Double Pipe And Welded Joint

Abstract: A double pipe equipped with a first pipe and a second pipe, wherein the chemical composition of the first pipe is, in mass%, C: more than 0.060% to 0.400%, Si: 0.01-1.00%, Mn: 0.01-1.20%, P: 0.0350% or less, S: 0.0150% or less, Sn: 0.0005-0.0400%, Al: 0.040% or less, N: 0.050% or less, O: 0.030% or less, remainder: Fe and impurities, the chemical composition of the second pipe is, in mass%, C: 0.003-0.100%, Si: 0.01-1.50%, Mn: 0.01-2.20%, P: 0.0400% or less, S: 0.0100% or less, Sn: 0.0005-0.0300%, Ni: 7.0-52.0%, Cr: 15.0-27.0%, Al: 0.001-0.600%, N: 0.001-0.150%, O: 0.030% or less, remainder: Fe and impurities, and satisfies [Siave + 6xPave + 20xSave + 2xSnave ? 1.1000] and [0.0015 ? 4 x Save + Snave].

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