Method of producing steel pipes, and welded pipes

Details Method of producing steel pipes, and welded pipes Method of producing steel pipes, and welded pipes

2005-09-27

2005-09-27

Edmondson, L. (Department: 1725)

Metal fusion bonding

Process

With shaping

C228S173100, C228S141100, C228S146000, C072S367100, C072S369000, C148S320000, C148S521000, C148S590000, C148S648000

Reexamination Certificate

active

06948649

ABSTRACT:
The high yield ratio problem intrinsic in high-strength steel pipes is solved and a method of producing a steel pipe, while securing the pipe roundness is provided. A steel pipe produced from a steel plate by forming and welding is subjected to 0.3 to 1.2% of expansion and then to 0.1 to 1.0% of reduction. The steel pipe produced by this method has a structure in which martensite and/or bainite accounts for more than 80% as expressed in terms of area percentage, and has a yield strength of not lower than 551 MPa and a yield ratio of not higher than 93%. The pipe reduction is desirably carried out at a lower work ratio as compared with the pipe expansion.

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