Are superior in deformation performance and low temperature Characteristic and HAZ Characteristic the high intensity metal tubing and its production

摘要

PROBLEM TO BE SOLVED: To provide a steel sheet for a line pipe and a steel line pipe excellent in deformability, low-temperature toughness and HAZ toughness.;SOLUTION: It is a characteristics of a high strength steel pipe that a structure of a parent material consists mainly of a bainite structure which contains ferrite of 5 μm or less of an average particle diameter in an area ratio of more than 20%, and the steel pipe is excellent in a deformation property, a low-temperature toughness, and a HAZ toughness by containing lower bainite of 5% or more in an area ratio in a structure generated on a coarse prior austenite grain boundary of a welding-heat affected zone near a fusion line.;COPYRIGHT: (C)2004,JPO