Process enhancement using hydrogen-induced shielding: H2-induced A-TIG welding process

Abstract

ABSTRACT Deeper penetration in a gas tungsten arc welding process is the essential requirement for the fabrication of duplex stainless steel pipes. Activated fluxes and associated activated tungsten inert gas’ (A-TIG) welding process has proved itself as the better option for improved dilution and the deeper penetration. Use of hydrogen in shielding environment of A-TIG process for different ranges of activated fluxes needs to assess for deeper penetration and associated weld properties. Present investigation addresses the issue of deeper penetration using different activated fluxes in A-TIG process along with mixing of 2.5% H2 in the argon gas shielding. An effect of H2-induced shielding during CrO3, MoS2, TiO2, and SiO2 fluxes in A-TIG process has been investigated with weld pool morphology, depth of penetration, weld chemistry, scanning electron microscopy, optical microscopy, energy dispersive spectroscopy, and X-ray diffraction analysis. The extra heat produced due to activated fluxes in H2-induced shielding have been quantify in the study. The decomposed oxygen in the weld pool reacts with hydrogen in shielding and enhances the arc density. The growths of ferrite and austenite grains as well as the dendrite arm spacing have been significantly affected due to the presence of H2 in the shielding. Oxide-based fluxes with H2-induced shielding could promote the arc constriction behavior and Peclet number with enhanced heat density.