KR970008705B1 - Refractories brick - Google Patents

Abstract

The refractory bricks having a good rust resistance was manufactured by adding Mg-Al composite metal and chromium oxide into a refractory material of magnesia and chromium. Sintered magnesia clinker containing 0.23 wt.% of SiO2, 0.12 wt.% of Al2O6, 0.06 wt.% of Fe2O6, 0.33 wt.% of CaO, and 99.14 wt.% of MgO, chromium iron ore containing 4.67 wt.% of SiO2, 26.92 wt.% of Al2O6, 12.99 wt.% of Fe2O: , 0.79 wt.% of CaO, and 20.68 wt.% of MgO, 32.88 wt.% of Cr2O6, and chromium oxide contg. 0.02 wt.% of SiO2, 0.01 wt.% of Al2O6, 0.03 wt.% of Fe2O6, 0.01 wt.% of CaO, and 0.01 wt.% of MgO and 99.80 wt.% of Cr2O6 was molded at 800 kg/cm2 with 2.5 wt.% of phenol resin binder, and sintered at 1,750 deg.c to give the brick.

Description

Plastic fireproof brick for refining processing equipment

The present invention relates to a magnesia and chromium refractory bricks used as interior materials of molten metal refining equipment such as AOD, RH furnace and DH furnace. It relates to a plastic refractory brick for refining treatment equipment having a complex addition of chromium oxide and excellent corrosion resistance.

Magnesia-chromiatrile refractory bricks having high fire resistance and excellent corrosion resistance to basic slag have been widely used as internal refractories for molten metal refining treatments such as AOD, RH and DH furnace. However, in recent years, as the demand for high-grade steel increases, secondary refining treatment costs increase, and the lifespan of the internal refractories is problematic in terms of life expectancy management.

Currently used magnesia-chromia refractory brick is a direct bond containing about 10-20% by weight of chromia based on the amount of chromia contained in the entire magnesia-chromia refractory brick. Magnesia-chromia refractory bricks are the mainstream, and magnesia-chromia refractory bricks containing 30% by weight of chromia proposed in Japanese Patent Laid-Open Publication No. 59-190257 are also partially used.

In order to improve the corrosion resistance of the magnesia-chromiatrile refractory brick, a method of promoting sintering by mixing chromium oxide powder, which is a method proposed in Japanese Patent Application Laid-Open No. 57-57428, or having a low porosity regardless of the bonding method In order to improve the corrosion resistance of magnesia-chromiayl refractory bricks through, a method of selecting a particle size formulation capable of closest filling and firing it at 1800 ° C. or higher is generally performed.

In addition to the above methods, conventional methods have been proposed to improve the corrosion resistance of magnesia-chromiayl refractory bricks, and exemplified by Japanese Patent Application Laid-Open No. 4-285059.

Japanese Patent Application Laid-Open No. 4-285059 is a method for improving the corrosion resistance of magnesia-chromium refractory bricks by adding ferrochrome. However, this method has a disadvantage in that the increase in the iron oxide component by the addition of ferrochrome causes bursting by volume change before and after the operation of oxygen blowing, thereby deteriorating the life of the magnesia-chromiac refractory brick.

Accordingly, the present inventors have conducted research and experiments to solve the problems of the conventional methods described above, and the present invention has been proposed based on the results, and the present invention provides a Mg-Al composite metal in a refractory aggregate composed of magnesia and chromiazyl. It is an object of the present invention to provide a fire-resistant brick for refining treatment equipment having excellent corrosion resistance by adding chromium oxide to generate oxidation-expansion of Mg-Al composite metal and secondary spinel MgAlCrO ₄ at the grain boundary during firing.

Hereinafter, the present invention will be described.

The present invention relates to a refractory material comprising an Mg-Al composite metal powder having a particle size of less than 1 mm and an Al content of 25-85 wt%, and a chromic acid powder having a particle size of less than 1 mm in a refractory material composed of magnesia and chromium. It relates to a plastic refractory brick for refining treatment equipment is added by 2 to 10% by weight, respectively.

Hereinafter, the present invention will be described in more detail.

In general, refractory bricks are composed of 3-1mm assembly, 1-0.1m neutral and 0.1mm or less fine grain. Looking at the microstructure of such refractory bricks, the assembly and the neutral are filled with fine grains, and the surrounding part of the assembly and the neutral is a matrix. Therefore, in order to densify the structure of the refractory brick more effectively, it is important to uniformly disperse the Mg-Al composite metal powder and chromium oxide powder in the neutral and matrix portions.

In the present invention, the volume expansion due to the oxidation of the Mg-Al composite metal powder during the firing of the refractory brick contributes to the densification of the magnesia-chromiac refractory brick. In addition, chromium oxide migrates during the firing of refractory bricks, reacts with MgAl ₂ O ₄ produced from composite metal powders, and finally, secondary spinel precipitates at the grain boundaries as MgAl ₂ O _{4, which} is highly corrosion-resistant magnesia-chromiazyl. A refractory brick can be produced.

In order to manufacture the high corrosion-resistant magnesia-chromia refractory bricks in the present invention, the plastic refractory bricks for refining processing equipment has a particle size of less than 1 mm in the refractory material composed of magnesia and chromium, and the content of aluminum is 25 Mg-Al composite metal powder of -85% by weight and chromium oxide powder having a particle size of less than 1 mm are extrapolated to 2-10% by weight, respectively, for the following reasons.

The particle size of the Mg-Al composite metal powder and chromium oxide powder added to the refractory material of magnesia and chromium should be less than 1 mm. When the particle size is 1 mm or more, the oxidation-expansion behavior of the Mg-Al composite metal powder is unstable, so that a refractory brick having a good structure cannot be manufactured. The dispersibility is weakened, making chromium oxide difficult to move during firing. It is because there is a possibility that the corrosion resistance of the magnesia-chromiayl refractory brick is lowered because MgAlCrO _{4 which} is a primary spinel is hard to be produced.

The content of aluminum in the Mg-Al composite metal powder added to the refractory material of magnesia and chromium should be 25 to 85% by weight. The reason is that when the content of aluminum in the composite metal powder is less than 25% by weight, excessive weight of chromium oxide is required and the densification is lowered.When the content of aluminum is more than 85% by weight, the corrosion resistance is increased by increasing the alumina component. This is because it is degraded.

Addition amount of Mg-Al composite metal powder and chromium oxide powder added to the refractory material of magnesia and chromium should be 2 to 10% by weight, respectively. In addition, in the present invention, when the Mg-Al composite metal powder and the chromium oxide powder are not used alone, the Mg-Al composite metal powder and the chromium oxide powder may not be improved due to the densification of the magnesia-chromia refractory brick. It must be compounded.

When the addition amount of either of the Mg-Al composite metal powder and the chromium oxide powder is extrapolated to less than 2% by weight, the amount of secondary spinel precipitated at grain boundary is insufficient or due to the lack of chromium oxide component. Since densification is impossible, the corrosion resistance of the magnesia-chromiayl refractory brick is not improved.

When the added amount of the Mg-Al composite metal powder exceeds 10 wt% by extrapolation, the reaction with the CaO and SIO ₂ components in the slag component is facilitated, and the corrosion resistance of the magnesia-chromiayl refractory brick decreases.

When the amount of added chromium oxide powder is extrapolated by weight, cracks are generated in the magnesia-chromiayl refractory brick, which causes problems such as deterioration of corrosion resistance due to tissue deterioration, and thus cannot be put to practical use.

The raw material for the chromium oxide powder is not particularly limited, but in order to minimize the content of impurities, it is preferably at least 90% pure.

There are no particular limitations on the method of mixing the raw materials in the manufacture of the fire resistant brick for the refining treatment plant of the present invention, but after premixing these raw materials to maximize the reactivity of the Mg-Al composite metal powder and chromium oxide powder It is preferable to mix with magnesia and chromium refractories.

Hereinafter, the present invention will be described in more detail with reference to Examples.

EXAMPLE

After weighing to the composition shown in Table 2 using a sintered magnesia clinker, a natural chromite iron and chromium oxide having the components shown in Table 1, 2.5 wt% of a phenol resin as a binder was added to form a pressure of 800 kg / ㎠ After firing these molded bodies at 1750 ° C. to produce a refractory brick, the working ratio, volume specific gravity, high temperature bending strength and inner finger index were measured, and the results are shown in Table 2 below. Inventive Examples (1-3) and Comparative Example (1-11) was obtained.

TABLE 1

TABLE 2

In Table 2, the content loss index was introduced into a slag having a CaO / SiO ₂ ratio of 2.0 and tested using a rotary erosion tester under conditions of 1700 ° C. × 1 hour × slag slag × 3 repetitions, and Comparative Example 9 was 100. Relative value when

As can be seen in Table 2, the Mg-Al composite metal powder having a particle size of less than 1 mm and an aluminum content of 25-80 wt% and a particle size of less than 1 mm in a refractory material composed of magnesia and chromamizyl In the case of Inventive Example (1-3) in which 2-10% by weight of each compound was extrapolated by extrapolation of chromium oxide powder, the object of the present invention was achieved, but in the case of Comparative Example (1-11) outside the scope of the present invention, It can be seen that the strength and corrosion resistance are reduced.

As described above, the fire resistant brick for the refining treatment plant manufactured according to the present invention has high temperature strength and excellent corrosion resistance. In addition, by adopting Mg-Al composite metal powder and chromium oxide powder in combination with magnesia and chromium, refractory materials for refining processing equipment for stable production of steel and reduction of manufacturing cost can be reduced because of excellent high temperature strength and corrosion resistance. There is an effect that can provide a brick.

Claims (1)

Mg-Al composite metal powder having a particle size of less than 1 mm and an Al content of 25-85% by weight and a chromium oxide powder having a particle size of less than 1 mm are used in the refractory material composed of magnesia and chromiazil, respectively. Plastic refractory brick for refining treatment equipment characterized in that the composition is added by 2-10% by weight.