Estudo da variação de gases de proteção na soldagem GMAW-STT® do aço ASTM A-36

Abstract

Due to the advance of research and development of new welding processes, it is important to investigate the effects that the variables of entry perform on the variables of output. Therefore, the aim of this work is to investigate the influence of the welding parameters, mainly the shielding gas, on the GMAW STT® (Surface Tension TransferTM) derivative process applied in the welding of the ASTM A-36 structural steel, and compare its results with the GMAW process. For this purpose, a design of experiments was carried out, in form to evaluate the interaction of the variables studied at all levels. In the first phase of the research, screening experiments were conducted, using fractional factorial design, to explore the main effects of the input variables with less quantity of runs. After, in the next phase of the project, a full factorial design was used to responses modeling, once it did not present curvature. The welds were made in BOP (bead on plate) using GMAW STT® welding. For the analysis of the bead geometry the test specimens were prepared by mettalography and later submitted to optical macroscopy. The optimal condition will be repeated in top joints and welded by GMAW and STT® process welding, and the welded specimens prepared for the mechanical tests of traction, microhardness, Heat Afected Zone and Penetration measurement. The variation of the protection gas was determinant at the geometrical proprieties of the welded joint, and the STT process shower smaller results of ZTA size than the conventional GMAW. As of Penetration, both processes had similar response.