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 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 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 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.

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.

A method for joining different kinds of metal materials includes: preparing a rivet, a plurality of metal members, and a first electrode and a second electrode, each having shanks and electrode portions provided at the tips of the shanks; sandwiching the rivet and the plurality of metal members between a first electrode and a second electrode; and embedding the rivet into the metal member by pressurization and energization using the first electrode and the second electrode. The preparation step includes preparing, as the first electrode and the second electrode, two electrodes that satisfy a condition in which each of electrical resistance values of the first and second electrodes is lower than or equal to a sum of an electrical resistance value of the plurality of metal members to be joined and an electrical resistance value of the rivet.

In the present invention, while a welding current is applied with respect to a laminate body comprising thick metal plates and thin metal plates, a first welding pressure (F1) with respect to the laminate body from an upper tip contacting the metal plate and a second welding pressure (F2) with respect to the laminate body from a lower tip contacting the metal plate are changed relative to each other. Specifically, F1<F2 in a first step which is an initial period of welding, F1=F2 in a second step which is an intermediate period of welding, and F1>F2 in a third step which is a final period of welding.

In the present invention, while a welding current is applied with respect to a laminate body comprising thick metal plates and thin metal plates, a first welding pressure (F1) with respect to the laminate body from an upper tip contacting the metal plate and a second welding pressure (F2) with respect to the laminate body from a lower tip contacting the metal plate are changed relative to each other. Specifically, F1<F2 in a first step which is an initial period of welding, F1=F2 in a second step which is an intermediate period of welding, and F1>F2 in a third step which is a final period of welding.

A resistance spot welding method of squeezing a predetermined sheet combination by a pair of electrodes and passing a current while applying an electrode force to join the sheet combination includes: performing test welding; and performing actual welding after the test welding, wherein in each of the test welding and the actual welding, a current pattern is divided into two or more steps including a first current passage step and a second current passage step subsequent to the first current passage step, and, in the actual welding, a current that causes no expulsion is selected to perform welding by constant current control in the first current passage step, and adaptive control welding is performed from the subsequent second current passage step onward.

A resistance spot welding method of squeezing a predetermined sheet combination by a pair of electrodes and passing a current while applying an electrode force to join the sheet combination includes: performing test welding; and performing actual welding after the test welding, wherein in each of the test welding and the actual welding, a current pattern is divided into two or more steps including a first current passage step and a second current passage step subsequent to the first current passage step, and, in the actual welding, a current that causes no expulsion is selected to perform welding by constant current control in the first current passage step, and adaptive control welding is performed from the subsequent second current passage step onward.