Apparatus and method for friction stir welding using a consumable pin tool

Abstract

The present invention provides a friction stir welding apparatus operable for welding one or more metals, metal alloys, or other materials. The friction stir welding apparatus includes a pin tool holder, a shoulder having a surface coupled to the pin tool holder, and a pin tool coupled to the pin tool holder, the pin tool at least partially protruding from the surface of the shoulder, wherein the pin tool is made of a consumable pin tool material. Optionally, the shoulder rotates at a predetermined rotational speed and is retractable into/extendable from the pin tool holder at a substantially constant rate. Optionally, the shoulder is also made of a consumable shoulder material that is at least partially incorporated into the volume of a joint to be welded. The consumable shoulder material comprises a material that is the same as, similar to, or dissimilar from one or more materials comprising a workpiece to be friction stir welded. Preferably, the pin tool rotates at a predetermined rotational speed and is retractable into/extendable from the surface of the shoulder at a substantially constant rate. The consumable pin tool material is at least partially incorporated into the volume of the joint to be welded. The consumable pin tool material comprises a material that is the same as, similar to, or dissimilar from one or more materials comprising the workpiece to be friction stir welded.

Description

FIELD OF THE INVENTION [0001] The present invention relates generally to an apparatus and a method for friction stir welding. More specifically, the present invention relates to an apparatus and a method for friction stir welding using a consumable pin tool. BACKGROUND OF THE INVENTION [0002] Friction stir welding is a solid-state joining technique that is well known to those of ordinary skill in the art. Typically, friction stir welding is used to join difficult-to-weld metals, metal alloys (such as aluminum alloys, titanium alloys, nickel alloys, and the like), and other materials. For example, certain aluminum alloys are sensitive in a plasticized heat-affected zone, where the base metal reaches temperatures between solidus and liquidus during welding. In this zone, partial melting at grain boundaries forms a network containing brittle compounds. As a result, weld ductility is substantially reduced. Likewise, other conventional joining techniques may create geometric distortions ...

AI Technical Summary

Benefits of technology

[0009] Advantageously, the friction stir welding apparatuses and methods of the present invention provide a defect-free weld joint, without entrapped pin tool debris. As a result, the weld joint demonstrates improved mechanical properties (e.g., mechanical strength). Because, in one embodiment of the present invention, the filler material is the same as or similar to the workpiece material, the weld joint demonstrates improved microstructure. Because, in another embodiment of the present invention, the filler material is dissimilar from the workpiece material, the mater...

Problems solved by technology

Likewise, other conventional joining techniques may create geometric distortions near a weld joint due to high temperature gradients induced in a workpiece during welding.

These distortions may cause warping and other dimensional defects in the workpiece, as well as residual stresses that may cause premature failure by cracking in the heat-affected zone or weld joint, lamellar tearing, or by stress-corrosion cracking in some metals and metal alloys.

In addition, some metals, metal alloys, other materials, an...

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