Effect of beam factors on beam-focusing characters and laser penetration welding

Laser beams could supply energy directly to a small region though focusing on different materials without heating the rest of the material. Characters of laser beam itself should be considered deeply. In this paper, beam-focusing characteristics and laser penetration welding were researched both in experiments and calculations with varied laser processing system. The focusing theory of multimode beam was discussed firstly based on the theory of basic mode. Beam quality, F-number and laser wavelength were three key factors had effect on focal beam properties. Beam quality decided the focusing ability of laser beam directly. Beam parameter product was used to evaluate beam quality in this paper. Focal length, focal point’s size, focal divergence, focal depth and focal shift with different laser processing system were calculated and compared with the results of measurement. The final results shown that the higher the beam quality was, the better beam-focusing properties were. Select laser manufacturing system and the optimum focusing optics system for the practical application was very important.