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Method of resistance spot welding aluminum to steel

  • US 10,625,367 B2
  • Filed: 04/04/2017
  • Issued: 04/21/2020
  • Est. Priority Date: 04/08/2016
  • Status: Active Grant
First Claim
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1. A method of resistance spot welding an aluminum workpiece and an adjacent overlapping steel workpiece, the method comprising:

  • locating a source of a reactive metal in a diffusible state along a faying interface of an aluminum workpiece and an adjacent overlapping steel workpiece, the reactive metal being able to react with molten aluminum to form metal aluminide particles, wherein the source of a reactive metal in a diffusible state is a reactive alloy surface layer that is part of the steel workpiece, the reactive alloy surface layer being adhered to a base metal substrate of the steel workpiece and having a thickness between 2 μ

    m and 100 μ

    m, the reactive alloy surface layer comprising a base metal element and one or more reactive constituent metal elements alloyed with the base metal element in a diffusible state, and wherein the reactive alloy surface layer of the steel workpiece makes proximate contact with a faying surface of the aluminum workpiece through an intervening organic material layer situated between the aluminum and steel workpieces at the faying interface;

    pressing a weld face of a first welding electrode against an aluminum workpiece surface that provides a first side of the workpiece stack-up;

    pressing a weld face of a second welding electrode against a steel workpiece surface that provides a second side of the workpiece stack-up;

    passing an electrical current through a workpiece stack-up between the weld faces of the opposed first and second welding electrodes at a weld zone to melt the aluminum workpiece that lies adjacent to the steel workpiece and create a molten aluminum weld pool within the aluminum workpiece that wets a faying surface of the adjacent steel workpiece, and wherein contact between the molten aluminum weld pool and the source of a reactive metal in a diffusible state results in the formation of metal aluminide particles that migrate into the molten aluminum weld pool; and

    terminating passage of the electrical current between the weld faces of the opposed first and second welding electrodes to allow the molten aluminum weld pool to solidify into a weld joint.

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