METHOD FOR MANUFACTURING MACHINE COMPONENT FOR AUTOMOBILES EXCELLENT IN FATIGUE STRENGTH AND MACHINE COMPONENT FOR AUTOMOBILES USING THE SAME

摘要

PROBLEM TO BE SOLVED: To provide a method for manufacturing a machine component for automobiles which is a steel component for carburization cold-forged and carburization hardened without conducting normalizing nor annealing, by which particle grain can be prevented from coarsening during carburization treatment, and to provide the machine component for automobiles using the method.;SOLUTION: A steel containing, by mass%, C:0.13 to 0.20%, Si:0.30 to 0.70%, Mn:0.20 to 0.50%, P:0.030% or less, S:0.030% or less, Cr:2.00 to 2.50%, Al:0.010 to 0.050%, Ti:0.02 to 0.08%, Nb:0.02 to 0.08%, B:0.0005 to 0.0035%, N:0.020% or less, and the balance Fe with inevitable impurities is rolled at 1250°C or more to a stab, cooled and then rolled at 800 to 1050°C to a steel material, further applied to a softening heat treatment, then molded into a part shape by cold-forging, and carburization hardening tempered at 950°C or more without normalizing nor annealing to obtain the steel material having the austenitic grain size number of 7 or more.;COPYRIGHT: (C)2015,JPO&INPIT