Laser beam welding method for an inner cicumferential surface of a tube.

摘要

A laser beam welding apparatus for an inner circumferential surface of a tube (11) is disclosed herein, which apparatus comprises an elongated flexible tube (33) containing an optical fiber extended along the length thereof so as to transmit a laser beam, position detecting means disposed in the vicinity of the top end of the flexible tube to determine relative positioning thereof with respect to a work tube (11) in which the flexible tube (33) is inserted, holding means (19') provided with an expander and disposed adjacent to the position detecting means for holding the tip end of the flexible tube in the work tube, rotary drive means (23) disposed closer to the tip end of the flexible tube than the holding means, a rotary cylinder (26) connected to the rotary drive means to be rotated with respect to the flexible tube (33), guide means (48) mounted on the rotary cylinder in a relatively rotatable manner with respect to the rotary cylinder and held in contact with the inner surface of the work tube for supporting the rotary cylinder in a concentric relation to the work tube, and an optical train (36) arranged with the rotary cylinder for receiving a laser beam emitted from the optical fiber and focusing a reflected laser beam onto the inner surface of the work tube (11).