| 摘要 |
<p>PROBLEM TO BE SOLVED: To enhance HAZ (Heat-Affected Zone) toughness of a weld zone of a UOE steel pipe.SOLUTION: There is provided the UOE steel pipe base material excellent in HAZ toughness which has a component composition containing, by mass%, C:0.01 to 0.20%, Si:0.03 to 0.30%, Mn:0.50 to 3.00%, P:0.02% or less, S:0.02% or less, Al:0.0005 to 0.0050%, O:0.001 to 0.010% and further two or more kind of Sn:0.0001 to 0.0020%, As:0.0001 to 0.0020% and Sb:0.0001 to 0.0020% in an amount of 0.0030% or less in total and the balance Fe with inevitable impurities and which has aΔT defined by the following formula of less than 250.ΔT=2.4×10[%Al]+2.6×10[%O]+4.4[%Mn]-30[%Si]-20.</p> |
