Friction stir welding is a new welding technology invented by the British Institute of Welding Technology in 2008. Its principle is shown in the figure below.

A worm in the form of a worm installed on the main shaft is inserted into the welding position under a certain pressure. The length of the stirring head is generally slightly shallower than the depth of the welding seam, so as to ensure that the shoulder of the main shaft can be close to the workpiece to be welded. surface. When the workpiece is heated by friction with the stirring head and the shaft shoulder, the material near the weld will undergo severe plastic deformation due to heat. However, it is not melted, but only becomes a 'plasticized' state. As the spindle drives the stirring head along the With the direction of the welding seam feeding, the stirring head continuously stirs the materials that have been in a 'plasticized' state to the back. When the main shaft leaves, these materials will cool and solidify, thereby forming a stable welding seam.

As we all know, light alloys represented by aluminum alloys and magnesium alloys are one of the main structural materials of aerospace vehicles. However, the weldability of these light alloys is very poor, and various traditional fusion welding processes cannot fundamentally eliminate the generation of welding defects such as hot cracks, pores and slag inclusions. Process to ensure welding quality. In addition, the high temperature of fusion welding will generate a lot of heat and toxic fumes, which also pose a great threat to the operator's health. The emergence of friction stir welding has fundamentally solved this series of problems. 

Since the main shaft will exert a great pressure on the workpiece to be welded, the forged shape is obtained near the weld. The fusion welding process is much better. The biggest advantage of friction stir welding is that its essence is to convert mechanical energy into heat energy required for welding, so a specific formula can be used to calculate the welding heat and the amount of thermal deformation of the workpiece caused by it quite accurately, so as to compensate in advance. and post-mortem corrections provide a quantitative basis that is almost independent of operator experience, which is beyond the reach of any traditional welding process.

In addition, friction stir welding does not require solder, which saves a lot of money since high-end solders tend to be very expensive. Of course, friction stir welding also has its own limitations. For example, it is only suitable for welding materials with relatively low melting points (such as aluminum alloys, magnesium alloys or copper alloys); the workpiece needs to be fixed on the worktable with a large tightening force. , and press with a large pressing force, which may cause additional deformation; the welding speed of irregular special-shaped welds is slow, and the material loss speed of the stirring head and the shoulder is fast, etc.

In a word, friction stir welding, as an emerging welding process, is being used in the high-end welding field. It is believed that with the development of technology, the application of this welding process will become more and more extensive.