公开(公告)号：EP2050835A4

公开(公告)日：2011-10-12

申请号：EP07792533

申请日：2007-08-08

申请人： NIPPON STEEL CORP ,  TOYOTA MOTOR CO LTD

发明人： NAKAMURA HIDEYUKI ,  ANAI ISAO ,  YAMAMOTO YASUSHI ,  FUKUSHI TAKAAKI ,  YAMAMOTO IZURU ,  KONDO MASAAKI ,  SHIMAZU SATORU

IPC分类号： C22C38/00 ,  B60G9/00 ,  B60G9/04 ,  B60G21/05 ,  C21D9/00 ,  C21D9/08 ,  C21D9/50 ,  C22C38/02 ,  C22C38/04 ,  C22C38/06 ,  C22C38/12 ,  C22C38/58

CPC分类号： B60G9/00 ,  B60G21/051 ,  B60G2200/20 ,  B60G2206/202 ,  B60G2206/72 ,  C21D9/00 ,  C21D9/08 ,  C21D9/50 ,  C22C38/001 ,  C22C38/02 ,  C22C38/04 ,  C22C38/06 ,  C22C38/12

摘要： The present invention provides a steel material for automobile chassis parts which has high fatigue characteristics, does not require much cost for heat treatment, and further is superior in shapeability and a method of production of automobile chassis parts using this steel material, that is, one being a steel material to which Nb and Mo have been compositely added and having a difference 50 to 150 points between a Vicker's hardness of the center of plate thickness and a maximum value of Vicker's hardness within 0.5 mm from the surface after bending by a bending R of the plate outer surface of 2 to 5 times the plate thickness. The surface is high in hardness and the center part is low in hardness, so the fatigue characteristics and shapeability are superior. Note that if annealing under conditions giving a tempering parameter » defined by »=T(20+log(t)) of 14000 to 19000 (where T is the absolute temperature, t is the time (h), and the temperature rise is 660°C), it is possible to relieve the internal stress and further improve the fatigue characteristics.