Uma contribuição à análise dos parâmetros de soldagem do processo plasma-MIG com eletrodos concêntricos

Abstract

The constant market demand for competitive welding processes during the latest years has raised the development of new process, among them the Plasma-MIG welding. The Plasma-MIG process figures among the so called "Hybrids Welding Processes", in which at least two other conventional processes are associated to obtain operational characteristics that would be impossible with other welding processes. In hybrid processes usually the association is made by using a process with uninterrupted material feeding and an autogenous process. The main advantage of such approach is the high independence between the material feeding rate and the total energy used in the process. Although the current literature mentions the benefits and potential applications for the Plasma-MIG process, there has not been found any report of its use in the Brazilian industry. In order to change this scenario, new research efforts on this process have been initiated by the Laprosolda/UFU working group. This work intends to identify and solve the main difficulties in using the process, evaluate the weld bead shape for different current combinations in the Plasma and the MIG/MAG circuits, asses the Plasma current influence on the MIG/MAG electrode melting rate, check some aspects of metal transfer and suggest some potential applications. Eventually, suggestions for future work with this welding process are proposed. The experiments were carried out using a Plasma-MIG torch with concentric electrodes, two dedicated power sources, a process control interface, a cooling system with temperature control, an electrical data acquisition system and a synchronized high speed filming method. The results indicated that it is possible to act on the weld bead geometry by setting the right currents for the Plasma and the MIG/MAG circuits and there is independence between the welding power and the amount of deposited material. In addition, by increasing the Plasma current it is possible to decrease the dilution of the weld bead in the base metal. Finally, it is worth mentioning that there is an interaction between the Plasma and the MIG/MAG electrical circuits and a resultant influence on the metal transfer.