Laser welding uses a high-energy-density laser to illuminate the material connection at a material source, so that the separated material absorbs the laser energy and then rapidly melts or vaporizes and forms a molten pool together, which solidifies together and then joins together in the subsequent cooling process. There are two common types of high-power lasers for laser welding: CO2 lasers and solid/fiber lasers. The former has a wavelength of 10.6 μm or a wavelength of 1.06/1.07 μm, both in the infrared range and invisible to the naked eye.

The ordinary welding principle is actually liquefying the metal, then cooling it and then dissolving it together. The body of the car is welded by four steel plates from top to bottom and left and right. The ordinary welding is spot welding, and the steel plates are connected together by one welding point.

Laser welding is the physical principle of using the high temperature of the laser, disrupting the molecular structure of the two steel plates, and rearranging the molecules to dissolve the molecules in the two steel plates. The actual operation is to use a polarizer to reflect the laser beam, so that it concentrates on the beam that produces great energy from the focusing device. The laser beam has a diameter in the range of 0.2-0.6 mm at the focus point, and a light intensity exceeding 106-108 watts/cm 2 is obtained, the focus is close to the workpiece, and the surface of the workpiece reaches a physical change of the fusion bond.

Therefore, laser welding turns two steel sheets into one steel sheet, so it has higher strength than ordinary welding.