Friction Stir Welding refers to the use of the heat generated by the friction between the high-speed rotating welding tool and the workpiece to partially melt the material to be welded. When the welding tool moves forward along the welding interface, the plasticized material is under the action of the rotational friction force of the welding tool. It flows from the front of the welding tool to the rear, and forms a dense solid-phase weld under the extrusion of the welding tool.

The Friction Stir Welding method is the same as conventional friction welding. Friction Stir Welding also uses friction heat and plastic deformation heat as welding heat sources. The difference is that the Friction Stir Welding welding process consists of a cylinder or other shape (such as a threaded cylinder) with a stirring needle extending into the seam of the workpiece, and through the high-speed rotation of the welding head, it rubs against the welding workpiece material, Thereby, the temperature of the material at the connection part increases and softens. At the same time, the material is subjected to friction stir to complete the welding. During the welding process, the workpiece should be rigidly fixed on the back pad, the welding head rotates at a high speed, and the edge moves relative to the workpiece along the seam of the workpiece. The protruding section of the welding head protrudes into the material for friction and stirring, and the shoulder of the welding head rubs against the surface of the workpiece to generate heat, and is used to prevent the overflow of the plastic material, and at the same time, it can remove the oxide film on the surface.
During the welding process, the stirring needle extends into the seam of the workpiece while rotating, and the frictional heat between the rotating stirring head (mainly the shaft shoulder) and the workpiece causes strong plastic deformation of the material in front of the welding head, and then with the With the movement of the welding head, the highly plastically deformed material is gradually deposited behind the stirring head, thereby forming a Friction Stir Welding weld. Friction Stir Welding does not have high requirements on equipment. The most basic requirements are the rotation of the welding head and the relative movement of the workpiece. Even a milling machine can easily meet the requirements of butt welding of small flat plates. But the rigidity of welding equipment and fixtures is extremely important. The stirring head is generally made of tool steel, and the length of the welding head is generally slightly shorter than the required welding depth. It should be noted that the Friction Stir Welding seam ends with a keyhole in the terminal. Usually this keyhole can be cut off, or it can be sealed by other welding methods. In response to the keyhole problem, a telescopic stirring head has been successfully developed, and the welding keyhole will not be left after welding.