Aplicação do processo de soldagem por plasma pela técnica “keyhole” no passe de raiz de uma junta chanfrada

Abstract

Plasma are welding is a fabrication process considered of high produetivity, but still used in a small scale in the industry. The main obstacles for the process implantation are lack of technical information and welding operational difficulties. These problems become more criticai in root welding of single-V-groove joints, in which little work was spent on, ordinarily in a superficial way. The aims of this work were: the elaboration of a parameter operational box for the root pass in a single-V-groove joint of carbon Steel, using the keyhole mode; the verification of weld bead repeatability into tolerance box borders; and the study of the effect of some welding operation variables on the repeatability of the process. The development of the operational box was made in terms of current, welding speed and plasma gas flow. The repeatability of the weld bead was not reached for the operational box welding conditions. An instability phenomenon was verified in the keyhole maintenance. Due to this fact, some factors were studied, such as: the welding equipment reliability, the metal cleaning technique, test plate dimensional variations, electrode setback and shielding gas compositions. From this study, it was verified that shielding gas composition was the most influential factor. The best results related to superficial quality and keyhole maintenance were obtained by using pure argon as plasma gas and argon with 10% CO2 or 5% O2 mixtures as shielding gases.