Development of steels for high-strength bolts with excellent delayed fracture resistance

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0A steel for high-strength bolts of a strength class over 12.9, which have excellent delayed fracture resistance, has been newly developed. It offers increased fracture toughness and decreased hydrogen through the addition of Mo, Ti, V and Ni, which improved delayed fracture resistance. This was accomplished through the refinement of grain size and the introduction of a hydrogen-trapping site by the precipitation of many fine Mo-Ti-V type complex carbides (less than 50 nm).

Description

0A steel for high-strength bolts of a strength class over 12.9, which have excellent delayed fracture resistance, has been newly developed. It offers increased fracture toughness and decreased hydrogen through the addition of Mo, Ti, V and Ni, which improved delayed fracture resistance. This was accomplished through the refinement of grain size and the introduction of a hydrogen-trapping site by the precipitation of many fine Mo-Ti-V type complex carbides (less than 50 nm).

Additional information

Author(s)

Yuichi Namimura, Nobuhiko Ibaraki, Wataru Wurushihara and Takenori Nakayama, Kobe Steel, Ltd., Japan

Publication/Event/Pages

Paper presented at WAI 72nd Annual Convention, Chicago, USA. Paper published in Wire Journal International, Jan. 2003, pg. 62.

Year

2002