Release agent for casting refractory material and preparation method thereof

Abstract

The invention discloses a release agent for casting a refractory material and a preparation method of the release agent. The formula of the release agent comprises 55-65% of high-purity silicon carbide, 35-46% of a polyvinyl alcohol solution, 0.4-0.9% of sodium benzoate, 0.01-0.05% of octanol and 0.5-2.0% of xanthan gum. Wherein the mass percentage SiC content of the high-purity silicon carbide is greater than or equal to 97%, and the particle size is 1-2mm; the mass percent concentration of the polyvinyl alcohol solution is 4-14%. The preparation method comprises the steps of weighing, burdening, stirring and mixing, dispersing by a colloid mill and the like. The release agent can obviously prevent sand burning of a sand mold to the fused-cast refractory product, reduces the demolding resistance of the product after annealing, and improves the casting quality of the fused-cast refractory product.

Description

Technical Field

[0001] The invention belongs to the category of refractory materials, relates to the casting technology of fused-cast refractory bricks, and particularly provides a release agent for fused-cast refractory materials and a preparation method of the release agent. Background Art

[0002] At present, the production of fused-cast refractory materials mainly uses high-refractory raw materials such as quartz sand as sand mold materials in the casting process. The casting temperature of the molten liquid is usually about 1800-2100℃. After the high-temperature molten liquid contacts the sand mold, the surface temperature drops sharply, and a thin soft shell can be formed on the surface of the casting in an instant. After 10-30 minutes, the semi-solidified layer of the casting can reach 30mm, and the surface temperature drops to about 1550℃. After about 30 minutes, the surface temperature can drop to 1350℃. Since quartz will undergo isomorphous transformation at 573℃, quartz can be transformed into tridymite above 870℃, and its phase change expansion volume increases by 17.26%. Moreover, in the temperature range of 1250-1350℃, the time for quartz in the sand mold to transform into tridymite will be greatly shortened. Therefore, when the casting temperature is the highest, the sand mold expands the fastest and the solidification of the product is the weakest. As a result, the overall expansion of the sand mold will generate an external force on the surface of the casting, causing thermal cracks and cross-edge cracks in the fused-cast refractory products. These cracks are usually generated within 10 minutes after casting, resulting in crack casting defects in the products.

[0003] In addition, sticky sand, scarring and orange peel-like defects are also common defects of fused-cast refractory bricks, and one of the causes is also the phase change expansion of sand. When the inner surface of the sand mold is heated to above 870°C after casting, the sand particles undergo phase change expansion, generating extrusion stress between the sand mold and the molten interface. When this stress is greater than the strength of the sand mold at this temperature, the surface of the sand mold is damaged, causing some sand particles and the molten liquid to stick together to form sticky sand. If the sand lumps are squeezed away, scarring defects will form on the surface of the casting; if the damage to the inner surface of the sand mold is carried out around more irregular small plates, orange peel-like defects will form on the surface of the casting.

[0004] In order to solve the above technical problems, eliminate the casting defects of fused-cast refractory products, improve the quality and service life of fused-cast refractory products, it is urgent to develop a low-cost, anti-sand special release agent for fused-cast refractory casting production. Summary of the invention

[0005] The object of the present invention is to provide a special release agent for fused-cast refractory materials and a preparation method thereof, wherein the release agent can significantly prevent sand from sticking to fused-cast refractory products by sand molds, significantly reduce the demoulding resistance of products after annealing, and eliminate casting defects of products.

[0006] The present invention provides a special release agent for fused casting refractory materials, characterized in that the release agent is prepared by compounding high-purity silicon carbide, polyvinyl alcohol solution, sodium benzoate, xanthan gum and octanol, and the mass percentage of the compound composition is: High purity silicon carbide: 55-65% Polyvinyl alcohol solution: 35-46% Sodium benzoate: 0.4-0.9% Octanol: 0.01-0.05% Xanthan gum: 0.5-2.0% The high-purity silicon carbide has a SiC content of ≥97% by mass and a particle size of 1-2 mm; the polyvinyl alcohol solution has a concentration of 4-14% by mass.

[0007] The present invention provides a method for preparing the above-mentioned release agent, which is characterized in that: polyvinyl alcohol solution, sodium benzoate, xanthan gum and octanol weighed in mass ratio are added into a stirring barrel, stirred for 20 minutes, and then high-purity silicon carbide material is added, and stirring is continued for 20 to 30 minutes. Then, the obtained slurry is added into a colloid mill for 5 to 10 minutes of dispersion treatment, and finally a small amount of release agent is taken and measured with a Baume hydrometer. If the Baume degree is 62 to 64, the material can be discharged and packaged.

[0008] The release agent provided by the present invention can be used in the preparation process of fused casting refractory material casting sand molds, and applicable sand mold types include: water glass combined with drying hardened quartz sand molds, ester hardened modified water glass self-hardening quartz sand molds, water glass combined with magnesia sand sand molds, and phosphate combined with white corundum sand molds.

[0009] The product of the present invention is mainly prepared by compounding high-purity silicon carbide, polyvinyl alcohol solution, sodium benzoate, xanthan gum and octanol. The high-purity silicon carbide in the batch material has stable chemical properties, a melting point of up to 2700°C, high thermal conductivity, and a small thermal expansion coefficient. It is not easy to react with the melt of the refractory material, and plays a barrier role on the inner surface of the sand mold to prevent the sand particles and the melt from sticking together to form sticky sand. On the other hand, the thermal expansion coefficient of high-purity silicon carbide is not large. In the range of 25°C to 1400°C, its average thermal expansion coefficient is only 4.4×10 -6 / ℃, good high temperature volume stability, no tensile stress on the casting surface, avoiding the occurrence of thermal cracks or cross-edge cracks in fused-cast refractory products, and is beneficial to reducing and eliminating casting defects of fused-cast refractory products.

[0010] The product of the present invention is applied on the inner surface of the sand mold, and after being dried and hardened to form a sand mold coating, the coating is dry and water-free and contains very little binder, so that the generation of surface pore defects of the fused-cast refractory product can be prevented during the casting process. At the same time, the product of the present invention does not add binders such as water glass, so that during use, the binder therein reduces the melting point of silicon carbide, fails to protect the sand mold, causes the sand mold surface to be damaged, and causes the formation of sticky sand on the surface of the fused-cast refractory product.

[0011] Moreover, the polyvinyl alcohol in the product batch of the present invention has unique strong adhesiveness, adding a small amount of octanol can inhibit the generation of slurry foam, and the other two additives respectively play the role of viscosity stabilizer and thickener, etc., so that the release agent coating after drying has a certain strength and will not crack. The release agent has low preparation cost, good wettability and adhesion to the sand mold, and the significant characteristics of good demoulding performance of the product after use, which can effectively avoid the formation of casting defects such as sand adhesion, thermal cracks, surface adhesion, and surface orange peel and scarring of the product, thereby significantly improving the surface and internal quality of the fused-cast refractory product. DETAILED DESCRIPTION Example 1

[0012] Ingredients: The batch is composed of high-purity silicon carbide, polyvinyl alcohol solution, sodium benzoate, xanthan gum and octanol. The mass percentage of the ingredients is: 55% high-purity silicon carbide, 43% polyvinyl alcohol solution, 0.7% sodium benzoate, 0.02% octanol and 1.28% xanthan gum. The SiC content of high-purity silicon carbide is ≥97%, and the particle size is 1-2mm; the mass percentage concentration of polyvinyl alcohol solution is 8%.

[0013] Preparation: First add 43 kg of polyvinyl alcohol solution into a stirring barrel, then add 0.7 kg of sodium benzoate, 1.28 kg of xanthan gum and 0.02 kg of octanol in sequence, stir for 20 minutes, then add 55 kg of high-purity silicon carbide material, and continue stirring for 20 to 30 minutes. Then, add the obtained slurry into a colloid mill for further dispersion, and finally take a small amount of release agent and measure it with a Baume hydrometer. If the Baume degree is greater than 62, the material can be discharged and barreled.

[0014] The product of the present invention has good quality, and its performance data are as follows:

[0015] ﹡Surface strength is measured by the amount of coating worn away, and the amount of coating worn away is used to measure the surface strength of the coating.

[0016] Example 2 Ingredients: The batch is composed of high-purity silicon carbide, polyvinyl alcohol solution, sodium benzoate, xanthan gum and octanol. The mass percentage of the ingredients is: 58% high-purity silicon carbide, 40% polyvinyl alcohol solution, 0.6% sodium benzoate, 0.03% octanol and 1.37% xanthan gum. The SiC content of high-purity silicon carbide is ≥97%, and the particle size is 1-2mm; the mass percentage concentration of polyvinyl alcohol solution is 12%.

[0017] Preparation: First add 40 kg of polyvinyl alcohol solution into a stirring barrel, then add 0.6 kg of sodium benzoate, 1.37 kg of xanthan gum and 0.03 kg of octanol in sequence, stir for 20 minutes, then add 58 kg of high-purity silicon carbide material, and continue stirring for 20 to 30 minutes. Then, add the obtained slurry into a colloid mill for further dispersion, and finally take a small amount of release agent and measure it with a Baume hydrometer. If the Baume degree is greater than 63, the material can be discharged and barreled for use.

[0018] The mold release agent invented has good product quality, and its performance data are as follows:

[0019] ﹡Surface strength is measured by the amount of coating worn away, and the amount of coating worn away is used to measure the surface strength of the coating.

Claims

1. A release agent for fused casting refractory material, characterized in that The mass percentage of each component of the release agent is: High purity silicon carbide: 55-65% Polyvinyl alcohol solution: 35-46% Sodium benzoate: 0.4-0.9% Octanol: 0.01-0.05% Xanthan gum: 0.5-2.0% The high-purity silicon carbide has a SiC content of ≥97% by mass and a particle size of 1-2 mm; and the polyvinyl alcohol solution has a concentration of 4-14% by mass.

2. The method for preparing a release agent for fused casting refractory material according to claim 1, characterized in that: Add the polyvinyl alcohol solution, sodium benzoate, xanthan gum and octanol weighed in mass ratio into a stirring barrel, stir for 20 minutes, then add high-purity silicon carbide material, and continue stirring for 20 to 30 minutes. Then, add the obtained slurry into a colloid mill for 5 to 10 minutes of dispersion treatment, and finally take a small amount of release agent and measure it with a Baume hydrometer. If the Baume degree is 62 to 64, the material can be discharged and packaged for use.

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