A series of many electrical resistance spot welds is to be formed in members of an assembled, but un-joined, body that presents workpiece stack-ups of various combinations of metal workpieces including all aluminum workpieces, all steel workpieces, and a combination of aluminum and steel workpieces. A pair of spot welding electrodes, each with a specified weld face that includes oxide-disrupting features, is used to form the required numbers of aluminum-to-aluminum spot welds, aluminum-to-steel spot welds, and steel-to-steel spot welds. A predetermined sequence of forming the various spot welds may be specified for extending the number of spot welds that can be made before the weld faces must be restored. And, during at least one of the aluminum-to-steel spot welds, a cover is inserted between the weld face of one of the welding electrodes and a side of a workpiece stack-up that includes the adjacent aluminum and steel workpieces.

A method of resistance spot welding a steel workpiece and an aluminum or aluminum alloy workpiece, and a welding electrode used therein. In one step of the method a workpiece stack-up is provided. The workpiece stack-up includes a steel workpiece and an aluminum or aluminum alloy workpiece. Another step of the method involves contacting the aluminum or aluminum alloy workpiece with a weld face of the welding electrode. The welding electrode has a body and an insert. The insert is composed of a material having an electrical resistivity that is greater than an electrical resistivity of the material of the body. The weld face has a first section defined by a surface of the insert and has a second section defined by a surface of the body. Both the first and second sections make surface-to-surface contact with the aluminum or aluminum alloy workpiece amid resistance spot welding.

A collet assembly including an actuator and a collet connected to the actuator. The collet assembly is adapted to be installed on a welding electrode holder having an electrode. The collet is moveable by the actuator from an advanced position, in which the collet is adapted to grip a fastener such as a welding rivet, and a retracted position, in which at least a portion of the collet is retracted into the actuator to enable the electrode to engage the fastener for welding to a work piece, and the collet is adapted to release the fastener.

A method of resistance spot welding workpiece stack-ups of different combinations of metal workpieces with a single weld gun using the same set of welding electrodes is disclosed. In this method, a set of opposed welding electrodes that include an original shape and oxide-disrupting structural features are used to resistance spot weld at least two of the following types of workpiece stack-ups in a particular sequence: (1) a workpiece stack-up of two or more aluminum workpieces; (2) a workpiece stack-up that includes an aluminum workpiece and an adjacent steel workpiece; and (3) a workpiece stack-up of two or more steel workpieces. The spot welding sequence calls for completing all of the aluminum-to-aluminum spot welds and/or all of the steel-to-steel spot welds last.

A spot welding electrode of a donut-shaped electrode wherein even when a welded member of a steel sheet is slanted with respect a plane perpendicular to an axis of the spot welding electrode, a cross tensile strength (CTS) of the spot welded joint can be improved. The donut shape spot welding electrode according to the present invention has an electrode tip and an electrode support. The electrode tip contacts the electrode support to be able to move. Due to this, it is possible to strikingly raise the ability of the donut-shaped electrode to track a steel sheet and make the entire surface of the donut shape contact-and-conduction part contact the steel sheet, so it is possible to secure a high CTS value even if the steel sheet is slanted.

A welding tip (20) for spot welding a first part (22) formed of conductive metal, for example aluminum, to a second part (24) formed of aluminum or another conductive metal, such as steel, is provided. The welding tip (20) includes a notch (30) at a distal end (38) and a convex contact surface (28) extending radially outwardly and upwardly from the notch (30) for engaging a surface of the first part (22). The rotating welding tip (20) forms a depression (32) on the surface of the first part (22) during the welding process. The notch (30) creates a pin (34) in the center of the depression (32) which provides a fixed axis of rotation for the rotating welding tip (20) and prevents the welding tip (20) from moving radially relative to the fixed axis, thereby improving the quality of the final spot weld (36) and reducing process time.

Disclosed is a method for manufacturing a spark plug of the type in which a tip is joined to a ground electrode. In a positioning step, the ground electrode is positioned with respect to a first electrode by means of a pressing member. In a tip pressing step, the tip is pressed against a tip weld site of the ground electrode by means of a second electrode. In a welding step, the tip is resistance welded to the tip weld site of the ground electrode by the passage of electric current between the first and second electrodes.

A transfer processing unit of a processing tool for an electrode for resistance spot welding that is configured to mold, through transfer processing, a projection portion and a plurality of recess portions at an electrode tip portion bulging into a projecting shape is provided with a plurality of protrusions that are configured to mold the plurality of the recess portions respectively. A virtual plane that links tips of the plurality of these protrusions with one another assumes a shape coinciding with a surface shape of the electrode tip portion bulging into the projecting shape before transfer processing.

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 electrical resistance spot welding electrode is disclosed for contact with a narrow or other selected spot weld region in a steel workpiece in a stack-up with an aluminum alloy workpiece for use in a spot welding method in which the weld nugget is carefully formed in the aluminum workpiece at the interface of the stack-up. The welding face of the welding electrode for contact with the steel workpiece is shaped with an aspect ratio greater than one, which fits against the contact surface of the steel workpiece, while the welding face for the aluminum-contacting weld electrode is circular (with an aspect ratio equal to one). The stack-up of workpieces may include a single steel workpiece facing two aluminum workpieces in a sandwich type stack-up or two steel workpieces facing a single aluminum workpiece with the outer steel workpiece having the narrow contact surface for the steel welding electrode.