Abstract
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, and γ + graphite eutectic, in hypoeutectic alloys proceeds in the order of primary γ, γ + MC, γ + graphite, γ + M6C, and γ + M7C3 eutectic, and in Ni-hard proceeds in the order of primary γ, γ + MC, γ + M3C, and γ + graphite eutectic. The γ + 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.
Highlights
In the roll material for hot rolling, the alloys which disperse a large amount of carbide in the matrix are widely used because they are superior in abrasion resistance
The effects of alloy elements and inoculation on graphite formation were investigated for high-speed steel type cast iron and Ni-hard type cast iron
(1) In case of high-speed steel type cast iron, the crystallization of hypereutectic alloy proceeds in the order of primary MC, γ + MC, γ + M6C, γ + M7C3, and γ + graphite eutectic, while hypoeutectic alloys solidify in the order of primary γ, γ + MC, γ + graphite, γ + M6C, and γ + M7C3 eutectic
Summary
In the roll material for hot rolling, the alloys which disperse a large amount of carbide in the matrix are widely used because they are superior in abrasion resistance. High-alloy white cast irons, in which a large amount of carbides disperse in the hardenable matrix, are widely used for abrasion resistant parts. The control of the amount and distribution of carbides and graphite is essential to get a high-quality cast iron roll. The dispersion of MC carbide in the matrix would raise the wear resistance performance on the cast iron alloy where it is added. As they are the stronger carbide formers, the effects of Nb and V on the microstructure and the graphite formation must be investigated. Carbide and graphite formation and redistribution of alloy elements during solidification were investigated on high-speed steel alloys (HS) and Ni-hard type cast irons
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