Working principle of laser welding

        Laser welding of metal materials is a process in which the laser interacts with the metal. This process is extremely complicated. The metal reflects and absorbs light under the action of the laser, and then melts and vaporizes. Laser welding can be achieved by continuous or pulsed laser beams. There are two principles of laser welding: one is heat conduction welding, and the other is laser deep penetration welding. How to distinguish them? Generally speaking, when the power density is less than 104-105 W/cm2, it is thermal conduction welding. At this time, the penetration depth is shallow and the welding speed is slow; when the power density is greater than 105-107 W/cm2, the metal surface is concave into a “hole” under the action of heat, forming a deep penetration. It has the characteristics of fast welding speed and large aspect ratio.

        The self-oscillation effect occurs during the interaction between the laser and the workpiece, and the flow phenomenon of the molten pool, the small holes in the molten pool, and the metal changes periodically. The frequency of this oscillation is related to the parameters of the laser beam, the thermophysical properties of the metal and the kinetic characteristics of the metal vapor. The periodic change of the molten pool will produce two unique phenomena in the weld: one is the pores filled with metal vapor. Due to the periodic change, the metal of the molten pool flows from front to back around it, plus The disturbance caused by metal evaporation may cut off the small hole at the waist, so that the vapor remains in the welding seam and forms pores after solidification. The other is the periodic change of the penetration depth at the root of the weld, which is related to the periodic change of the small hole.

        The welding methods are divided into manual welding and automatic welding. Manual laser welding machines are mainly used in the sheet metal industry to weld various metal plates. Automatic welding machine is divided into a variety of different functions: jewelry laser welding machine, lithium battery laser welding machine, data line laser welding machine and so on. In addition, because of the different shapes of workpieces, it is often necessary to customize corresponding laser welding machines for different needs.