Control of Carbides and Graphite in Cast Irons Type Alloy’s Microstructures for Hot Strip Mills

[摘要] The carbide and graphite formation and redistribution of alloy elements during solidification were investigated on high-speed steel (HS) and Ni-hard type cast irons with Nb and V. The crystallization of hypereutectic HSS proceeds in the order of primary MC,γ + MC,γ + M6C,γ + M7C3, andγ +  graphite eutectic, in hypoeutectic alloys proceeds in the order of primaryγ,γ + MC,γ + graphite,γ + M6C, andγ + M7C3eutectic, andin Ni-hard proceeds in the order of primaryγ,γ + MC,γ + M3C, andγ +  graphite eutectic. Theγ +  graphite eutectic solidifies with the decrease of V, Nb, and Cr and the increase of Si and C contents in residual liquid during solidification. The behavior in graphite forming tendency in the residual liquid is estimated by the parameter∑CLimi′. The eutectic graphite crystallizes at the solid fraction when∑CLimi′takes a minimum value. The amount of graphite increases with the decrease in∑CLimi′of initial alloy content in both specimens. Inoculation with ferrosilicon effectively increases the graphite content in both specimens.

[学科分类] 工业化学