Laser welding method for workpiece

A method of laser welding a first workpiece and a second workpiece stacked so as to surface-contact with each other, the first workpiece and the second workpiece each including a base material, at least one of the first workpiece and the second workpiece including a cover material interposed between the base materials of the first workpiece and the second workpiece, the method comprising:

• generating a laser beam by a laser oscillator and irradiating the first workpiece with the laser beam;
• swinging an irradiation point of the laser beam within a heating area, which is set on the first workpiece so as to encompass a welding location on which the laser welding is to be executed, and heating a mating surface area of the first workpiece and the second workpiece, which corresponds to the heating area, to a temperature being equal to or higher than a boiling point of the cover material and lower than a melting point of the base material of the first workpiece;
• forming a gap between the first workpiece and the second workpiece by vaporizing the cover material in the mating surface area by the heating, and discharging the cover material to outside of the mating surface area through the gap;
• and
• melting and welding the base materials of the first workpiece and the second workpiece to each other in the welding location by irradiating the welding location with the laser beam, after discharging the cover material to the outside of the mating surface area.