Influence of cooling rate on as cast microstructure of multi-component white cast iron

摘要

Four kinds of multi-component white cast irons with different combinations of carbide type were poured into furan molds with different diameters, and cooling curves were taken using a R thermocouple inserted at the center of each mold cavity. The microstructural components in as cast iron, such asγdendrite arm spacing (D{sub}P) diameter (D{sub}(MC)) of MC carbide, lamellar spacing (λ{sub}(M2C)) of M{sub}2C carbide, area fraction (S{sub}(eut)) of (γ+M{sub}2C) eutectic or that of both (γ+M{sub}2C) plus (γ+ M{sub}7C{sub}3) eutectics, were well related to each characteristic cooling rate, while the area fraction of MC carbide was little affected by the cooling rate. The relations are expressed by, D{sub}P=25.1·V{sub}P{sup}(-0.36) (V{sub}P : cooling rate during precipitation of primaryγ) D{sub}(MC)=4.4.·V{sub}(E-MC){sup}(-0.18) (V{sub}(E-MC) : cooling rate during precipitation of (γ+MC) eutectic),λ{sub}(M2C)=(1.1～2.0) V{sub}(E-M2C){sup}(-0.28～-0.21) (V{sub}(E-M2C) : cooling rate during precipitation of (γ+ M{sub}2C) eutectic, S{sub}(eut)=(2.0～15.3)·V{sub}A{sup}(-0.23～-0.16) (V{sub}A : average cooling rate from start to end of solidification).