Friction stir welding
Friction stir welding heats metals by friction and joins them plastically. No melting, no solidification defects.
Physical-Chemical Mechanism of Action
The rotating tool generates friction heat that plastically deforms the metals on a microscopic level. The materials are stirred together so intimately that they unite into a solid whole.
Metallurgical Relevance & Risks in Welding
Since no material melts, no pores or gas bubbles form. This prevents cracks and solidification defects. However, excessive friction can damage the surface or wear the tool. Uneven heat distribution can cause local stresses, which may lead to hardness problems or cracks.
Workshop Practice & Instructions
• Tools: Use high-quality friction stir tools with good lubrication.
• Speed: Keep the tool's rotational speed constant, typically between 500 and 1000 rpm.
• Pressure: Apply firm pressure to the tool to ensure uniform deformation.
• Dwell time: Welding time depends on material thickness. For steel, this is typically 10 to 20 seconds per inch of thickness.