| 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 solidifed. The resulting casting is taken out of the mold at a prescribed temp. above the A1 transformation range, and it is rapidly cooled. At this time, the castig is rapidly cooled from said temp. at a cooling rate at which pearlitic transformation is not caused, and it is held at a temp. at which a mixed structure consisting of bainite and austenite is stably formed. 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 machanical properties such as high strength and toughness is obtd. |
