Influência da mistura de gases de proteção no perfil geométrico na microestrutura e na corrente de transição na soldagem Mig/Mag

Abstract

With the advancement of technology for the development of the various Base Industries, Capital Goods and Services, welding has become very important from an industrial point of view, being extensively used in the manufacture and recovery of parts, equipment and structures. This work aims to evaluate the influence of shielding gas mixture used in MIG / MAG welding. Each type of gas or mixture of these contributes to obtaining particular results regarding arc behavior, metal transfer, weld quality, bead geometry and metallurgical properties. In this regard, we highlight the effects of the use of shielding gas mixtures containing Helium and Argon with small percentages of oxidizing gases (Oxygen and Carbon Dioxide). Argon-based mixtures varying the He, CO2 and O2 contents were obtained using a gas mixer and a ternary analyzer. Welding was performed with binary mixtures (Ar + CO2 and Ar + O2) and ternary mixtures (Ar + He + CO2 and Ar + He + O2) with simple deposition on an ASTM A36 steel plate as base metal and an alloy of low carbon (AWS ER80S-B2) as the filler metal. A definitive exploratory study with the source in constant current mode was carried out in order to evaluate the best welding mode, to obtain the best conditions of arc stability and better metallurgical properties of welded materials. The analysis of arc stability, metal transfer and transition current was performed by studying the current signals, with the source in constant voltage mode, varying the feed speed to identify the droplet metal transfer and the transition current. These data were observed and investigated experimentally using filming techniques with a special high speed camera. In addition to the visual aspect of the arc flash, the metallurgical characterization of the base metal materials and weld beads was also studied. The results showed significant changes regarding the geometric aspect of the cord. However, the increase in oxygen or carbon dioxide content in the shielding gas generated an increase in the amount of oxide on the weld bead surface and an increase in the transition current.