Machine parts such as grilled steel for mechanical structures excellent in pitting resistance used in Carburizing and steel grilled gears made of steel

摘要

PROBLEM TO BE SOLVED: To provide a case hardened steel excellent in pitching resistance when used for a carburization case.;SOLUTION: There is provided a steel for machine structure excellent in pitching resistance, containing, by mass%, C:0.10 to 0.35%, Si:0.40 to 1.00%, Mn:0.15 to 0.45%, P:0.030% or less, S:0.030% or less, Cr:1.50 to 2.50%, Ni:0.20% or less, Mo:0.10% or less, further one or more kind selected from V:0.01 to 0.50%, Nb:0.01 to 0.20% and Ti:0.01 to 0.20%, and the balance Fe with inevitable impurities, at a state that a carburization abnormal layer in which hardness at a 0.30 mm position from an outermost surface in gas carburization or gas carbonitriding of the steel is 700 HV or more, maximum particle boundary oxide depth D1 of 15 μm or less, and maximum depth D2 from the outermost surface with indentation hardness of 9000 HIT or less satisfies the following formula (1). -5 μm≤D2-D1≤10 μm (1).;SELECTED DRAWING: Figure 1;COPYRIGHT: (C)2019,JPO&INPIT