ELECTROSEAMED STEEL PIPE FOR LINEPIPE AND MANUFACTURING METHOD THEREFOR

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PROBLEM TO BE SOLVED : To provide an electroseamed steel pipe for linepipe having excellent HIC resistance and low temperature toughness in an electro-resistance-welded part. SOLUTION : The electroseamed steel pipe for linepipe contains, by mass%, C : 0.02 to 0.10%, Si : 0.1 to 0.2%, Mn : 0.5 to 2%, P : 0.03% or less, S : 0.0020% or less, O : 0.0035% or less, Al : 0.010 to 0.040%, N : 0.001 to 0.008%, Nb : 0.01 to 0.10%, Ti : 0.005 to 0.03%, Ni : 0.03 to 0.25%, Mo : 0.07 to 0.2%, Ca : 0.0010 to 0.0040% and rare earth element : 0.0005 to 0.0050% and the balance Fe with inevitable impurities, having a chemical composition satisfying the formula (I), average crystal diameter of 6.0 μm or less and major axis/minor axis ratio AR of an inclusion of 2.0 or less, in a structure at a t/8 depth position of an electro-resistance-welded part. 0.020<1/40 Ni+1/4Mo<0.050 (1). SELECTED DRAWING : Figure 1 COPYRIGHT : (C)2019, JPO&INPIT