Original Date: 04/24/2007
Revision Date: / /
Best Practice : Solid-State Friction Stir Welding
Solid-State Friction Stir Welding produces a stronger and more reliable weld than other types of welding operations. This welding operation also reduces and eliminates the need for consumable welding materials and reduces hazardous fumes.
The National Center for Advanced Manufacturing, in a joint venture with the state of Louisiana, the National Aeronautics and Space Administration, the University of New Orleans, and Lockheed Martin Space Systems Company - Michoud Operations, researched the application of the Universal Friction Stir Welding System (UFSWS). The system eliminates the need for consumable welding products and increases the strength of the welded surfaces. Present technology allows only the welding of one side of two metal items at a time. For both sides to be welded, two passes must be performed. An external material must also be used to join the two items (i.e., welding rods). When joining two metal surfaces, gases are expended.
UFSWS is performed by the use of a pin-tool that rotates at a speed causing the metal to plasticize. Two types of pin-tools are used. First, a retractable pin-tool that is the approximate thickness of the material being welded rotates at a speed that allows the pin-tool to penetrate the two units to be welded. The tool is pressed down into the two units until the pin-tool’s shoulder impacts the two surfaces. Once the shoulder contacts the surfaces, the rotating pin- tool will generate enough frictional heat to plasticize the metal edges. When this occurs, the pin-tool traverses along the weld seam and plasticizes the metal, generating a combination of extrusion and forging. After the tool moves away from the plasticized metal, it solidifies to become solidly welded, yielding a ductile, high-strength, solid-state weld. The second pin-tool is self-reacting where a hole is drilled between the two items to be welded. The self- reacting pin-tool has two shoulders that impact the front and back of the items being welded and a pin that goes through them. In a similar process, as is performed with the retractable pin-tool, the metal edges are plasticine, mixed together, and resolidified. This operation allows the pin-tool to weld the full thickness of the metal being welded, which ensures welding on both faces at the same time. At the end of this process, only a hole is left to plug. A special plug has been manufactured that allows the plug material and previously welded materials to fuse together. With this process, no external materials are used.
UFSWS also allows welding of diverse material, increases fatigue resistance by up to 30%, improves ductility, prevents fumes, ensures safe operation, reduces weld defects, welds tapered thickness joints, and reduces and eliminates the need for external materials. UFSWS also eliminates porosity and solidification cracking.
For more information see the
Point of Contact for this survey.