairing the corrosion resistance in Al ₂ O ₃ -SiC-C brick for hot metal pretreatment vessel (hereinafter referred to as "hot metal pretreatment vessel bricks") It is to greatly improve the spalling resistance.

[0010]

According to the present invention, in a brick for a hot metal pretreatment container, the shape of the alumina aggregate is extremely important for the spalling resistance and is effective for improving the spalling resistance. I found it.

That is, the brick for a hot metal pretreatment container of the present invention contains 3 to 70% by weight, preferably 10 to 70% by weight, of a plate-like alumina refractory aggregate, and the balance is a carbonaceous raw material, silicon carbide, or an alumina type. It is characterized by containing a refractory raw material and an antioxidant.

In particular, the plate-like alumina-based refractory aggregate has a thickness of 0.2 to 2 mm and a surface length or width / thickness (hereinafter referred to as "D ratio") ratio of 2 to 50. preferable.

As the plate-like alumina-based refractory aggregate, a dense high-alumina raw material having a high corrosion resistance with an alumina content of 85% by weight or more is desirable. For example, in consideration of economic efficiency and availability, an alumina-based IC substrate material or the like may be crushed or the like to be used in the above-mentioned shape.

The remaining carbonaceous raw materials, silicon carbide, alumina-based refractory raw materials, and various antioxidants such as various metals may be those normally used in Al ₂ O ₃ --SiC--C bricks, and are not particularly limited. There is not. For example, the alumina-based refractory raw material includes fused alumina, sintered alumina, poxite, bread clay shale, mullite, spinel, and the like, and an alumina raw material having an alumina content of 50% or more can be used. Examples of carbonaceous raw materials include anthracite, natural graphite, earthy graphite, electrode scrap, pitch coke, carbon plaque, and mesophase carbon, in addition to scaly graphite, and one or more of them may be used in combination and used. The amount is generally in the range of 5 to 20% by weight. Silicon carbide is preferably used in an amount of 5 to 10% by weight in consideration of the desired antioxidant effect and corrosion resistance to iron oxide in the slag. Further, as the carbonaceous raw material antioxidant, Al, Si, which are generally used for refractories,
In addition to metals such as Al-Mg alloys, glass, carbides, borides and the like can be mentioned, and it is general to use one kind or two or more kinds in combination.

Further, it is possible to add a magnesia raw material for enhancing the oxidation resistance and imparting the residual expansion property.

Phenol resin is preferable as the binder, and it is used as a so-called unfired brick that has been heat-treated at about 150 to 300 ° C.
A baking treatment at 1000 ° C. or higher can also be performed.

[0017]

[Function] The use of the plate-shaped alumina-based refractory aggregate has a larger effect of suppressing the propagation of cracks generated in the refractory material than that of the commonly used granular alumina raw material. The time required for peeling and peeling is extended, and the spalling resistance is greatly improved. Also,
As a general wear mode of Al ₂ O ₃ —SiC—C bricks for hot metal pretreatment container, there is matrix preceding melt loss, and when this wear mode is worn, the plate-like alumina-based refractory aggregate becomes comb-shaped. It becomes possible to perform slag coating due to the spiking effect of the protrusions and the deposits on the working surface.

Regarding the shape factor, if the D ratio is smaller than 2, the cracks generated in the refractory material propagate and spread, and a part of the refractory material is likely to collapse and fall off. If it is larger than 50, the raw material itself is easily broken. If the thickness of the raw material is smaller than 0.2 mm, the strength is significantly reduced, and the spalling resistance larger than 2 mm is poorly improved. Regarding the composition of the plate-like alumina-based refractory aggregate, if it is less than 3% by weight, the effect of improving the spalling resistance is poor, and if it is more than 70% by weight, the formability is poor and internal cracks may occur. .

[0019]

EXAMPLES Table 1 shows Examples 1 to 11 and Comparative Examples 1 to 3 relating to the brick for a hot metal pretreatment container of the present invention.

[0020]

[Table 1] An appropriate amount of liquid phenolic resin binder is added to each of the raw material compositions shown in Table 1, kneaded and molded by a vacuum friction press, and then dried at 90 ° C. for 24 hours.
Hardened by holding at 0 ℃ for 6 hours, unburned Al ₂ O
_{A 3-} SiC-C quality brick was obtained. Here, as the plate-shaped alumina raw material, a material obtained by crushing an alumina-based IC substrate and adjusting the D ratio was used. Other than that, fused alumina having a purity of 99% was used. As the carbon raw material, scaly graphite having a purity of 98% and silicon carbide having a purity of 97% were used. The plate-like alumina refractory aggregate was oriented perpendicular to the contact surface with the hot metal or slag during molding. This brick was subjected to a corrosion resistance test by the rotary erosion method and a spalling resistance test by immersing it in hot metal at 1500 ° C for 90 seconds and water cooling for 30 seconds and air cooling for 15 minutes. As shown in the table, samples 1 to 11 were obtained. The Al ₂ O ₃ —SiC—C bricks of the example shown have the result that the spalling resistance is improved without lowering the corrosion resistance. In particular, when the thickness of the plate-like alumina-based refractory aggregate is 0.2 to 2 mm and the surface length or width / thickness ratio is 2 to 50, the effect is particularly excellent. There is.

As a comparative example, when only granular fused alumina was used for Comparative Samples 1 to 3 and samples were prepared in the same manner and subjected to the same actual furnace test, as shown in Table 1. I got good results. As can be seen from the table, these comparative examples are inferior in either corrosion resistance or spalling resistance. In particular, the use of the rod-shaped alumina raw material resulted in a poor improvement in spalling resistance as compared with the plate-shaped alumina raw material.

[0022]

According to the present invention, the following effects can be obtained.

(1) For a hot metal pretreatment container, the spalling resistance can be improved without changing the chemical composition and without lowering the corrosion resistance.

(2) By further improving the corrosion resistance and spalling resistance by orienting the plate-shaped alumina-based refractory aggregate in the direction perpendicular to the contact surface with the hot metal or slag by devising the molding method, etc. It can also be improved.

Claims (2)

[Claims] 1. A hot metal pretreatment container comprising 3 to 70% by weight of a plate-shaped alumina-based refractory aggregate, and the balance containing a carbonaceous raw material, silicon carbide, an alumina-based refractory raw material, and an antioxidant. Refractory bricks. 2. The thickness of the plate-shaped alumina-based refractory aggregate is 0.2.
The refractory brick for a hot metal pretreatment container according to claim 1, wherein the refractory brick has a surface length or a width / thickness ratio of 2 to 50 mm.