| 摘要 |
PURPOSE:To provide spheroidal graphite cast iron giving a metallic mold having a fine appearance and satisfactory mechanical characteristics by specifying the contents of C, Si, Ni, Cu, Mo and Mg and regulating the carbon equiv. CONSTITUTION:This spheroidal graphite cast iron for a metallic mold consists of, by weight, 2.8-3.8% C, 1.5-3.0% Si, (C+1/3Si=3.8-4.3%), 4.5-6.0% Ni, 0.3-2.5% Cu, 0.2-1.0% Mo, 0.02-0.07% Mg and the balance Fe with inevitable impurities. The spheroidal graphite cast iron does not contain spheroidal graphite of >100mum maximum grain size by the graphite grain refining effect of Ni and Cu, and the average grain size of graphite is <=60mum. The average grain size of graphite in a casting surface is reduced to <=30mum by a rapid cooling effect produced by contact with the surface of a casting mold. When a metallic mold made of the cast iron is used, a thick-walled casting having a smooth surface and high dimensional accuracy is obtd.
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