CN102320845A - An Al2O3-SiO2 tundish breathable brick and its preparation method - Google Patents

Abstract

The invention relates to an Al ₂ O ₃ -SiO ₂ tundish breathable brick and a preparation method thereof. 65-78wt% platy corundum particles, 7-20wt% mullite particles, 2-10wt% white corundum fine powder _, 1-4wt% ρ- _Al2O3 fine powder and 1-3wt% Silica powder as raw material, with 0.10~0.20wt% mixture of sodium hexametaphosphate and sodium tripolyphosphate, 0.05~0.20wt% yellow dextrin, 0.01~0.20wt% azodicarbonamide, 1~4wt% Al ₂ O ₃ -SiO ₂ gel powder and 0.20-1.0 wt% aluminum fluoride are additives. The preparation method is: premix the admixture and silicon micropowder evenly according to the content, add platy corundum particles and mullite particles for mixing and grinding, then add white corundum fine powder and ρ-Al ₂ O ₃ fine powder for mixing and grinding, and then add 5-7wt% water, stirring, pouring, molding, heat preservation at 110-200°C for 12-48 hours, and finally firing at 1200-1500°C for 3 hours. The prepared breathable brick has good air permeability, high strength, erosion resistance and environmental friendliness.

Description

An Al2O3-SiO2 tundish breathable brick and its preparation method

technical field

The invention belongs to the technical field of Al ₂ O ₃ -SiO ₂ refractory materials. It specifically relates to an Al ₂ O ₃ -SiO ₂ tundish breathable brick and a preparation method thereof.

Background technique

With the development of tundish metallurgical technology, blowing inert gas into the molten steel for stirring through the breathable brick installed at the bottom of the tundish can not only effectively improve the flow of molten steel, prolong the residence time of molten steel, and promote the mixing of molten steel It is conducive to uniform temperature, and can use the generated micro-bubbles to capture inclusions, promote the floating and removal of inclusions, reduce the total oxygen content in molten steel, and facilitate the production of clean steel. Therefore, it is an important subject to develop a tundish diffused air brick with good air permeability, thermal shock stability, high strength and resistance to steel slag penetration and erosion.

The alkaline material (MgO) used in the early permeable bricks has the problems of poor peeling and thermal shock resistance, so such products are rarely used at present. In contrast, corundum material has the characteristics of good high temperature performance, thermal shock resistance and relatively large wetting angle to molten steel, and has become the main material to replace magnesia material. However, due to the poor corrosion resistance of pure corundum gas permeable bricks during use, and serious peeling off, people have carried out research on Al ₂ O ₃ -MgO materials. MgO is usually added in the form of fine powder. During the firing process, it reacts with Al ₂ O ₃ to form spinel. The expansion coefficient of the material increases and the structure becomes denser. Although the corrosion resistance and oxidation resistance of the permeable brick are improved, But its breathability is seriously affected.

While ensuring the air permeability of the diffused air permeable brick, it has good high-temperature mechanical strength, load softening temperature and thermal shock stability. People have invented corundum-mullite tundish breathable bricks with in-situ reinforcement of mullite whiskers, such as the patented technology of "a tundish breathable brick and its preparation method" (CN1699267A) which uses mullite as dry gel powder The form is added to generate mullite whiskers, which maintains air permeability and increases strength. However, the dry gel powder is not easy to disperse, the pores are unevenly distributed, there are still many large pores, the steel slag is easy to penetrate and corrode, resulting in short life, and the introduction of whiskers also seals many through pores, and its efficiency needs to be improved.

Contents of the invention

The purpose of the present invention is to overcome the defects of the existing technology, and the purpose is to provide an Al ₂ O ₃ with high apparent porosity, good gas permeability, high strength, thermal shock resistance, steel slag penetration resistance, erosion resistance, environmental friendliness and long service life. -SiO ₂ tundish breathable brick and its preparation method.

In order to achieve the above tasks, the technical solution adopted by the present invention is: the raw materials and mass percentages of the tundish air brick are: 65-78wt% platy corundum particles, 7-20wt% mullite particles, 2 ~10wt% white corundum fine powder, 1~4wt% ρ-Al ₂ O ₃ fine powder, 1~3wt% silicon micropowder.

Taking the above raw materials as mass percentage, add the following additives: 0.10-0.20wt% mixture of sodium hexametaphosphate and sodium tripolyphosphate, 0.05-0.20wt% yellow dextrin, 0.01-0.20wt% azobis Formamide, 1-4wt% Al ₂ O ₃ -SiO ₂ gel powder, 0.20-1.0wt% aluminum fluoride.

According to the mass percentage of the above-mentioned raw materials and additives, the additives and silicon micropowder are pre-mixed uniformly to make a premix; grinding; then white corundum fine powder, ρ-Al ₂ O ₃ fine powder and mixed grinding material are mixed, and 5-7wt% of water is added to the above-mentioned raw materials, stirred evenly, poured, vibrated and formed, and the green body after forming is at 110- Insulate at 200°C for 12-48 hours, and finally fire at 1200-1500°C for 3 hours.

In the above technical scheme: the Al ₂ O ₃ content of the platy corundum particles is >95wt%, and its particle size is 3-0.088 mm; the Al ₂ O ₃ content of the mullite particles is > 65 wt%, and its particle size is 1-0.088mm mm; Al ₂ O ₃ content of white corundum fine powder > 99wt%, and its particle size <0.088mm; Al 2 O ₃ content of ρ-Al ₂ O ₃ fine powder > 99wt%, and its particle size <_0.01mm; SiO ₂ content>92wt%, its particle size<0.001mm; the mixture of sodium hexametaphosphate and sodium tripolyphosphate is a mixture of sodium hexametaphosphate: sodium tripolyphosphate with a mass ratio of 2:1; Al ₂ O ₃ -SiO ₂ gel powder is a gel made of sol-gel mullite precursor, which is dried at 110°C×24h; the decomposition temperature of azodicarbonamide is 120-180°C, and its particle size <0.005mm.

Due to the adoption of the above technical scheme, the present invention premixes azodicarbonamide, silicon micropowder and yellow dextrin to eliminate the agglomeration and agglomeration of azodicarbonamide, ensure its dispersibility, and the acidic environment constructed avoids accidental Decomposition of azodicarbonamide at room temperature; when heat-treated, azodicarbonamide decomposes rapidly, using bubbles to grow rapidly on the polymer melt to generate a large tensile stress, resulting in an in-situ expansion-cracking effect, and realizing fine alumina Uniform dispersion of powder, mullite xerogel powder, yellow dextrin, silica powder, etc. As a result, the evenly distributed alumina fine powder and silicon micropowder react in situ to form a more reasonable mullite network structure, and the mullite whiskers are better formed, with better aspect ratio, more uniform distribution, and less likely to block pores. The air permeability and strength of the breathable brick are greatly improved, and the steel slag is not easy to penetrate and corrode. The Al ₂ O ₃ -SiO ₂ tundish breathable brick prepared by the present invention has an apparent porosity of 35-45%, an average pore diameter of 1-10 μm, and an air permeability of 20-20 μm after being fired at 1200-1500 ° C for 3 hours. 40μm ² and compressive strength of 40 ~ 60MPa.

Therefore, the breathable brick prepared by this method has the characteristics of high apparent porosity, good air permeability, high strength, thermal shock resistance, steel slag penetration resistance, erosion resistance, environmental friendliness and long service life.

Detailed ways

The present invention will be further described below in combination with specific embodiments, which are not intended to limit the protection scope thereof.

In order to avoid duplication, the technical parameters of the raw materials involved in this specific embodiment and the admixture are first described as follows, and will not be repeated in the examples:

The Al ₂ O ₃ content of the platy corundum particles is > 95wt%, and its particle size is 3-0.088mm; the Al ₂ O ₃ content of the mullite particles is > 65wt%, and its particle size is 1-0.088mm; white corundum fine powder The Al ₂ O ₃ content of ρ-Al ₂ O ₃ fine powder>99wt%, its particle size<0.088mm; the Al 2 _O 3 content of ρ-Al ₂ O ₃ fine powder>99wt%, its particle size<0.01mm; %, its particle size <0.001mm; the mixture of sodium hexametaphosphate and sodium tripolyphosphate is a mixture of sodium hexametaphosphate: sodium tripolyphosphate with a mass ratio of 2:1; Al ₂ O ₃ -SiO ₂ gel powder The gel prepared for the sol-gel mullite precursor is dried under the condition of 110°C×24h; the decomposition temperature of azodicarbonamide is 120-180°C, and its particle size is less than 0.005mm.

Example 1

An Al ₂ O ₃ -SiO ₂ tundish breathable brick and a preparation method thereof. The raw materials and mass percentages of the tundish air brick are: 65-70wt% of platy corundum particles, 15-20wt% of mullite particles, 8-10wt% of white corundum fine powder, 2-4wt% of ρ-Al ₂ O ₃ fine powder, 2-3 wt% silicon micropowder.

Taking the above raw materials as mass percentage, add the following additives: 0.10-0.15wt% mixture of sodium hexametaphosphate and sodium tripolyphosphate, 0.05-0.10wt% yellow dextrin, 0.01-0.05wt% azobis Formamide, 1-2wt% Al ₂ O ₃ -SiO ₂ gel powder, 0.20-0.50wt% aluminum fluoride.

According to the mass percentage of the above-mentioned raw materials and additives, the additives and silicon micropowder are pre-mixed uniformly to make a premix; grinding; then mix white corundum fine powder, ρ-Al ₂ O ₃ fine powder and the mixed grinding material, add 5-6wt% water of the above-mentioned raw materials, stir evenly, pour, vibrate and form, and the green body after forming is at 110- Keep warm at 160°C for 24-48 hours, and finally fire at 1200-1300°C for 3 hours.

The apparent porosity of the Al ₂ O ₃ -SiO ₂ tundish air brick produced in Example 1 is 35-40%, the average pore diameter is 1-6 μm, and the air permeability is 20 ～28μm ² , the compressive strength is 40～48MPa.

Example 2

An Al ₂ O ₃ -SiO ₂ tundish breathable brick and a preparation method thereof. The raw materials and mass percentages of the tundish breathable brick are: 68-72wt% of platy corundum particles, 12-18wt% of mullite particles, 7-9wt% of white corundum fine powder, 1-3wt% of ρ-Al ₂ O ₃ fine powder, 2-3 wt% silicon micropowder.

Taking the above raw materials as mass percentage, add the following additives: 0.12-0.18wt% mixture of sodium hexametaphosphate and sodium tripolyphosphate, 0.08-0.13wt% yellow dextrin, 0.05-0.10wt% azobis Formamide, 2-3 wt% Al ₂ O ₃ -SiO ₂ gel powder, 0.40-0.70 wt% aluminum fluoride.

According to the mass percentage of the above-mentioned raw materials and additives, the additives and silicon micropowder are pre-mixed uniformly to make a premix; grinding; then white corundum fine powder, ρ-Al ₂ O ₃ fine powder and mixed grinding material are mixed, and 6-7wt% water of the above-mentioned raw materials is added, stirred evenly, poured, vibrated and formed, and the green body after forming is at 150- Keep warm at 200°C for 12-24 hours, and finally fire at 1300-1400°C for 3 hours.

The apparent porosity of the Al ₂ O ₃ -SiO ₂ tundish breathable brick prepared in Example 2 is 38-42%, the average pore diameter is 3-8 μm, and the air permeability is 25 ~32μm ² , the compressive strength is 45~50MPa.

Example 3

An Al ₂ O ₃ -SiO ₂ tundish breathable brick and a preparation method thereof. The raw materials and mass percentages of the tundish air brick are: 70-75wt% platy corundum particles, 10-17wt% mullite particles, 5-8wt% white corundum fine powder, 2-4wt% ρ-Al ₂ O ₃ fine powder, 1-2 wt% silicon micropowder.

Taking the above raw materials as mass percentage, add the following additives: 0.15-0.20wt% mixture of sodium hexametaphosphate and sodium tripolyphosphate, 0.10-0.15wt% yellow dextrin, 0.10-0.15wt% azobis Formamide, 3-4 wt% Al ₂ O ₃ -SiO ₂ gel powder, 0.50-0.80 wt% aluminum fluoride.

According to the mass percentage of the above-mentioned raw materials and additives, the additives and silicon micropowder are pre-mixed uniformly to make a premix; grinding; then mix white corundum fine powder, ρ-Al ₂ O ₃ fine powder and the mixed grinding material, add 5-6wt% water of the above-mentioned raw materials, stir evenly, pour, vibrate and form, and the green body after forming is at 110- Keep warm at 160°C for 24-48 hours, and finally fire at 1400-1500°C for 3 hours.

The apparent porosity of the Al ₂ O ₃ -SiO ₂ tundish breathable brick prepared in Example 3 is 40-44%, the average pore diameter is 4-9 μm, and the air permeability is 28 ~35μm ² , the compressive strength is 50~55MPa.

Example 4

An Al ₂ O ₃ -SiO ₂ tundish breathable brick and a preparation method thereof. The raw materials and mass percentages of the tundish air brick are: 74-78wt% platy corundum particles, 7-15wt% mullite particles, 2-7wt% white corundum fine powder, 1-3wt% ρ-Al ₂ O ₃ fine powder, 1-2 wt% silicon micropowder.

Taking the above raw materials as mass percentage, add the following additives: 0.12-0.18wt% mixture of sodium hexametaphosphate and sodium tripolyphosphate, 0.14-0.20wt% yellow dextrin, 0.15-0.20wt% azobis Formamide, 2-3 wt% Al ₂ O ₃ -SiO ₂ gel powder, 0.70-1.0 wt% aluminum fluoride.

According to the mass percentage of the above-mentioned raw materials and additives, the additives and silicon micropowder are pre-mixed uniformly to make a premix; grinding; then white corundum fine powder, ρ-Al ₂ O ₃ fine powder and mixed grinding material are mixed, and 6-7wt% water of the above-mentioned raw materials is added, stirred evenly, poured, vibrated and formed, and the green body after forming is at 150- Keep warm at 200°C for 12-24 hours, and finally fire at 1300-1400°C for 3 hours.

The apparent porosity of the Al ₂ O ₃ -SiO ₂ tundish breathable brick prepared in Example 4 is 42-45%, the average pore diameter is 6-10 μm, and the air permeability is 32 ~40μm ² , the compressive strength is 55~60MPa.

In this specific embodiment, premixing azodicarbonamide with silicon micropowder and yellow dextrin can eliminate the agglomeration and agglomeration of azodicarbonamide, ensure its dispersibility, and the slightly acidic environment constructed avoids azodicarbonamide Decomposition at room temperature; when heat-treated, azodicarbonamide decomposes rapidly, and uses bubbles to grow rapidly on the polymer melt to generate a large tensile stress, resulting in in-situ expansion-cracking effect, and realizes alumina fine powder, molybdenum Uniform dispersion of stone xerogel powder, yellow dextrin, silicon micropowder, etc. As a result, the evenly distributed alumina fine powder and silicon micropowder react in situ to form a more reasonable mullite network structure, and the mullite whiskers are better formed, with better aspect ratio, more uniform distribution, and less likely to block pores. The air permeability and strength of the breathable brick are greatly improved, and the steel slag is not easy to penetrate and corrode. The Al ₂ O ₃ -SiO ₂ tundish breathable brick prepared in this specific embodiment has an apparent porosity of 35-45%, an average pore diameter of 1-10 μm, and an air permeability of 20 ~ 40μm ² and compressive strength of 40 ~ 60MPa.

Therefore, the Al ₂ O ₃ -SiO ₂ tundish breathable brick prepared in this specific embodiment has high apparent porosity, good air permeability, high strength, thermal shock resistance, steel slag penetration resistance, erosion resistance, environmental friendliness and use Long life characteristics.

Claims (10)

1. Al ₂O ₃-SiO ₂The preparation method of matter tundish gas permeable brick is characterized in that the raw material of this tundish gas permeable brick and quality percentage composition thereof are: the plate diamond spar particle of 65～78wt%, the mullite particle of 7～20wt%, the white fused alumina fine powder of 2～10wt%, ρ-Al of 1～4wt% ₂O ₃Fine powder, the silicon powder of 1～3wt%;

With the above-mentioned raw materials is mass percent, adds the Sodium hexametaphosphate 99 of following admixture: 0.10～0.20wt% and the mixture of tripoly phosphate sodium STPP, the yellow starch gum of 0.05～0.20wt%, the Cellmic C 121 of 0.01～0.20wt%, the Al of 1～4wt% again ₂O ₃-SiO ₂The gel powder, the ALUMNIUM FLUORIDE of 0.20～1.0wt%;

Press the quality percentage composition of above-mentioned raw materials and admixture, earlier that admixture and silicon powder premix is even, process Preblend; Again plate diamond spar particle, mullite particle and Preblend are mixed and grind, process to mix and grind material; Then with white fused alumina fine powder, ρ-Al ₂O ₃Fine powder with mix to grind material and mix, add the water of above-mentioned raw materials 5～7wt%, stir, cast, vibratory compaction, the base substrate after the moulding is incubated 12～48 hours under 110～200 ℃ of conditions, under 1200～1500 ℃ of conditions, burnt till in 3 hours at last.

2. Al according to claim 1 ₂O ₃-SiO ₂The preparation method of matter tundish gas permeable brick is characterized in that described plate diamond spar particulate Al ₂O ₃Content＞95wt%, its particle diameter are 3～0.088mm.

3. Al according to claim 1 ₂O ₃-SiO ₂The preparation method of matter tundish gas permeable brick is characterized in that the Al of described mullite particle ₂O ₃Content＞65wt%, its particle diameter are 1～0.088mm.

4. Al according to claim 1 ₂O ₃-SiO ₂The preparation method of matter tundish gas permeable brick is characterized in that the Al of described white fused alumina fine powder ₂O ₃Content＞99wt%, its particle diameter＜0.088mm.

5. Al according to claim 1 ₂O ₃-SiO ₂The preparation method of matter tundish gas permeable brick is characterized in that described ρ-Al ₂O ₃The Al of fine powder ₂O ₃Content＞99wt%, its particle diameter＜0.01mm.

6. Al according to claim 1 ₂O ₃-SiO ₂The preparation method of matter tundish gas permeable brick is characterized in that the SiO of described silicon powder ₂Content＞92wt%, its particle diameter＜0.001mm.

7. Al according to claim 1 ₂O ₃-SiO ₂The preparation method of matter tundish gas permeable brick, the mixture that it is characterized in that described Sodium hexametaphosphate 99 and tripoly phosphate sodium STPP is a Sodium hexametaphosphate 99: the mass ratio of tripoly phosphate sodium STPP is 2: 1 a mixture.

8. Al according to claim 1 ₂O ₃-SiO ₂The preparation method of matter tundish gas permeable brick is characterized in that described Al ₂O ₃-SiO ₂The gel powder be the sol-gel mullite precursor made gel, under 110 ℃ * 24h condition, dry.

9. Al according to claim 1 ₂O ₃-SiO ₂The preparation method of matter tundish gas permeable brick, the decomposition temperature that it is characterized in that described Cellmic C 121 is 120～180 ℃, its particle diameter＜0.005mm.

10. according to each described Al in the claim 1～9 ₂O ₃-SiO ₂The prepared Al of preparation method of matter tundish gas permeable brick ₂O ₃-SiO ₂Matter tundish gas permeable brick.