IJRET: International Journal of Research in Engineering and Technology eISSN: 2319-1163 | pISSN: 2321-7308 _______________________________________________________________________________________ Volume: 03 Special Issue: 11 | NCAMESHE - 2014 | Jun-2014, Available @ http://www.ijret.org 213 PARAMETRIC OPTIMISATION OF PULSED – TIG WELDING PROCESS IN BUTT JOINING OF 304L AUSTENITIC STAINLESS STEEL SHEETS Dinesh Kumar.R 1 , Elangovan.S 2 , Siva Shanmugam.N 3 1 PG Student, ME-Production Engineering, PSG College of Technology, Coimbatore, Tamil Nadu, India 2 Associate Professor, Production Engineering, PSG College of Technology, Coimbatore, Tamil Nadu, India 3 Assistant Professor, Mechanical Engineering, National Institute of Technology, Tiruchirappalli, Tamil Nadu, India Abstract Stainless steels are widely used in thermal power plant, pressure vessels and automobiles components due to their superior fracture toughness, good inter granular corrosion resistance and non-requirement of post process annealing. Heat affected zone decreases the strength of the weld hence Pulsed TIG welding process is carried out to reduce the heat affected zone. This inherent property of the material reduces crack growth at high pressure which leads to the increase in efficiency of the pressure vessels and automobile components, when operated at high pressure. This paper describes the optimization of process parameters like current, voltage, stand-off distance, pulse on time, pulse off time and weld speed, gas flow to improve weld quality. In this work Taguchi method is used to get the optimal parameters. In Taguchi method, L27 orthogonal array is used for experimentation. Further, the experimental values and the various settings of the process parameters are fed as input to Taguchi and hence the S/N ratio values are obtained. Weld speed and input current are found to be the most significant parameters. Finally, the strength of the weld is validated by tensile and bending test. Keywords: Stainless Steel, Pulsed TIG welding, Inter-granular corrosion resistance, Fracture toughness, strength testing, Taguchi method. --------------------------------------------------------------------***---------------------------------------------------------------------- 1. INTRODUCTION In today’s scenario welding of thin sheets is being the challenging task in the field of Engineering. The major reason behind this is perfection, which is being the nominal factor considered during the joining process of sheets because, in such joining of plate, two pass and three pass welding cannot be carried out in thin sheets below 4mm, as under welding results in predominant reduction in strength and over weld results in formation of hole. Hence optimization of weld parameter plays a predominant role in joining of thin sheets. This research is to make the thin sheet welding easy and compatible by optimizing the process parameters. And in this paper, we have explained about the suitable parameters for butt joining on 304L Stainless Steel material of thickness 1.6mm which has good inter-granular corrosion resistance which increase the life span pressure vessels and automobile components. Superior fracture toughness reduces the crack initiation and crack growth under high pressure. These two factors enhances the maximum pressure withstandability , apart from this Pulsed- TIG welding process is used for welding which reduces the heat affected zone by welding the material by alternate melting and cooling which forms a good grain boundary layered by chromium with maximum strength. And this material does not require post process annealing for hardening which is used to increase the strength of the material. Quality of weld is based on the protrusion of weld from face to root and good quality weld can be obtained by optimizing the process parameters like current, voltage, stand-off distance, pulse on time, pulse off time, weld speed to improve weld quality. In this paper, experimental investigation detail of various process parameters to obtain good quality weld is discussed. The Taguchi design of experiments is a powerful method used to achieve high quality in lesser no of experiments. It provides better settings as compared to traditional experimental designs which are time consuming due to a large number of experiments and most of the time not feasible. The Taguchi method reduces the sensitivity of quality characteristics to various unknown noise factors. 2. LITERATURE SURVEY Balasubramaniyan et al.,[1] discussed about the Effect of microstructure on impact toughness of pulsed current GTA welded α–β titanium alloy, the pulsed current has been found to be beneficial primarily due to its advantages over the conventional continuous current process. Aniruth et al.,[2] discussed about the study on laser cleaning and pulsed gas tungsten arc welding of Ti–3Al–2.5V alloy tubes, Welding of laser-cleaned samples show excellent weld quality. G.Lothongkum et al[4] discussed the Study on the effects of pulsed TIG welding parameters on delta-ferrite content, shape factor and bead quality in orbital welding of AISI 316L stainless steel plate, because of the high nitrogen content of the cover gas and lowest pulse currents compared to all other welding positions. Radiography showed