激光深熔焊接小孔效应的传热性研究

激光焊接由于其焊缝深宽比高、热影响区小以及高的焊接速度而在工业上得到越来越广泛的应用。激光深熔焊接的本质特征就是存在着小孔效应。采用高速摄影的方法清晰、完整地观测了激光深熔焊接GG17玻璃时的小孔，实验研究了离焦量、焊接速度对小孔和熔池形状、尺寸的影响。在分层假设的基础上建立了激光深熔焊接小孔效应的传热模型，并根据观测到的小孔形状和尺寸，用有限元法计算了小孔周围的温度场和流场。实验与模拟计算结果表明，小孔前沿的温度梯度比后沿的大；焊接熔池中的最大对流速度达到了焊接速度的10倍左右；小孔形状和尺寸的实验观测为系统研究激光深熔焊接时的小孔效应提供了一种新的方法。

Diathermancy Study on Keyhole Effects in Laser Deep Penetration Welding

Laser beam welding has gained increasing application in the industry, because of its high ratio of penetration deep to weld width, low heat effects and high welding speed. Keyhole effects are the essential characteristic in laser deep penetration welding. A clear stable keyhole was observed with a high-speed camera in laser welding of GG17 glass. The effects of defocus and welding speed on the size and the appearance of the keyhole and the welding pool were experimentally studied. Under the assumption of the keyhole per thin layer being cylindrical, a heat transfer model was proposed to obtain the temperature distribution and the fluid velocity distribution around the keyhole by a finite element method based on the keyhole observed. Experimental study and simulation show that temperature gradient on the front keyhole wall is steeper than that on the rear, the mass flow rate in the welding pool is about ten times the welding speed, and a new technology for quantitative study of keyhole effects in deep penetration laser welding is developed.