PULSE YAG LASER BEAM WELDING METHOD FOR LAP JOINT OF GALVANIZED STEEL SHEET

摘要

PROBLEM TO BE SOLVED: To provide a defect-free joint by setting the joint clearance to the prescribed value or over only during the laser beam irradiation in the pulse YAG laser beam welding of a lap joint of a galvanized steel sheet with its Zn coating weight in the prescribed range, and returning the joint clearance to zero until the time when the metal is solidified in the non-irradiation condition of the laser beam. SOLUTION: A lap joint of a galvanized steel sheet (of the thickness =0.3mm and =2.0mm) in which the Zn coating weight is =20g/m2 and =60g/m2 on one side, is welded by the pulse YAG laser beam. When a galvanized steel sheet 7 is irradiated with the laser beam 2, the steel is started to melt. The joint clearance is set to 50m immediately before the laser beam irradiation, the Zn gas in which the galvanized layer is gasified passes through the clearance without blowing a molten part 8, and the clearance is secured and de-aerated while the Zn gas is generated. The joint clearance is returned to zero during 30msec while the laser beam irradiation is stopped and the metal is solidified. The weld zone obtains the welding quality excellent in the joint efficiency free from undercut.