論文
V単独，V-Nb複合添加超高強度ホットスタンピング部材の組織と機械的性質
キーワード:
hot stamping,
high strength steel,
automotive components,
delayed fracture,
reverse transformation
2014 年 100 巻 9 号 p. 1114-1122
詳細
2014 年 100 巻 9 号 p. 1114-1122
As a method for producing ultrahigh strength automotive steel components with high gauge accuracy, the hot stamping technology draws attention and the amount of hot stamped automotive components has exponentially increased in the last decade. The concerns about the potential danger of embrittlement and delayed fracture, however, limit the strength of conventional hot stamped components to 1500 MPa. If these concerns are eliminated, automotive steel components with higher strength which is demanded by the automotive industry can be further commercialized.
In this study, microstructures and mechanical properties of V and/or Nb bearing ultrahigh strength hot stamped steel components have been investigated. The V addition improves the resistance to delayed fracture by forming VC whose interface with matrix is supposed to act as preferential hydrogen trap site. The Nb addition refines the microstructure, which improves both the toughness and the resistance to delayed fracture. Proper hot stamping conditions for these steels has been discussed to create an ultrafine martensite microstructure and finely dispersed precipitates. The results indicate that 1900 MPa class steel components with good toughness and high resistance to delayed fracture can be produced.
