Friction Stir Repair Welding
Friction repair welding of flaws is a friction stir welding process where material defects, cracks, or porosity in castings are machined out and closed by friction with a pin tool. It restores the original microstructure without macroscopic voids.
Physical-Chemical Working Mechanism
This process uses friction stir welding principles, where a pin tool rotates and the molten material penetrates the defects. This leads to uniform deformation and sealing of the flaws.
Metallurgical Relevance & Welding Risks
Friction processing of defects is particularly useful for castings with complex structures or low material density. It prevents macro porosity and improves mechanical strength. However, faulty friction can cause overheating and deformation, leading to further defects or cracks.
Shop Practice & Action Instructions
• Prep: The pin tool must be clean and defect-free. The molten material should match the original material composition.
• Temperature: Keep the melting temperature below the material's deformation limit to ensure even flow.
• Time: Friction should last at least 30 seconds to fully close the defect. Excessive time can overheat and deform the material.