[Damage types of automotive sheet metal parts]During the use of the vehicle body sheet metal parts, various damages will occur. Common ones are: wear, corrosion, fracture, unevenness or tearing of the metal plate surface, wrinkles, bending and twisting, etc. Damages during the use of vehicles include: wear, corrosion, cracks, etc.; mechanical damages include: bumps, tears, wrinkle skirts, bending and twisting caused by accidents; sometimes due to design reasons, such as structural strength If it is not enough, the process design is unreasonable, and it will also cause damage to the sheet metal parts. When car sheet metal parts are damaged, there are often more than one damage. Therefore, when repairing, it should be observed and analyzed, and different repair methods and sequences should be used for different damage conditions in order to obtain satisfactory results.
【Repair of wrinkles and bumps】Wrinkles and concavities and convexities caused by impact or extrusion by external force, such as minor damage and no extension of the metal, belong to elastic deformation. The heavier, the metal will expand, which is a plastic deformation. Tearing occurs when the impact or crush is particularly severe. The exposed parts of the body sheet metal parts may have wrinkles and concave-convex damage.
Convex trimming:For the repair of convex surfaces with large curvature, see that for concave-convex damage, hammering method or top-pulling method can be used to repair. For minor concave-convex damage, the pad iron can be placed on the back of the lower part of the recess, hit with a hammer, and the position of the pad iron can be changed accordingly. When the convex part is basically knocked flat, the concave part will mostly recover due to the reaction force of the horn. Then observe the overall smoothness of the board surface, and make some subtle trimmings in a targeted manner to repair the concave and convex damage.
Larger depressions:You can use a backing plate to cushion the back of the depression, and directly lift it up with a jacking tool. In order to reduce the jacking force, if necessary, the concave part can be heated to dark red. Rebound should be considered when ejecting, which can make it “overkill”. If there are large ductile protrusions on the surface, the metal at the extension can be properly shrunk. If it is difficult to put the horn in the damaged part, drill holes in the concave part with as few holes as possible and the hole diameter as small as possible, then fold it into a hook shape with iron wire, fasten it from the hole, and then apply external force to stretch it until it meets the requirements. When required, pull out the wire, weld the hole, and grind it flat.
Wrinkle damage repairFor fold damage, an external force (opposite to the impact force) can be applied to the fold to transform the unfolding of the fold into concave-convex damage. Then use the concave-convex damage repair method to repair. The repair tool can be a manual hoist. One end is fixed at the fold of the sheet metal part, and the other end is fixed on the solid column and wall. The guide chain is tightened, and the fold is gradually unfolded. The degree of extension should be observed at any time to avoid tearing.
【Repair of bending and twisting】There are many reasons for bending and twisting caused by external impact or extrusion, and the common one is the damage caused by accident. Generally speaking, bending and twisting deformation near the center of impact or extrusion is severe and easy to detect. The slight deformation depends on the detection tool and the comparison with the design dimensional data to determine the degree of deformation. Sometimes it can also be judged by observing the relative position of the adjacent parts of the sheet parts. The deformation of the body frame, beam and column can be corrected by the support-pull method, and the direction of the support-pull force should be opposite to the direction of the deformation force. For example, the right front corner of the roof collapses after being hit, resulting in deformation of the right door frame and the right front corner of the windshield frame, and the door cannot be closed. Use the top supporter between the upper right corner and the lower left corner of the door frame, and rotate the handle to extend the screws at both ends. With the extension of the top supporter screw, the upper right corner of the roof gradually rises, the wind window frame is also reset accordingly, and the door frame can also be gradually restored. Another example is that the left side of the car is hit and the center column between the two doors on the left side is concave. At this time, a manual hoist can be used, one end is fixed on the damaged center column, and the other end is fixed on a solid column and wall, and the guide chain is pulled to make The chain is shortened, and the depression of the central column will gradually reset. When calibrating the body frame, beam and column by the stretch method, a pad should be placed at the contact point between the body sheet metal parts and the stretch tool to avoid new damage.
【Repair of tearing】The tearing caused by the impact and extrusion of external force is accompanied by the extension of the sheet metal in light, and part of the sheet material is lost in heavy, commonly known as “lack of meat”. If the damage is minor, the torn part should be repaired and smoothed first, and then the welding should be performed. If conditions permit, CO2 gas shielded welding should be used. repair. Those with severe damage and “lack of meat” should consider digging up or replace them with new ones depending on their degree and shape. If it is necessary to dig up, the “meat lack” should be dug into a simple geometric shape as much as possible, and then measure the size of the hole and fill it with the same material and thickness as the original. When cutting, there is generally a welding port of no more than 1mm around. It is better to use CO2 gas shielded welding, which can reduce the deformation of the workpiece after welding, and has strong rust resistance. In addition, due to the low hydrogen content of the welding wire, its crack resistance is good, and the structural strength after welding is high.
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