In the daily work and processing, it is found in the laser welding test of magnesium alloy that the porosity is one of the main welding defects. The existence of weld hole causes structural discontinuity easily, reduce air tightness, weaken the mechanical strength of the metal. In this paper, through the change of laser welding process parameters to investigate its influence on porosity, so as to get familiar with the production of porosity and find a way to reduce the porosity.

The material used in the experiment was wrought magnesium alloy AZ31B, and the sample size was 100mm×60mm×1mm. A CO2 laser welding machine was used to carry out tailboard welding. The main process parameters considered in the experiment are as follows: the laser power range is 600 ~ 1100W; Welding speed 2 ~ 5m/min; Defocus is fixed at -0.5mm; The protection gas adopts Ar with 99.9% purity, and the gas blowing Angle is 30°. After welding, metallographic samples were prepared and eroded with picric acid solution of 2g+ alcohol 50ml+ acetic acid 5mL. The weld morphology and defect characteristics were observed with metallographic microscope.

With the improvement of welding speed, the porosity in the magnesium alloy weld first increases, and then shows a downward trend after rising to a certain value. The effect of laser power on the porosity of magnesium alloy weld has no significant regularity. The porosity in the weld can be reduced by preheating before welding and optimizing welding parameters. If there is a premise, try to choose double-sided gas protection. Therefore, we should do a good job in the protection of magnesium alloy when processing.