NON-HEAT TREATED MACHINE PARTS AND PRODUCTION THEREOF

摘要

PURPOSE: To produce high strength steel parts by less machining without subjecting the cast part to hardening and tempering, at the time of working a steel by cold or hot forging, by using a steel stock contg. a specified small amt. of B. ;CONSTITUTION: A steel having a compsn. contg., by wt.%, 0.05 to 0.35% C, 0.02 to 1.5% Si, 0.3 to 1.5% Mn, 0.0005 to 0.010% B, 1.5% Cr, 0.2% Mo and 0.3% Ni, contg. total 0.001, to 0.6% of one or more kinds among S, Pb, Ca, Bi and Te and total 0.005 to 0.2% of one or more kinds among Al, Nb. Ti and V is worked into a bar or wire shape by hot rolling, and immediately after that, the surface is cooled to 500°C at ≥5°C/sec cooling rate. Or, it is furthermore heated to 550 to 800°C for 10min to 20hr, is thereafter subjected to cold or warm forging at 0.3 to 1.8 working strains and is moreover held at 100 to 350°C for ≥10min to remove the strains. Without requiring the subsequent hardening and tempering, the high strength steel parts free from the damage to tools at the time of the casting and having 80 to 150kgf/mm² tensile strength can be produced.;COPYRIGHT: (C)1995,JPO