An Experimental Investigation on Welding Aspects of Stainless Steel (SS202 and SS304) During GTAW

Abstract

The aim of present study was to investigate the welding aspects like weld bead geometry, bulk hardness, surface cracks using dye penetrant test, impact strength, microhardness, joint quality and chemical composition of stainless steel (SS202 & SS304) during GTAW using the three levels of welding current, shielding gas, gas flow rate and grove angle and to optimize the process following Taguchi experimental design. Bead geometry of the welded specimens was measured and bead width was mainly dependent on welding current and nature of shielding gas used. Bead height for SS202 was dependent on shielding gas and gas flow rate whereas the same for SS304 was depending on gas flow rate and grove angle. Rockwell hardness test showed that there was no significant variation in hardness value in weld metal and heat affected zone (HAZ) in comparison to base materials for both grades of steel. Dye penetrant test showed that welding was of very good quality and there were negligible amount of defects at corners. Charpy impact test results for SS202 steel showed that toughness at room temperature mainly depends on the value of current used and shielding gas chosen. Maximum value of toughness (71.1225 Joules) was obtained in the welded joint of parameters 180 A, Ar, 12 l/min. & 900. For SS304 maximum value of toughness is 93.195 Joule and was observed when welded with parameters 180 A, Ar+He mixture, 9 l/min. & 750. Toughness is higher for 180 A and for shielding gas Ar and also at 9 l/min. At -20 0C Charpy test showed that SS202 is having negligible strength making it unsuitable for use in colder places and that for SS304 showed that it mainly depends on the welding current followed by gas flow rate. Highest value of toughness (63.765 Joule) at this temperature was when welded with 220 A, He gas, 9 l/min. & 900. Toughness value is maximum on and after 180 A of current and also highest for gas flow rate of 9 l/min. Microhardness test showed that for SS202 the value of HVN was mainly dependent on welding current and grove angle and it was observed that HVN is mainly influenced by the value of welding current for SS304 grade. Joint quality result showed that for both the materials in welded region there were no major flaws and inclusion except a crack observed in a particular sample of SS202 steel. Chemical composition analysis showed that there was a decrease in the value of chromium for both grades of steel in the welded region which may be because of formation of any compound in the welded region.