0 Preface The power density (Power Density) of high-energy beam welding can reach 105W/cm?2 or more. The beam can be composed of a single electron, photon, electron and ion or a combination of two or more particles. At present, the high energy beam used in the field of welding is mainly a plasma arc, an electron beam and a laser beam. TIG (Activating-Flux TIG) welding also features high-energy beam welding. The same explosive welding can, especially combinations of different metals, simple, quick, and strong welded together, which is the maximum use different shapes for producing large area, and multi-metal composite bimetallic materials of different sizes, for different purposes> > Into the colorful world of laser welding  The Laser-TIG Hybrid can significantly increase the welding speed, which is about 2 times that of TIG welding; the tungsten burning loss is also greatly reduced, and the life is increased; the groove angle also reduces the weld area to be similar to that of laser welding. Avon University's Fran and Fei Laser Technology Institute has developed a hybrid laser double-arc hybrid welding (HyDRA-Hybrid Welding With Double Rapid Arc), which can increase the welding speed by about one-third compared with laser single-arc hybrid welding. Energy is reduced by 25%. The University of Conventry's Centre f Advanced Joining also has the PALW-Plasma Arc augmented Laser Welding. The advantages are: increasing the welding speed and penetration; due to arc heating, the metal temperature is increased, the reflectivity of the metal to the laser is lowered, and the absorption of light energy is increased. Based on the low-power CO2 laser test, it is also carried out on a 12000W CO2 laser and a 2kW YAG laser for fiber transmission, and it is the basis for PALW for robots. 2.5 Research on interaction between laser, workpiece and shielding gas The interaction between laser, workpiece and shielding gas is closely related to the amount of defocusing. It is deep-melting welding within a certain defocusing range, producing a remarkable plasma. If it exceeds a certain defocusing range, it is heat conduction welding, and the influence of plasma is relatively small. . The plasma has refraction, absorption, defocusing and shielding effects on the incident laser, which is an important issue in laser welding. France A · Poueyo-Verwaerde and other diagnosed CO2 laser welding plasma. Thermoelectric detectors are used to record reflected lasers, visible light phototubes are used to collect plasma radiation, spectral analysis is performed by multichannel spectrometers, and plasma images are recorded using high speed cameras. After analysis, the relationship between electron temperature, electron density and surface distance of the workpiece and the relationship between reflectivity and plasma brightness were obtained. The University of Stuttgart, Germany, conducted a study on the effect of laser welding plasma on laser focusing during CO2 laser deep penetration welding. The concept of effective power density distribution on the focal plane is proposed. The power density reduction in the focal plane is caused by the absorption and refraction of the laser by the plasma. The plasma refraction depends on the plasma size, position and temperature. The He-Ar mixture is used. The negative effects of plasma can be suppressed more effectively than with a single gas. Helmut Schmalenstroth et al. used 1 kW Nd:YAG for laser welding. The gases used were Ar, He, N2 and Ar + O2 , Ar + CO2 , Ar + CO2 + O2 . The proper mixture can increase the penetration and weld. Speed, reduce costs, In the field of laser welding process control, there is a use of a capacitive sensing system to measure and control the focus position report. The mechanism is based on the sensor's oscillation frequency being disturbed by the focus change rather than constant. When the ionization density and extent of the metal vapor and the shielding gas vary, the dielectric constant of the medium between the nozzle electrode and the workpiece changes. Dr. Hillerich of Germany pointed out that the influence of ionized atoms and ionized molecules on the dielectric constant ε can be expressed by the Drudench formula. Based on the same principle, capacitive sensing systems can also be used for the detection and control of welding speeds and weld defects. In the research of laser welding bath kinetics, V.Semak of the University of Tennessee in the United States focused low-power argon ion laser on the molten pool, removed the light emitted by the plasma through a narrow-band interference filter, and then passed the photomultiplier tube. Photography records the shape of the molten pool. Studies have shown that the recoil force in the molten pool far exceeds the surface tension and static pressure, and thus, high-amplitude molten metal bumps are generated around the edge of the small hole. The high recoil force causes the wall of the small hole composed of molten metal to leave the laser beam, and then the surface tension brings the wall of the small hole closer to the beam. Due to the pulsation of the recoil force, the volume of the high-amplitude, low-frequency oscillations in the molten pool is simultaneously It also causes a significant change in the shape of the opening of the molten pool, which in turn affects the direction of movement of the vapor, producing a high frequency acoustic signal. Studies have also shown that during laser spot welding, the oscillation frequency of the molten pool increases during solidification of the molten pool. In the research on the melting model of laser welding, J.O Milewski of the National Laboratory of the United States uses a computer with a narrow V-groove as a model to analyze the propagation and absorption of laser energy. The model is a good illustration of the small hole. Inside, the light reflection frequency and the incident angle increase with the penetration depth and the peak at which the energy is absorbed is at the bottom of the aperture. In laser welding simulation, since this is a high-order, nonlinear, free-surface three-dimensional problem, many boundary conditions and parameters must be determined for accurate calculation and simulation, but the simulation predicts results, engineering design, and physics. The nature reveals an important role, and related research has not been interrupted. 2.6 Laser welding of aluminum alloy The difficulty in CO 2 laser welding of aluminum alloys is mainly due to high reflectivity and good thermal conductivity, difficulty in reaching evaporation temperature, difficulty in inducing the formation of small pores (especially when the Mg content is relatively small), and easy generation of pores. In addition to surface chemical modification (such as anodizing), surface coating, surface coating, etc., laser-TIG, laser-MIG reports are also available, in which the MIG-DC electrode position (DCEP) method is due to surface The cleaning effect is strong and the alloying effect of the wire is better. Recently, L.Cretteur of Belgium and S.Marya of France performed CO 2 laser welding of mixed gas and flux on 6061 aluminum alloy. Under the given test conditions, it shows that 70% He +30% Ar, the direction of the air flow is opposite to the welding direction, and the effect is good for the back side of the weld when penetration welding, 75% LiF+25%LiCl The flux acts to remove oxidation, improve the bonding of the molten metal to the backing base metal, and has an "upward" effect on the back weld, forming a regular weld bead in a wide parameter range. Welding of the 6061 aluminum alloy shows that the weld strength can reach 90% of the base metal. 2.7 Laser cladding Compared with other surface modification methods, laser cladding has faster heating speed, less heat input and minimal deformation; high bonding strength; low dilution rate; the thickness of the modified layer can be precisely controlled, locality is good, and accessibility is good. high productivity. In addition to civilian products, laser cladding is also used in the heat-resistant and wear-resistant layers of aircraft engine Ni-based turbine blades. 3 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 e-beam welding in France is also very interesting. Regarding non-vacuum electron beam welding, Germany completed the wire-bonding of the rotating parts of the base material Al Mg0.4 Si1.2, 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 (EBW-NV) 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. 4 Domestic high-energy beam welding status 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. 4.1 Laser welding In the production and research of equipment, there are mainly the National Engineering Center for Gas Laser Processing of Huagong, the National Engineering Center for Solid State Laser Processing of 11 Departments of Electronics, China Daheng Laser Engineering Company, Shanghai United Baichao CNC Laser Equipment Co., Ltd., etc. Kilowatt CO2 laser equipment and solid YAG laser equipment below 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, super steel welding, underwater laser welding, wide Tailored Blank Laser Welding, wire laser welding, aluminum alloy laser welding, laser cutting quality control, etc. There are many laser welding researches, including Huazhong University of Science and Technology, National Institute of Production and Research Laser Technology, Tsinghua University, Harbin Welding Research Institute, Beijing Aviation Technology Research Institute, Harbin Institute of Technology, and Northwestern Polytechnical University. 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. The Harbin Welding Research Institute introduced a 2kW Nd:YAG laser generator from HAAS, Germany, and established a high-power solid-state laser machining center to develop high-power solid-state lasers with various materials such as carbon steel, stainless steel, aluminum alloy and titanium alloy. Welding process research and laser-arc hybrid heat source welding technology research. 4.2 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. In this way, Beijing Aviation Technology Research Institute implemented the overall design and assembly of equipment for an aviation plant, and realized vacuum electron beam welding of a certain component; Guilin Electric Apparatus Research Institute also developed HDG(Z)-6 type in this way. Bi-metal strip high-voltage electron beam continuous automatic welding production line, the machine accelerating voltage 120kV, beam current 0 ~ 50mA, electron beam power 6kW, strip running speed 0 ~ 15m / min, so that China is able to produce this in the world One of several countries in the production line. Beijing Zhongke Electric High-tech Co., Ltd. recently developed the electronic beam welding machine for the hydraulic torque converter turbine assembly for Shanghai General Motors Co., Ltd., which can complete the welding of the two end round welds within 70 s and has been put into commercial production. . 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 similar products abroad, 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 by the Harbin Welding Research Institute involves the small hole dynamics of the molten pool, electron beam brazing, joint fatigue crack propagation behavior, joint residual stress, wire filler welding, and weld trajectory teaching during partial vacuum welding. 4.3 Plasma arc welding In terms of plasma arc welding equipment, Li Jinglong and Bai Gang of Northwestern Polytechnical University carried out research on pulsating plasma spray welding technology, and successfully realized the transfer by connecting high-frequency IGBT contactless switch between the workpiece and the nozzle anode (nozzle). The alternating high frequency operation of the arc and the non-transfer arc realizes plasma spray welding under a single power source. Wang Yasheng of Xi'an Jiaotong University has carried out research on variable polarity plasma arc welding equipment suitable for AI, Mg and its alloy. The positive and negative half waves of the main arc are respectively powered by two DC power sources, which realize the workpiece (aluminum). Variable polarity 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-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. 5 New progress in special welding At present, the domestic research units engaged in explosive welding mainly include Northwest Nonferrous Metal Research Institute, Dalian University of Technology, Taiyuan Iron and Steel Group Co., Ltd., Dalian Shipyard, and 725 Shipyards. Recently, Central South University published the book "Explosive Welding and Metal Composite Materials and Their Engineering Applications" edited by Zheng Yuanmou. The principle and process of explosive welding were introduced in detail. The book reached 1.52 million words. Li Guoping and Wang Lixin of the Institute of Steel Research of Taiyuan Iron and Steel Group Co., Ltd. studied the heat treatment process of 00Cr22Ni5Mo3N + Q345C stainless steel composite plate for explosive welding, and applied it to the construction of the Yangtze Three Gorges Water Control Project; Li Rongfeng of WISCO Technology Center carried out explosion pretreatment The effect of cold cracking sensitivity on 14MnNiDR low temperature pressure vessel steel welding was studied. The results show that the explosion pretreatment has a significant effect on reducing the cold crack sensitivity of welded joints while improving the weld joint toughness. Explosive pretreatment can be exempted from welding. Preheating or lowering the preheating temperature brings great convenience to the construction of large welded structures. A-TIG welding can significantly increase the penetration depth under the condition of constant input power, and the weld cross section has the characteristics of high-energy beam welding. In China, Harbin Institute of Technology, Beijing Aviation Manufacturing Engineering Research Institute, Northwestern Polytechnical University, etc. A great deal of attention has been given, and the Beijing Aviation Manufacturing Engineering Research Institute has developed a series of active fluxes. Zhang Keke and Yang Yunlin of Luoyang Institute of Technology studied the deformation characteristics of heterogeneous steel thermostatic superplastic solid welded joints. The results show that the deformation of constant temperature superplastic solid phase welded joints mainly shows the time accumulation of strain. Song Tianmin of Fushun Petroleum Institute carried out the influence of vibration submerged arc welding on the fatigue life of weldment and its mechanism. The results show that mechanical vibration welding can reduce the residual stress of welding, refine the metallographic structure of weld and heat affected zone, and improve Welded parts fatigue life. Under the given experimental conditions, the longitudinal residual stress is reduced by 43%, the lateral residual stress is reduced by 25%, and the fatigue life of the sample is increased by 35%. references 1. Proceedings of the Tenth National Welding Conference, Volume 1, Book 2, Heilongjiang People's Publishing House, 2001 2. U · Dilfhey et al , Prospects by combining and coupling laser beam and arc welding process, Welding in the world, Vo.l44, No.3 2000 3. M · Kern, P. Berger and H. Hügel, Magneto-Fluid dynamic control of seam quality in CO2 laser beam welding, welding research supplement, March, 2000 4. Zheng Yuanmou, Explosive Welding and Metal Composites and Their Engineering Applications, Central South University Press, 2002 5. Applied Laser, Vol.22 No.2. 2002 Liu Jinhe, Northwestern Polytechnical University We are a professional bathroom Faucet accessories manufacturer and supplier in China. Here you can find high-quality products in a competitive price. Also we supply OEM service of products for you. Faucet Accessories,Angle Valve,Water Tap,Hand Shower Heshan Dingquan Sanitary Ware Industry Co., Ltd , https://www.dqoksanitary.com
1 High-energy beam welding is currently the focus of the field
The main areas of concern for current high-energy beam soldering are:
(1) Large-scale high-energy beam equipment - large-scale power and large-scale processing of parts (and even parts integration).
(2) Development of new types of equipment, such as pulse mode and short-wavelength lasers.
(3) The intelligence of the equipment and the flexibility of processing.
(4) Improvement and diagnosis of beam quality.
(5) Research on the interaction mechanism of beam, workpiece and process medium.
(6) The composite of the beam.
(7) Welding of new materials (8) Extension of application fields.
2 Latest developments in laser welding
2.1 New laser
1) DC Slab CO2 laser, which is regarded as a new milestone of CO2 laser, excellent beam quality (k > 0.8), low gas consumption (0.3L / h), reliable operation, maintenance-free The operating cost is low, and the commercial type has reached 3500W.
2) Diode-pumped YAG laser, diode pump can be used for nearly 20,000 hours, while LAMP pumping, about 500 hours to replace the pump lamp, this type of laser has reached 5000W.
3) CO laser, wavelength 5.3μm, is half of CO2 laser, and the divergence angle is also half of that of CO2 laser. Under the same conditions, PD is 4 times of CO2.
4) Semiconductor laser, with a wavelength of 0.85~1.65μm, can be transmitted by optical fiber, with small volume and output power of 3 kW.
5) Excimer laser, the wavelength is in the ultraviolet range, ranging from 193 to 351 nm, which is about 1/5 of the YAG laser and 1/50 of the CO2 laser. The single photon energy is higher than the chemical bond energy of most molecules, and can penetrate into the interior of the material molecule. Processing, the processing basis is based on photochemical action, under non-exothermic effects, so the material deformation is minimal. Excimer lasers can also be tuned, with power levels up to kilowatts in the laboratory.
2.2 Large-scale laser power, pulse mode and high-quality beam mode
Take the example of Penn Research Corporation (the largest manufacturer of fast axial CO2 lasers in North America) in the United States. A few years ago, the power of CO2 lasers used for cutting was mainly 1500-2000W, and the leading products in the near future were 4000-6000W. , 6000W cuttable stainless steel thickness, carbon steel thickness of 35mm and 40mm respectively.
PRC lasers are available in three pulse modes. When the cutting metal plate starts to be punched, the ultra-pulse can be used to instantly evaporate the metal to form a perforation; the gate pulse can be used to reduce the heat-affected zone during cutting, the slit is narrow, and the cutting surface is high; the hyperpulse is used. When welding highly reflective Al and Cu, the pulse peak first raises or even melts the surface temperature of the material to improve the absorption of the laser energy by the material, so that the continuous wave welding is stable; for the surface galvanized material, the spike of super pulse It can be evaporated to facilitate the continuous wave laser welding; the use of ultra-strong pulses during cutting can reduce or even eliminate the phenomenon of dross. Lasers of different power ranges have different requirements for beam mode for different purposes.
2.3 Equipment intelligence and flexible processing
Especially for the YAG laser, it is extremely convenient to process due to the transmission of available optical fibers. The LASAG FLS series YAG solid-state laser machine from Switzerland is representative of this. Its main features are:
(1) One machine is multi-purpose, and one laser machine has functions such as welding, cutting, punching and peeling (Laser Ablation).
(2) Multi-station (up to 6) processing can be performed with one laser machine. It can carry out time-sharing processing of different stations, and can also perform simultaneous processing of several (up to 6) stations (energy multi-station allocation).
(3) The length of the fiber (distance from the laser processing machine to the station) can be up to 60m.
(4) Open control interface, which can be directly connected to CNC, PLC, PC, etc.
(5) It has a long-distance diagnostic function.
2.4 Beam composite
The most important is the Laser Arc Hybrid. In composite processing, the plasma generated by the laser is beneficial to the stability of the arc; the composite processing can improve the processing efficiency; the weldability of materials with poor weldability such as aluminum alloy, duplex steel, etc. can be improved; the stability and reliability of the welding can be increased; Generally, laser wire bonding is very sensitive, and it becomes easy and reliable by being combined with an electric arc.
Laser-arc composites are primarily lasers with TIG, Plasma and GMA. Through the mutual influence of laser and arc, each method's own deficiencies can be overcome, and a good composite effect is produced.
GMA (GAS Metal Arc) has low cost and uses wire filling. It has strong applicability. The disadvantages are shallow penetration, low welding speed and high thermal load on the workpiece. Laser welding can form deep and narrow welds with high welding speed and low heat input, but the investment is high, the preparation precision of the workpiece is high, and the adaptability to aluminum and other materials is poor. The composite effect of Laser-GMA is manifested in: the arc increases the efficiency of the gap bridging for two reasons: one is to fill the welding wire, the other is that the arc heating range is wider; the arc power determines the width of the top of the weld; The laser-generated plasma reduces the arc ignition and maintenance resistance, making the arc more stable; the laser power determines the depth of the weld; and further, the recombination leads to increased efficiency and increased weldability.
Laser-arc composites were proposed in 1970. However, stable processing has only appeared in recent years, mainly due to the development of laser technology and arc welding equipment, especially laser power and current control technology.
The improvement of welding efficiency by laser arc recombination is very significant. This is mainly based on two effects. One is that higher energy density leads to higher welding speed, workpiece convection loss is reduced, and the other is the superposition effect of two heat source interactions. When welding steel, the laser plasma makes the arc more stable. At the same time, the arc also enters the pore of the molten pool, which reduces the energy loss. When the aluminum is welded, the superposition effect is almost independent of the laser wavelength, and its physical mechanism and characteristics need further the study.
In the magnetohydrodynamic control of the weld quality of CO 2 laser welding, М·Kern of Stuttgart University in Germany proposed magnetically supported laser beam welding (MSLBW), see Figure 5. Experiments show that this method can suppress the bead bulge, improve the quality of the bead top and the shape of the weld cross section, reduce the splash, make the plasma above the molten pool more stable, and increase the stability of the process. The effect of this method is related to the direction of the magnetic field, provided that there is an electric current. Studies have shown that the current is caused not only by the thermal voltage between the parent metal and the molten metal, but also by the thermal voltage between the solidified weld and the molten metal.
Development of high energy beam and special laser welding technology