?????????The car body adopts a block combination of metal components and cover parts. Assemble various prefabricated structural parts, such as window pillars, door pillars, door horizontals, front and rear Jizi boards, front and rear wall panels, top cover and other components by welding and riveting. Among them, welding is an indispensable process on the automobile assembly line.
???????Body welding mainly includes resistance welding, seam welding, carbon dioxide welding and other methods. Resistance welding uses the current applied to the spot welding electrode to melt the contact surfaces of the parts and then connect them together under pressure. It is mainly used for welding body members and frame. Seam welding uses a roller electrode to replace the spot welding electrode of resistance welding. The roller electrode transmits welding current and pressure. Its rotation is coordinated with the movement of parts to produce a continuous weld. It is mainly used for sealing welding or seam spot welding of workpieces, such as fuel tanks. . Carbon dioxide welding is an arc welding, which is a welding method that locally heats to melt and connect parts without applying pressure. The arc between the electrode and the workpiece is used as a heat source, and carbon dioxide is applied to shield the arc and the melting zone to make it It is separated from the atmosphere and is mainly used for welding the body skin.
???????According to different parts and requirements, a variety of welding techniques are used in the automotive industry. The welding techniques applied include flash welding, electron beam welding, bolt welding, pulse welding, friction welding and so on. In recent years, laser welding has also appeared, and it has developed rapidly. Some of the car body welding produced in my country have also used laser welding.
???????Laser technology uses a polarizer to reflect the laser beam and concentrate it in the focusing device to generate a beam of huge energy. If the focus is close to the workpiece, the work will melt and evaporate in a few milliseconds. This effect can be used in the welding process. The key to laser welding equipment is high-power lasers. There are two main types. One is solid-state lasers, also known as Nd: YAG lasers. Nd (neodymium) is a rare earth element, YAG stands for yttrium aluminum garnet, and its crystal structure is similar to ruby. The wavelength of the Nd: YAG laser is 1.06μm. The main advantage is that the generated beam can be transmitted through the optical fiber. Therefore, the complex beam transmission system can be omitted. It is suitable for flexible manufacturing systems or remote processing. It is usually used for workpieces with high welding accuracy requirements. The Nd: YAG laser with an output power of 3-4 kW is commonly used in the automotive industry. The other type is a gas laser, also known as a CO2 laser. Molecular gas is used as a working medium to produce an infrared laser with an average of 10.6 μm. It can work continuously and output high power. The standard laser power is between 2-5 kW.
???????The characteristic of laser welding is that the deformation of the workpiece to be welded is extremely small, there is almost no connection gap, and the welding depth / width ratio is high, so the welding quality is higher than the traditional welding method. However, if you want to ensure the quality of laser welding, that is, laser welding process monitoring and quality control is an important content in the field of laser utilization, including the use of various sensors such as inductance, capacitance, sound wave, photoelectricity, etc., through electronic computer processing, for different welding Objects and requirements, realize items such as weld seam tracking, defect detection, weld seam quality monitoring, etc., and adjust the welding process parameters through feedback control, thereby realizing automated laser welding.
???????In laser welding, the beam focus position is one of the most critical control process parameters. At a certain laser power and welding speed, the maximum penetration and good weld shape can be obtained only when the focus is in the optimal position range. In actual laser welding, in order to avoid and reduce the factors that affect the stability of the focus position, special clamping and equipment technology are required, and the accuracy of this equipment is complementary to the quality of laser welding.
???????In the automotive industry, laser technology is mainly used for body welding, welding and parts welding. Laser tailor welding is to design different steel plates according to different design and performance requirements of the car body in the design and manufacture of the car body, and complete the manufacturing of a certain part of the car body through laser cutting and assembly technology, such as the front windshield frame and the door inner panel , Underbody, neutral pillar, etc. Laser tailored welding has the advantages of reducing the number of parts and molds, reducing the number of spot welding, optimizing the amount of materials, reducing the weight of parts, reducing costs and improving dimensional accuracy. It has been adopted by many major automobile manufacturers and accessory suppliers. Laser welding is mainly used for welding the frame structure of the body, such as the welding of the roof and the side body. The resistance spot welding of the traditional welding method has been gradually replaced by laser welding. With laser welding technology, the width of the joint surface between the workpiece connections can be reduced, which not only reduces the amount of plate used but also increases the rigidity of the car body. Laser welding parts, the welding parts of the parts are almost not deformed, the welding speed is fast, and there is no need for post-weld heat treatment. At present, laser welding parts have been widely used, commonly found in transmission gears, valve lifters, door hinges and so on.