| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for preventing transverse cracks caused in the weld metal of a seam-welded part when manufacturing a UOE steel tube of high strength of≥800 N/mm<SP>2</SP>. SOLUTION: In a method for manufacturing the high-strength UOE steel tube having a tensile strength of a base material of≥800 MPa, an outer diameter of≥406 mm, and a thickness of≥10 mm, a steel plate is formed into a tube, and butt parts of the tubes are temporarily welded. A seam welding by a submerged arc welding is performed on an inner surface and an outer surface of the steel tube by using a welding flux of diffusible hydrogen of≤20 ml/100 g under a condition that the tensile strength of a seam weld metal is≤1,400 MPa, and 0.8 to 1.4 times the tensile strength of the base metal. After the lapse of 30 minutes from the completion of the welding, the steel tube is expanded under a condition that the expansion ratio is≤5%. COPYRIGHT: (C)2004,JPO |
