A laser welding robot is a welding method that uses energy (visible light or ultraviolet light) as a heat source to melt and connect workpieces. Laser energy can be achieved not only because the laser itself has extremely high energy, but more importantly, because the laser energy is highly focused at a point, which increases its energy density.
During welding, the laser illuminates the surface of the material to be welded and reacts with it, causing some to be reflected and some to be absorbed, entering the interior of the material. For opaque materials, the transmitted light is absorbed, and the linear absorption coefficient of the metal is 10 * 7~10 * 8/m. For metals, the laser is absorbed and transformed into thermal energy in a thickness of 0.01-0.1m on the metal surface, causing the temperature on the metal surface to rise and then transmit to the interior of the metal.
Photons bombard the metal surface to form a vapor, and the evaporated metal prevents the remaining energy from being reflected off by the metal. If the welded metal has good thermal conductivity, it will achieve a greater penetration depth. The reflection, transmission, and absorption of laser on the surface of a material are essentially the result of the interaction between the electromagnetic field of light waves and the material.
When laser light waves incident on a material, charged particles in the material vibrate according to the step of the light wave electric vector, transforming the radiation energy of photons into the kinetic energy of electrons. After absorbing the laser, substances first generate excess energy of certain particles, such as the kinetic energy of free electrons, the excitation energy of bound electrons, or an excess of phonons. These original excitation energies are converted into thermal energy through a certain process.
In addition to being electromagnetic waves like other light sources, the laser also has characteristics that other light sources do not have, such as high directivity, high brightness (photon intensity), high monochromaticity, and high coherence. During laser welding processing, the conversion of light energy absorbed by the material into thermal energy is completed in an extremely short time (approximately 10 seconds). During this time, thermal energy is limited to the laser radiation zone of the material and then transmitted through thermal conduction from the high-temperature zone to the low-temperature zone.
The absorption of lasers by metals is mainly related to factors such as laser wavelength, material properties, temperature, surface condition, and laser power density. Generally speaking, the absorption rate of metal to laser increases with increasing temperature and resistivity.
