Abstract: A method for producing a flared or lap joint including a steel sheet and an aluminum-based sheet material through brazing, wherein a preceding laser beam irradiates ahead of a steel sheet joining position and the aluminum-based sheet material in the joining direction to preheat a joining position, an electrically-heated aluminum-based filler wire feeds to the joining position, a following laser beam is irradiated behind the filler wire so the wire melts performin brazing, and the filler wire is fed with a tilt ranging from 0°?D?19° to a front or rear side in the joining direction with respect to a line passing through a groove center of the flared joint and is perpendicular to the joining direction, so that a flared joint or lap joint including a steel sheet and aluminum-based sheet material is produced without appearance defects of a bead and with a sufficient joint strength.

Abstract: A resistance spot welding method includes: performing test welding; and performing actual welding after the test welding, wherein in subsequent current passage in the test welding, current passage is performed by constant current control under a condition: 0.5 ? Vtp/Vtm ? 2.0 when tc<800 ms; 0.5?0.3·(tc?800)/800 ? Vtp/Vtm ? 2.0?0.5·(tc?800)/800 when 800 ms ? tc<1600 ms; and 0.2 ? Vtp/Vtm ? 1.5 when tc ? 1600 ms, and wherein in main current passage in the actual welding, adaptive control welding is performed, and in subsequent current passage in the actual welding, current passage is performed by constant current control under a condition: 0.8·Itp ? Imp ? 1.2·Itp.

Abstract: A resistance spot welding method comprises: performing test welding; and performing actual welding after the test welding, wherein the test welding is performed under each of two or more welding conditions. In the test welding, for each of the welding conditions, an electrode force parameter from when electrode force application to parts to be welded starts to when a set electrode force is reached before start of current passage and a time variation curve of an instantaneous amount of heat generated and a cumulative amount of heat generated are stored.

Abstract: A resistance spot welding method comprises: performing test welding; and performing actual welding after the test welding, wherein in the test welding, 0.2?Vtp/Vtm?1.5 is satisfied where Vtm is an average value of a voltage between the electrodes in main current passage in the test welding and Vtp is an average value of a voltage between the electrodes in subsequent current passage in the test welding, and in each of main current passage and subsequent current passage in the actual welding, a time variation curve of an instantaneous amount of heat generated per unit volume and a cumulative amount of heat generated per unit volume that are stored in a corresponding one of the main current passage and the subsequent current passage in the test welding are set as a target, and adaptive control welding is performed to control a current passage amount according to the target.

Abstract: Provided are an arc welded joint and an arc welding method. The arc welded joint has a slag-coverage area ratio SRATIO (%) of 15% or less, and a weld bead width ratio WRATIO (%) of 60% or more. The SRATIO is calculated by using an equation SRATIO=100×SSLAG/SBEAD. In this equation, an area of a surface of a weld bead formed by performing arc welding on a steel sheet is defined as a weld bead surface area SBEAD (mm2) and, of the weld bead surface area SBEAD, an area of a region covered with slag is defined as a slag surface area SSLAG (mm2). The WRATIO is calculated by using an equation WRATIO=100×WMIN/WMAX from a maximum value WMAX (mm) and a minimum value WMIN (mm) of a weld bead width in a direction perpendicular to a welding line of the weld bead.

Abstract: Provided is a resistance spot welding method wherein main current passage includes two or more electrode force application steps including a first electrode force application step and a second electrode force application step following the first electrode force application step, an electrode force F1 in the first electrode force application step and an electrode force F2 in the second electrode force application step in the main current passage satisfy a relationship F1<F2, and an electrode force switching point Tf from the first electrode force application step to the second electrode force application step in the main current passage is set to satisfy predetermined relational formulas.

Abstract: Provided is a resistance spot welding method wherein main current passage includes two or more electrode force application steps including a first electrode force application step and a second electrode force application step following the first electrode force application step, an electrode force F1 in the first electrode force application step and an electrode force F2 in the second electrode force application step in the main current passage satisfy a relationship F1>F2, and an electrode force switching point Tf from the first electrode force application step to the second electrode force application step in the main current passage is set to satisfy predetermined relational formulas.

Abstract: A resistance spot welding method comprises: performing test welding; and performing actual welding after the test welding. The test welding is performed under each of two or more welding conditions. In the actual welding, preliminary current passage is performed by constant current control in the same current pattern as in the preliminary current passage of the test welding, an electrical property between the electrodes in the preliminary current passage in the actual welding and an electrical property between the electrodes stored in the preliminary current passage in the test welding are compared for each welding condition to set a target in main current passage in the actual welding, and thereafter adaptive control welding is performed to control a current passage amount as the main current passage.

Abstract: A MIG welding method for carbon steels using an Ar shielding gas. The method includes short-circuiting a welding wire and a base material. The average short-circuiting frequency in welding is 20 Hz to 300 Hz and the maximum short-circuiting period is 1.5 s or less.

Abstract: Proposed is a resistance spot welding method to join parts to be welded which are a plurality of overlapping metal sheets, including: dividing a current pattern into two or more steps for welding; before actual welding, performing test welding; and subsequently, as actual welding, performing adaptive control welding, in which the two or more steps for welding include a step of securing a current path between the sheets directly below the electrodes and a subsequent step of forming a nugget having a predetermined diameter, and a welding interval time is provided between these steps. This method thus yields a good nugget without causing splashing even under special welding conditions.

Abstract: A welding determination method is provided, which determines whether a spot welding part is joined to an electrode without using resistance generated when separating the electrode from a workpiece. In the method, the workpiece made by laminating multiple metal sheets is clamped under pressure by a pair of electrodes and melted by a current applied, and after that the conduction is stopped to hold the workpiece in a pressurized state to determine whether the joining occurs. The method includes the steps of: deriving resistance between the pair of electrodes and pressurizing force by the pair of electrodes during conduction to the workpiece; and determining whether the spot welding part is joined to the electrodes based on a first index value calculated using the derived resistance and resistance in an ideal welding, and on a second index value calculated using the derived pressurizing force and pressurizing force in the ideal welding.

Abstract: Provided is a resistance spot welding method by which a desired nugget diameter can be stably obtained without expulsion even when the effect of a disturbance is significant. An electrode force FA of a main current passage after an intermediate welding time Ta is set based on an average value or time integration value RA of a resistance between electrodes from the start of main current passage to the intermediate welding time Ta.

Abstract: Provided is a resistance spot welding method. The resistance spot welding method for joining a sheet set including a plurality of lapped steel sheets includes: holding the sheet set between a pair of electrodes; and energizing the sheet set under application of electrode force to thereby join the steel sheets together. At least one of the plurality of lapped steel sheets is a surface-treated steel sheet including a metal coating layer on a surface thereof. The energizing includes: a primary energizing step of performing energization to form a nugget portion; a non-energizing step in which, after the primary energizing step, the energization is suspended for an energization suspension time Tc (cycles); and a secondary energizing step of, after the non-energizing step, performing energization for reheating while the nugget portion is prevented from growing. During the energizing, the relations of a particular formula are satisfied.

Abstract: Disclosed is a hot-pressed member that can exhibit very high tensile strength after hot pressing as high as TS: 1780 MPa or more, excellent resistance to resistance welding cracking, and excellent delayed fracture resistance after resistance welding by having a specific chemical composition, and a microstructure such that a prior austenite average grain size is 7 ?m or less, a volume fraction of martensite is 90% or more, and at least 5 Nb-based precipitates having a grain size of less than 0.08 ?m are present on average per 100 ?m2 of a cross section parallel to a thickness direction of the member within a range of 100 ?m in the thickness direction from a surface of the member, and such that a Ni diffusion region having a thickness of 0.5 ?m or more is present in a surface layer of the member.

Abstract: A resistance spot welding method comprises: performing test welding; and performing actual welding after the test welding, wherein in subsequent current passage in the test welding, current passage is performed by constant current control under a condition: 0.5?Vtp/Vtm?2.0 when tc<800 ms; 0.5?0.3×(tc?800)/800?Vtp/Vtm?2.0?0.5×(tc?800)/800 when 800 ms?tc<1600 ms; and 0.2?Vtp/Vtm?1.5 when tc?1600 ms, where Vtm is an average value of a voltage between the electrodes in main current passage in the test welding, and Vtp is an average value of a voltage between the electrodes in the subsequent current passage in the test welding, and wherein in main current passage in the actual welding, adaptive control welding is performed, and in subsequent current passage in the actual welding, current passage is performed by constant current control under a condition: 0.8×Itp?Imp?1.

Abstract: A resistance spot welding method comprises: performing test welding; and performing actual welding after the test welding, wherein in the test welding, 0.2?Vtp/Vtm?1.5 is satisfied where Vtm is an average value of a voltage between the electrodes in main current passage in the test welding and Vtp is an average value of a voltage between the electrodes in subsequent current passage in the test welding, and in each of main current passage and subsequent current passage in the actual welding, a time variation curve of an instantaneous amount of heat generated per unit volume and a cumulative amount of heat generated per unit volume that are stored in a corresponding one of the main current passage and the subsequent current passage in the test welding are set as a target, and adaptive control welding is performed to control a current passage amount according to the target.

Abstract: A resistance spot welding method of squeezing parts to be welded, which are a plurality of overlapping metal sheets, by a pair of electrodes and passing a current while applying an electrode force to join the parts to be welded comprises: a first step of passing a current by constant current control to form a fusion zone having a diameter of not less than 2?{square root over (t)}, expressed in mm, between the metal sheets, where t, expressed in mm, is a sheet thickness of a thinnest metal sheet of the metal sheets; a second step of cooling the fusion zone to have a diameter of not greater than 80% of D, where D, expressed in mm, is a diameter of the fusion zone formed in the first step; and a third step of performing adaptive control welding by controlling a current passage amount according to a target that is set.

Abstract: A resistance spot welding method comprises: performing test welding; and performing actual welding after the test welding, wherein in main current passage in the actual welding, adaptive control welding is performed, and in subsequent current passage in the actual welding, current passage is performed by constant current control with a current determined based on an electrical property between electrodes in each of main current passage in the test welding and the main current passage in the actual welding.

Abstract: Provided is a resistance spot welding method that inhibits, in accordance with the degree of axis misalignment between electrodes, the occurrence of cracking in a weld regardless of the steel grade. In resistance spot welding methods according to the present invention, H (ms) is an electrode force retaining time after completion of current passage, D (mm) is an amount of axis misalignment between the electrodes, t (mm) is a total sum of sheet thicknesses of a plurality of overlapping steel sheets, T (MPa) is a tensile strength of a steel sheet having a highest tensile strength among the plurality of steel sheets, F (N) is an electrode force, and d (mm) is a tip diameter of one electrode of the pair of electrodes that has a smaller tip diameter. The electrode force retaining time H is specified to be a predetermined value or greater.

Abstract: A resistance spot welding method comprises: performing test welding; and performing actual welding after the test welding. The test welding is performed under each of two or more welding conditions. In the actual welding, preliminary current passage is performed by constant current control in the same current pattern as in the preliminary current passage of the test welding, an electrical property between the electrodes in the preliminary current passage in the actual welding and an electrical property between the electrodes stored in the preliminary current passage in the test welding are compared for each welding condition to set a target in main current passage in the actual welding, and thereafter adaptive control welding is performed to control a current passage amount as the main current passage.