Adjustment Of The Plasma Heat And Pressure Distribution With Keyhole Evolution

In keyhole plasma arc welding, the interaction between keyhole and weld pool occurs when the keyhole appears inside the weld pool. The change of the keyhole shape and dimensions has direct effect on the fluid flow and heat transfer in the weld pool. Thus, it has a significant impact on the quality of the weld seam. Adjustment of the plasma heat and pressure distribution with keyhole evolution is studied on the base of the study of our team, improve the accuracy of numerical analysis of heat transfer and fluid flow in PAW weld pool and keyhole. It will lay solid foundation for optimizing the welding parameters and improving the stability of PAW process.Based on the characteristics of PAW process, appropriate heat source model and arc pressure model are established which are adjusted dynamically with the variation of the depth of keyhole. Dynamic adjusting of heat source include two parts. Firstly, affect zone of the heat source is adjusted dynamically. Secondly, two parts heat source accounts for the proportion of total calories is adjusted dynamically. The arc pressure model is adjusted dynamically with the variation of the depth of keyhole, when the keyhole does not form, the arc affects the surface of the weld pool, when the keyhole forms, the zone which the arc affects is changing. Thus, as the increasing of the depth of keyhole, the arc pressure which distributes on the interface of the keyhole should be adjusting.Numerical simulation of PAW process is conducted on stainless steel plates of thickness6mm and8mm. The physical phenomenon, such as the weld pool development, the keyhole formation, the evolution of fluid flow and thermal field, the full-penetration of the these plates, and the emergency of an open keyhole, are quantitatively analyzed.The experiments of Keyhole PAW are conducted. The calculated keyhole shape at backside and the transverse cross-section of PAW welds are compared with the experimental measurements. Both agree with each other generally. It indicates that the developed model can be useful for different welding conditions.