| 摘要 |
PROBLEM TO BE SOLVED: To manufacture a low alloy steel welded tube whose welded zone has performance equal to that of a base stock and whose thickness in >=5mm. SOLUTION: A steel plate containg, by wt., 0.02-0.30% C, <=0.08% Si, 1.30-3.0% Mn, 0.005-0.30% Nb, 0.005-0.03% Ti, 0.001-0.010% sol-Al, <=0.010% N, 0-0.0050% Ca, and one or more kinds of 0-0.40% Cr, 0-0.40% Mo, 0-0.05% V and 0-0.0020% B, the balance Fe and inevitable impurities, and satisfying the composition of -0.010<=Ti-3.4N<=0.020 is formed into an open tube, and while the periphery of the abutting part is shielded by an inactive gas, the abutting part is irradiated and welded with a directional high energy beam, and then the welded zone or the entire tube is subjected to heat treatment. As a result, the product capable of suppressing especially the increase of hardness as the performance of the weld zone including heat, affected zone is obtained. |
