Patent ID: 8841577

Claim:
A laser lap welding method for parts made of galvanized steel sheet, comprising the steps of: press-forming two parts from galvanized steel sheet into three-dimensional shapes such that the two parts include elongated regions to be welded together on mutually opposed surfaces thereof and a plurality of protrusions are formed on at least any one of the elongated regions of the two parts at predetermined intervals in a longitudinal direction of the elongated region, wherein each of the protrusions is formed into a ridge-shape having a ridge line extending in a substantially orthogonal direction to the longitudinal direction of the elongated regions; retaining the two parts in a state in which the elongated regions are overlapped one over the other such that a gap according to a height of the protrusions is formed between the elongated regions; and irradiating a laser onto one surface of the overlapped elongated regions of the two parts between the protrusions such that the overlapped elongated regions are fused and welded by energy of the laser, and zinc gas produced by fusing is discharged through the gap, wherein irradiating the laser includes discrete unit laser scanning each of which is scanned along a curved line surrounding a unit spot of an equivalent area to a welded spot, the unit spot being disposed away from regions where the two parts are in contact with one another.