7075铝合金中厚板激光扫描焊接气孔抑制机理研究

Study on the Porosity Control Mechanism of Medium Thick 7075 Aluminum Alloy Plate by Scanning Laser Welding

针对7075-T6铝合金10 mm中厚板开展了激光扫描焊试验和模拟研究,通过X射线无损检测以及熔池流动模拟,探究激光扫描焊接对焊缝气孔的抑制规律。试验结果表明,随着扫描频率和扫描振幅的增加,焊缝气孔率有降低趋势。分析不同扫描频率下的模拟结果发现,高频扫描下由于匙孔叠加会产生“大匙孔”结构,此结构相较低频扫描下的细长匙孔来说更加稳定,更不容易坍塌形成气泡;同时光束扫描增加了熔池宽度,增大了气泡逸出的概率。分析不同扫描振幅下的模拟结果发现,大振幅显著降低了匙孔的深度,从而降低了匙孔的深宽比,增强了匙孔的稳定性;同时增大振幅进一步扩大了熔池的宽度,增大了气泡逸出概率,进而降低了焊缝中的气孔率。

Laser scanning welding experiment and simulation study were carried out for 7075-T6 aluminum alloy 10 mm medium thickness plate.The inhibition law of laser scanning welding on weld porosity was investigated by X-ray nondestructive testing and molten pool flow simulation.Experimental results show that the porosity decreases with the increase of scanning frequency and amplitude.By analyzing the simulation results at different scanning frequencies,it is found that the"large keyhole"structure is more stable and less likely to collapse and form bubbles due to the superposition of keyholes at high frequency scanning,compared with the slender keyhole at low frequency scanning.At the same time,the beam scanning increases the width of molten pool and the probability of bubbles escaping.By analyzing the simulation results under different scanning amplitudes,it is found that the large amplitude significantly reduces the depth of the keyhole,which reduces the aspect ratio of the keyhole and enhances the stability of the keyhole.At the same time,the increase of amplitude further expands the width of the molten pool,which increases the probability of bubble escape and then reduces the porosity in the weld.