METHOD OF SHIELDING WELDED PART OF ORIGINAL PIPE OF ELECTRIC RESISTANCE WELDED STEEL PIPE, AND METHOD OF MANUFACTURING ELECTRIC RESISTANCE WELDED STEEL PIPE

摘要

PROBLEM TO BE SOLVED: To provide a method of shielding a welded part of an original pipe which realizes secure gas shield of the welded part during electric resistance welding to prevent generation of penetrators without sacrificing pipe manufacturing cost or efficiency.SOLUTION: A shielding-gas spraying nozzle 1 comprises a gas outlet 1A at a position 5-300 mm above the upper edge of a welded part 11. By spraying a shielding gas 5 from the gas outlet at a flow rate of 0.5 to 50 m/s over the welded part, the oxygen concentration in the welded part during electric resistance welding can be maintained at a sufficiently low level, improving a weld characteristic of the electric resistance welded steel pipe.