摘要 |
An ultrahigh-strength and low-yield-ratio line-pipe steel being excellent in HAZ toughness and field weldability and having a tensile strength of at least 950 MPa (exceeding the API Specification 100). The steel comprises a low-C-high-Mn-Ni-Mo-Nb-trace Ti steel, further selectively contains if necessary B, Cu, Cr and V, and has as the microstructure a hard-soft two-phase mixed structure comprising martensite/bainite and 20-90 % of ferrite, the ferrite containing 50-100 % of worked ferrite and having a grain diameter of 5 mu m or less. It has thus become possible to produce an ultrahigh-strength and low-yield-ratio line-pipe steel (exceeding the API Specification 100) excellent in low-temperature toughness and field weldability. As a result, it has become possible to improve the pipeline safety remarkably and to improve the pipe-lining performance and conveying efficiency largely.
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申请人 |
NIPPON STEEL CORPORATION;TAMEHIRO, HIROSHI,;ASAHI, HITOSHI,;HARA, TAKUYA,;TERADA, YOSHIO |
发明人 |
TAMEHIRO, HIROSHI,;ASAHI, HITOSHI,;HARA, TAKUYA,;TERADA, YOSHIO |