A resistance welding machine includes a first electrode and a second electrode which are configured so that the first and second electrodes can hold a workpiece therebetween and apply a current to the workpiece. The first electrode includes a first inner electrode and a first outer electrode disposed outside the first inner electrode at a predetermined interval. The second electrode includes a second inner electrode and a second outer electrode disposed outside the second inner electrode at a predetermined interval. The resistance welding machine further includes a control unit that can control a pressing state of the workpiece with the first and second electrodes according to predetermined welding conditions and selects a pair of electrodes that apply a current to the workpiece from the first inner electrode, the first outer electrode, the second inner electrode, and the second outer electrode.

An indirect spot welding apparatus includes a welding electrode that is brought into pressure contact with one of surfaces of a plurality of plate-shaped members that are objects to be welded in one side in a stacking direction of the plate-shaped members, a ground electrode that is brought into pressure contact with the one of the surfaces in the one side or another one of the surfaces in the other side in the stacking direction in a position shifted from an axial center of the welding electrode, and an opposed member disposed coaxially with the ground electrode to be opposed to the ground electrode so as to hold at least one of the plate-shaped members between the opposed member and the ground electrode, and the welding electrode is mechanically integrated with the ground electrode to be movable in a direction parallel to an axial direction of the ground electrode.

A welded assembly and a method of reaction metallurgical welding are disclosed. The assembly includes a first metallic workpiece and a second metallic workpiece attached together by at least two overlapping weld joints. The overlapping weld joints are reaction metallurgically joined (RMJ) weld joints, and each overlapping weld joint overlaps with the other overlapping weld joint by 10-75%. The method of welding includes providing a reactive material between and in contact with the first and second workpieces. In a first position, the workpieces and the reactive material are pressed together, heated, and held between first and second tools to form a first RMJ weld joint between the workpieces. Then, in a second position, the workpieces are pressed together, heated, and held between the tools to form a second RMJ weld joint that overlaps with the first RMJ weld joint.

An equipment main bod includes an intermediate electrode set disposed between upper and lower welding electrodes and provided at at least one of the upper and lower welding electrode sides. The intermediate electrode set includes a plurality of intermediate units, each intermediate unit having an intermediate electrode set jig and an intermediate electrode attachable to and detachable from the intermediate electrode set jig, and is configured as a rotary type in which the plurality of intermediate units are provided so as to be rotatable in a circumferential direction such that the plurality of intermediate units sequentially stop at a welding position that is aligned with the upper and lower welding electrodes in an up-down direction. The intermediate electrode set is configured to resistance-weld the workpiece, while pressing the workpiece by the pressing unit, via the intermediate electrode of the intermediate unit at the welding position.

A method for spot-welding metallic materials includes: sandwiching the metallic materials with a pair of electrodes; a pre-heating step for pre-heating a region different from a given region which should be welded by applying electric power having a high frequency to the pair of electrodes; and a welding step for spot-welding a given region of the metallic materials by applying electric power for welding to the pair of electrodes. The heating time in the pre-heating step and that in the welding step are independently controlled.

A welding equipment for metallic materials capable of performing heat treatment such as tempering based on partial heating in spot welding is provided. The welding equipment sandwiches metallic materials with a pair of electrodes, and heats different regions of the metallic materials by energization, with the pair of electrodes maintained at the same position with respect to the metallic materials. The welding equipment includes a first heating means connected to the pair of electrodes for heating and welding the internal region of the circle defined by projecting the cross-sectional area of the axis of the electrodes on the metallic materials by applying power having a low first frequency, a second heating means for heating a ring-shaped region along the circle by applying power having a second frequency that is higher than the first frequency, and an energization control unit for independently controlling the first and the second heating means.

A welding device for joining components by resistance welding includes a pair of electrodes which can introduce an electrode force and an electrical welding current I.sub.S1 into the components, at least one further pair of electrodes which can introduce an electrode force and a further electrical welding current I.sub.S2 into the components, a power source which can generate the electrode forces, a coupling link which is mechanically connected between the power source and the pairs of electrodes and which can divide a total electrode force that can be generated by the power source into the electrode force and the further electrode force.

A welding gun includes first and second movable arms, and first and second welding electrodes. The first and second movable arms are movable upward and downward. The first and second welding electrode are disposed respectively on the first and second movable arms. The welding gun is capable of performing a first mode in which the first and second welding electrodes are brought into contact with one side of a workpiece to weld the workpiece, and a second mode in which the workpiece is sandwiched by the first and second welding electrodes to weld the workpiece. The first and second welding electrodes are pivotally supported by the first and second movable arms, respectively. Each of the first and second welding electrodes has a rotatable roller shape. The first movable arm includes a first slide mechanism configured to allow the first welding electrodes to slide to below the second welding electrode.

A welding device for wire meshes which extend in a plane with a predefined width and have meshes, wherein said welding device comprises multiple electrodes which are connected to transformers via current paths.

A spot welding apparatus includes a stationary frame having a housing formed therein. An upper welding gun is mounted to a length direction of a pressing unit disposed in the housing of the stationary frame. A plurality of lower welding guns are mounted on an outside of the stationary frame and ends of the plurality of lower welding guns selectively face one end of the upper welding gun in a length direction of the lower welding guns by the plurality of lower welding guns. A plurality of actuators are mounted on the outside of the stationary frame. A plurality of link units are disposed between the actuators and the lower welding guns, connect the actuators and the lower welding guns, respectively, and rotate as the actuators are operated.