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 method of joining an aluminum workpiece and an adjacent overlapping steel workpiece by reaction metallurgical joining, and the resultant metallurgical joint formed between the two workpieces, are disclosed. The method involves compressing a reaction material located between the aluminum and steel workpieces and heating the reaction material momentarily to form a metallurgical joint that comprises bonding interface between the reaction material and the steel workpiece and a bonding interface between the reaction material and the aluminum workpiece. The reaction material is formulated to be able to interact with both aluminum and steel in order to establish the bonding interfaces of the metallurgical joint. Moreover, the practice of oscillating wire arc welding may be employed to deposit the reaction material in the form of a reaction material deposit onto the steel workpiece prior to assembling the steel and aluminum workpieces in a workpiece stack-up.

A method of joining an aluminum workpiece and an adjacent overlapping steel workpiece by reaction metallurgical joining, and the resultant metallurgical joint formed between the two workpieces, are disclosed. The method involves compressing a reaction material located between the aluminum and steel workpieces and heating the reaction material momentarily to form a metallurgical joint that comprises bonding interface between the reaction material and the steel workpiece and a bonding interface between the reaction material and the aluminum workpiece. The reaction material is formulated to be able to interact with both aluminum and steel in order to establish the bonding interfaces of the metallurgical joint. Moreover, the practice of oscillating wire arc welding may be employed to deposit the reaction material in the form of a reaction material deposit onto the steel workpiece prior to assembling the steel and aluminum workpieces in a workpiece stack-up.

A method of resistance spot welding a workpiece stack-up that includes an aluminum workpiece and an overlapping adjacent steel workpiece so as to minimize the thickness of an intermetallic layer comprising Fe—Al intermetallic compounds involves providing reaction-slowing elements at the faying interface of the aluminum and steel workpieces. The reaction-slowing elements may include at least one of carbon, copper, silicon, nickel, manganese, cobalt, or chromium. Various ways are available for making the one or more reaction-slowing elements available at the faying interface of the aluminum and steel workpieces including being dissolved in a high strength steel or being present in an interlayer that may take on a variety of forms including a rigid shim, a flexible foil, a deposited layer adhered to and metallurgically bonded with a faying surface of the steel workpiece, or an interadjacent organic material layer that includes particles containing the reaction-slowing elements.

A method of resistance spot welding a workpiece stack-up that includes an aluminum workpiece and an overlapping adjacent steel workpiece so as to minimize the thickness of an intermetallic layer comprising Fe—Al intermetallic compounds involves providing reaction-slowing elements at the faying interface of the aluminum and steel workpieces. The reaction-slowing elements may include at least one of carbon, copper, silicon, nickel, manganese, cobalt, or chromium. Various ways are available for making the one or more reaction-slowing elements available at the faying interface of the aluminum and steel workpieces including being dissolved in a high strength steel or being present in an interlayer that may take on a variety of forms including a rigid shim, a flexible foil, a deposited layer adhered to and metallurgically bonded with a faying surface of the steel workpiece, or an interadjacent organic material layer that includes particles containing the reaction-slowing elements.

A method of resistance spot welding a workpiece stack-up that that includes an aluminum workpiece and an adjacent overlapping steel workpiece involves assembling the workpiece stack-up so that an intermediate metallurgical additive is positioned between the faying surfaces of the aluminum and steel workpieces. The intermediate metallurgical additive includes at least one of carbon, silicon, nickel, manganese, chromium, cobalt, or copper, and has the capability to counteract the growth and formation of Fe—Al intermetallic compounds within a molten metal weld pool created within the aluminum workpiece during resistance spot welding of the workpiece stack-up. In certain aspects of the disclosed method, the intermediate metallurgical additive may be one or more metallurgical additive deposits that are deposited onto the faying surface of the aluminum workpiece or the faying surface of the steel workpiece by an oscillating wire arc welding process.

A method of resistance spot welding a workpiece stack-up that that includes an aluminum workpiece and an adjacent overlapping steel workpiece involves assembling the workpiece stack-up so that an intermediate metallurgical additive is positioned between the faying surfaces of the aluminum and steel workpieces. The intermediate metallurgical additive includes at least one of carbon, silicon, nickel, manganese, chromium, cobalt, or copper, and has the capability to counteract the growth and formation of Fe—Al intermetallic compounds within a molten metal weld pool created within the aluminum workpiece during resistance spot welding of the workpiece stack-up. In certain aspects of the disclosed method, the intermediate metallurgical additive may be one or more metallurgical additive deposits that are deposited onto the faying surface of the aluminum workpiece or the faying surface of the steel workpiece by an oscillating wire arc welding process.

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 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 steel plate frame and a thin plate are made of different materials. A plurality of through holes are formed in a portion of the thin plate to be placed on the steel plate frame. A plurality of projections 6c are formed on a support plate, each of the projections being allowed to be inserted into a corresponding one of the through holes. An adhesive is applied to a portion of the steel plate frame on which the thin plate is placed. The thin plate is placed on the steel plate frame, and the steel plate frame and the thin plate are bonded together by the adhesive. The support plate is placed on the thin plate to insert the projections into the through holes. The projections and the steel plate frame are welded to form a plurality of welded spots.