Comparison of Mechanical and Metallurgical Properties of Modified 9Cr–1Mo Steel for Conventional TIG and A-TIG Welds

Abstract

This work attempts to investigate the effect of flux activation on mechanical and metallurgical properties of modified 9Cr–1Mo steel during activated TIG (A-TIG) welding. Composition-based oxide flux MnO2 was identified to produce a 6-mm-thick square-groove butt weld joint in P91 steel plates considering the satisfactory bead penetration during “bead-on-plate” experiment. During the experiment, it was found that using MnO2, the process of “A-TIG” can increase the penetration of the joint and depth-to-width ratio (D/W) of the weld for welding P91 steel up to 231% and 0.93 respectively. The base metal and the multipass GTA weld joint’s mechanical properties have been compared with the modified 9Cr–1Mo steel A-TIG weld joint. To study other metallurgical aspects of the TIG and A-TIG process, tests such as microhardness, tensile, bend, impact test and chemical analysis were performed. Optical microscopy was used to conduct the characterization of microstructure.