Gas Tungsten Arc Welding of Stainless Steel 304 and 202 Grades for Optimum Weld Bead Width and Hardness Value

Abstract

Gas tungsten arc welding of two different stainless steel grades of 304 and 202 of 3 mm thickness is attempted through this experimentation to produce the weld joint without any weld defects. The pure argon is supplied to protect the molten weld pool from any form of contaminations. The welding factors like weld current and travel speed are chosen to prepare the welded joints. The response surface central composite experimental design is used to draw 10 numbers of welding conditions. The gas tungsten arc welded butt joint is produced in a single pass manually for complete penetration. The ranges of weld current are chosen as 86, 90, 100, 110, and 114amps. The welding speed is set as 1.54, 2.05, 4.64, 5.09, and 7.5mm/min. The welded sheets are evaluated for weld bead width which is measured with the help of a Vernier caliper. The hardness of the welded joints is also measured. The chosen factors and measured width of the weld bead and hardness value of the weld joints are analyzed by the use of different statistical terms such as R square, ANOVA analysis, lack of fit, t-test, F-test, and effect tests to state a regression expression at 95% assurance level. It is thus understood from the regression analysis that the welding current and travel speed having major influences upon the weld bead width and hardness of the welded joints. In the manual welding technique, both factors are supposed to be carefully matched by the welder otherwise the penetration depth and proper formation of weld bead width are quite difficult to obtain which further increases the total heat input leading to the degradation of mechanical properties. The current experiment is performed to get an optimum condition by optimizing the weld current and speed to get a well-formed weld bead structure by controlling the total heat input. Thus the experiment will be useful to get the desired quality gas tungsten arc welded joints which are most essential in particular for aerospace and automotive industries for various structural applications.