Numerical Simulation Of The Behaviors Of Arc And Weld Pool Of GTAW

By its own welding advantages, such as the perfect weld-forming, the good weld-quality, the high intelligence-automation and so on, GTAW are widely applied in many fields. During the process of GTAW, the welding quality is obviously influenced by the behavior characteristics of the arc and weld pool. Thus, studying on them would basically improve the weld-quality. However, owing to the special properties of the arc and the weld pool, it is hard to observe, measure and study them by the regular design methods. With the rapid development of computer technology, numerical simulation technology is widely used in some fields step by step. Now, studying on relevant problems of welding by using the numerical simulation technology has become a kind of newly arisen means researching on welding problems. In this paper, arc and weld pool of GTAW were studied by the method of numerical simulation.At first, based on some characteristics of GTAW and hydrodynamic theory, a two-dimension axial symmetry transient model of GTAW that the complete coupling of arc and weld pool was developed in this paper. A set of governing equations of the mathematical model were solved by using the Fluent software and redeveloping its UDF.Secondly, to verify the correctness of the model, combining the basic calculated case with experiments, the results showed that the bullied mold could meet the requirement. Then, based on the basic of extension, modification and optimization of the basic calculated case, the studying of arc and weld pool of GTAW under the protection of mixed gas of argon and helium could be realized.Finally, the solved results of the basic calculated case and extended cases were post-processed. The processed results indicated that morphologies of arc of GTAW were the shape of bell jar both under the protection of pure argon and mixed gas, and that the presence of helium made the arc wholly constrict and the arc around base metal up warp. These phenomena resulted in the reduction of effective area heating from arc to base metal, which became more obvious with the increase of helium content. In addition, the presence of helium could strengthen the stability of the arc, which would be further strengthened with the increase of helium content. Electromagnetic force and surface tension of the weld pool of GTAW were main impetus of the dynamic evolution of shapes of weld pool both under the protection of pure argon and mixed gas. Among them, surface tension was the main driving force of forming a weld pool that has a shape of spoon, and electromagnetic force was the main driving force of forming a weld pool that has a shape of bowl. Compared with the fluid flow of the weld pool under the protection of pure argon, however, the most distinguished feature of the fluid flow of the weld pool under the protection of mixed gas was that helium content had certain influence on the ownership of leading force of the weld pool. Besides, the weld penetration was increased in a large rates of increase with the increase of helium content. But, the weld width was decreased in various rates of decrease until it finally reached a steady-state.The calculation results have certain theoretical reference value for the research of the behavior characteristics of arc and weld pool of GTAW, for the improvement of the welding process and welding quality of GTAW.