| 摘要 |
PURPOSE:To obtain a high tensile electric welded steel pipe having excellent low temp. toughness in an electric weld zone and base metal part by cooling quickly a steel having a prescribed component compsn. at a specific rate or above with a run-out table after the end of hot finish rolling. CONSTITUTION:A steel contg., by wt%, 0.0005-0.04% C, <=0.5% Si, 1.0-1.7% Mn, <=0.04% Ti, 0.001-0.050% V, 0.001-0.050% Nb, <=0.03% P, <=0.008% S, and <=0.010% N, and consisting of the balance Fe and unavoidable impurities is prepd. The hot rolling of said steel is ended at a low temp. of about 780-850 deg.C to form fine grains and thereafter the steel plate is quickly cooled at >=30 deg.C/sec with a run-out table to fine the pearlite. As a result, the high tensile electric welded steel pipe having excellent low temp. toughness in the weld zone and base metal part is otd. even if the pipe is not subjected to a heat treatment after electric welding, i.e., post annealing, etc. |
