In mechanical manufacturing and processing operations, it is common to see workpiece metal surfaces become adhered and welded together due to friction-generated heat, such as in lathe-turned machine parts. By analyzing these adhesion and welding phenomena, we can gain insight into the essence of friction welding. Friction welding utilizes the frictional heat and plastic deformation heat generated by the contact surfaces of the workpieces, raising the temperature in the adjacent areas near the interface to a range close to but below the melting point. This causes the workpieces to undergo plastic deformation and flow under pressure, achieving welding through interfacial molecular diffusion and recrystallization.
There are numerous methods of friction welding. Based on the friction motion trajectories and process characteristics, commonly seen in actual production are continuous drive friction welding, stored energy friction welding, phase-controlled friction welding, inertia friction welding, orbital friction welding, and friction stir welding, among others. Among them, continuous drive friction welding, phase-controlled friction welding, inertia friction welding, and orbital friction welding rely on relative frictional motion between the weldments to generate heat energy, collectively referred to as traditional friction welding. Friction stir welding, insert friction welding, third-body friction welding, and friction surfacing welding are welding methods that rely on the heat generated by the relative frictional motion between the stirring head and the weldment.
The friction welding process can be broadly divided into four stages: 

1) conversion of mechanical friction energy into thermal energy; 

2) plastic deformation of materials; 

3) forging pressure under thermoplastic conditions; 

4) intermolecular diffusion and recrystallization leading to welding. 

Compared to traditional welding, friction welding operates at lower temperatures and consumes less energy, with electrical energy consumption as low as 20% of traditional welding. It can effectively weld both similar and dissimilar metals. Moreover, friction welding boasts high precision, with a maximum length deviation of ±0.1 mm for the pre-combustion chamber of diesel engines produced through friction welding. The welding quality is stable and high in strength, significantly extending the product's service life. The welding process does not use any welding consumables, making it clean, hygienic, and pollution-free. Additionally, the heat-affected zone is small, and the welding speed is fast, with the process temperature below the melting point, effectively reducing solidification defects. Unlike traditional arc welding, friction welding does not produce sparks, arcs, or harmful gases, making it more conducive to environmental, health, and safety protection.
With its technical characteristics of high quality, efficiency, energy saving, and pollution-free, friction welding has found increasing applications in aerospace, nuclear energy, automotive, machinery manufacturing, and other fields. It has received significant attention from industrially developed countries, which have invested substantial funds in technology development and application. Friction welding is widely recognized as a reliable, reproducible, and trustworthy welding technology.

In the aerospace industry, the engines of the Airbus A380 use friction welding technology, resulting in a fuel efficiency improvement of one-quarter compared to competitors. At the same time, its first repair time and overall equipment life are significantly extended. For all internal combustion engine crankshaft components, the use of friction welding enables more efficient, high-quality, low-cost, and lean production.
In the automotive manufacturing sector, friction welding is also widely used for the butt welding of round workpieces, disk-shaped workpieces, and bar and tube materials, such as intake and exhaust valves, tie bars, hubs, rotors, etc. Lightweight hubs produced using friction welding technology effectively reduce unit weight by more than 30% and significantly enhance overall performance in multiple aspects. A single welding operation can be completed in 10 seconds, with a work efficiency more than three times that of the spinning process. Compared to current casting, spinning, and other processes, welded hubs have a higher yield rate and superior performance. In new energy vehicles, the use of friction welding for full-face welding of copper rotors in electric motors significantly enhances the electrical conductivity of the rotor end ring and adapts to more complex product design requirements such as hollow rotor manufacturing.
Thanks to the excellent welding performance of friction welding, this technology can also effectively complete various repair tasks, such as cracks in critical structural components, incorrect hole positions in sheet metal, casting defects, quenching cracks, and other issues. Friction plug welding is a solid-phase welding process with fast welding speeds and a small heat-affected zone. The repair strength reaches over 90% of the base material's strength, and the repair process is fully automated, ensuring reliable quality. The welded components meet high-standard usage requirements, reducing economic and schedule losses due to material and component scrap.
After reading the above content, do you have a preliminary understanding of the technology and applications of friction welding? It is believed that with continuous development and engineering practice of friction welding technology, its applications will become increasingly widespread.