Laser welding uses a high-energy-density laser as a heat source to irradiate the joint of the material, so that the separated material quickly melts and even vaporizes after absorbing the laser energy and forms a molten pool together, which solidifies together in the subsequent cooling process and is connected together. There are two common high-power lasers for laser welding: CO2 lasers and solid/fiber lasers. The former has a wavelength of 10.6μm, or a wavelength of 1.06/1.07μm, both in the infrared band and invisible to the naked eye.
1. Laser welded car body
The common welding principle is to liquefy metals, then cool them and dissolve them together. The body of the car is composed of four steel plates welded up and down, and ordinary welding is spot welding, and the steel plates are connected together through a welding spot.
The laser welding is the physical principle of using the high-temperature of the laser to disrupt the molecular structure in the two steel plates, and the molecules are rearranged so that the molecules in the two steel plates are dissolved as one. The actual operation is to use a polarizer to reflect the beam generated by the laser, so that it is concentrated in the focusing device to produce a huge energy of the beam. The diameter of the laser beam at the focus is 0.2-0.6 mm, and the light intensity of more than 106-108 watts/cm2 can be obtained. The focal point is close to the workpiece, and the surface of the workpiece reaches a physical change of melting combination.
Therefore, laser welding turns two steel plates into one steel plate, so it has higher strength than ordinary welding.
2. Laser welding body features
What are the advantages of laser welding technology?
Laser welding mainly has the characteristics of centralized heating range and precise control, small welding deformation, and fast welding speed. Compared with common arc welding, laser spot diameter can be precisely controlled, and the spot diameter of the surface of the material is usually in the range of 0.2-0.6mm. And the closer to the center of the spot the higher the energy (energy from the center to the edge is exponentially attenuated, that is, Gaussian distribution), laser welding weld width can be controlled below 2mm. The arc width of arc welding cannot be precisely controlled and is much larger than the laser spot diameter. The weld width of arc welding is also much larger than that of laser welding, usually more than 6mm. Because the energy of laser welding is very concentrated, the melting material is less and the total heat required is small, so the welding deformation is small and the welding speed is fast.
How strong is laser welding compared with resistance spot welding? The laser welded joint is a long, continuous straight line, while the resistance spot welded joint is a row of slightly recessed discrete dots. If the laser welded joint is like a zipper to connect the two buttons of the clothes, the resistance spot welded joint is like a button of the clothes. The weld metal of laser welding is obtained through rapid solidification, and its grain (the basic component unit of the metal, which can be understood as the cell of the metal) is smaller. This is conducive to improving the strength of the weld metal, so the strength of the laser welding weld metal is higher than the strength of the resistance spot welding weld metal. At the same time, do not forget that the resistance spot welding joint is a series of discrete points, just take the part of the welding and laser welding are already better than, and those not welded on the place also "drag", that the average down resistance spot welding is more than laser welding. Therefore, for welded joints of the same length, the strength of laser welding is higher than that of resistance spot welding.
3. Is laser welding body safer?
Although the strength of the resistance spot welding joint is not better than the laser welding, it is still higher than the metal base material, and the weakest link of the overall welded car body is the welding heat affected zone on the base material. That is to say, the metal base metal is the weakest link, so once the body is subjected to a strong external force, the vast majority of cases are the metal base metal damage, rather than welded joints. It is precisely because of the existence of the short plate of the metal base metal that there is almost no difference in the strength of the laser welded body and the resistance spot welded body. Therefore, the laser welding body is not safer than the resistance spot welding body when affected by external forces.
Xi'an Guosheng Laser Technology Co., Ltd. is a high-tech enterprise specializing in R&D, manufacturing and sales of automatic laser cladding machine, high-speed laser cladding machine, laser quenching machine, laser welding machine and laser 3D printing equipment. Our products are cost-effective and sold domestically and abroad. If you're interested in our products, please contact us at bob@gshenglaser.com.