| 摘要 |
PROBLEM TO BE SOLVED: To provide a spiral steel tube which can be efficiently produced using inside-outside continuous welding capable of obtaining high productivity, and is provided with a weld metal part having sufficient toughness. SOLUTION: The method for producing a spiral steel tube includes: a step where, while a steel strip 1 is coiled into a spiral shape, the edge faces in the width direction of the steel strip are welded each other to either side of the inside and outside faces to form a precedence weld metal part 4, and, continuously, by welding to the other side, a succeeding weld metal part is formed to form a tubular body 5 having the weld metal part with a prescribed chemical composition; a heating step where the weld metal part is heated at 1,000 to 1,150°C for 5 s to 20 min; a cooling step where, after the heating step, the weld metal part at a temperature of 900 to 500°C is cooled at the average cooling rate of≥10°C/s; and a step where the weld metal part is heated and held at 300 to 600°C for a time of 5 to 90 min per the sheet thickness of 25.4 mm, and is subjected to tempering treatment. COPYRIGHT: (C)2011,JPO&INPIT |
