| 摘要 |
PURPOSE:To manufacture ductile cast iron having high strength and ductility, by innoculation treating a molten cast iron contg. specified ratios of C, Si, Mn and casting it, and carrying out heating holding, preliminary cooling, heating holding and rapidly cooling holding of the ingot in order under specified conditions. CONSTITUTION:The molten cast iron composed of, by weight 3.0-4.0% C, 1.7-2.8% Si, 0.1-0.4% Mn and the balance Fe with impurity is inoculation treated in mold or inoculation treated during the pouring flow, then cast. Next, the ingot is held at 900-950 deg.C for 0.5-5 hr, then subjected to preliminary treatment such as furnace cooling or air cooling or furnace cooling up to austenitizing temp. of subsequent process. Or without the preliminary treatment, the ingot is held at 820-880 deg.C for 0.5-5 hr, immediately cooled rapidly to 350-400 deg.C and held at the temp. for >=0.5 hr. By applying isothermal transformation treatment in such a way, ductile cast iron superior in mechanical property is obtd.
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