Girth welded joint of steel pipe

A girth welded joint of steel pipe comprising:

• a base metal portion and a girth welded portion, wherein
• the girth welded portion is formed of a weld metal portion and a weld heat affected zone,
• a chemical composition of the base metal portion consists of, by mass %,
• C:
• 0.10 to 0.20%,
• Si:
• 0.05 to 1.00%,
• Mn:
• 0.05 to 1.20%,
• P:
• 0.025% or less,
• S:
• 0.005% or less,
• Cu:
• 0.20% or less,
• N:
• 0.007% or less,
• Ni:
• 0.20 to 0.50%,
• Cr:
• 0.30% or more and less than 0.50%,
• Mo:
• 0.30 to 0.50%,
• Nb:
• 0.01 to 0.05%,
• Al:
• 0.001 to 0.100%,
• B:
• 0.0005 to 0.0020%,
• Ti:
• 0.003 to 0.050%,
• V:
• 0.01 to 0.20%,
• a total of any one or more selected from Ca, Mg, and REM:
• 0 to 0.0250%, and
• balance:
• Fe and impurities,
• a value of Pcm expressed by a formula [A] described below is within a range of 0.25 to 0.30,
• a chemical composition of the weld metal portion consists of, by mass %,
• C:
• 0.04 to 0.14%,
• Si:
• 0.05 to 1.00%,
• Mn:
• 1.00 to 2.00%,
• P:
• 0.025% or less,
• S:
• 0.005% or less,
• Cu:
• 0.50% or less,
• N:
• 0.007% or less,
• Ni:
• 2.50 to 3.00%,
• Cr:
• 0.90% or more and less than 1.40%,
• Mo:
• 0.40 to 0.90%,
• Nb:
• 0.010% or less,
• Al:
• 0.010% or less,
• B:
• 0.0010% or less,
• Ti:
• 0.003 to 0.050%,
• V:
• 0.01 to 0.20%,
• a total of any one or more selected from Ca, Mg, and REM:
• 0 to 0.0250%, and
• balance:
• Fe and impurities,
• each of tensile strength of the base metal portion and tensile strength of the girth welded portion in a cross weld tensile test is 980 MPa or more, and
• average hardness of the base metal portion is 300 HV10 or more, an average softening width of the weld heat affected zone is 4.0 mm or less, and an average softening degree of the weld heat affected zone is 80 HV10 or less:
• Pcm
• =
• C
• +
• (
• Si
• /
• 30
• )
• +
• (
• Mn
• /
• 20
• )
• +
• (
• Cu
• /
• 20
• )
• +
• (
• Ni
• /
• 60
• )
• +
• (
• Cr
• /
• 20
• )
• +
• (
• Mo
• /
• 15
• )
• +
• (
• V
• /
• 10
• )
• +
• 5
• ⁢
• B
• [
• A
• ]
• where each symbol of an element in the formula [A] denotes a content (mass %) of the element contained in steel, and 0 is given when the element is not contained in the steel.