| 摘要 |
PURPOSE:To reduce the Mo and Ni contents of spheroidal graphite cast iron without deteriorating the heat treatability, to enable normal austempering, and to reduce the production of a strain by regulating the amounts of Mn and Cu in the cast iron to proper values. CONSTITUTION:Spheroidal graphite cast iron consisting of, by weight, 3-4% C, 1.5-3% Si, 0.3-0.8% Mn, 0.3-2% Cu, 0.005-0.2% graphite spheroidizing agent and the balance Fe is cooled from a temp. at which austenite is stable to the bainite forming temp. at a cooling rate at which no pearlite structure is precipitated. Though little Mo and Ni are contained as mentioned above, extremely superior spheroidal graphite cast iron for austempering is obtd. The cast iron is especially suitable for use as the material of thick-walled parts to be austempered, and when the cast iron is subjected to austempering by making use of upper bainite or to austempering followed by air cooling, a high strength product can be obtd. at a low cost.
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