What Is Friction Welding?

Friction welding refers to a method of using frictional heat generated by friction between thermoplastics to melt and heat friction surfaces, and then press and cool them to connect them together. Welding efficiency is 30 ~ 70%. Generally, the efficiency of large dynamic friction coefficient is high. ^[1]

The method of using frictional heat generated by friction between thermoplastics to melt it on the friction surface, and then pressurizing and cooling it under a force is called friction welding. This method is most suitable for rotating parts. Similar to metal friction welding, one piece is fixed during welding, and the other is rotated and pressurized.

When welding solid parts, due to the high linear velocity of the outer periphery of the rotating body, the frictional heat increases from the center to the outer edge, which causes welding stress at the joint. To this end, the welding surface can be made spherical, so that friction occurs at the center first. Then gradually pushed to the edge.

For thermoplastics, a satisfactory joint can be obtained by welding. In addition to welding, in actual production, plastics can also be bonded and mechanically connected, especially those plastics that cannot be welded by welding can only be bonded and mechanically connected. ^[2]

Apply a certain axial pressure on the welding end faces of the two weldments, and make the contact surface make a violent frictional movement, and the heat generated by the friction will heat the contact surface to a certain welding temperature (generally slightly lower than the melting point of the material, Such as

Combined with the analysis of the welding process, friction welding of similar metals can be divided into three stages:

The contact surfaces of the two weldments began to rub. First, the oxides and impurities attached to the surface were destroyed and eliminated, and at the same time, the contact surface was unevenly deformed.

Production practice proves that friction welding, which is one of the thermal compression welding, has its outstanding advantages in addition to the advantages of general thermal compression welding.

1. The quality of the welded joints is high and stable. Basically, it can reach a 100% pass rate, and the joint strength generally exceeds the base material. This is because during the entire process of friction welding, the welding surface is always upset by the axial force in the solid state. In addition, because the mutual friction of the welding surfaces is used as a heat source, the entire surface is heated at the same time, the welding time is extremely short, and the heat affected zone is small. Therefore, as long as the welding specification is properly selected, the welding machine is properly designed and the welding specification is reproducible It can completely avoid the common defects in fusion welding such as cracks, pores, slag inclusion and infiltration, and obtain uniform joint quality.

2. Has a wider range of solderability. Not only can it be used to weld the same metal materials, but it is especially suitable for welding dissimilar metals with large differences in performance. When some dissimilar metals are welded by common fusion welding or flash butt welding, the intermetallic brittle compounds are generated in the joint, which makes it impossible to weld or obtain high-quality joints. When friction welding is used, the welding temperature can be selected and controlled in a wide range, and the welding time is short. Therefore, it is relatively easy to prevent or greatly reduce the formation of intermetallic brittle compounds, thereby obtaining good welded joints.

3 The dimensional accuracy and geometric accuracy of the weldment are high. The friction welding machine is actually equivalent to a lathe with a pressurizing mechanism. According to the design and manufacturing technology of modern machine tools, it is not difficult to make it have sufficient accuracy and rigidity. In addition, using appropriate control methods, the length error of the weldment after welding can be less than ± 0.2 mm, and the eccentricity can be within 0.2 mm.

4 Reduced manufacturing costs. In friction welding, the welding allowance of the weldment is small, the assembly requirements of the welding joint are not high, the welding power is small, and the energy is saved.

5. Good working conditions. No sparks, arcs, harmful gases, no vibration, no noise, etc.

6. Friction welding is easy to achieve full automation. ^[4]