STEEL FOR INDUCTION HARDENING AND PARTS FOR MACHINE STRUCTURE EXCELLENT IN COLD WORKABILITY, ROLLING FATIGUE STRENGTH AND TWISTING FATIGUE STRENGTH

摘要

PROBLEM TO BE SOLVED: To obtain steel and parts high in cold workability, rolling fatigue strength and twisting fatigue strength and small in the variation of fatigue strength by specifying the contents of chemical components in steel, the diameter equivalent to a circle of the maximum dimensions of oxide, nitride and suldife nonmetallic inclusions to be contained and the number of nonmetallic inclusions in which the diameter equivalent to a circle is equal to or above the specified value.;SOLUTION: This steel for induction hardening contains, by mass, 0.45 to 0.60% C, 0.01 to 0.15% Si, 0.20 to 0.60% Mn, ≤0.012% S, 0.015 to 0.040% Al, 0.005 to 0.050% Ti, 0.0005 to 0.O050% B, ≤0.010% N and ≤0.0010% O, and the balance Fe, the diameter equivalent to a circle of the maximum dimensions of nonmetallic inclusions to be contained is ≤15 μm as for the oxide series, ≤5 μm as for the nitride series, and ≤5 μm as for the sulfide series, and the number of nonmetallic inclusions of ≥1 μm diameter equivalent to a circle per mm2 is ≤5 pieces as for the oxide series, ≤10 pieces as for the nitride series, and ≤5 pieces as for the sulfide series.;COPYRIGHT: (C)2001,JPO