Welding is a necessary modern mechanical manufacturing process method has been widely in automotive applications. Automobile engines, transmissions, axles, frame, body, total of six cars can not do without welding technology in Chengdu . in the manufacture of automotive parts, spot welding, projection welding, seam welding, roll welding, arc welding electrodes, CO2 gas welding, arc welding, gas welding, brazing, friction welding, electron beam welding and laser welding, etc. various welding methods, due to spot welding, gas welding, brazing with the production capacity, high degree of automation, high-speed, low power, welding deformation is small, easy to operate features, so the auto body sheet metal cover parts particularly suitable for Therefore, the most widely used in automobile production. spot in the investment costs of about 75%, and other welding methods account for only 25%.
With the development of automobile industry, auto body welding line direction is gradually to the fully automated development, in order to catch up with international standards, while improving the yield, requiring efforts to improve the quality of car manufacturing. we all know, the premise is to automate the manufacture of precision components to high, I hope the minimum welding distortion, welding parts look to be fresh, and called for welding technology is increasing. China joined the WTO is facing opportunities and challenges, welding, application of new technologies to enhance the brand of the automotive industry has an important role.
one welding method used in automobile and parts application of welding applications
automotive industry is one of the industries most extensive, the use of a wide variety of welding methods, its application as follows:
1. welding
(1) is mainly used for spot welding body assembly, flooring, doors, side panels, after the Circuit, before the bridge and other small parts.
(2) multi-spot welding for the underbody, trucks cars, doors, hood and trunk lid and so on.
(3) welding and roll welding for body parts, shock absorber stem, brake shoes, screws, nuts and small, such as stents.
(4) seam welding for body cover Rain canopies, shock absorbers head, fuel tank, muffler and oil pan, etc..
(5) welding for steel ring, behind the intake valve stem, and cutting tools.
2. Arc
( 1) CO2 arc welding for the trunk, rear axle, frame, shock absorber stem, beam, shell and tube rear axle, drive shaft, hydraulic cylinders and jacks such as welding.
(2) welding for oil pan, aluminum welding and repair welding of parts.
(3) arc welding electrode for thick parts such as brackets, spare tire racks, chassis, etc..
(4) for submerged arc welding half-pipe, flanges, pressure vessels, natural gas vehicles.
3. special welding
(1) friction welding for automotive valve stem, rear axle, axle, steering rod and attendant tools.
(2) electron beam welding for the gear, after the bridges.
(3) for the underbody of laser welding and cutting gear, spare parts and so under the materials and trimming.
4. oxyacetylene welding
welding for body assembly.
5.
for brazing radiators, copper and steel, hard alloy welding.
Second, the auto industry in the application of new welding technology < br> Today, advanced welding technology in the automotive industry are many, just to cite the relevant body welding and welding technology.
1. welding and control of energy-saving technology
(1) hanging spot CIS machine is the most widely used in the automotive industry hanging spot welding machine, a workshop is often tens or hundreds, mostly in its capacity above 100kVA, the welding of automotive sheet has been widely used.
(2) Currently a lot of resistance welding machine welding machine AC 50Hz single-phase AC power supply, large capacity, low power factor. the development of three-phase low-frequency resistance welding machine, three-phase secondary rectification welding exposure (in ordinary type spot welder, seam welder, welder application) and the IGBT inverter resistance welding machine, can solve the power imbalances and improve the power factor (up to 09 or more) of the problem. while also further save power, computer control parameters conducive to the realization, can be better for welding aluminum, stainless steel and other hard to weld metal welding. It may also further reduce the weight of equipment.
(3) the control of resistance welding Southwest Jiaotong University, aluminum rim for a welding plant development rim welded into a PLC (programmable controller) intelligent controller, to transform the original machine to solve the aluminum rim of the welding quality problems and improve welding productivity. and then developed the same factory seam welding controllers PLC, general clean-up requirements to solve parts of the seam welding problems. by the development of these two controllers proved more than single-chip computer controller PLC anti-interference ability, high reliability; than industrial controller, small size, cost low, using a common single-phase industrial frequency AC resistance welding machine to complete the difficult work of welding and seam welding.
2. gas shielded welding technology
(1) transition of the surface tension of the key method of waveform control method is completed by two current pulses a droplet, the first current pulse to form a droplet and make it grow, until the droplet and the workpiece short circuit; the first two current pulses is a short-term and continuously detect narrow pulse di / dt, while the value of control current pulses to generate the appropriate electromagnetic contraction, contraction of the droplet neck thinner, and finally pulled off by the surface tension of molten pool to complete a transition without causing droplet spatter (see Figure 1 ).
(2) waveform control of inverter power inverter power good use of the dynamic features and flexible controllability, the use of waveform control, in the early stages of inhibition of short circuit current is increased to reduce the electromagnetic force when the newly formed bridge Droplet break barriers and explosion, reduce large particles splash, and help droplet spread in the pool; when droplets spread in the pool after the current rapid rise in order to accelerate the formation of necking at a later slow rise to a lower peak, so that when the splash off the bridge explosion reduced.
(3) welding the new technology of non-metal arc welding (TIG) and metal arc (MIG) two, are used for automotive industry non-ferrous metals and high-alloy steel welding. In order to improve the forming CO2 gas shielded welding spatter and reducing by adding 80% or 20% Ar mixed gas arc welding.
3. high energy beam welding and heat processing technology
high energy beam heat source is the energy density is greater than 5t108W/m2 heat source (electron beam, ion beam and laser), are applied in the automotive industry, the current development of new technologies abroad:
(1) laser and arc composite heat welding laser welding can be a narrow and deep weld welding, arc welding can weld a wide and shallow weld; former investment, the latter low-cost combination of both characteristics, will greatly improve welding efficiency. laser and arc composite heat welding torch design is particularly important, the angle between the two heat sources should be as small as possible, also designed the laser torch + dual-arc power.
The method has been in the 4 ~ 8mm thick steel structures used, are intended to for thinner aluminum auto parts production and welding (see Figure 2). In addition to welding and precision laser cutting applications, also the formation of friction surface pattern or remelted composite thin oil layer, to improve wear resistance the application.
(2) the application of argon plasma in plasma welding and cutting applications already in the industry, mainly for steel and nonferrous metal processing. At present the air plasma cutting has been widely applied to general steel and nonferrous metals cutting, the introduction of the domestic rail passenger car plant underwater plasma cutting, in order to reduce distortion and improve accuracy. engine valve body already filled circle with plasma welding. Over the last decade a great powder plasma welding development, can be smaller than the fusion fine welding thin materials, to a variety of special alloy welding.
Third, the automotive industry's development trend of new welding materials
With the development of increasingly compact car compact, lightweight, application of new materials the car had significant changes in material composition, the future is still steel car body materials mainly for the thinning of the plate thickness, the widespread adoption of high-strength steel. Meanwhile, in order to improve corrosion resistance of the body, many of the world automobile manufacturers in the car applied to the production of a large number of galvanized steel. In addition, use of aluminum, plastic and ceramic materials. According to experts predict that by the end of the century and will not appear in high-volume production of aluminum car body or the plastic body.
1. galvanized steel
chapter in the American Welding Society meeting on the application of automotive sheet metal welding problems, the experts pointed out that welding galvanized steel is the most promising laser welding. However, due to the process degree of automation is not enough, we must improve access to widely used in automotive spot welding method. The main disadvantage of this approach is to weld pieces of zinc electrode contact with the transition of leaving a large number of electrodes wear rapidly. it is suggested that use of Al2O3 dispersion particle reinforced Cu-Zn and Cu-Cr alloy electrode can be welded in the smallest reactor in order to guarantee access to the minimum size of welded joints.
2.
order to achieve high strength steel lightweight vehicles to improve vehicle safety performance, high-strength steel in the automotive application is increasing year by year, now appears a new generation of high-strength steel material mm ultra-fine grain steel. This mainly refers to steel to further improve the economic indicators, based on iron and steel materials strength and toughness of steel than the existing double. a new generation of ultra-fine grain steel in the organizational structure with ultra-fine grain, high purity and high uniformity of properties.
currently used to study a new generation of super- fine-grained steel are 400MPa and 800MPa grade two level.
in the study of a new generation of iron and steel, China and the international level and there is no gap, almost the same time started, with Japan and Korea lead the world live together . However, due to the short time there, so the unit does not participate in a lot of research, mainly in iron and steel Research Institute and Department of Mechanical Engineering, Tsinghua University based. in the ultra-fine grain steel welding technology for a certain study, achieved some advanced results.
3.
aluminum alloy with a light weight, high strength and corrosion resistance, etc., is an excellent building material, automobile industry has gradually aluminum alloy parts used. aluminum alloy welding has five main features:
(1) dense surface layer of aluminum oxide film (melting point of about 2050 ℃), if not can get rid of welding, the melting will affect the quality of basic metals, the quality of the formation of inclusions.
(2) large thermal conductivity (about 4 times steel), electrical conductivity, welding and steel to achieve the same welding speed, the welding heat input than when welding steel about 2 ~ 4 times.
(3) linear expansion coefficient, weldments have a greater thermal stress, deformation and cracking tendency.
(4) prone to porosity.
(5) aluminum alloy reduces the strength of welded joints.
aluminum alloy welding of these features, what we in the development of welding equipment and welding problems should be taken seriously, the only way to develop a suitable aluminum alloy welding equipment, materials and welding technology .
Fourth, the overall automotive industry trends welding
1
development of automated flexible manufacturing system status throughout the entire automotive industry for welding, soldering is not difficult to analyze the development trend of the automotive industry: development of an automated flexible production system. while industrial robots, automated production, and flexibility for set production features in one, so the large-scale car production in recent years, the rapid use of the robot. in welding, the main use is to spot welding robots and welding machines people.
shown in Figure 3, the robot's use in cars is rapidly increasing. welding production line is to be highly automated, widely used in 6 degrees of freedom robot, and robot welding guns store, according to the welding welding of different parts of the product change request or automatically from the repository grasping for the necessary welding clamp. transmission devices already developed into a more flexible use of unmanned induction driven car.
2 development of lightweight modular Intelligent automatic welding
level of domestic and foreign auto welding lags far behind. In recent years, the domestic auto manufacturers attach great importance to the automation of welding. such as the introduction of the Jetta of FAW 13 body assembly plant production line automation rate more than 80%. the line by computer (programmable logic controller PLC-3) control, automatic transmission and welding to complete the workpiece. Welding by the R30-type robot and the G60 polar toggle Robot 61 units conducted robot driven by computer control, numbers and text display, the tape recorder input and output procedures. robotic action sequence with point-of-step path, with a high level of automation of welding, both to improve the working conditions, improved product quality and productivity, and reduce material consumption.
similar high level of production lines in Shanghai, Wuhan and other places have Gezi and introduction, including Germany, the United States, France and Japan, advanced automotive manufacturing technology. But these after all far can not adapt to the rapid development of China's national auto industry needs, we must adhere to the technical innovation, to accelerate the development of energy efficient welding new materials, new technology and new equipment, development and application of robot technology, the development of lightweight smart intelligent devices, the establishment of efficient and economical welding automation systems, we must use computers and information technology to transform traditional industries, improve grades.
believe that in the near future, through our joint efforts, the domestic auto industry's welding technology will be gradually reduced with advanced welding technology the gap and meet the WTO challenges and opportunities brought to the automobile industry.
Body Manufacturing Technology Center, Shanghai Jiaotong University Zhang Yansong
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