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The main advantages of friction welding technology are summarized as follows:
(1) The joint quality is good and stable. The welding process is controlled by the machine. It is easy to monitor after parameter setting, and has good repeatability. It does not depend on the technical level and working attitude of the operator. The welding process does not melt, it is solid-phase thermocompression welding, the joint is satin-made structure, so the weld will not have pores, segregation and inclusions, cracks and other crystal defects of the cast structure, the strength of the welded joint is much greater than that of fusion welding and brazing. Strength, reaching or exceeding the strength of the base metal;
(2) High efficiency. The welding parts are usually not required to be prepared, the welding equipment is easy to automate, and can be produced on the assembly line. The welding time per piece is measured in seconds, generally only a few tenths of a second to several tens of seconds. Other welding methods such as welding and brazing cannot. Compared
(3) Energy saving, material saving and low consumption. The required power is only 1/5 to 1/15 of the traditional welding process. It does not require welding rods, flux, solder, protective gas, no need to fill metal, and does not need to consume electrodes;
(4) Good weldability. Particularly suitable for the welding of dissimilar materials, friction welding has unique advantages compared to other welding methods, such as steel and copper, steel and aluminum, steel and brass, etc.;
(5) Environmental protection, no pollution. The welding process does not produce soot or harmful gases, no splashing, no lone light and sparks, no radiation.
Due to these advantages, friction welding technology is known as the future of green welding technology.
Development and application of friction welding technology in China
After decades of development, friction welding technology has already possessed a complete set of professional technology scales including process, equipment, control and inspection, and has formed a certain independent system in basic theoretical research.
1 Research and application of friction welding technology
At present, the friction welding technology in China is widely used. It can weld workpieces with a diameter of 3.0-120mm and large-section Pipe Fittings of 8000mm?, and also develops phase welding and radial friction welding technology, as well as friction stir welding technology. It can not only weld steel, aluminum, copper, but also successfully weld dissimilar steels and dissimilar metals with high temperature strength levels, and dissimilar metals that form low-melting eutectic and brittle compounds. Such as high-speed steel - carbon steel, heat-resistant steel - low alloy steel, high temperature and gold - alloy steel, stainless steel - low carbon steel, stainless steel - electromagnet and aluminum - copper, aluminum - steel. In recent years, with the development of China's aerospace industry, it has also accelerated the penetration of friction welding technology into these fields, and carried out aero-engine rotors, landing gear structural parts, fasteners and other materials (Ln718 Ti17 300M GH159 GH4169) and metal and ceramics. The friction welding process of composite materials and powder superalloys has been studied. The brazing process of some electrical materials has also been replaced by friction welding. Such as electromagnets - stainless steel, tungsten copper alloys, etc. At present, the products welded by friction welding in China include: serpentine tube friction welding in the boiler industry, friction welding of the valve flange and valve body sealing seat in the valve industry, friction welding of the thrust side bearing bush in the bearing industry, and drill bit in the tool industry. Friction welding of the cutting edge and the shank of the milling cutter and the reamer, the bimetal exhaust valve of the engine of the automobile and the locomotive industry, the valve ejector, the preheating chamber nozzle of the diesel engine, the half shaft, the torsion tube, the turbocharger of the internal combustion engine Shaft, submersible pump shaft, copper stainless steel water joint, aluminum-copper transition joint, textile machine shuttle core, joint bearing, masonry tool, geological drill pipe, oil drill pipe, solid, hollow sucker rod, aero engine integrated gear, woodworking Use the cutter shaft on the machine and so on.
2 Theoretical research and engineering applications
The formation, flow, expansion and welding joint formation mechanism of high temperature plastic metal layer on friction welding surface, energy conversion and process control of friction welding, large section oil drill pipe friction welding process and toughness control, friction welding joint gray spot The defect formation mechanism and fracture joint morphology and fracture strain of welded joints, friction-welding mechanism of aluminum-copper thin-walled tubes, joint performance and formation mechanism of weld compound phase have been deeply studied.
In engineering applications, the topic of friction welding technology research has been carried out for a series of problems that need to be solved urgently. The process test research of friction welding head deformation heat treatment is a representative applied scientific research work. This research is the first to introduce the combination of deformation strengthening and phase transformation strengthening in the field of friction welding by changing the traditional continuous driving friction welding process. The welding process is combined with the post-weld heat treatment process, and the friction welding joint is directly subjected to deformation heat treatment on the friction welding machine by using the welding waste heat and the braking energy consumption, and the heat treatment device equipped on the machine can more effectively realize the control of the phase change condition, so that It is possible to firmly pin a large number of dislocations introduced into the high-temperature deformation during the friction welding process by the quenching phase transformation, and to fully exert the strengthening and toughening effect which cannot be achieved by a single method obtained by the dual effects of deformation strengthening and phase transformation strengthening. The toughness exceeds the level of the quenched and tempered base material without reducing the joint strength. This technology not only improves the welding quality but also simplifies the process, reduces the number of heating times after the post-weld heat treatment, and reduces the cost. The research results are in the world's leading position and are currently being promoted and applied in the production of sucker rods and tubing and the repair of drill pipes. In order to control the generation of the brittle layer of the aluminum-copper transition joint, low temperature friction welding was studied and applied to production. In recent years, the friction welding below the phase transformation temperature in the superplastic temperature range has been studied, and the phase results have been achieved. In the aspect of welding quality monitoring, the friction welding power extreme value controller and the microcomputer quality monitoring device have been developed. The microcomputer quality monitoring device monitors the changes of the main parameters affecting the quality of the welded joint, such as the axial pressure, the spindle speed, the friction torque, the axial shortening of the weldment, the time, the welding temperature and the deformation heat treatment temperature. Weldability in new materials, friction welding information process and sensing technology, friction welding parameter calculation and real-time monitoring and closed-loop control, friction weld defect formation mechanism and mechanical behavior, friction welding joint strength and toughness control, friction welding physical parameter field ( Numerical simulation of temperature field, stress-strain field, and related experimental techniques such as high-speed photography and spectrum analysis have also carried out systematic and in-depth research work.
In recent years, the friction stir welding technology has also attracted the attention of Chinese scientists and technicians. It has carried out the stirring of aluminum alloys (such as rust-proof aluminum, wrought aluminum, hard aluminum, super-hard aluminum, etc.), copper, PVC plastics and other materials. Friction welding research, and active research on friction stir welding of titanium alloy, magnesium alloy and ferrous metal, and deepening the mechanism, microstructure, mechanical properties of the friction stir welding and the stirring technology of the core technology of friction stir welding. Research. And achieved certain engineering applications.
3 Friction welder production and related technology
There are more than 600 friction welding machines in China, most of which are continuous drive friction welding machines. In recent years, due to the strengthening of the exchange and introduction of prototypes with friction welding machine manufacturing companies such as KUKA, Nitto Zhushi, and MTI of the United States, the welding machine has adopted a hydraulic motor-driven spindle system, a series bearing group - balancing cylinder fluid Force balance rotary piston, multi-piece powder metallurgy coated clutch, rolling guide and programmable controller (PLC) control and other advanced technologies have greatly improved the level of welding machine manufacturing.
With the needs of actual production. Domestically, other types of friction welding machines have also been developed. For example, Changchun Welding Equipment Factory has developed a small tonnage inertia welding machine, phase friction welding machine, and Harbin Welding Research Institute has developed a quenching device with a deformation heat treatment function and automatic flight. Hybrid friction welding machine for side device, frequency control phase friction welding machine. Harbin Measuring and Cutting Tool Factory has developed 20T double-head friction welding machine. China Armed Industry No. 59 Research Institute has developed a small-tonnage radial friction welding machine. Beijing Saifusite Technology Co., Ltd. has developed a series of friction stir welding machines, etc. The technical indicators and manufacturing level of the welder have reached or are close to the level of similar foreign welding machines.
Faced with the needs of the domestic market, the production of friction welding machines is also developing in the direction of serialization. At present, the maximum tonnage of domestically produced welding machines is 1250kN, and the minimum is 5KN. In short, in the domestic welding machine series, there are few variants, and the varieties are relatively simple. There are no supercomputers and microcomputers. There are different types of deflashing devices, automatic loading and unloading devices, post-weld heat treatment, and non-destructive testing devices, which are matched with the welding machine. However, these are also more specialized, and there is no standard general-purpose series, which needs to be continuously improved. China also has its own industry standard for friction welding machines. With the improvement of manufacturing technology, this standard will also need to be revised to a higher level.
Prospects for the development of friction welding technology
The development status of friction welding technology in China is still not suitable for the needs of the rapid development of the national economy. In the next 5-10 years, China's friction welding workers will conduct more in-depth research in the field of welding properties of materials, welding methods of friction welding, friction welding equipment and friction welding.
1 Weldability of materials
Mainly aimed at the welding of difficult-to-weld and emerging welding materials, such as friction welding of titanium alloy and stainless steel, friction welding of titanium and aluminum, friction welding of pure titanium and pure copper, friction welding of high melting point materials, friction of light metal Friction welding of materials such as welding, friction welding of powdered alloy materials, friction welding of emerging materials, friction welding of cast alloys, friction welding of steel and active metals, and the like. Further research on the basic theory of physical, chemical and mechanical metallurgy of material friction welding, and broaden the field of friction welding solderable materials.
2 friction welding method
In the next 5-10 years, we will intensify efforts to develop some new friction welding methods, and gradually improve and expand its application range.
(1) Phase friction welding
Friction welding of workpieces with phase requirements can be realized, expanding the application field of friction welding. At present, phase friction welding is required for parts such as hexagonal sections, Octagon steel, automobile operating levers, spline shafts, shifting forks, and flanges with flanges at both ends. Under the premise of high development of electronic control technology and mechanical technology, it provides the possibility for the development of large-tonnage phase friction welding machine.
(2) Linear friction welding
Linear friction welding technology is a welding in which two workpieces reciprocate at a certain frequency and amplitude to generate heat. It can weld square or round, polygonal cross-section metal or plastic together. It can weld more irregular sections of components, such as blades and turbines. Later, it is necessary to carry out research on the principle of linear friction welding machine, vibration system dynamics, etc., in preparation for the development of large-tonnage friction welding machines.
(3) Radial friction welding
Radial friction welding not only changes the direction of the friction surface due to its introduction of the intermediate rotary pressure ring, but also the weldment is changed from relative rotary pressure to relatively fixed pressure. It is very suitable for welding long pipes, and it can also Welding thin-walled copper rings to the outer wall of the bomb can upgrade military products. In the future, it is necessary to strengthen the research of radial friction welding mechanism and instantaneous large-flow hydraulic system, and lay a theoretical foundation for the development of large-tonnage radial friction welding machine.
(4) Friction stir welding
Friction stir welding technology is a solid phase connection technology invented by the British Welding Research Institute in 1991. Its application research in light structure manufacturing in the fields of aviation, aerospace, marine, marine industry, weaponry and high-speed trains has been widely carried out. At the same time, it has also attracted the attention of science and technology workers in China. It has carried out some research work on friction stir welding. In the future, it will carry out more in-depth research on the mechanism, microstructure, mechanical properties of friction stir welding and the stirring technology of the core technology of friction stir welding. the study. Expand the welding range of friction stir welding materials, especially to strengthen the research on friction stir of dissimilar materials, and further expand the engineering application of friction stir welding. At the same time, research on friction surfacing, third body friction welding and embedded friction welding is also required.
3 friction welding equipment and engineering applications
With the wide application of friction welding technology, friction welding equipment has also developed rapidly. In 2000, there were not more than 6,000 friction welding machines in the world for welding production.
In order to adapt to the welding of large and special parts, we must develop large and small friction welding machines in China. In order to adapt to special purposes, we also develop a variety of special friction welding machines such as inertia friction welding, radial friction welding, friction stir welding, double-head friction welding, vertical friction welding and underwater friction welding. Designed in terms of manufacturing and monitoring technology with flexibility and automation. The welder can be equipped with many automation equipment and processing equipment to create a complete system that is highly flexible and automated to suit the user's requirements. In order to strengthen the quality assurance of the welding process, in addition to time control, deformation control, energy control, special process control technology should be developed. Such as friction torque and acoustic emission monitoring technology.
In order to meet the automation requirements of welding production, it is necessary to strengthen the research of related technologies and peripheral equipment. For different types of deflashing devices, robots or other loading and unloading devices, heat treatment and non-destructive testing techniques, workpieces can be machined on the welder before or after welding, and some can even be CNC machined. Make it run reliably on the production line. It can also be used with a flexible manufacturing system (FMS).
In the future, the automotive industry will become the most dynamic market for friction welding. The components used for friction welding include turbochargers, airbag booster pumps, transmission and gearbox drive shafts, rear axles, exhaust valves, and pneumatics. Use a cam or the like. In engineering machinery, friction welding is mainly used to weld hydraulic transmission components, such as hydraulic cylinders, piston rods, especially flanges and valve bodies, and in the manufacture of track rollers, shock absorbers and gear pump rotors. Friction welding is used.
It is necessary to increase the friction welding of the tube and the tie rod of the aircraft landing gear, the friction welding of the alloy gear of the helicopter main shaft of the helicopter landing gear and the high nickel alloy steel pipe shaft, the double metal rivet, the aircraft hook bolt and the like. Gradually expand the field of friction welding applications.
in conclusion
Looking at the current status of friction welding development at home and abroad, China is still far behind the international advanced level. The research, development, and application of friction welding technology in China cannot meet the needs of the rapid development of the national economy. Faced with the demand of the domestic market and the increasingly fierce international competition, China's vast friction welding technology workers have a long way to go. In order to adapt to the needs of China's scientific and technological development and shorten the gap with similar foreign products, in order to accelerate the modernization of China's friction welding technology. While realizing the development of friction welding technology itself, it strengthens the combination with other disciplines and marginal disciplines. May we join hands and use our dedication to hold up the future and future of friction welding in China.
Development and Prospect of Friction Welding Technology
The use of frictional heat welding originated more than one hundred years ago. After more than half a century of research and development, the friction welding technology has gradually matured and entered the stage of promotion and application. Since the welding of qualified welded joints by friction welding in the 1950s, it has been valued by all industrial powers for its outstanding advantages of high quality, high efficiency, low cost and environmental protection. China's friction welding research began in 1957, the birthplace of Harbin Welding Research Institute, is one of the first countries in the world to conduct friction welding research, and has achieved many remarkable results.