Abstract: A highly corrosion-resistant spot weldment can be produced at low cost without occurrence of prominent protrusions and the like on the surface. The spot weldment is joined by a nugget formed inside stacked sheet materials through bringing a pair of electrodes arranged opposite to each other into pressure contact with the stacked sheet materials from outside and energizing the stacked sheet materials from the electrodes. The nugget has a diameter that is ?4?t (t: thickness of sheet material) and a flattening level of 3.5 to 8, which is a ratio of diameter to thickness. Both outer surface parts of the sheet materials are free from protrusions formed due to bulging of molten metal. Even when the electrodes are made of a copper alloy, the increased amount of Cu in the outer surface parts is 0.2 mass % or less with respect to the component composition before spot welding.

Abstract: An electrode tip for resistance spot welding includes a main body with tip and base portions. The tip portion has a bottomed and substantially cylindrical shape. The base portion has a substantially cylindrical shape and merges into the tip portion. The main body is made of a copper alloy such as chromium copper. The tip portion has a bottom part and a barrel part. The bottom part has a pressure-contact surface that is not recessed with respect to a workpiece to be pressed. The barrel part has a substantially cylindrical shape and merges into the bottom part. The electrode tip may have an inner diameter ratio (inner diameter of the barrel part to an outer diameter of the base portion) of 0.4 to 0.6, and may also have a bottom thickness ratio (thickness of the bottom part to the outer diameter of the base portion) of 0.15 to 0.5.

Abstract: Provided is a laser welding method for performing lap welding on a plurality of laminated metal plates by applying a laser beam to the metal plates. The metal plates are constituted by n pieces of metal plates laminated in order from a first metal plate to an n-th metal plate, n being an integer not less than 2. The laser welding method includes: forming a recess serving as an escape route for gas by applying a first laser beam from the first metal plate side, the escape route penetrating through the first metal plate to an (n?1)th metal plate in the laminating direction to reach the n-th metal plate; and forming a welding pool around the recess so as to maintain the shape of the recess, the welding pool being formed by applying a second laser beam to the outside of the recess.

Abstract: A laser welding method and a welded structure are provided to improve joining strength by increasing the throat depth and to prevent cracks due to stress concentration by increasing an angle at the back of the throat. The laser welding method for lap welding of multiple layered steel plates by irradiation with a laser beam includes: a step of forming a molten pool penetrating the first steel plate in a layer direction and reaching the second steel plate by irradiating the first steel plate with a first laser beam LB1; and a step of melting an outer peripheral edge of the molten pool by irradiating an outer periphery of the molten pool on the first steel plate with a second laser beam LB2 having a spot diameter D2 larger than a spot diameter D1 of the first laser beam LB1.

Abstract: In a laser welding method, generation of relatively large blow holes in a welding part is prevented while decrease in productivity is reduced. The laser welding method for lap welding, using a laser beam LB, of a plurality of metal plates and including an aluminum alloy cast plate includes: a melting path of scanning and irradiating circularly a superimposed part of the aluminum alloy plate and the aluminum alloy cast plate with a first laser beam LB1 to form a molten pool of the molten aluminum alloy plate and the molten aluminum alloy cast plate; and a stirring path of scanning and irradiating circularly the molten pool with a second laser beam LB2 having a scanning speed V2 faster than a scanning speed V1 of the first laser beam LB1 to stir the molten pool.

Abstract: A laser welding method is provided to ensure a sufficient joining strength between metal plates by increasing the area of a joining region while preventing “burn through” of a molten metal. In the laser welding method by applying a laser beam to a surface of multiple metal plates superimposed on each other, a scanning locus with the laser beam is sequentially shifted from an inner circular scanning locus to an outer one in a predetermined joining region on the metal plates, and an emission interval is provided to temporally stop the metal-plate-surface irradiation when the scanning locus is shifted. Thus, every time the scanning locus is shifted, the molten metal due to the previous irradiation is cooled and increases its viscosity. Accordingly, the “burn through” is prevented regardless of increase of the area of the joining region, which results in a sufficient joining strength between the metal plates.

Abstract: A welding method for joining together a plurality of welding objects by overlapping the plurality of welding objects and performing laser welding includes forming a weld by forming a plurality of nuggets along a virtual closed curve on the welding objects, by laser welding. A ratio of a diameter of the nuggets to a pitch dimension between the nuggets that are adjacent to each other is larger than ½ and no more than 1.

Abstract: Partial welding of partially joining together two metal plates by melting at least one area inside a joining region of the metal plates is performed. After a lapse of a predetermined time from completion of the partial welding, main welding of joining together the metal plates by melting the joining region entirely is performed.

Abstract: Provided are a method and an apparatus for resistance spot welding in which preliminary current application is executed and then main welding is executed in accordance with master patterns of various parameters obtained during the preliminary current application. The main welding is executed under welding conditions of the master patterns, and whether a welding abnormality has occurred and whether the welding abnormality is likely to occur are determined. When the welding abnormality is likely to occur, the welding conditions for the main welding are corrected so as to prevent the welding abnormality. When the welding abnormality is unlikely to occur, the welding conditions for the main welding are corrected so as to match the master patterns.

Abstract: A resistance spot welding method includes sandwiching metal plates put on top of one another between a pair of electrodes and performing resistance spot welding sequentially on a plurality of welding points close to each other on the metal plates by performing a current application between the electrodes so as to join the metal plates to each other. A welding current value to form a welding nugget at a welding point to be subjected to the resistance spot welding second or later among the welding points is set to be higher than a first welding current value to form a first welding nugget at a first welding point to be subjected to the resistance spot welding first among the welding points.

Abstract: A welding method for integrally welding three or more superposed metal plates includes a spot welding of joining the first vehicle body structure plate and the second vehicle body structure plate by spot welding in a plurality of places along an opening edge of the door opening portion in a state where each of the metal plates is superposed, and a laser welding of joining the surface plate and the first vehicle body structure plate in a plurality of places including a place between welding places of the spot welding after the spot welding. The joining being performed by emitting laser light to the surface plate and by scanning the laser light to stir a molten pool including a molten metal of the surface plate and the first vehicle body structure plate melted by the laser light.

Abstract: While a laser-beam application position is moved along a locus which circularly or elliptically circles around a locus center so as to cross a weld line that is a boundary between a first metal plate and a second metal plate overlapped with each other, the locus center is moved in a direction parallel to a weld line. A moving direction of the laser-beam application position is set such that the laser beam is first applied to the first metal plate and then to the second metal plate when the laser beam passes through an unmelted zone of the first metal plate and the second metal plate. The unmelted zone is located downstream of a range through which the laser beam has already passed in the direction parallel to the weld line.

Abstract: Provided is a laser beam welding apparatus capable of correctly detecting the beginning and the end of one welding point even in remote laser beam welding. The laser beam welding apparatus includes a head which irradiates a workpiece with a laser beam, an optical receiver which receives a reflected light of the laser beam from the workpiece, and a controller. The optical receiver receives only a laser beam and a plasma of the reflected light. The controller determines that one welding point begins when a time during which intensity of the reflected light is larger than or equal to a second set-intensity is longer than or equal to a first set-time, and determines that the one welding point ends when a time during which the intensity of the reflected light is smaller than or equal to a first set-intensity is longer than or equal to a second set-time.

Abstract: A laser welding apparatus generates laser by a laser oscillator, converges the laser by a condenser lens, and applies the laser to an upper sheet and a lower sheet superposed together so as to weld the upper sheet and the lower sheet to each other. According to this apparatus, by laser irradiation, a melt pool Y is formed in the upper sheet and the lower sheet superposed together. Furthermore, by laser irradiation, the melt pool Y is caused to flow, and the upper sheet and the lower sheet are welded together.

Abstract: A welded portion inspection method accurately identifies emitted light from a molten portion during inspection laser light irradiation, enabling reliable inspection. When transitioning from welding laser light irradiation to inspection laser light irradiation, the welding laser light irradiation is interrupted and then the welding laser light is switched to the inspection laser light. In inspecting a welded portion, two points in time at which the emitted light intensity is equal to or less than a certain threshold value are extracted from an intensity waveform of the emitted light as an inspection start point in time and an inspection end point in time. The interval between the inspection start and end points is estimated as being a irradiation period of the inspection laser light. The welded state is inspected based on the intensity waveform of the emitted light in the irradiation period.

Abstract: A laser welding apparatus generates laser by a laser oscillator, converges the laser by a condenser lens, and applies the laser to an upper sheet and a lower sheet superposed together so as to weld the upper sheet and the lower sheet to each other. According to this apparatus, by laser irradiation, a melt pool Y is formed in the upper sheet and the lower sheet superposed together. Furthermore, by laser irradiation, the melt pool Y is caused to flow, and the upper sheet and the lower sheet are welded together.

Abstract: A laser welding apparatus generates laser by a laser oscillator, converges the laser by a condenser lens, and applies the laser to an upper sheet and a lower sheet superposed together so as to weld the upper sheet and the lower sheet to each other. According to this apparatus, by laser irradiation, a melt pool Y is formed in the upper sheet and the lower sheet superposed together. Furthermore, by laser irradiation, the melt pool Y is caused to flow, and the upper sheet and the lower sheet are welded together.

Abstract: A laser welding method is capable of easily restraining poor welding when spatters adhere to a protective glass of an optical system. The laser welding method includes a step of calculating a decrease-amount of the laser power before laser welding is performed by irradiating a welding portion of a workpiece with the laser beam having a predetermined power. The step of calculating the decrease-amount includes irradiating the welding portion with an inspecting laser beam having a power smaller than the predetermined power, receiving a return beam of the inspecting laser beam, measuring an intensity of the return beam, and comparing the intensity of the return beam with a standard intensity to calculate an amount of decrease in power of the inspecting laser beam at the welding portion.

Abstract: Provided is a laser welding inspection apparatus capable of improving the accuracy for determining the welding defect. The laser welding inspection apparatus includes a head which irradiates a welded portion of a workpiece with a laser beam for inspection, an optical receiver which receives a return light of the laser beam for inspection from the welded portion, an optical system which adjusts at least a focal diameter of the laser beam for inspection applied to the welded portion and a region where the return light from the welded portion is recognized, and a controller which controls the optical system and determines, based on intensity of the return light, whether a welding defect exists in the welded portion. The controller controls the optical system so that a diameter of the region is not more than 1.5 times as large as the focal diameter.

Abstract: A welding laser beam (L1) is radiated along welding loci (C11, C12) set in workpieces (W1, W2), or an inspection laser beam (L5) is radiated along scanning loci (C51, C52) set in a molten pool (Y1) of the workpieces that are molten by radiation of the welding laser beam, a returned light beam (L2) including reflection light from the molten pool, vapor light caused due to melting and evaporation of the workpieces, and thermal radiation light emitted from the molten pool is received, and a welding state of a welded portion of the workpieces is inspected based on an intensity of a returned light beam received in a first region inside the molten pool which is relatively close to a given point and an intensity of a returned light beam received in a second region inside the molten pool which is relatively spaced from the given point.