【作者】 裴利程；

【导师】 林三宝；

【作者基本信息】 哈尔滨工业大学 ， 材料加工工程， 2006， 硕士

【摘要】 穿孔的稳定过渡是影响等离子焊缝成形的重要因素。基于其过程复杂、研究手段有限的特点,本文以温度场分布对过渡成形的影响为主要研究对象,实现穿孔稳定成形过程的控制。通过穿孔过程分解研究,揭示出焊接工艺参数在小孔稳定建立过程中的影响规律。试验结果表明,焊接电流是影响穿孔加热速度及温度场分布的主要因素;离子气流量是影响穿孔挖掘速度及小孔形状的重要因素,并通过改变穿孔时间对加热过程施加影响;送丝时刻可改变穿孔成形,但对温度变化影响小。鉴于穿孔过程的复杂性,起弧程序采用弱规范加热、强规范挖掘的控制策略,使穿孔加热过程与穿孔挖掘过程相对独立,达到降低控制难度,提高控制精度的目的。在此基础上,通过控制起弧程序,确保穿孔时刻小孔周围的温度场分布接近优良焊缝的温度场分布,最终实现起弧的稳定成形。试验证实,穿孔时刻的温度场分布状态是影响起弧稳定成形的决定因素,其实质是保证穿孔时刻的熔池分别达到力和热的稳定平衡状态,小孔自稳定调节过程最短。更多还原

【Abstract】 The stable transition of the keyhole weld pool in starting process seriously influences on the formation of weld during plasma arc welding. This keyhole establishing process is very complex and is not researched diffusely recently. By investigating the temperature field distribution’influence on the stable transition, as the main subject investigated, how to control the process parameters to complete the stable keyhole transition will be studied in this paper.By analysis of the establishing process of the keyhole weld pool, the regularities of the welding parameters are obtained. The welding current mainly influences on the heating rate and the temperature distribution in the establishing of the keyhole. The plasma gas flow rate, which also affects the heating process by changing the occurrence time of the keyhole, can influences on the rate of excavating the keyhole and the geometrical size of the keyhole severely. The wire feed time can change the formation of weld in the starting process, but it doesn’t have any effect on the temperature.Owing to the complexity of the keyhole establishing process, a new control mode, heating the weld pool by weak process parameters and excavating the keyhole by strong process parameters, is adopted. This control mode can reduce the difficulty of the control, improve the accuracy by making the heating process independent of the excavating process relatively.Based on the above results, make sure the temperature filed distribution near the keyhole close to that near the satisfactory weld at the occurrence time of the keyhole by controlling the process parameters, the uniform formation of weld in the starting process is finished at last. The conclusion that the temperature fired distribution near the keyhole at the occurrence time of the keyhole is the decisive effect of the uniform formation of weld in starting process is proved. To keep the keyhole weld pool’s thermal and mechanical conditions balance respectively at the occurrence time of the keyhole, which aim is to shorten the keyhole’s self-regulating process seriously, is the essential of success.更多还原