PRODUCTION OF 21/4CR-1MO WELDED STEEL PIPE

摘要

PURPOSE:To produce a Cr-Mo type welded steel pipe of high weld hardenability and remarkably immune from low temp. cracking and transverse cracking easily by subjecting the inside and outside surface of a Cr-Mo type steel plate to SAW or single run welding wherein preceding welding is MIG and succeeding one is SAW under the conditions specified by the equations. CONSTITUTION:A 21/4Cr-1Mo steel plate is formed to a tubular shape, and while the quantity of weld heat input at the inside and outside surfaces thereof is controlled in the range specified by the equations in the relation with the thicknesses of the welding plates, these surfaces are subjected to submerged arc welding or to the single run welding wherein the preceding welding is large current MIG and the succeding one is submerged arc welding. In the equations, H, I are weld heat inputs Kj/cm (=15), W, T are plate thicknesses (=40). If necessary, the pipe is subjected to expanding and sizing properly followed by stress relief annealing.