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Austenitic stainless-steels are commonly employed in numerous engineering applications in fabrication industries due to their good oxidation and corrosion resistance property. Its application includes chemical and process industries, food processing industries, heat exchangers, automobile, petrochemical industries, cryogenic vessels, vessel internals, LNG tanks, and nuclear industries (Shashi, Murugan & Ramachandran, 2019; Holmberg, 2004). Nickel is used as an alloying element to stabilize the austenitic phase in stainless steel (SS) resulting in higher cost of SS grade (AISI 304). The AISI 201LN grade steel with manganese and nitrogen as alloying elements is found good replacement for AISI 304 SS in many industrial applications that include repairing parts in automobile sector, marine and cryogenic applications (Vashishtha, Taiwade, Sharma & Patil, 2017; Chuaiphan & Srijaroenpramong, 2014). Nitrogen-alloyed stainless steels are highly preferred in fabrication industry due to excellent mechanical property, corrosion resistance, and work hardening characteristics and reduced tendency to grain boundary sensitization. The nitrogen addition in AISI 201LN stabilizes the austenitic matrix, increasing yield strength, improve pitting corrosion resistance, solid solution strengthening and fracture toughness. Recent development has proved that the increase of nitrogen content in austenitic stainless steel can double the yield strength (Toit & Pistorius, 2003; Saeedipour, Kermanpur, Najafizadeh & Abbasi, 2012). The material used for liquefied natural gas (LNG) tank can be substituted by AISI 201LN due to its economy, excellent toughness property at low temperatures, higher strength and ductility; hence it is an attractive alternative material for the fabrication of low-cost LNG tanks. The addition of nitrogen acts as a strengthening mechanism with increased strength and maintaining toughness that makes suitable for cryogenic applications (Choi, Lee, Park, Han, & Morris, 2012; K. Lee, Chun, Kim, & J. Lee, 2009). The primary manufacturing process for the fabrication of these LNG tanks or other structural applications is welding.
The fabrication industries face a number of challenges in welding of thin sheets due to higher heat input associated with a conventional arc welding process. The welding investigation of thin sheet of AISI 201LN for higher productivity employing GMAW−CMT is not reported in literature. Literature reports welding investigation of austenitic SS mainly using conventional arc welding method. Kumar and Shahi (2011) have reported influence of heat input on microstructure and mechanical property of AISI-304 with GTAW process. They observed formation of finer dendritic structure at lower heat input resulting in increased ductility and tensile strength of weld joint. Vashishtha et al. (2017) studied mechanical properties and micro-structure during dissimilar welding of AISI-201 and AISI-304 grade steels using shielded metal arc welding and GTAW at different welding speeds. They observed that the better mechanical property and microstructure is obtained at faster welding speed. Chuaiphan and Srijaroenpramong (2014) studied the welding investigation using GTAW process AISI 201 welded joint exhibited higher strength, hardness and better anti-corrosion property at higher welding speeds. Agrawal et al. (2017) have carried out welding investigation on SS 304 with pulsed GTAW process at higher welding speed. They found that during higher welding speed the tensile strength and hardness are increasing as compared to lower welding speed. Mazar et al. (2018) investigated on hybrid laser combined with GMAW high-strength steel. They found that the optimum welding parameter for the full penetration butt joint at higher weld speed.The present work investigates the welding of AISI 201LN sheets for producing superior weld quality by employing a new hybrid welding approach employing different welding speeds.