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: A spot welding electrode includes a copper alloy, and a sintered tungsten alloy disposed in a tip portion of the spot welding electrode, the tip portion of the spot welding electrode being brought into contact with an object to be welded. The sintered tungsten alloy is connected only at a single flat surface to the copper alloy. A thermal conductivity of the spot welding electrode is within a range from 60 W/mK to 120 W/mK.

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.

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 1/2 and no more than 1.

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: 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 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 welded portion (1) formed at a joint between a plurality of steel plates (10) is formed of a plurality of nuggets (11) arranged along a virtual closed curve (12), and when the thickness of the thinnest steel plate (10) of the steel plates (10) is denoted by t, the diameter d of each nugget (11) is 3 ?t or less, and the pitch p between adjacent nuggets is 2 d or more but no more than 5 d, and the number of nuggets is three or more.

Abstract: There are provided an electrode tip dressing apparatus and an electrode tip dressing tool for resistance welding, which are miniaturized by reducing a rotational driving-force of a dressing tool. By adjusting a curvature radius of a dressing portion 4 of a dressing tool 2, a contact width, wherein a top electrode tip 5 abuts to the dressing portion 4 of the dressing tool 2, is adjusted from a rotational center of the dressing tool 2 to the outer side of the dressing tool 2. Dressing work done with the dressing tool 2 is thus made to be constant at the whole area of the dressing portion 4, from the rotational center of the dressing tool 2 to the outer side of the dressing tool 2. Accordingly, excess dressing work, which brings decline of productivity, can be avoided, thus enabling to dress the top electrode tip 5 with the minimal dressing work. A rotational driving-power of the dressing tool 2 is thereby reduced, enabling to labor-save and miniaturize the electrode tip dressing apparatus.

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: There are provided an electrode tip dressing apparatus and an electrode tip dressing tool for resistance welding, which are miniaturized by reducing a rotational driving-force of a dressing tool. By adjusting a curvature radius of a dressing portion 4 of a dressing tool 2, a contact width, wherein a top electrode tip 5 abuts to the dressing portion 4 of the dressing tool 2, is adjusted from a rotational center of the dressing tool 2 to the outer side of the dressing tool 2. Dressing work done with the dressing tool 2 is thus made to be constant at the whole area of the dressing portion 4, from the rotational center of the dressing tool 2 to the outer side of the dressing tool 2. Accordingly, excess dressing work, which brings decline of productivity, can be avoided, thus enabling to dress the top electrode tip 5 with the minimal dressing work. A rotational driving-power of the dressing tool 2 is thereby reduced, enabling to labor-save and miniaturize the electrode tip dressing apparatus.