| 摘要 |
PROBLEM TO BE SOLVED: To prevent the generation of cracks by heating a casting composed of respectively specified amounts of Si, Mn, Cr and Mo, and the balance Fe with inevitable imupurities to a specified temp. and thereafter executing air blast cooling and tempering. SOLUTION: A casting composed of, by weight, 0.3 to 0.5% C, 0.5 to 1.5% Si, 0.5 to 1.5% Mn, 3.0 to 5.0% Cr, 0.05 to 0.5% Mo, and the balance Fe with inevitable impurities is heated at 900 to 1050 deg.C, is thereafter subjected to air blast cooling and is tempered at 300 to 400 deg.C. The air blast cooling is executed preferably till the temp. of the casting reaches 100 to 300 deg.C. By executing the mold-deassembling of the casting at the point of time in which the temp. of the casting reaches 200 to 600 deg.C, quenching is suppressed. C secures the hardness (wear resistance) of the cast steel, Si tranfers its low temp. tempering brittlenss to the high temp. side together with Cr and Mo, Mn distributes to deoxidation and desulfurization, and Cr transfers the low temp. tempering brittleness to the high temp. side.
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