| 摘要 |
PURPOSE:To obtain the titled cast iron having by far larger elongation, impact value and fatigue limit than conventional in a relatively short time, by isothermally heat treating ductile cast iron having prescribed ratios of C, Mn respectively and component compsn. contained ordinarily. CONSTITUTION:Ductile cast iron having, by weight 2.5-3.6% C, <=0.3% Mn and the other ordinary component compsn. is treated as follows. Namely, the cast iron is firstly heated to 900+ or -50 deg.C for austenitizing, then subjected to isothermal heat treatment in which it is held in salt bath of 360-410 deg.C for 10-25min and the structure is converted to bainite. As the result, productivity and quality of gear, bracket and the other ductile cast iron product to which isothermal heat treatment is applied, having previously described characteristics can be improved.
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