What is Friction Stir Welding?
Friction stir welding (FSW) is a solid-state joining process that creates high quality, high strength welds. This produces welds of high quality in materials such as aluminum and copper.
During FSW, heat is generated by a rotating pin tool that creates a plasticized state when it is passed through the material being joined. The rotating tool creates a plasticized state so as the tool is progressed, a continuous joint is created. FSW, like other types of friction welds, is solid state in nature. As a result, friction stir welds are not susceptible to solidification related defect such as porosity or hot cracking, that may hinder fusion welding processes.
Parts can be oriented as butt welds, lap welds, and even fillet welds on highly sophisticated machines, but the most common orientation is butt welds. The rotating tool is then brought into contact with the work pieces. The tool has two basic components: the pin tool, which protrudes from the lower surface of the tool, and the shoulder, which is relatively large diameter. The length of the pin tool is directly correlated to the thickness of the work pieces.
Welding is initiated by first plunging the rotating pin tool into the work pieces until the shoulder is in close contact with the components top surface. Friction heat is generated as the rotating shoulder rubs on the top surface under an applied force. Once sufficient heat is generated and conducted into the work piece, the rotating tool is propelled forward. Material is softened by the heating action of the shoulder, and transported by the pin tool across the bondline, facilitating the joint. Friction stir welding is fast becoming the process of choice for welding.
- Joins Wide Variety of Materials
- High Strength Joints/High Toughness
- Localized Processing Capabilities
- Low Heat Input/Low Distortion
- Part Accessibility is Required
- Process Forces Require Ample Fixturing
- Localized Material Temper Disruption
Process for Square Butt Weld
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Equipment for Friction Stir Welding
Friction Stir Welding Machine
This is the most important piece of equipment used in friction stir welding. It consists of a rotating spindle that holds the tool, a motor that drives the spindle, and a mechanism for applying force to the tool. The machine is designed to provide precise control over the speed, rotation, and axial force applied to the tool.
Friction Stir Welding Pin Tool
This is the tool that is used to generate the heat and plastic deformation necessary for welding. The tool consists of a shoulder and a pin, both of which are made from a high-strength, wear-resistant material such as tool steel.
Workholding Fixtures
Friction stir welding requires the material being welded to be held in place, usually with the use of workholding fixtures. These fixtures can range from simple clamps to more complex, custom-made setups that are designed to accommodate the specific geometry of the part being welded.
One of the key advantages of FSW is that it can be performed using customized computer numerical control (CNC) machines. When using a CNC machine for FSW, the machine is programmed with the desired welding parameters, such as tool rotation speed, travel speed, and vertical axial load. This allows for a high level of repeatability and consistency. CNC machines can be programmed to perform the same welding process multiple times, ensuring that the final product is of consistent quality. Additionally, CNC machines can be programmed to adjust the welding parameters in real-time based on feedback, allowing for consistent welding performance.