采用理论和实验两种方法研究了光束聚焦特性对激光焊接的影响。结果表明,获得足够高的功率密度是实现激光深熔焊接的前提条件,焊缝形状和深度、宽度取决于焊接能量的输入。在相同工艺参量条件下,焦斑大小决定了可以获得的功率密度;焦深决定了聚焦光束准直的范围;聚焦角影响到小孔壁的菲涅耳吸收。可以说,光束聚焦特性反映了聚焦光束不同横截面处光束束宽,导致了可以获得的功率密度的不同,进而对激光焊接结果产生影响。实际应用中,应根据需求选择合适激光器、聚焦系统以及焦点位置,得到最优的聚焦状态,获得理想的加工质量。

Focal spot shape and size, beam power intensity distribution, convergence angle and depth of focus which are determined by beam quality and focus system describe the characteristics of focal beam. The influences of these parameters on depth and width of weld seam are studied in theory and experiment. Results shown that enough power intensity is the precondition of realizing laser penetration welding. Depth and width of weld seam rely on energy penetrating into materials. With the same processing parameters, focal spot size decides the acquired power intensity, depth of focus decides the algnment distance and convergence angle has effect on Fresnel absorption in keyhol wall. All in all, beam-focusing characteristics have effect on results of laser welding with different energy acquired at different focus beam cross section. In reality application, laser system, focus system and focal spot position should be selected according to the practical requirements in order to acquire ideal quality of processing.