IJRET: International Journal of Research in Engineering and Technology eISSN: 2319-1163 | pISSN: 2321-7308 https://doi.org/10.15623/ijret.2018.0706013 Received: 05-04-2018, Accepted: 17-05-2018, Published: 07-06-2018 _______________________________________________________________________________________ Volume: 07 Issue: 06 | Jun-2018, Available @ www.ijret.org 92 MATHEMATICAL MODELING FOR PREDICTING ANGULAR DISTORTION IN TIG WELDING OF STAINLESS STEEL 409L BUTT WELDS Ishika Aggarwal 1 , Nimeshka Faujdar 2 , Anusua Das 3 , Pradeep Khanna 4 1 Student, Manufacturing Processes & Automation Engineering Department, NSIT, New-Delhi, India 2 Student, Manufacturing Processes & Automation Engineering Department, NSIT, New-Delhi, India 3 Student, Manufacturing Processes & Automation Engineering Department, NSIT, New-Delhi, India 4 Associate Professor, MPAED, NSIT, New-Delhi, India Abstract TIG welding process has increasingly been used in the fabrication of ferrous and non-ferrous materials alike owing to its adaptability and ease of welding any known weldable material. The process also lends itself to automation, making it ideal for mass manufacturing industries. When automated, it can successfully weld autogenous joints. The process is largely used to weld thin gauge sheets. The present work is aimed to investigate the effects of controllable input parameters like welding current, welding speed and torch angle on the response parameters which is angular distortion of the resulting weldments in this case. An attempt has also been made to develop a mathematical equation relating input parameters to the response so that an optimized setting of these parameters can be obtained to have minimum possible angular distortion. Central composite face centered technique has been used to developed the mathematical model, whose adequacy has been tested by ANOVA analysis. Significance of the regression coefficients has been tested by t-test. Response Surface Methodology has been used for optimization of the developed model. Keywords: - Autogenous, automation, response surface methodology, optimization, mathematical modeling. --------------------------------------------------------------------***---------------------------------------------------------------------- 1. INTRODUCTION Tungsten inert gas welding, TIG is widely used in manufacturing process for different types of materials like Aluminum, Mild steel and different type of stainless and alloy steels. The optimization of TIG welding process parameters play important role for the final product quality in terms of weld distortions, joint efficiency and mechanical properties. As welding process involves the heating and cooling process in non-uniform manner, the distortions are unavoidable. The weld process contributes to the development of several kinds of distortions like longitudinal, transverse or angular distortion [1]. Every effort should be made to keep these distortions minimum as they not only spoil the esthetics of the joint but also result in dimensional deviations causing misfits in the final assembly. The present work is aimed at investigating the effects of input process parameters on angular distortion (fig.1). An elaborated experimental work has been carried out to evolve a mathematical model which might help in correctly selecting the process parameters so as to have minimal angular distortion. The material selected for present investigation work is stainless steel 409L which is a newly developed low carbon variant of stainless steel. The material has good workability and because of the less amount of carbon has reasonably good weld ability with less chances of cracking and material also possess good inter-granular corrosion resistance [2, 3]. Literature survey has also revealed that not much experimental work has been conducted on material so far. This makes a strong base for conducting experiments on this material. The chemical properties on material are given in table-1 and distinctive mechanical and physical properties of the material are given in table-2. An elaborated experimental work was carried out with the selected input parameters by using statistical technique of using design of experiments (DOE). Fig 1: Angular Distortion [2] Table 1: Chemical composition of Stainless Steel 409L Element C Mn P S Si Cr Ni Max percentage 0.03 1 0.04 0.03 1 10.5- 11.7 0.5 Table 2: Physical and Chemical properties of 409L Mechanical Properties Yield Strength (N/mm 2 ) Tensile Strength (N/mm 2 ) Elongation (%) Hardness (Hv) ≥175 ≥360 ≥25 ≤175