Automotive sheet metal is a method of automobile maintenance, also called cold working. If the appearance of the car body is damaged and deformed, the process of sheet metal is needed, and the car collision repair has developed from the initial "welding patch" to the secondary manufacturing and assembly of the car body. The repair of vehicles in collision accidents is no longer a simple beating in automotive sheet metal, and the quality of repair is not good. The maintenance personnel should not only know the technical parameters and dimensions of the car body, but also master the material characteristics of the car body. The stress characteristics convey the deformation trend, stress points and production technology of the car body. Such as welding process. On the basis of mastering these knowledge, maintenance personnel should also use advanced measuring tools and accurate three-dimensional measurement of the car body to judge the direct and indirect damage and deformation of the car body, formulate a complete car body repair plan, and cooperate with the correct car body repair plan to restore the key points of the car body to the original position.

1. The commonly used hand-built tools in automotive sheet metal include: general tools, body repair tools, etc.

1. General tool

Automotive sheet metal maintenance tools such as wrenches, screwdrivers, pliers, iron scissors and other common hand tools.

2. Body repair tools

(1) ball hammer. Multi-purpose drawing tool is used to correct bending structure, and is generally used for the preliminary forming of car body parts.

(2) rubber hammer. Used to tap the steel plate lightly without damaging the painted surface.

(3) hammer. Hammer is an essential tool for repairing damaged sheet metal parts. It is used to knock the damaged metal plate back to its original shape and to clean the damaged metal plate when replacing it.

(4) pickaxe hammer. Repair the small depression, the tip is used to hammer out the depression from the inside, gently tap the central part, and the flat end cooperates with the top iron to remove the high points and ripples.

(5) impact hammer. When repairing large dents, impact hammers are used for initial correction of dents, or for processing internal plates and strengthening related parts. This situation requires more strength, not a smooth surface.

(6) fine hammer. After the dent is repaired with an impact hammer, a finishing hammer is needed to obtain the final shape.

(7) top iron. Usually, the hammer hits the back of the metal plate, and the hammer and the top iron work together to lower the convex part and raise the concave part.

(8) wedge iron. It has a variety of shapes and sizes and can be used with different panel shapes.

(9) pick. Used to enter a limited space to pry up the pit, with different lengths and shapes.

Second, the common welding equipment for sheet metal maintenance:

1. inert gas shielded welding machine

Inert gas shielded welding machine is mainly used for welding high-strength and low-alloy steel bodies, and can also weld cast aluminum parts, such as cracked transmission, cylinder and intake pipe.

2. Resistance spot welding machine

Resistance spot welding is one of the most commonly used welding methods for the whole car body.

This way. Resistance spot welding machine is suitable for thin steel plate with high welding strength and no deformation of car body. Applications include roofs, doors and windows, doorsills and external parts.

3. Oxygen-acetylene welder

Oxygen-acetylene welding is a form of fusion welding. After acetylene and oxygen are mixed, they are ignited at the nozzle and melted as a high-temperature heat source (about 3000℃) to connect the covered electrode with the base material. Because it is difficult to concentrate heat in a certain part, it will affect the surrounding area and reduce the strength of the steel plate. Therefore, automobile manufacturers do not recommend using oxyacetylene welding machine to repair damaged cars. Oxygen-acetylene welding machine can also be used to repair damaged automobile body, perform heat shrinkage, brazing and welding, clean surface and cut non-structural parts in repair shop.

4. Brazing machine

Brazing can only be used for sealing structures. Brazing only melts non-ferrous metals in the welding process, but does not melt the base metal. Brazing is generally carried out on the automobile body (commonly called brazing, using brass or nickel). Brazing is similar to sticking two objects together. The molten brass fully diffuses between the two base metals to form a solid fusion zone, and the bending strength of the welded joint against collision is less than that of the base metal. It should be noted that only the parts that have been brazed by the manufacturer can be brazed, and other parts cannot be brazed.

5. Aluminum welding machine

With the use of new materials for automobiles, various plates on many automobiles are made of aluminum. Compared with steel, aluminum plate is more difficult to repair. Aluminum is softer than steel. After work hardening, it is more difficult to process and shape, and it is easy to deform when heated. The thickness of aluminum car body and automobile parts is usually 1.5 ~ 2.0 times that of steel parts.

Three, the body and beam correction equipment

Correcting equipment is a multifunctional car body fixing system. A good calibration equipment should have various shapes of sheet metal stretching tools, all-round stretching force applying devices and practical measuring systems. Especially for the repair of the whole car body, its measuring system must simultaneously display the size and direction of misalignment of each reference point. Only with such equipment can maintenance personnel accurately determine the stretching correction sequence, monitor the whole correction process and determine the effect of each pulling force.