MULTI-STEP DIRECT WELDING OF AN ALUMINUM-BASED WORKPIECE TO A STEEL WORKPIECE

摘要

A workpiece stack-up that includes at least a steel workpiece and an aluminum-based workpiece can be resistance spot welded by employing a multi-stage spot welding method in which the passage of electrical current is controlled to perform multiple stages of weld joint development. The multiple stages include: (1) a molten weld pool growth stage in which a molten weld pool is initiated and grown within the aluminum-based workpiece; (2) a molten weld pool solidification stage in which the molten weld pool is allowed to cool and solidify into a weld nugget that forms all or part of a weld joint; (3) a weld nugget re-melting stage in which at least a portion of the weld nugget is re-melted; and (4) a re-melted weld nugget solidification stage in which the re-melted portion of the weld nugget is allowed to cool and solidify.

主权项

1. A method of resistance spot welding a workpiece stack-up, which includes an aluminum-based workpiece and a steel workpiece, so as to form a resistance spot weld joint between the aluminum-based workpiece and the steel workpiece, the method comprising:
contacting a workpiece stack-up with a pair of spot welding electrodes such that the spot welding electrodes make contact with opposed sides of the workpiece stack-up, the workpiece stack-up comprising an aluminum-based workpiece and a steel workpiece, the aluminum-based workpiece having a faying surface and the steel workpiece having a faying surface, and wherein the faying surfaces of the aluminum-based workpiece and the steel workpiece overlap and contact one another to provide a faying interface between the workpieces; and controlling the passage of electrical current between the spot welding electrodes and through the aluminum-based workpiece and the steel workpiece to perform multiple stages of weld joint development that include:
growing a molten weld pool in the aluminum-based workpiece that extends from the faying interface into the aluminum-based workpiece;allowing the molten weld pool to cool and solidify into a weld nugget that includes a weld bond area joined to the faying surface of the steel workpiece;re-melting at least a portion of the weld nugget including at least part of the weld bond area of the weld nugget;allowing the re-melted portion of the weld nugget to cool and solidify.