| 摘要 |
PURPOSE:To obtain a superior product in shortened working stages without adding expensive elements in large quantities by releasing a casting from the mold at a prescribed temp. above the A1 transformation range, and rapidly cooling the casting under specified conditions. CONSTITUTION:Molten metal having the composition of gray cast iron is charged into a casting mold and solidified. The resulting casting is taken out of the mold at a pescribed temp. above the A1 transformation range, and it is rapidly cooled. At this time, the casting is rapidly cooled from said temp. at a cooling rate at which pearlitic transformation is not caused, and the cooling is stopped once at a temp. above the Ms point. The temp. is slowly dropped, and after the lapse of a prescribed time, the casting is allowed to cool, or it is rapidly cooled. Thus, tough and hard gray cast iron having extremely superior mechanical properties such as high strength and toughness is obtd. |
