| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a high strength steel pipe excellent in an anti-SSC property not only in a welded steel pipe but in a circumferential welded part between steel pipes. <P>SOLUTION: The high strength welded steel pipe having an excellent anti-sulfide stress corrosion cracking property and a tensile strength of 600 MPa or higher comprises: a base material which contains, in mass%, 0.02-0.06% C and others, and has a CP value of 1.1 or smaller prescribed by a formula (1) and a Py value of 0.175 or smaller prescribed by a formula (2); and a welded metal in which a value of the formula (2) calculated in a welded metal composition of a pipe inner surface satisfies 0.160-0.175 and a value of the formula (2) calculated in a welded metal composition of a pipe outer surface is larger than the pipe inner surface by 0.03 or larger. The formula (1): CP=4.46C+2.37Mn/6+(1.18Cr+1.95Mo+1.74V)/5+(1.74Cu+1.7Ni)/15+22.36P. The formula (2): Py=C+Si/30+Mn/20+(Cu+Cr)/20+Ni/60+Mo/7+V/10+5×B. <P>COPYRIGHT: (C)2013,JPO&INPIT |
