A process for producing hot forging steels having excellent fatigue strength, yield strength and machinability (excellent fatigue strength, yield strength and cuttability)

摘要

0.003 to 0.05% of Ti, 0.003 to 0.05% of N, 0.003 to 0.05% of Ti, 0.003 to 0.05% of Al, 0.03 to 0.10% of Si, And 0.30 to 0.70% of V, and further containing at least one of Cr, Mo, Nb, Pb and Ca in a specific ratio, Bismuth type heat quenching steel characterized in that at least 80% of the structure is a ferrite + bainite structure and aging treatment is further performed at a temperature of 200 to 700C. According to the present invention, sufficient fatigue strength Machinability It is possible to produce a steel for heat treatment having a yield strength, which is very industrially effective.