【作者】 余忠贵；

【导师】 华学明；

【作者基本信息】 上海交通大学 ， 材料工程， 2012， 硕士

【摘要】 交流焊接电源因为具有阴极清理作用而应用于铝及其合金的焊接。交流氩弧焊的一大核心问题是最大限度的减少钨极烧损同时获得良好的清理效果。目前对阴极清理的认识还不够充分,对这一领域内仍存在较多的疑问,尤其是阴极清理作用的影响因素、机理,阴极清理的过程至今仍存在较大的争议。本课题从阴极清理的影响因素和机理出发,研究焊接参数对阴极清理的影响规律,以及铝合金交流氩弧焊阴极清理的过程和机理。本文提出了阴极清理效果的简单评价方法,即当清理宽度大于熔池宽度时清理效果好。实验中同时考虑清理宽度和熔池宽度的变化,确定了影响交流TIG焊阴极清理效果的焊接参数,获得了焊接参数对阴极清理效果的影响规律。并采用复合式滤光方法建立了焊接熔池和阴极清理区的视觉检测系统,得到了清晰的焊接熔池和清理区图像,为清理效果的智能化控制做好了准备。本课题利用高速摄影拍摄到了清晰的阴极斑点,得出了阴极斑点的运动规律,即阴极斑点从熔池内部向外运动,斑点数量增加,亮度增大;利用扫描电镜拍摄到了焊缝、清理区不同区域的表面微观形貌,并对各区域表面成分进行了分析研究,提出了清理后氧化膜的两个去处,即残余氧化膜和圆形氧化物颗粒。提出了阴极斑点痕迹在清理区与母材交界处的观点,并进行了解释。本文对清理区各区域表面的形成过程和阴极清理过程进行了解释此外,传统观点一般认为交流焊接时反极性比增大会使得工件获得的能量输入减少,使焊缝熔深熔宽减小,本文得出了与此相反的结论,即熔宽熔深随反极性比增大而增大,只有少数文献得出的结论与本文一致。本文研究了反极性比对焊接电压、电弧形态、能量分配的影响,从理论上对实验结果进行了很好的解释。更多还原

【Abstract】 AC power supply is widely used to weld aluminum and its alloy for the cathode cleaning phenomenon during which the surface oxides can be cleaned during the direct current electrode positive (DCEP) polarity. However, there are still many controversy over cathode cleaning, especially in the influencing factors, cleaning process and mechanics. Based on experiments, the influence of several welding parameters on the cathode cleaning effect are studied and the relationship curve are obtained, then the cathode cleaning mechanics and the cleaning process was studied.In this work, a simple criteria is raised to evaluate the cleaning effect. Both the width of the cleaning zone and molten pool are taken into account during the study of the influence of the welding parameters on the cathode cleaning effect. The influencing welding parameters of the cleaning are determined and the relations between the welding parameters and the cleaning effect are obtained. a vision system is designed to observe the molten pool and the cathode cleaning zone, and clear images are obtained, this will pave the way for the intelligent control of the cathode cleaning effect.Clear images of the cathode cleaning spots have been captured by a fast speed vision system, and the behavior of cathode spots is observed. The surface micro-topography of the molten pool and the cleaning area are examined by scanning electron microscope, and after cathode cleaning the oxide is found in two forms: the remaining oxide layer and the white oxide particles. It is suggested that the craters of the cathode spots are in the area adhering to the base metal. The formation process of the cleaning area surface and the cleaning process are explained.In addition, It’s conventionally thought that the width and penetration of the weld bead will increase as a function of the increase of electrode positive polarity time in a period(or EP ratio),while in this research results contrary to conventional expectations are obtained, only several recent literatures agreed with this report. And in the article the effect of the EP ratio on the Voltage, the Current, the arc status and the heat generation and distribution is studied and the experiment result is well explained from theoretically perspective.更多还原