METHOD FOR LASER BEAM BUTT WELDING OF TUBE AND LASER BEAM BUTT WELDING MACHINE OF OUTER SURFACE OF TUBE

PURPOSE:To realize the welding at a high speed and with low heat input by continuously executing the butt welding of tubes by making use of the laser beam welding along the butt part while the position of the tubes is fixed. CONSTITUTION:In the end surface butt welding of tubes, a tube 2b to be welded is supported by a plurality of frames 21, 22 in executing the laser beam welding of the outer circumferential surface of the tube at the butt part 2c, and these frames are constituted to be expandable in the vertical direction. On the other hand, a laser beam welding nozzle 1 0 which is extended in the direction of the generating line of the outer circumferential surface of this tube 2b to be welded is provided on the tip of the tube. In the constitution of a welding arm 9 revolving around the circumferential surface, a bend part capable of detouring this arm at the position opposite to either of the frames is provided. Welding is executed by the interaction of the bend part provided in the middle of the welding arm and the expandable frames according to the welding position of the outer circumferential surface of the tube 2b to be welded while the laser beam welding nozzle 10 is continuously revolved along the outer circumferential surface of the tube 2b to be welded.