| 摘要 |
PURPOSE:To manufacture a high-strength seam-welded steel tube having superior toughness at low temp. by destroying the cast structure of a seam welded steel tube formed by seam welding. CONSTITUTION:The composition of a seam welded steel tube is composed of, by weight, 0.05-0.15% C, <0.5% Si and 1.2-2% Mn as essential components, one or more among <0.05% each of Nb, V and Ti, and the balance Fe with inevitable impurities. The weld zone of the seam welded steel tube is heated at 850-1,050 deg.C, air-cooled and heated at 700-800 deg.C for <=30min.
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