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The filter works under special conditions. The material selection and requirements are as follows: (1) In the process of long-term contact with molten steel, the filter can withstand the effects of thermal and mechanical stress; (2) It can resist molten steel and slag Corrosion without chemical reaction; (3) It can effectively remove inclusions without excessive resistance to the flow of molten steel. Because the filter can remove inclusions, pure copper water, reduce nozzle clogging, avoid nozzle clogging, and lower production costs, it has developed rapidly in recent years, and foam ceramic filters are mostly used.

In the 1980s, it was used for the filtration of high-temperature alloy steel and stainless steel. Its appearance is similar to that of sponge ceramic foam filter. It has developed from the original Al2O3 quality to laystone (3Al203 2SiO2), zirconia (ZrO2 97%), and ZrO2-Al203. Quality, SiC quality, CaO quality and cordierite, etc.

Japan mainly uses filters made of ZrO2, Al2O3, CaO and 3AI203 2Si02. Nippon Steel Co., Ltd. adopts Zr02 filter (ZrO297%, linear expansion coefficient 9.03×10-6K-1, processing stainless steel, reducing inclusions by 15%.

The United States has developed a filter made of Al2O3 with a silicon oxide coating with a thickness of more than 10Ornm. Comparing the two cases of filters, the uncoated filter only filters 11.3 kg of steel, and the coated filter filters 76.6 kg of metal, and almost completely removes the inclusions containing slag.

Foam ceramic filters produced by American High-tech Ceramics Company, with many varieties

When the molten steel passes through the pores of the filter, the small non-metallic inclusions, such as Al203, SiO2, S, P, etc., are adsorbed by the pore walls due to chemical action, and the reaction product reaches the surface of the molten steel. In the slag, the molten steel is purified. It not only ensures the smooth operation of continuous casting, but also improves the quality of the cast billet. The effect is obvious. (1) The double-strand bloom continuous caster casts 304 stainless steel, adds a slag retaining wall in the tundish and uses a filter. The comparison test shows that the filter makes the square The silico-manganese inclusions in the billet were reduced by 74%. (2) The aluminum-containing steel (Al2O30.024%) is poured by the billet continuous caster, and the pouring time is about 90 minutes. The first-class filter is installed on the edge of the tundish. The test shows that the molten steel only needs to be burned after passing through the sizing nozzle. Oxygen is used once to remove the blockage of Al2O3, while the other streams need to be burned 45 times. It can be seen that the filter can significantly reduce Al2O3 inclusions.

In 1998, the lime filter developed by WISCO has the following performance: CaO 94.75%, apparent porosity 12%, bulk density 2.85g/Cm3, normal temperature compressive strength 25MPa, and good results when used on the tundish, and the removal rate of non-metallic inclusions Reached 10%3.

There are two types of high-purity calcium oxide ceramic filters: barrier type and erosion type. The barrier filter is prone to blockage by non-metallic inclusions, and it is difficult to use it on the tundish with a large amount of steel. The mechanism of the calcium oxide ceramic filter to remove inclusions is adsorption and erosion, and the filter holes are gradually enlarged until the later stage of casting does not affect the passage of molten steel. Calcium oxide has a strong ability to remove non-metallic inclusions such as SiO2 and S. The high-purity calcium oxide (CaO>98.97%) filter developed by Beijing Iron and Steel Research Institute has technically solved two difficulties: (1) Calcium hydroxide is used as the raw material, no additives are added, and no clinker is burned. , The process of directly making calcium oxide products solves the problem of easy hydration of calcium oxide during the production process. When the Al2O3 of molten steel or calcium aluminate with higher Al2O3 content is in contact with the calcium oxide filter, the absorption of CaO is low. The melting point of calcium aluminate rises. The filter is continuously eroded to purify the molten steel; the Al203 filter that is not eroded still functions as a refractory material, and there is no problem of excessive CaO suspended in the molten steel. The filter is used on the slag retaining wall of the IOt tundish of the willow steel plate broken continuous caster. The filter brick type, hole type, installation position in the tundish, and masonry method are reasonable in design, and the life span reaches 78 furnaces. Other refractory materials are synchronized, and the total efficiency of removing inclusions is 22.7% and 40.0%.

Researched out measures to prevent the hydration of calcium oxide ceramic filters during the production process, and achieved satisfactory results: (1) Reduce the humidity of the environment during the production process (2) Reduce the exposure time of calcium oxide raw materials in the air; (3) Use non-aqueous substances as binding agents; (4) Firing in an electric furnace or vacuum electric furnace; (5) Coating water-repellent agent on the surface of the product; (6) The development of a vacuum-packed CaO filter is a refractory material for the realization of the tundish system. For example, the "calcification" of slag retaining walls, ladle linings, stoppers, nozzles, etc. opened up new ways.

Using organic foam dipping process, successfully developed zirconium corundum mullite, fused magnesia, foam ceramic filters, high raw material purity (alumina 98.5%, zircon Zr02 65%, fused magnesia filter has good Thermal shock resistance, flexural strength up to 3.15MPa. The content of filtered cast steel inclusions is reduced, the size is reduced, and the inclusions distributed in the form of a network are eliminated. After filtering, the impact toughness of cast europium parts is significantly improved. The average value is increased by 38%. Tests show that: there are very few sulfides in the steel, so the splitting and weakening effect of metal inclusions on the metal matrix is weakened, and the impact toughness of the metal has been significantly improved.

Ceramic filter plate: Performance characteristics of ceramic filter plate in a refractory plant in Changsha:

(1) Light weight, volume density of 0.30.5g/cm3; (2) Porosity as high as 80% 90%; (3) Large surface area in contact with molten metal; (4) High strength, its thermal stability and The chemical stability is good. It can replace Fosec0's products and successfully used in continuous casting aluminum alloy ceramic filter plates. Its physical and chemical indicators: A1203≥70%, Fe2O3≤0.2%, apparent porosity ≥85%, air permeability ≥1.5X10-4, resistance to bending Strength ≥0.3MP, compressive strength will be 0.2MPa.

The thermal shock resistance of sintered mullite is significantly better than that of fused mullite, and the addition of expansion agents (AI2O3 56.2%, SiO2 39.1%) can significantly improve the thermal shock resistance of the material. Choose to add sintered mullite and add 6% of expansion agent to make double cone oriented corundum-mullite-silicon carbide filter. Used on the slag retaining weir of the continuous caster of the steel plant, through the sampling and analysis of the three furnaces continuous casting, the reduction rate of the inclusions in the steel is 30.3%, and no nodules on the immersion nozzle (two) and the short nozzle (one) are found. Phenomenon, the pouring is very smooth, and the filter is slightly corroded after pouring, which can meet the requirements of steel mills.