Abstract: A laser lap welding method by irradiating of a laser beam from one side of a plurality of overlapped workpieces (1, 2), the method includes the steps of: scanning (La) the laser beam in the forward direction along a predetermined section of the workpieces; reversing the scanning direction of the laser beam at a terminating end (t) of the predetermined section; scanning (Lb) the laser beam in the backward direction and terminating of the irradiating of the laser beam onto the predetermined section, wherein the scanning of the laser beam in the backward direction is offset from the scanning of the laser beam in the forward direction such that a part of weld bead (12) formed by the laser scanning in the backward direction overlaps the weld bead (11) formed by the laser scan in the forward direction.

Abstract: A laser lap welding method for parts made of galvanized steel sheet includes steps of: press-forming two parts from galvanized steel sheet such that the two parts include elongated joining regions to be welded together on mutually opposed surfaces thereof and a plurality of protrusions are formed on at least any one of the joining regions of the two parts at predetermined intervals in a longitudinal direction of the joining region; retaining the two parts in a state in which the joining regions are overlapped one on the other such that a gap according to a height of the protrusions is formed between the joining regions; and irradiating a laser onto one surface of the overlapped joining regions of the two parts such that the overlapped joining regions are fused and welded by energy of the laser, and zinc gas produced with fusing is discharged through the gap.

Abstract: An apparatus 1 of the present invention includes a laser emitting unit 2, a monitor unit 3, a storage unit 4, an image extraction unit 5, a bead recognition unit 6, and a bead shape determination unit 7. The bead shape determination unit 7 is configured to calculate the position of the end of a bead region based on the bead region recognized by the bead recognition unit 6, and to determine whether the shape of the end of the bead region is convex or concave in the extending direction of the bead region.

Abstract: A laser lap welding method for parts made of galvanized steel sheet includes steps of press-forming two parts from galvanized steel sheet such that the two parts include elongated joining regions to be welded together on mutually opposed surfaces thereof and a plurality of protrusions are formed on at least any one of the joining regions of the two parts at predetermined intervals in a longitudinal direction of the joining region; retaining the two parts in a state in which the joining regions are overlapped one on the other such that a gap according to a height of the protrusions is formed between the joining regions; and irradiating a laser onto one surface of the overlapped joining regions of the two parts such that the overlapped joining regions are fused and welded by energy of the laser, and zinc gas produced with fusing is discharged through the gap.

Abstract: Provided is a laser lap welding method including the steps of: preparing two steel sheets, at least one of which is a galvanized steel sheet, in such a manner that the steel sheets are directly lapped one over the other with a galvanized layer of the galvanized steel sheet located as an interface of the steel sheets; and irradiating an outer surface of any one steel sheet in the lap region of the two steel sheets with a laser beam under predetermined power and speed conditions, so that an elongated hole is formed in a molten pool extending backward from a laser irradiation position at least in the steel sheet on the outer surface side. Welding of the two steel sheets is performed while venting metal vapor produced by the laser irradiation through the elongated hole backwards in a laser travelling direction and towards a laser irradiation source.

Abstract: To provide a laser lap welding method including: performing lap welding (11; 21) by irradiating a laser beam (La) on a plurality of overlapped workpieces (1, 2); and irradiating, after a very short interruption time period of the laser beam irradiation, a defocused laser beam (Lc) on a terminating end (12; 22) of the lap welding. Preferably, the laser lap welding method including: interrupting the irradiation of the laser beam for a very short time period and moving, during the interruption time period, the optical axis of the laser beam from the terminating end of the lap welding to the side of the starting end of the lap welding; and irradiating a defocused laser beam from the position to which the optical axis of the laser beam is moved, to the terminating end of the lap welding.

Abstract: A laser lap welding method by irradiating of a laser beam from one side of a plurality of overlapped workpieces (1, 2), the method includes the steps of: scanning (La) the laser beam in the forward direction along a predetermined section of the workpieces; reversing the scanning direction of the laser beam at a terminating end (t) of the predetermined section; scanning (Lb) the laser beam in the backward direction and terminating of the irradiating of the laser beam onto the predetermined section, wherein the scanning of the laser beam in the backward direction is offset from the scanning of the laser beam in the forward direction such that a part of weld bead (12) formed by the laser scanning in the backward direction overlaps the weld bead (11) formed by the laser scan in the forward direction.

Abstract: A laser lap welding method for parts made of galvanized steel sheet includes steps of: press-forming two parts from galvanized steel sheet such that the two parts include elongated joining regions to be welded together on mutually opposed surfaces thereof and a plurality of protrusions are formed on at least any one of the joining regions of the two parts at predetermined intervals in a longitudinal direction of the joining region; retaining the two parts in a state in which the joining regions are overlapped one on the other such that a gap according to a height of the protrusions is formed between the joining regions; and irradiating a laser onto one surface of the overlapped joining regions of the two parts such that the overlapped joining regions are fused and welded by energy of the laser, and zinc gas produced with fusing is discharged through the gap.

Abstract: A laser lap welding method for parts made of galvanized steel sheet includes steps of press-forming two parts from galvanized steel sheet such that the two parts include elongated joining regions to be welded together on mutually opposed surfaces thereof and a plurality of protrusions are formed on at least any one of the joining regions of the two parts at predetermined intervals in a longitudinal direction of the joining region; retaining the two parts in a state in which the joining regions are overlapped one on the other such that a gap according to a height of the protrusions is formed between the joining regions; and irradiating a laser onto one surface of the overlapped joining regions of the two parts such that the overlapped joining regions are fused and welded by energy of the laser, and zinc gas produced with fusing is discharged through the gap.

Abstract: An apparatus 1 of the present invention includes a laser emitting unit 2, a monitor unit 3, a storage unit 4, an image extraction unit 5, a bead recognition unit 6, and a bead shape determination unit 7. The bead shape determination unit 7 is configured to calculate the position of the end of a bead region based on the bead region recognized by the bead recognition unit 6, and to determine whether the shape of the end of the bead region is convex or concave in the extending direction of the bead region.

Abstract: Provided is a laser lap welding method for a galvanized steel sheet, comprising the steps of: preparing two steel sheets (11, 12), at least one of which is a galvanized steel sheet, in such a manner that the steel sheets are directly lapped one over the other with a galvanized layer of the galvanized steel sheet located as an interface of the steel sheets; and irradiating an outer surface of any one steel sheet in the lap region of the two steel sheets with a laser beam under predetermined power and speed conditions, so that an elongated hole (20) is formed in a molten pool (2) extending backward from a laser irradiation position (10) at least in the steel sheet on the outer surface side, whereby welding (3) of the two steel sheets is performed while venting metal vapor (23) produced by the laser irradiation through the elongated hole (20) backwards (R) in a laser travelling direction and towards a laser irradiation source, wherein at a starting end portion (131, 231, 331) of a welding section (103, 203, 303)

Abstract: A laser lap welding method, for a galvanized sheet, includes, irradiating a laser beam while traveling at a laser traveling speed (v) mm/sec which leads a power per volume in unit time (P/øtv) of the laser beam within a range from 0.07 to 0.11 kWsec/mm3 when the laser beam has a power (P) which is not less than 7 kW and an irradiation spot diameter (ø) which is not less than 0.4 mm and a galvanized steel sheet has a thickness (t) mm, so that an elongated hole is formed in a molten pool extending backward from a laser irradiation spot at least in the steel sheet on the outer surface side, whereby metal vapor produced by laser irradiation is vented through the elongated hole backward in a laser traveling direction and in a direction towards a laser irradiation source.