Feb 04, 2021
Laser can achieve welding, not only because the laser itself has extremely high energy, but more importantly, because the laser energy is highly focused to a point, which increases its energy density.
During laser welding, the laser is irradiated on the surface of the material to be welded, and it acts on it, and part of it is reflected and part is absorbed into the material. The laser is absorbed in the thickness of 0.01~0.1m on the metal surface and converted into heat energy, which causes the temperature of the metal surface to rise and melt.
The photon bombards the metal surface to form vapor, and the evaporated metal can prevent the remaining energy from being reflected by the metal. If the welded metal has good thermal conductivity, a greater penetration depth will be obtained. The reflection, transmission and absorption of laser light on the surface of the material are essentially the result of the interaction between the electromagnetic field of light waves and the material.
The absorption of laser light by metal is mainly related to factors such as laser wavelength, material properties, temperature, surface condition and laser power density. Generally speaking, the absorption rate of the metal to the laser increases with the increase of temperature, and increases with the increase of the resistivity.
Two types of lasers are currently used in the welding field: YAG solid-state lasers (Yttri-um-Aluminium-Garnet with Nd3+, YAG for short) and continuous fiber lasers.