Process Parameter Selection for Optimizing the Mechanical Properties of Stainless Steel (SS 202 & SS 316) in the Gas Tungsten Arc Welding

Abstract

Tungsten Inert Gas (TIG) welding is one of the widely used techniques for joining ferrous and non-ferrous metals. The TIG welding parameters are the most significant factors affecting the quality, productivity and cost of welding. In this study, SS 202 and SS 316 types of austenitic stainless steels were welded by GTAW (Gas Tungsten Arc Welding) using SS 202 and SS 316 (ER 316L) filler metals, respectively. The present study aims to search out the optimization of process parameters for Gas Tungsten Arc Welding (GTAW). The process parameters like welding current, wire diameter, shielding gas, and groove angle were varied at different levels to find out the influence of parameters on Hardness and Toughness. After performing Charpy Impact Test on SS 202 steel at room temperature, the results show that toughness mainly depends on the shielding gas chosen whereas for SS 316 steel the toughness increases as well as decreases as per the changes in the process parameters. Up to the magnitude of 150 A, the Microhardness value increases and then decreases with further rise in its magnitude. Keywords: GTAW, SS 202, SS 316, Microhardness, Toughness I.INTRODUCTION Tungsten Inert Gas (TIG) welding which uses a non-consumable tungsten electrode and an inert gas for arc shielding, is a highly relevant arc welding process. It is frequently used for welding hard-to-weld metals such as aluminium, stainless steel, magnesium, and titanium. TIG welding is a multi-objective and multi-factor metal fabrication technique, where Argon or Helium is used for shielding purpose. TIG weld quality is strongly characterized by the weld pool geometry because it plays a major role in determining the mechanical properties of the weld. Therefore, it becomes necessary to select the welding process parameters for obtaining an optimal weld pool geometry. Optimization of weld pool geometry has been attained by using TIG welding on a stainless-steel plate by varying welding parameters, and results showed that 'higher the better' quality characteristics are better used in the analysis of Signal-to-Noise ratio (S/N) and analysis of variance (ANOVA). A mathematical model has been developed to study the effects of process parameters on weld pool geometry in GTAW using ANOVA and found that wire feed rate, travel speed, and wire diameter are the major parameters that influence bead geometry in GTAW. Investigation of Weldments obtained in stainless steel (304L and 316L) by GTAW yields better mechanical properties than by GMAW, i.e., yield strength, tensile strength, hardness and impact energy values of 304L and 316L stainless steels welded by GTAW are higher than that welded by GMAW. It optimized SS 316L stainless steel and observed that Gas flow has a major impact and Bevel angle has the slightest impact in affecting the tensile strength. Use of active flux, TiO2 in GTAW increases the depth of penetration. Peak current has the highest contribution in affecting the micro weld hardness; grain size and HAZ width in the GTA Welded Aluminium Alloy 7039. N...

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