| 摘要 |
PURPOSE:To produce a welded steel pipe having no projecting weld beads on the inner and outer surfaces of the pipe at a low cost by forming a high alloy steel strip into a tubular form, welding the butting edges to produce a steel pipe, grinding and removing the outside weld beads and rolling and removing the inside weld beads with an inserting jig and an outside embracing roll. CONSTITUTION:After an entry stage, a steel strip W of high alloy steel such as stainless steel, is formed by a side guide roll 6 and a plurality of forming rolls 7 in a tubular form, and in a weld stage consisting of squeeze rolls 8, 8 and a welding torch 9, butting edges of a tubular formed body are welded to obtain a steel pipe P. The outside weld beads are removed by cutting or grinding to obtain a smooth surface. Then, a ceramic plug 110b mounted on a core bar 110a is inserted into the steel pipe P and the inside weld beads WB is removed by a rolling mill 11 consisting of an outside embracing rolls 110e. Then, the steel pipe is shaped by sizing rolls 12, heat-treated by an induction heating 13, cooled quickly by a cooled water jet header 14, made free from scale by a cleaning equipment 15 and cut to standard length.
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