| 摘要 |
PURPOSE:To prevent effectively the formation of a chilled part of iron casting, especially for an iron casting having a thin metal part, by using a molding material prepared by mixing an SiO2, having prescribed grain-size index and gas permeability, and a phenolic resin large in fire catching speed at a specific fashion point. CONSTITUTION:This molding material is prepared by mixing a 3-4% phenolic resin, having a 95-105 deg.C fusion point and a large fire-catching speed, with a major component SiO2 having a 60-90 grain-size index and 80-130 gas permeability. When a dumping-type shell mold is molded by the shell-mold send obtained in such manner, the gas permeability is properly lowered as well as the fire-catching speed of resin is enhanced, to improve the heat retentivity of the inside of shell mold. Also, the fluidity of molten metal is enhanced by the soot, etc. produced by the combustion of resin, to improve the run of molten metal. As a result, the solidifying speed by quenching of the molten metal can be delayed to prevent the formation of chilled part. |
