| 摘要 |
PURPOSE:To enable arc welding with covered electrode by eliminating preheating and postheating treatments by prescribing the range of contents of C, Mn, P, S, of Cr-Mo steel and tube stock thickness. CONSTITUTION:1.25Cr-0.5Mo steel tube has a composition consisting of, by weight, 0.03-0.10% C, 0.50-1.00% Si, 0.0-0.60% Mn, <=0.020% P, <=0.007% S, 1.00-1.50% Cr, 0.45-0.65% Mo, 0.002-0.010% Al, 0.002-0.010% N, and the balance Fe with inevitable impurities. This steel is made to a tube of 13mm wall thickness. Arc welding with covered electrode is executed without having heat treatment of either preheating or postheating, between the steel tubes or between the steel tube and steel tube joint of the same composition as that of the steel tube. By this method, welding crack is prevented without specifying the temp. between passes and the hardness at welding part is kept under approximate Hv250.
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