Study Of Thermal Mechanical Coupled Model Of Keyhole Plasma Arc Welding With Hot Wire

Keyhole Plasma arc welding(K-PAW) is an efficient welding method. It gets the attention because of its ability of penetrating a thick work piece without weld groove. After feeding the hot wire, the defects of collapsing of weld pool up-surface and undercut due to the powerful plasma arc pressure will be compensated well. Therefore, it has far-reaching significance of theoretical guidance for the development of keyhole plasma arc welding process to analyze the mechanism of K-PAW, the changing process of keyhole and weld pool and the influence of droplet transfer to keyhole during welding deeply.In this paper the K-PAW process experiment was carried out firstly and the pictures of keyhole on the back of the work piece, which showed the evolution process of keyhole,were taken by the high-speed camera at different welding time with different welding parameters. Through the analysis it is found that the current of 120 A is the critical current of penetrating 304 stainless steel 6mm thickness continuously when the other parameters keep same. Based of the process experiment, energy distribution of penetrating process was analyzed. A thermal mechanical coupled model of energy attenuating gradually was established. And the energy attenuate as the law of two times changes with the depth of keyhole increasing. The K-PAW process of different welding parameters was simulated with this calculation model of mathematics. The weld pool flow fluid and keyhole shape was simulated. The results are consistent to compare simulated and actual results. Advantages and disadvantages of formal and improved model were analyzed, which laid the foundation for future study.In addition, the welding process of K-PAW with filling hot wire is studied in these paper. 304 stainless steel were welded with two different wire feeding speed of 0.5m / min and 1.0m / min. The welding time increased every time than before. The penetration and fusion width were obtained at different welding time. The pictures of droplet transfer were taken by high speed camera. Through analysis these pictures, it is found that the droplet transfer method is “bypass transfer”, and the frequency of droplet transfer and the size of droplet are obtained. The thermal-mechanical coupled model of K-PAW with hot wire was established and the effects of droplet transfer to keyhole were simulated with this model.Finally, the simulated results were verified by experiments.The process mechanism of K-PAW with hot wire can be understood deeply by studying this paper. The characteristics and development direction of this welding method can begrasped easily, which can help to lay a good foundation to promote the applications of K-PAW in engineering and has a strong theoretical guidance.