Abstract: A laser welding method and a laser welding apparatus used for this method are proposed. In the laser welding method, when Si-containing steel sheets are passed through a continuous processing line, a tail end of a preceding steel sheet and a leading end of a succeeding steel sheet are placed in contact with each other on a line entry side, and while a filler wire is supplied to a contact part, laser is applied and a filler is melted and solidified to weld the Si-containing steel sheets together. This method includes injecting a shielding gas containing a He gas or an Ar gas and further containing at least one type selected from a CO2 gas and an N2 gas by 10 vol % or higher and 30 vol % or lower in total to a front surface and a back surface of a part being welded.

Abstract: The present invention includes a laser-welded lap joint including a weld zone formed by laser lap welding in a lapped portion including a plurality of lapped steel sheets. The weld zone includes a main weld zone that penetrates the steel sheets in the lapped portion and a final weld zone formed at one end of the main weld zone and having a crater, and the weld zone satisfies formulas (1) to (4): L?15.0;??(1) 10.0?L2?2lc;??(2) t1?2dc;??(3) wc>dc??(4).

Abstract: A laser-welded lap joint includes a weld zone formed by joining a plurality of steel sheets one over another together by laser welding. The weld zone has a J shape and includes a main weld zone having a linear weld line shape and a weld terminal end zone having an arcuate or circular weld line shape. The length L1 of the main weld zone is ? or more and ? or less of the full length L of the weld zone represented by formula (1). The radius R of the weld terminal end zone satisfies formula (2). The angle ? of the weld terminal end zone satisfies formula (3). The total size of a gap between the plurality of steel sheets in a lapped portion is 0% or more and 15% or less of the total thickness of the plurality of steel sheets.

Abstract: A weld inspection apparatus that detects a weld defect in a welded portion of metal plates and includes a liquid application head disposed over one side surface of the metal plates and capable of moving in a welding direction of the metal plates, and an air jet head disposed over another side surface of the metal plates and capable of moving in the welding direction of the metal plates. The liquid application head includes a liquid application nozzle that projects toward the one side surface of the metal plates and applies liquid for sealing the welded portion. The air jet head includes an air jet nozzle that projects toward the another side surface of the metal plates and discharges air toward the welded portion to which the liquid has been applied.

Abstract: A laser-welded lap joint includes a weld zone formed by joining a plurality of steel sheets one over another together by laser welding. The weld zone has a J shape and includes a main weld zone having a linear weld line shape and a weld terminal end zone having an arcuate or circular weld line shape. The length L1 of the main weld zone is ? or more and ? or less of the full length L of the weld zone represented by formula (1). The radius R of the weld terminal end zone satisfies formula (2). The angle ? of the weld terminal end zone satisfies formula (3). The total size of a gap between the plurality of steel sheets in a lapped portion is 0% or more and 15% or less of the total thickness of the plurality of steel sheets.

Abstract: The present invention includes a laser-welded lap joint including a weld zone formed by laser lap welding in a lapped portion including a plurality of lapped steel sheets. The weld zone includes a main weld zone that penetrates the steel sheets in the lapped portion and a final weld zone formed at one end of the main weld zone and having a crater, and the weld zone satisfies formulas (1) to (4): L?15.0;??(1) 10.0?L2?2lc;??(2) t1?2dc;??(3) wc>dc??(4).

Abstract: A laser lap-welded joint being formed from stacked steel sheets and including a plurality of welded portions each having a substantially C-shaped surface, each of the welded portions being formed of a first linear portion and second linear portions having a surface having a semicircular shape. The radius R of the semicircular shape and the sheet thickness t of one of the steel sheets having a larger sheet thickness satisfy 0<R?1.5 t. The pitch ? between the adjacent welded portions and a weld length l satisfy 0.4?l/?<0.7. The space X between an end of a contact portion where the steel sheets are in contact with each other and each of the welded portions satisfy 2 t?X?4 t. The sheet thickness t and the width W of each of the welded portions satisfy 0.3?W/t?1.0.

Abstract: A laser lap-welded joint being formed from stacked steel sheets and including a plurality of welded portions each having a substantially C-shaped surface, each of the welded portions being formed of a first linear portion and second linear portions having a surface having a semicircular shape. The radius R of the semicircular shape and the sheet thickness t of one of the steel sheets having a larger sheet thickness satisfy 0<R?1.5 t. The pitch ? between the adjacent welded portions and a weld length l satisfy 0.4?l/?<0.7. The space X between an end of a contact portion where the steel sheets are in contact with each other and each of the welded portions satisfy 2 t?X?4 t. The sheet thickness t and the width W of each of the welded portions satisfy 0.3?W/t?1.0.