Influence of the beam oscillation pattern and oscillation frequency on the temperature field in laser brazing with keyhole formation
Influence of the beam oscillation pattern and oscillation frequency on the temperature field in laser brazing with keyhole formation
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DOI：
10.1007/s00170-020-06111-1
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发表时间：
2020-10
期刊：
影响因子：
--
通讯作者：
I. Henze;P. Woizeschke
中科院分区：
文献类型：
--
作者：
I. Henze;P. Woizeschke
激光锁孔钎焊是提高激光钎焊工艺效率的一个契机。当超过特定材料的阈值时，使用小的光斑尺寸会增加强度，并导致在钎焊材料中形成蒸汽毛细管（锁孔）。由于锁孔中激光束的多次反射/吸收，与表面单菲涅耳吸收的传统钎焊工艺相比，工艺效率提高，特别是当使用高反射率钎焊材料时，如铝基或铜基合金。必须通过在钎焊方向上施加横截面的光束振荡来充分分配能量。在激光钎焊过程中，钎焊与基体材料界面的温度场是影响钎焊性能的主要因素。为了分析光束振荡的影响，本研究假设熔池表面的温度分布是基底界面温度分布的适当近似。根据均匀性，定义了两个关键参数来量化温度场：局部时间温度-时间曲线和钎焊方向横向温度分布。振荡频率通过减小局部激光通过的时间间隔来影响第一个参数，而振荡模式通过调节局部实际光束速度及其一致性来影响第二个参数。
Laser keyhole brazing is an opportunity to increase the process efficiency in laser brazing processes. Using small spot sizes increases the intensity and leads to the formation of a vapour capillary (keyhole) in the brazing material when a material-specific threshold value is exceeded. Due to multiple reflections/absorptions of the laser beam in the keyhole, the process efficiency increases in comparison with conventional brazing processes with single Fresnel absorption on the surface, especially when using high-reflectivity braze materials, such as aluminium-based or copper-based alloys. The energy must be distributed adequately by applying beam oscillation transversal to the brazing direction. In laser brazing processes, the temperature field in the interface between brazing and substrate material is a major factor. To analyse the effect of beam oscillation, it is assumed in this study that the temperature distribution at the surface of the melt pool is a suitable approximation for the temperature distribution at the interface to the substrate. Two key parameters are defined to quantify the temperature field referring to the homogeneity: the temporal local temperature-time curve and the temperature distribution transverse to the brazing direction. While the oscillation frequency influences the first mentioned parameter by decreasing the time interval between the local laser passes, the oscillation pattern affects the second parameter by adjusting the local actual beam velocity and its consistency.