Patent ID: 9731379
Date: 2017-08-15
CPC Classifications: B23K

Claim:
1. A method of forming a solid-state weld between a first joining surface of a light metal alloy workpiece and a second joining surface of a coated steel workpiece where the joining surface of the steel workpiece is coated with a metallic protective layer with a composition comprising one or both of the group consisting of zinc and aluminum, the method comprising: placing only a predetermined quantity of reactive material, compatible with the metallic protective layer composition, between, and in direct contact with, the joining surfaces of the light metal alloy workpiece and the coated steel workpiece, the metallic protective layer coating composition and the reactive material cooperating to react with at least the light metal alloy joining surface to form a reaction product upon being heated to a temperature below the solidus temperature of the light metal alloy, the reaction product comprising a liquid, the liquid comprising the reactive material, the metallic protective layer composition and a surface portion of the light metal alloy; the following steps being conducted at ambient conditions, assembling the workpieces with their respective joining surfaces face-to-face separated only by the reactive material and thereby applying a first interfacial pressure to the joining surfaces; applying a second interfacial pressure, greater than the first interfacial pressure, to the assembly so that the facing surfaces engage, and then, while maintaining the second interfacial pressure, heating the reactive material for a predetermined time to form the reaction product and consume the metallic protective coating on the steel and a portion of the light metal alloy workpiece joining surface to form, on each of the steel and light metal alloy workpieces, a residual joining surface; applying a third interfacial pressure, greater than the second interfacial pressure, to the assembly to force substantially all formed reaction product from between the residual joining surfaces while limiting the displacement of the joining surfaces to a predetermined value; and, thereafter, holding the joining surfaces against each other under the third interfacial pressure until a solid-state welded bond is formed between the light metal alloy and steel workpieces at their respective residual joining surfaces.