2, the latest developments in electron beam welding and plasma arc welding
The development of foreign electron beam welding can be summarized as: the development of ultra-high energy density devices, the intelligentization of equipment, the diagnosis of electron beam characteristics, the study of beam and material action mechanism, and the research of non-vacuum electron beam welding equipment and processes.
In Japan, an ultra-high pressure electron beam welder with an accelerating voltage of 600kV and a power of 300kW has been introduced. It can weld 200mm stainless steel at a time, with an aspect ratio of 70:1.
Japan, Russia and Germany have carried out research on double gun and wire-filled electron beam welding technology. On the basis of the first welding of the large-thickness plate, the top undercut or undercut defect is compensated by the second filling; the double-grab is used in Japan to realize the ultra-high-speed welding of the thin plate, and the reverse surface has no splash and is well formed.
The successful development of bimetal and trimetal strip electronic beam welding machines in France has also attracted attention.
Regarding non-vacuum electron beam welding, the wire joining of the rotating parts of the base material Al Mg0.4 Si1.2 was realized in Germany. The wire material was AlMg4.5Mn, the wire feeding speed was 35m/min, and the welding speed was as high as 60m/min. The study was done on a 25kW electron beam welder at the University of Stuttgart.
Non-vacuum electron beam welding has been highly valued in the automotive industry. For example, in the manual transmission, the non-vacuum electron beam welding of the synchronizing ring and the gear has a productivity of more than 500 pieces per hour.
Recently, German and Polish scholars jointly developed a non-contact temperature measuring device installed in a vacuum chamber during vacuum electron beam welding. The measuring point has a minimum diameter of 1.8 mm and is mainly used for brazing of ceramics and hard alloys. Random heat flow interference, high measurement accuracy.
In plasma arc welding, variable polarity plasma arc welding and aluminum alloy perforated plasma vertical welding are one of the concerns.
3. Status of domestic high energy beam welding
In China, high-energy beam welding has increasingly attracted the attention of more concerned people such as welding, physics, lasers, materials, machine tools, computers and so on. At the domestic level of equipment, there is a certain gap with foreign countries, but in terms of process research, the level is relatively close, and even in some aspects, it has its own characteristics.
3.1 Laser welding
In the production and research of equipment, it mainly produces kilowatt-class CO2 laser equipment and solid YAG laser equipment of less than 1 kW.
Domestic research on laser welding mainly focuses on laser welding plasma formation mechanism, characteristic analysis, detection, control, deep-fusion laser welding simulation, laser-arc composite heat source application, laser surfacing and so on. From the perspective of sound and electricity, Tsinghua University analyzed the acoustic signal of the penetration state, and proposed the mathematical model of the equivalent circuit and electrical characteristics of the laser welding plasma. In the suppression of the negative effects of the plasma, Zhang Xudong and Chen Wuzhu of Tsinghua University proposed The side suction method; Xiao Rongshi and Zuo Tiezhen of the National Center for Production, Research and Research Laser Technology proposed a double-layer internal and external circular tube blowing heterogeneous gas method; Liu Jinhe of Northwestern Polytechnical University proposed an external magnetic field method.
3.2 Electron beam welding
China's self-developed electron beam welding machine began in the 1960s. Up to now, it has developed and produced hundreds of different types and functions of electron beam welding machines, and formed a technical team for research and production, which can provide low-power electronic products for the domestic market. Beam welder.
In recent years, the introduction of key components (electron guns, high-voltage power supplies, etc.) and the introduction of other components have been introduced. The advantage of this method is that the equipment not only maintains a high level of technology, but also greatly reduces the cost. Provide users with better after-sales service.
At present, the special beam welding machine for automobile gears represented by the EBW series of the Institute of Electrical Engineering of the Academy of Sciences occupies the main market share of domestic automotive gear beam welding; China's small and medium power electron beam welding machines have approached or caught up with the advanced products of similar foreign products. Level, and the price is only about 1/4 of the foreign similar products, with obvious performance and price advantage.
In the mechanism and process research, Beijing Aviation Technology Research Institute, Beijing University of Aeronautics and Astronautics, Tianjin University, Shanghai Jiaotong University, Northwestern Polytechnical University, China Science and Technology Institute, Guilin Institute of Electrical Science, Xi'an Aero Engine Company, Aerospace Materials and Process Research The work carried out involves the hole kinetics of the molten pool, electron beam brazing, joint fatigue crack propagation behavior, joint residual stress, wire-filling welding, and weld trajectory teaching during partial vacuum welding.
3.3 Plasma arc welding
In the field of plasma arc welding equipment, Northwestern Polytechnical University carried out research on pulsed plasma spray welding technology. By connecting high-frequency IGBT contactless switches between the workpiece and the anode (nozzle) of the spray gun, the transfer arc and non-transfer arc were successfully realized. The high frequency alternates to achieve plasma spray welding under a single power source. Xi'an Jiaotong University has carried out research on variable polarity plasma arc welding equipment suitable for Al, Mg and their alloys. The positive and negative half waves of the main arc are respectively powered by two DC power sources, and the workpiece (aluminum) is polarized. Welding, which not only stabilizes the arc, but also has a reliable cathode cleaning effect. Beijing Aeronautical Technology Research Institute carried out the "one pulse and one hole" process research of pulsed plasma arc welding; in the perforation plasma arc welding small hole characteristics and behavior detection, Harbin Institute of Technology, Beijing Institute of Aeronautical Technology and Tsinghua University respectively passed the spectrum Spectrum analysis of information, arc voltage and current, detecting the establishment, closure and pore size of small holes; Wang Xibao and Zhang Wenzhao of Tianjin University analyzed the transport operation of powder in transfer arc during plasma arc powder surfacing and its main influencing factors The iron-based alloy powder and boron carbide powder, the transport velocity distribution in the arc column under different parameters and the powder flux distribution along the cross section of the arc column are calculated. In terms of important applications, Xi'an Aero Engine Company realized the improvement of an aero engine process by using self-made power equipment and imported plasma torch.
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