In the welding process, welding speed mainly affects the heat input and high-temperature residence time of the stirring pin. When the welding speed is slow, on the one hand, more heat is input per unit length of the weld, and on the other hand, the high-temperature residence time of the weld metal is longer. Therefore, when the welding speed is slow, the stirring degree of the weld metal is stronger, and the flow of plastic metal is more sufficient. Conversely, as the welding speed increases, the heat input per unit length of the weld decreases, the temperature at the bottom of the weld decreases, the high-temperature residence time of the weld metal shortens, and the softening degree and plasticity of the weld metal decrease. At high welding speeds, the travel resistance of the stirring pin also increases. Therefore, excessively high welding speeds are not conducive to the full migration of plastic metal and the formation of weld seams.
FSW friction stir welding is an innovative solid-state welding technology that is green, environmentally friendly, does not require welding materials, can directly penetrate, and is automatically mechanically welded. FSW friction stir welding uses the heat generated by relative friction motion and plastic deformation between the contact surfaces of the welding parts to make the material in the contact surface and its adjacent area reach a thermoplastic state, and completes welding through mutual diffusion and dynamic recrystallization between the two-sided materials. FSW friction stir welding is carried out below the melting point of the material, and belongs to solid-state welding, which can avoid problems such as pores, cracks, deformation, and oxidation caused by fusion welding. Importantly, the welding heating temperature is low, reducing the softening degree of the welded joints and improving the performance. FSW friction stir welding has been applied to the manufacturing of aluminum alloy car bodies internationally.
Fsw friction stir welding has the following characteristics:
Non-melting and solid-state welding. FSW friction stir welding has a low welding temperature, but does not melt and softens into a thermoplastic state.
Environmentally friendly, healthy, and safe. FSW friction stir welding does not produce high temperatures and toxic gases, making it much friendlier to operators' health and work environment.
No welding materials required, and low cost. FSW friction stir welding does not require welding materials, saving companies a lot of costs because good welding materials are often expensive.
Metallurgical fusion, high welding strength. By heating (below the melting point), softening and plasticizing the material through rotation, stirring and mixing, and finally achieving metal fusion through recovery and recrystallization, the strength is close to the base metal.
Automatic mechanical welding can be achieved. FSW friction stir welding can use specific formulas to accurately calculate the welding heat and the resulting workpiece thermal deformation, thereby providing a quantitative basis that is almost independent of operator experience for advance compensation and post-correction. The automation of fsw friction stir welding equipment becomes quite easy.