High temperature-resistant easy-collapsing precoated sand for casting

Abstract

The invention discloses a high temperature-resistant easy-collapsing precoated sand for casting. The high temperature-resistant easy-collapsing precoated sand is prepared from the following componentsin parts by weight: 87 to 118 parts of raw sand, 2 to 2.5 parts of benzoxazine resin, 0.7 to 3.1 parts of polyvinyl butyral, 3.7 to 5.6 parts of inorganic polymer, 0.3 to 0.5 part of sodium alginate,3 to 11 parts of bauxite, 3 to 13 parts of mullite powder, 5 to 15 parts of diatomite, 0.3 to 0.4 part of hexamethylenetetramine, 0.1 to 0.2 part of barium stearate, 0.1 to 0. 2 part of zinc stearate, 0.15 to 0.2 part of calcium stearate, 0.45 to 3.8 parts of flake graphite, 0.7 to 3.3 parts of dolomite powder, and 0.1 to 0.3 part of potassium nitrate. The high temperature-resistant easy-collapsing precoated sand for casting has the advantages that the combination of components is optimized; especially, the decomposing temperature of the potassium nitrate is high, the heat-resistant propertyof the benzoxazine resin is high, and the components can reach the synergistic cooperation function; the preparation method is simple, the sources of the raw materials are wide, and the high temperature-resistant property and the post-casting collapsing property of the precoated sand are guaranteed.

Description

technical field [0001] The invention relates to a coated sand used in the field of casting, in particular to a high-temperature-resistant and easily collapsed coated sand for casting. Background technique [0002] When ordinary coated sand is used to produce steel castings and some special iron castings (thick-walled thin-core castings) as sand cores, cracks in the sand cores are often found after pouring, and sometimes even the sand cores are broken, resulting in orange formation on the surface of the castings. Skin defects. This is due to the fact that after the sand core is in contact with the high-temperature molten metal, the benzoxazine resin is carbonized, burned and decomposed at high temperature, and its strength is reduced, while the phase change of the silica sand produces a large volume expansion, which destroys the sand core under the rapid thermal expansion of the sand core. . When the pouring temperature is too high and the quality of the molten iron is rela...

AI Technical Summary

Problems solved by technology

When the pouring temperature is too high and the mass of molten iron is relatively large, the sand mold may even have core penetration, resulting in the casting being scrapped

Another situation is that when the sand core is completely surrounded by molten iron, the sand core may become soft and deformed under the buoyancy of the molten iron, resulting in a change in the size of the casting, and even serious scrapping.

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