| 摘要 |
PURPOSE:To obtain spheroidal graphite cast iron with high strength and toughness at a low cost in a shortened working stage by rapidly cooling a casting from a temp. above the A1 transformation point, suspending the cooling once, and slowly dropping the temp. CONSTITUTION:A molten metal having the composition of shperoidal graphite cast iron is charged into a casting mold, solidified, and held at a prescribed temp. The resulting casting is taken out of the mold, and it is rapidly cooled from a temp. above the A1 transformation point at such a cooling rate as to cause no pearlitic transformation. The cooling is suspended once at a temp. above the Ms point, and the temp. is slowly dropped after the lapse of a prescribed time. After dropping the temp. for a prescribed time, the casting is allowed to cool or is rapidly cooled. By this method the manufacturing cost can be reduced because reheating is eliminated. |
