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Principle Of Friction Stir Welding

Friction stir welding is the same as conventional friction welding. Friction stir welding is a kind of welding heat source by using friction heat and plastic deformation heat. The difference is that the friction stir welding process is composed of a cylinder or other shapes (such as threaded cylinder) pin (welding pin) joint into the workpiece, through the high-speed welding, the welding material and friction, so that the junction temperature of material softening. At the same time, the material friction stir welding. The welding process is shown in the figure. In the process of welding workpiece to be rigidly fixed on the back cushion, head side rotating speed, workpiece and workpiece edge joint relative movement. Some prominent head into the internal friction material and stirring, the shoulder and the workpiece surface friction welding, and to prevent the plastic material overflow, and can play the role of removing surface oxide film.

In the welding process, the pin in the rotation of the workpiece into the joints, rotate the head (mainly shoulder) and friction between the workpiece and the welding heat, in front of the materials with strong plastic deformation, and then as the head of mobile, highly plastic deformation of the material gradually deposited in the behind of the mixing head. So as to form a friction stir welding weld. Stirring friction welding requirements of equipment is not high, the most basic requirement is the relative movement of welding head rotation and the workpiece, even if a milling machine can also be achieved simply small butt welding requirements. But the rigidity of welding equipment and fixture is extremely important. The stirring head generally use the tool steel, welding head length of welding depth slightly shorter than required. It should be noted that the friction stir weld ends with a keyhole at the terminal. Usually the keyhole can be removed, you can also live with other welding method of welding. To solve the problem of the key hole, the telescopic stirring head has been developed successfully.

In the process of friction stir, the movement of the interface atoms is still in the research stage.