WELDED STEEL PIPE EXCELLENT IN COLLAPSE RESISTANCE AND INTERNAL PRESSURE FRACTURE RESISTANCE, AND MANUFACTURING METHOD THEREOF

摘要

PROBLEM TO BE SOLVED: To provide a line pipe with high strength which can realize both characteristics of collapse resistance and internal pressure fracture resistance, and to provide a method of manufacturing the line pipe.;SOLUTION: A welded steel pipe with excellent collapse resistance and internal pressure fracture resistance is formed by cold-working a steel material to a tubular shape and welding its butting portion and cold-forming a welded pipe by expansion and diameter reduction. In the welded steel pipe, tensile yield stress CT in a pipe circumferential direction, compressive yield stress CC in the pipe circumferential direction and tensile yield stress LT in a pipe lengthwise direction are all 420 MPa or more, a mutual difference of the CT, CC and LT is 50 MPa or less.;COPYRIGHT: (C)2013,JPO&INPIT