The carburization hardening steel and the carburization hardening part null mass which are superior low in cycle

摘要

PROBLEM TO BE SOLVED: To provide a steel material for carburizing and quenching having excellent low cycle fatigue properties.;SOLUTION: The steel material is characterized in that: a projected core hardness Hp-core=Hcore/(1-t/r) is ≥390 HV; the hardness at a position of 13 mm from the quenched edge in a Jominy test is ≥60×C^0.5-5(HRC); and A=(Mo+0.227Ni+190B-0.087Si-17.2P-2.74V-7.18Cs-0.00955Hs+0.0344Nγ) and B=(t×(Hcore)²) satisfy the relation of A-0.00000293×B≥14; wherein, Hcore is a core hardness; (t) is an effective hardened layer depth; (r) is the radius of the failure zone or the half of the wall thickness of the failure zone; Cs is the carburization concentration (mass%) in the surface layer; Hs is a surface hardness (HV); and Nγ is the old austenite grain size of a carburized layer.;COPYRIGHT: (C)2008,JPO&INPIT