1) Pulse mode welding
The appropriate welding waveform should be selected during laser welding. The commonly used pulse waveforms include square wave, peak wave, double peak wave, etc. The reflectivity of the aluminum alloy surface to light is too high. When the high-intensity laser beam hits the surface of the material, the metal surface will 60%-98% of the laser energy is lost due to reflection, and the reflectivity varies with surface temperature. Generally, sharp wave and double peak wave are the best choices when welding aluminum alloys. The pulse width of the slow-down part behind this welding waveform is longer, which can effectively reduce the generation of pores and cracks.
Pulsed laser welding samples
Due to the high reflectivity of the aluminum alloy to the laser, in order to prevent the vertical reflection of the laser beam from causing vertical reflection and damage to the laser focusing mirror, the welding head is usually deflected by a certain angle during the welding process. The diameter of the solder joint and the diameter of the effective joint surface increase with the increase of the laser inclination angle. When the inclination angle of the laser is 40°, the largest solder joint and the effective joint surface are obtained. The welding point penetration and effective penetration decrease with the laser inclination angle, and when it is greater than 60°, the effective welding penetration decreases to zero. Therefore, by tilting the welding head to a certain angle, the penetration depth and width of the weld can be appropriately increased.
In addition, when welding, with the weld as the boundary, the laser welding spot needs to be 65% off the cover plate and 35% on the shell, which can effectively reduce the explosion caused by the problem of closing the cover.
2) Continuous mode welding
Because the heating process of continuous laser welding is not like the sudden cooling and sudden heating of pulse machines, the tendency of cracks during welding is not very obvious. In order to improve the quality of the weld, continuous laser welding is used. The surface of the weld is smooth and uniform, no spatter, and no defects. No cracks were found. In the welding of aluminum alloys, the advantages of continuous lasers are obvious. Compared with traditional welding methods, the production efficiency is high, and no wire filler is required; compared with pulsed laser welding, it can solve the defects generated after welding, such as cracks, Air holes, splashes, etc., ensure that the aluminum alloy has good mechanical properties after welding; it will not sag after welding, and the amount of polishing and grinding after welding is reduced, which saves production costs, but because the spot of the continuous laser is relatively small, so the workpiece assembly accuracy Higher requirements.