光斑直径对纯钛薄片激光封孔的影响

Effect of Spot Size on Joint Formation of Laser Hole Sealing of CP-Ti Sheet

摘要:

采用Nd：YAG低功率脉冲激光对0.4mm纯钛薄片的微孔进行封焊，研究光斑直径对焊缝成形的影响规律，并分析作用于封接区的激光能量变化。研究表明，当光斑直径不大于0.4mm时小孔能够完全封接，封接区有效厚度随着光斑直径的增大呈先增大后减小的趋势，其最大有效封接厚度约为352μm，封接接头主要由不同形态的α晶粒组成，在封接区边缘存在较大的热影响区。另外，随着光斑直径的增大，封接区上表面熔化面积基本不变，但封接模式由匙孔型向热导型转变，其中热导型模式更适合小孔封接。对作用于封接区的激光能量计算发现，理论能量值与光斑直径成正相关，而实际金属熔化量与光斑直径成反相关，造成此现象的原因是小孔边缘熔化的金属在重力等力的作用下向小孔内流动，从而可以吸收更多的激光能量。

Abstract:

Laser seal welding of 0.4mm thickness pure titanium with holes was achieved by N d: YAG pulse laser. The effect of laser spot size on the weld geometry of the sealed joint was studied. The results show that full seal welded joint can be achieved when the spot diameter is no more than 0.4mm. The effective thickness of sealing area increases at first then decreases with the increasing of spot diameter. The maximum effective sealing thickness is about 352μm.The sealing joint was consisted of alpha grains with different shapes, and there was a large HAZ in the joint. Besides, with the increase of the spot diameter, the surface melting area of the sealed joint is basically unchanged, but the sealing mode is changed from the keyhole to the heat-conduction type, and the heat-conduction model is more suitable for the hole sealing. Further, calculated laser energy of sealing area shown that there was a positive proportion between the theoretical energy value and laser spot size, but the theoretical analysis does not match with the actual situation. The reason may be that the molten metal beside the hole flow into the hole under the effect of gravity and other forces, which cause the increasing of actual absorption of laser energy.