SOME STUDIES ON WELDABILITY ASPECTS OF NITRONIC STEELS

Abstract

Nitrogen in austenitic stainless steels is effective in improving the mechanical and corrosion - properties of steels. A nitrogen strengthen austenitic stainless steel having low Ni and high concentration of C. known as Nitronic steel (21-4-N) has been developed for improved mechanical properties. The unavailability of the matching tiller material, it is a challenging task to weld this steel with desired combination of properties. The nitrogen escaped from the molten metal pool and causes decrease nitrogen content in the weld metal. This leads to the degraded properties of the weidment as compare to the base material. 'l'his study leads to the selection of matching filler E-309LMo and ER2209 SS materials. The mechanical properties such as tensile, impact and hardness of the Nitronic steel (21-4-N hot rolled) are tested with both filler and diFferent nitrogen shielding. The metallographic study of the base metal, weld metal and heat affected zone is done. It is found that nitrogen shielding causes decreased cooling rate and coarser grains in the HAZ. The hardness with nitrogen alloyed filler wire is more comparatively.