Study on the influence of heat input on mechanical property and microstructure of weld in GMAW of AISI 201LN stainless steel

Nitrogen alloyed austenitic stainless steels are popular among manufacturing industries due to its excellent mechanical properties and resistance to corrosion, used for the production of various components in food and petrochemical industries. Due to its improved strength and corrosion resistance, AISI 201LN replaces the commonly used SS 304 grade. In gas metal arc welding (GMAW) of AISI 201LN stainless steel the evaluation of heat greatly affects mechanical strength of the weld. In this work, the microstructure and mechanical strength of the weld were investigated in three different heat inputs viz., low, medium and high. The quality assessment of weld joint is examined by radiographic examination. The welded joint at low heat input was found to exhibit higher ultimate tensile strength and hardness compared to the welded joint at medium and higher heat input. The variation of hardness value for all three welded joint was found to increase from weld centre towards the base metal. The micro-structural examination shows finer morphology in heat-affected zone region in welded joint at lower heat input. The fine structure observed is due to higher cooling rate that causes restriction of grain growth.