Application of welding methods and parts used in t

Application status and development trend of welding methods and parts used in the automotive industry technology status and development trend

welding technology status and development trend in automotive manufacturing

welding is a necessary process method in modern mechanical manufacturing, which is widely used in automotive manufacturing. The six assemblies of automobile engine, transmission, axle, frame, body and carriage cannot be separated from the application of welding technology. In the manufacturing of auto parts, spot welding, projection welding, seam welding, roll (projection) welding, electrode arc welding, CO2 gas shielded welding, argon arc welding, gas welding, brazing, friction welding, electron beam welding, laser welding and other welding methods, because spot welding, gas shielded welding, brazing tools have the characteristics of large production, high degree of automation, high speed, low consumption, small welding deformation and easy operation, Therefore, it is especially suitable for the welding of automobile body sheet covering parts, so it is most used in automobile production. Midpoint welding accounts for about 75% of the investment cost, while other welding methods account for only 25%

application of welding methods and parts used in the automotive industry

1 Resistance welding

(1) spot welding: mainly used for the welding of body assembly, floor, door, side wall, rear wall, front axle and small parts. (2) Multi spot welding: used for the welding of underbody, truck compartment, door, hood and trunk cover. (3) Projection welding and roll projection welding: used for the welding of body parts, shock absorber valve rods, brake shoes, screws, nuts and small supports. (4) Seam welding: used for the welding of roof canopy rain eaves, shock absorber heads, fuel tanks, silencers and oil pans. (5) Butt welding: used for welding steel rings, inlet and exhaust valve stems, knives, etc

2. Arc welding

(1) CO2 shielded welding: used for the welding of carriage, rear axle, frame, shock absorber valve rod, cross beam, rear axle housing pipe, transmission shaft, hydraulic cylinder and Jack. (2) Argon arc welding: used for welding and repair welding of oil pan and aluminum alloy parts. (3) Electrode arc welding: used for welding thick plate parts, such as brackets, spare tire racks, frames, etc. (4) Submerged arc welding: used for the welding of half bridge casing, flanges, pressure vessels of natural gas vehicles, etc

3. Special welding

(1) friction welding: used for the welding of automobile valve rod, rear axle, half axle, steering rod and on-board tools. (2) Electron beam welding: used for welding gears, rear axles, etc. (3) Laser welding and cutting: used for the welding of underbody, gears, parts blanking and trimming

4. Oxyacetylene welding

is used for repair welding of body assembly

5. Brazing

is used for the welding of radiators, copper and steel parts, and cemented carbide

current situation and development trend of resistance spot (projection) welding technology

1 Current status of resistance spot (projection) welding technology at present, the secondary output of resistance welding equipment used by automobile manufacturers is mainly power frequency AC and DC, and its rated power is generally above 63kva, the highest is 400KVA or higher, and the power consumption is large. Most welding resistance controllers are WDK or HW series controllers produced by Tianjin Luhua technology development company and a small number of kd7 and Kd9 controllers. Kd7 controller, its control accuracy is poor; WDK or HW series controllers have high control accuracy of current, about ± 3%, and have the function of multi pulse welding, which can basically meet the welding of low carbon steel or galvanized sheet

in the process of spot welding, the factors that affect the quality of the welding spot include welding time, welding current, welding pressure, the shape of the end face of the electrode, ferromagnetic materials passing through the electrode, shunting, etc. Especially in the welding workshop with more resistance welding equipment, the welding machines working at the same time are inductive to each other, which affects the electricity, and seriously affects the triggering of the controller, resulting in poor stability and consistency of welding quality

in automobile manufacturing, the quality of welding is the common focus of manufacturers and users, and the welding quality is mainly guaranteed by welding equipment. For body spot welding, the controller mainly ensures that the welding parameters are set within a certain fluctuation range, so as to obtain stable spot welding quality. The domestic controller based on constant current control mode can basically meet the welding of mild steel and galvanized steel, but its control accuracy needs to be further improved. The control of welding current is still open-loop control, and it is difficult to ensure the consistency of welding spot quality with the change of working conditions

in order to obtain reliable welding quality, welding inspection is essential. In car body manufacturing, non-destructive sampling inspection is used for weld joint detection, which may not be detected, seriously affecting the quality of products. If you can ensure that the welding points are 100% qualified, each vehicle body can reduce the number of welding points by about 200, which can save about 80 yuan

therefore, the detection and control technology of spot (projection) welding quality is very important to ensure the reliability and consistency of spot (projection) welding quality. This technology has been widely concerned and studied by scholars at home and abroad. There are many methods of real-time monitoring, but those that can be applied to actual production are not common

2. Development trend of spot welding quality control technology

(1) control mode. From single-mode control to multi-mode control, dynamic resistance monitoring and dynamic electrode displacement monitoring are comprehensive modes to realize this control, that is, the dynamic resistance difference is integrated with the dynamic resistance change rate; The maximum displacement is integrated with the displacement velocity

(2) control method. From one monitoring method to a variety of monitoring methods

(3) adjust parameters. From the initial single variable adjustment (welding time or welding current) to multivariable adjustment, that is, the welding current, welding time and welding pressure are adjusted at the same time in the welding process

(4) in terms of control decision-making, it has developed from the conventional control decision-making mode (the deviation value of the controlled parameter is determined by looking up the table) to the artificial intelligence (neural network, fuzzy logic, etc.) decision-making mode

the service life of spot welding and seam welding electrodes directly affects the manufacturing cost and welding quality of automobiles, especially in the welding of coated steel plates. Spot welding electrode materials mainly include: chromium zirconium copper, dispersion strengthened copper, beryllium bronze, etc. The hardness and conductivity of dispersion strengthened copper alloy at room temperature and high temperature are better than those of chromium zirconium copper. The service life of dispersion strengthened copper electrode is 2 ~ 4 times that of chromium zirconium copper electrode. But its cost is higher than that of Cr Zr Cu material. In China, automobile manufacturers mainly use chromium zirconium copper electrodes, and a few joint ventures use dispersion strengthened copper electrodes, which depend on imports. In order to improve the service life of electrode, domestic and foreign scholars are studying the application of coated electrode. It is reported that its service life can be increased by 5 ~ 6 times compared with the commonly used chromium zirconium copper electrode, and the cost is also low

at present, resistance welding machines widely use single-phase AC power supply with AC 50Hz, which has large capacity and low power factor. The development of three-phase low-frequency resistance welding machine, three-phase secondary rectification welding machine (which has been applied in ordinary spot welding machine, seam welding machine and projection welding machine) and IGBT inverter resistance welding machine can solve the problems of electric imbalance and improve power factor. At the same time, it can further save electric energy, facilitate the microcomputer control of parameters, and be better suitable for the welding of aluminum alloy, stainless steel and other difficult to weld metals. In addition, it can further reduce the quality of the equipment

at present, since the performance of domestic inverter spot welding machine can not meet the use requirements, the inverter spot welding machine used in China mainly depends on imports. In the manufacture of truck body, the materials used are 08Al and galvanized sheet, and the common spot welding machine can be used. But in the car body manufacturing, with the increasing use of aluminum magnesium alloy, only using inverter spot welding machine can obtain better spot welding quality

current situation and development trend of arc welding technology

1 Current situation of arc welding technology in automobile manufacturing, a large number of arc welding processes are used, mainly mig/mag welding. The welding power supply mainly adopts thyristor power supply and inverter power supply, and adopts a large number of welding methods with high degree of automation for different welding structural parts. However, due to the poor repetition accuracy of the welding groove position, the walking track of the welding gun is easy to deviate from the groove position, resulting in weld defects, which seriously affects the product quality. For example, the straight weld of the gas reservoir body and the circumferential weld at the connection with the end cover; Punching and welding the longitudinal and circumferential seams of the axle housing. At present, the seam tracking technology is not used in the automatic welding machine of such parts. In actual production, the position of the welding gun must be manually monitored, and its position must be continuously adjusted according to the deviation position of the welding gun relative to the groove. Its controllability is poor, it is prone to product quality problems, and it increases the labor intensity of workers. In addition, in the assembly and welding of the body in white, due to the poor repetition accuracy of the body assembly, the welding gun of the arc welding robot on the body welding line is easy to deviate from the welding position in production after teaching programming, resulting in welding defects. By adopting seam tracking technology, welding defects can be reduced, weld quality and production efficiency can be improved, and cost can be reduced

at present, the forms of seam tracking include mechanical tracking, arc tracking, CCD camera, laser tracking and other methods. The mechanical tracking method is easy to realize and the accuracy is relatively low; The accuracy of arc tracking and CCD camera is relatively high, and the control accuracy of actuator is required to be high. Because of the errors and assembly errors in preparing the workpiece groove, the welding robot with high precision welding special equipment or robot lacks the adaptive ability to the workpiece. The better effect is to use the laser vision sensor system, which can automatically identify the weld position, find and track the weld in space, find the start and end points of the weld, and realize the adaptive control of the welding gun following the weld position. However, this method is not suitable for the welding of car chassis parts. Because the fixture of car chassis parts robot system allows the robot to work in a small space, it is difficult to realize the welding with laser tracking head welding gun. Therefore, the automatic seam tracking technology that can be used is the arc voltage tracking sensor. The system can find the starting point, end point and arc length reference point of the weld, and use the arc sensor to control the voltage adaptive control according to the change of arc length in the welding process. This method can only be applied to the form of fillet joint. For a large number of thin plate lap welds of car chassis parts, it can not be applied because it is impossible to find the reference point of arc length

2. The development trend of high-efficiency arc welding technology

Pulse GMAW (P-GMAW), twin wire mig/mag welding (tandem wire) and so on represent the new high-efficiency and high-speed welding processes currently applied in automobile manufacturing. These two welding methods cooperate with robots, which can fully reflect the characteristics of efficient welding and realize the perfect coordination and combination of robot system accessibility in space and welding speed

p-gmaw arc process has good stability, which can effectively ensure the consistency of weld quality, and improve the insufficient penetration caused by low heat input in short-circuit transition welding process. The jet transfer mode of P-GMAW is suitable for high-speed welding of sheet materials and all position welding of steel or aluminum alloy body frame structure. P-GMAW process is widely used in the welding of tubular sections and joints of Audi A8 all aluminum alloy body frame structure

there are two basic forms of double wire mig/mag welding: one is double wire welding process, and the two welding wires adopt the same welding parameters; The other is tandem wire, which uses two independent nozzles and two independent power supplies. Each arc has its own independent welding parameters. The welding speed of aluminum alloy pulse MIG welding and tandem welding of robot is 60 ~ 80cm/min and 1 respectively