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Laser Welding
- Oct 25, 2016 -

Laser welding

Laser welding is the use of high-energy-density laser beam as a heat source of an efficient precision welding method. Laser welding is one of the important aspects of laser material processing technology. In the 1970s, mainly used for welding thin-walled materials and low-speed welding, the welding process is heat conduction, that is, laser radiation heating the surface of the workpiece, the surface heat diffusion through the heat transfer to the internal, by controlling the laser pulse width, energy, peak power and repetition rate And other parameters, the workpiece melting, forming a specific pool. Because of its unique advantages, has been successfully applied to micro, small parts of the precision welding.

Laser welding can be used to achieve continuous or pulsed laser beam, the principle of laser welding can be divided into heat conduction welding and laser deep penetration welding. The power density is less than 104 ~ 105 W / cm2 for the heat conduction welding, when the welding depth of shallow, slow welding speed; power density greater than 105 ~ 107 W / cm2, the metal surface heat under the concave into a "hole" to form deep welding, Welding speed, deep aspect ratio characteristics.

Laser deep penetration welding generally uses a continuous laser beam to complete the material connection, the metallurgical physical process and electron beam welding is very similar, that is, energy conversion mechanism is through the "small hole" (Key-hole) structure to complete. At sufficiently high power density laser irradiation, the material evaporates and forms pores. The vapor-filled hole acts like a black body, absorbing almost all of the incident beam energy, and the equilibrium temperature in the cavity is about 2500 ° C. The heat is transferred from the outer wall of the high-temperature cavity to melt the metal surrounding the cavity. The holes are filled with high-temperature steam generated by continuous evaporation of the wall material under the irradiation of a beam of light surrounded by molten metal surrounded by liquid metal surrounded by a solid material (in most conventional welding processes and laser welding, Deposited on the workpiece surface, and then transported to the internal transmission). The liquid flow and the surface tension of the wall surface are in constant equilibrium with the pressure of steam generated continuously in the cavity. The beam continues to enter the hole, the material outside the hole in the continuous flow, with the beam movement, the hole is always in a steady state of flow. That is, the small holes and the molten metal surrounding the cell walls move forward with the advancing speed of the leading light beam, and the molten metal fills the voids left after the small holes are removed and is condensed, and the weld is formed. All of the above-mentioned processes happen so fast that the welding speed can easily reach several meters per minute.