Automotive sheet metal's Repair Technology Paper —— automotive sheet metal's Tensile Repair Analysis
Abstract: The car is the place where drivers work, and it also needs to accommodate a large number of passengers and articles. Automobile body should provide convenience factors for drivers, make passengers enjoy a comfortable riding environment, ensure that they are not affected by noise, waste gas pollution and bad external climate during driving, and ensure the integrity and convenience of loading and unloading. In the process of vehicle use, the body sheet metal will produce all kinds of damage, such as fracture, wear, corrosion, tear and inequality of the metal panel. The damage caused by automobile in use includes: wear and tear, cracks, etc. Mechanical damage includes: twisting, hemline wrinkling, etc. Sometimes, due to design reasons, such as the lack of a certain strength structure and unreasonable design process, sheet metal will also be damaged. In the process of repair, we should strictly analyze and observe, and apply different repair sequences and methods according to different damage conditions to obtain better results.
1 automotive sheet metal definition
By comparing and analyzing various concepts of sheet metal, automotive sheet metal is constantly improving the overall concept of sheet metal design, and also shows the sheet metal development technology that keeps pace with the times. Automotive sheet metal refers to a means of repairing cars. At this level, automotive sheet metal also belongs to repair automotive sheet metal. It can also be considered as the repair of the car body after the collision, that is, all the work except the anti-corrosion and decorative spraying of the car body. For example, analyzing automobile body damage, measuring, correcting stretching, and adjusting and assembling automobile accessories. Traditional car body maintenance, such as the previous liberation and Dongfeng truck maintenance, is only a simple cold work period, and the maintenance tools used are basically hammers and other equipment. That is to say, with hammers of various shapes, the metal sheet on the back is repeatedly struck to shape it. When the dent appears in the car body, the gasket is welded by the car body repair machine, and then the hook is pulled out to repair the dent position. For slender sheet metal parts, metal shrinkage is also required.
Due to the rapid development of the automobile industry in a leap-forward direction, new materials are used in the car body, and the specific structure of the car body has changed. At present, the collision and repair of the car has gradually developed into secondary car body assembly and manufacturing, that is, after the car body is repaired, it is necessary not only to restore its original appearance, but also to restore its various functions when it leaves the factory. The repair methods, tools, equipment and technology used in the whole process of this repair are different from the traditional repair methods, especially the overall repair of the car body. Only by adopting modern high measurement technology system, positioning tools, correction and lifting, correct correction and stretching methods and scientific welding art can the car body be truly repaired.
2 Using stretch repair to analyze automobile body
2. 1 tensile fracture repair
In the process of stretching repair of automobile body, it is found that the folding deformation zone is very easy to break when stretching the front longitudinal beam. The causes of these problems are usually related to the quality types of steel plates used in automobiles. Among the components constituting automobile body, hot rolled steel plate is used for heavy vehicles and other components. But cold-rolled steel plates are mostly used in the single shell form of passenger cars. Because the outer plate of longitudinal beam has anti-corrosion requirements, galvanized cold-rolled plate factory is gradually used. For accident vehicles with severe deformation, the hardness of the deformed parts is better than that before deformation. Due to the external impact, a series of changes and stresses occur in the metal mold grains in the steel plate at the same time, which also causes hardening during processing. Therefore, in the process of repairing the car body, it is necessary to adopt heating annealing to deal with these existing stresses.
2.2 The stress caused by stretching shall be eliminated by heating annealing.
In order to prevent the tearing phenomenon that is easy to occur in stretching as much as possible, the severely deformed front longitudinal beam is subjected to necessary heat treatment. In the process of heating treatment, it should be noted that heating can only be carried out at the position connecting two layers of plates or edges and corners. It is very important to control the temperature during heating, because with the gradual heating of the steel plate, its plasticity will gradually strengthen, and when the temperature of the steel plate reaches a certain critical point, the hardening and brittleness of the material will change. When heating in a relatively tight folding and stretching position, the temperature should not be higher than 600℃. In the process of heating, you can also beat the steel plate with a hammer. Effectively stimulate metal grains, and recover in the metal when the grains are deformed. Usually, carbonization flame is used to heat the pressure existing in finance.
3 automotive sheet metal's Stretching Repair Process
1) Put the vehicle with accident on the platform for correcting a large number of car bodies, select a specially designed tool for correcting a large number of instruments to clamp the car bodies, and clamp the front position of the deformed longitudinal beam with clamping and pulling equipment;
2) After clamping, make necessary analysis of the damage caused by the car body, and remove the related parts of the car that collided during the last maintenance before the tension correction work begins. Because the damage in the process of car body bearing is easy to spread far away, it often spreads to some unexpected positions. When the damage to the car body is determined and the direction of the damage and collision force is completely clear, it can be completely guaranteed that there will be no blind operation. When correcting stretching, the repair planning procedure should follow certain principles to ensure that the damaged position can be repaired with the least processed metal, and at the same time, it will not cause further damage to the car body. According to the specific order of collision damage repair and the reverse procedure of damage, the drawing design order is implemented, and multi-point stretching is adopted when stretching the car body. If stretching is not correct, it is very likely to cause damage to body parts;
3) The process of equipment organization stretching. In the process of stretching, a small stretch is generated every time, and then the chain is measured and released. In the operation of the project, we should strictly pay attention to the completion order from the inside out. First of all, ask for the length, and stretch the car longitudinally along the center line set by the car. After that, the width is corrected and the lateral direction of the car body is strictly corrected. Finally, the height correction is guaranteed. Due to the heat sensitivity caused by the strength of car body steel plate, it is generally necessary to correct and maintain the tension without further. It is usually necessary to stretch, ensure balance, finally maintain balance, and repeat the cycle until the body is stretched and reshaped.
4 conclusion
Through the detailed analysis of the implementation process of stretch repair of car body, the causes of car body fracture and the characteristics of cold rolling of steel plate during serious folding repair are understood. Through the whole process of car body repair, fully understand the characteristics of steel car body, and take effective corresponding measures to prevent possible fracture in the process of stretching repair. In the repair process of cold-rolled steel car body, the appropriate temperature of heating metal should be properly controlled during stretching repair, so that the probability of folding and cracking of steel plate will not be greater, and the smooth implementation of stretching repair is ensured.
refer to
[1] Liu Sen. Repair technology of automobile sheet metal parts [M]. Beijing: Golden Shield Press, 2009.
[2] Zou Qun. Automobile maintenance sheet metal worker [M]. Beijing: China Labor and Social Security Press, 2009(3).
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