A method for welding a stack of sheets having a plurality of sheets of different materials is provided. In an aspect, the stack of sheets includes an aluminum sheet and a galvanneal steel sheet. In an aspect, the method includes resistively spot welding the galvanneal sheet to a hot-stamped steel sheet placed between the aluminum sheet and the galvanneal sheet, the sheet of hot-stamped steel including stress relief sections. The method further includes placing a metal foil on the aluminum sheet and vaporizing the metal foil to project portions of the aluminum sheet through the stress relief sections of the hot-stamped steel sheet to weld the portions of the aluminum sheet to the galvanized steel sheet. In another aspect, the method includes placing the metal foil on a raised portion of the aluminum sheet and projecting the raised portion of the aluminum onto the galvanneal steel sheet.

A method for welding a stack of sheets having a plurality of sheets of different materials is provided. In an aspect, the stack of sheets includes an aluminum sheet and a galvanneal steel sheet. In an aspect, the method includes resistively spot welding the galvanneal sheet to a hot-stamped steel sheet placed between the aluminum sheet and the galvanneal sheet, the sheet of hot-stamped steel including stress relief sections. The method further includes placing a metal foil on the aluminum sheet and vaporizing the metal foil to project portions of the aluminum sheet through the stress relief sections of the hot-stamped steel sheet to weld the portions of the aluminum sheet to the galvanized steel sheet. In another aspect, the method includes placing the metal foil on a raised portion of the aluminum sheet and projecting the raised portion of the aluminum onto the galvanneal steel sheet.

A method of spot welding a workpiece stack-up that includes a steel workpiece and an aluminum alloy workpiece involves passing an electrical current through the workpieces and between welding electrodes that are constructed to affect the current density of the electrical current. The welding electrodes, more specifically, are constructed to render the density of the electrical current greater in the steel workpiece than in the aluminum alloy workpiece. This difference in current densities can be accomplished by passing, at least initially, the electrical current between a weld face of the welding electrode in contact with the steel workpiece and a perimeter region of a weld face of the welding electrode in contact with the aluminum alloy workpiece.

A method of spot welding a workpiece stack-up that includes a steel workpiece and an aluminum alloy workpiece involves passing an electrical current through the workpieces and between welding electrodes that are constructed to affect the current density of the electrical current. The welding electrodes, more specifically, are constructed to render the density of the electrical current greater in the steel workpiece than in the aluminum alloy workpiece. This difference in current densities can be accomplished by passing, at least initially, the electrical current between a weld face of the welding electrode in contact with the steel workpiece and a perimeter region of a weld face of the welding electrode in contact with the aluminum alloy workpiece.

A method of resistance spot welding a workpiece stack-up. The workpiece stack-up includes at least a steel workpiece and an aluminum workpiece. The method involves attaching a steel plate to the steel workpiece at a weld-site of the workpiece stack-up, passing electrical current between a first welding electrode and a second welding electrode at the weld-site, and terminating passage of electrical current between the first and second welding electrodes in order to form a weld joint. The steel plate serves to stiffen the weld joint.

A method of resistance spot welding a workpiece stack-up. The workpiece stack-up includes at least a steel workpiece and an aluminum workpiece. The method involves attaching a steel plate to the steel workpiece at a weld-site of the workpiece stack-up, passing electrical current between a first welding electrode and a second welding electrode at the weld-site, and terminating passage of electrical current between the first and second welding electrodes in order to form a weld joint. The steel plate serves to stiffen the weld joint.

An aluminum plate (103) is overlaid on a steel plate (102). A distal end (113) of a button component (101) is pushed in from the obverse surface side of the aluminum plate (103), and the distal end (113) is abutted against the steel plate (102) by applying a first pressure to the button component (101) made of steel without heating. The distal end (113) of the button component (101) and the steel plate (102) are welded by resistance spot welding while applying a second pressure lower than the first pressure to the button component (101).

An aluminum plate (103) is overlaid on a steel plate (102). A distal end (113) of a button component (101) is pushed in from the obverse surface side of the aluminum plate (103), and the distal end (113) is abutted against the steel plate (102) by applying a first pressure to the button component (101) made of steel without heating. The distal end (113) of the button component (101) and the steel plate (102) are welded by resistance spot welding while applying a second pressure lower than the first pressure to the button component (101).

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.

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.