(1) Application of laser welding in foreign automobile industry (1) Online laser welding in automobile industry is widely used in assembly and connection of white body stamping parts. The main applications include laser welding of roof, laser brazing of trunk lid and laser welding of frame. Another important application of laser welding of automobile body is laser welding of automobile body structural parts (including doors, side frames and columns). The reason why laser welding is used is because it can improve the strength of the car body and solve the problem that it is difficult to implement conventional resistance spot welding in some parts. 2) Laser tailor-welded blanks with different thicknesses can reduce the weight of the car body, reduce the number of parts, improve safety and reliability, and reduce costs. 3) Welding of gears and transmission parts In the late 1980s, Cocomo Branch of Chrysler Company purchased nine 6kWCO2 lasers for laser welding of gears, and the production capacity increased by 40%. In the early 1990s, the three major American automobile companies invested more than 40 lasers in the welding of transmission parts. After research, Mercedes-Benz uses laser welding instead of electron beam welding because the former has a small heat affected zone. Ford Motor Company of the United States uses 4. 7kWCO2 laser is used to weld rims. Rim thickness 1mm, welding speed 2. 5 m/min. The company also uses a laser welding machine with a vision system to weld six shafts and forged gears together, which becomes the carrier parts of the automatic transmission of automobiles, with a productivity of 200 pieces per hour. (2) Application of fiber laser welding in shipbuilding and marine engineering Many ships first manufacture many independent local assembly structural units, and then assemble them one by one on the underwater slideway. It is very suitable to use laser welding technology to manufacture local components of marine buildings, because it combines welding and cutting automation technology with laser technology. Compared with arc welding, this technology can greatly improve productivity. In shipbuilding, using fiber laser technology, components can be welded together without pretreatment of welding edges or heat treatment before or after welding. Compared with arc welding, laser welding has narrow weld seam and small heat affected zone, and there are no welding defects caused by arc blowing or electrode wear in traditional arc welding methods. Therefore, a new welding structure design can be realized by using fiber laser welding, which is impossible to be more economical and of better quality than arc welding in the past. (3) Application of laser welding in aircraft manufacturing Laser beam welding has the advantages of high energy density, small heat affected zone, flexible spatial position conversion, welding in atmospheric environment and minimal welding deformation. It is mainly used for splicing large aircraft skins and welding skins and stringers to ensure the shape tolerance of aerodynamic surfaces. In addition, laser beam welding technology is also widely used in the assembly of fuselage accessories, such as ventral fins and wing boxes of flaps. The structure is not completed by internal rib support structure and external skin, but by advanced sheet metal forming technology and laser welding technology in three-dimensional space, which not only has good product quality and high production efficiency, but also has good process reproducibility and obvious weight reduction effect. Laser welding is also very common in the manufacture of thin-walled parts, such as air inlet, bellows, oil pipeline, variable cross-section conduit, special-shaped head and so on. The traditional welding methods of these parts are mostly micro-arc plasma arc welding or low current tungsten argon arc welding. With the extensive use of titanium alloy materials, even if these welding technologies with low linear energy are adopted, the traditional welding technology will face the fate of being eliminated because of the welding deformation and irreparable welding defects caused by thin-walled materials exceeding the tolerance range. Laser beam welding with local protective measures is very suitable for welding thin-walled titanium alloy shell parts. (4) Application of compound laser welding The compound laser welding technology combines the advantages of both laser welding and traditional gas shielded welding (GMAW), and laser welding can obtain larger penetration and smaller welding heat affected zone (HAZ) with less heat input; Additional gas shielded welding (GMAW) can greatly expand the gap at the root of the joint, and improve the surface state and the allowable amount of impurities. Improve the forming quality of root gap filling and strengthen the control of welding metallurgy. (5) Application of laser welding in medicine Laser welding is heated by laser, so it can penetrate the transparent medium and weld to the inside of the transparent medium container. This is difficult to achieve by other welding methods. This method is also used in medicine. For example, some of our patients have retinal detachment, and the retina is behind the eyeball. After the retina falls off, the eyes will be blind. The retina is welded to the eyeball by laser through the eyeball. This is already a very successful operation;