PURPOSE: To obtain a superior product in shortened working stages without adding expensive elements in large quantities by heat-treating a casting immediately after releasing from the mold and by rapidly cooling the casting from a prescribed temp. above the A1 transformation range under specified conditions.
CONSTITUTION: Molten metal having the composition of malleable cast iron is charged into a casting mold and solidified. The resulting casting is taken out of the mold, it is heat-treated at once at a prescribed temp. to decompose cementite, and the casting is rapidly cooled from a prescribed temp. above the A1 transformation range. At this time, the casting 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 stablly formed. After the lapse of a prescribed time, the casting is allowed to cool, or it is rapidly cooled. Thus, though and hard malleable cast iron having extremely superior mechanical properties such as high strength and toughness is obtd.
YANO MITSURU
ISHIHARA YASUOKI
OOTSUKA KIMITERU
| JPS54138812A | 1979-10-27 |
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