PRODUCTION OF WELDED PIPE

摘要

PURPOSE:To improve the quality of a welded pipe by keyhole type plasma welding and productivity by remelting the penetration bead on the inside surface side of a pipe formed by a plasma torch by a TIG torch using a specifically composed shielding gas. CONSTITUTION:An unwelded part 2 of the pipe 2 is subjected to the keyhole type plasma welding by the plasma torch 3 while the pipe is moved horizontally in an arrow (a) direction at a prescribed speed. The penetration bead 5 of a projecting shape is formed in this state on the inside surface of the pipe in the weld zone 2' as shown in the figure. The weld zone 2' is heated by the TIG torch 4 using the shielding gas composed of 5-15% H2 and 95-85% Ar from the inside surface of the pipe. The penetration bead 5 is thereby remelted and is improved to a shallow flat shape of the penetration bead 6.