LASER WELDING OF A SLEEVE WITHIN A TUBE

摘要

34 The invention relates to a method for welding a sleeve within a tube of a steam generator, the sleeve being in close contact with the tube. A welding head of a weld head apparatus is positioned within the tube at a predetermined weld site, a laser beam is directed to the welding head, the beam is focused with a focusing means, the focused laser beam is reflected with a welding mirror means into contact with a portion of the sleeve to be welded to the tube, the welding mirror means is maintained a predetermined focal distance from the inside surface of the sleeve, and the welding head is rotated to complete a weld fusion path about the inner periphery of the sleeve. Shielding gas is used to shield the weld site. A robotic arm positions the weld head apparatus within the steam generator. At each end of the sleeve, multiple discrete weld paths or a continuous helical multiple weld path are welded. The sleeve is preferably welded to the tube along the weld path with a fusion width at the interface between the sleeve and tube of at least 0.045 inches and the tube is penetrated to a depth of at least 0.25 inches. The laser delivers 500 to 700 watts to the weld area.