Mechanical Properties and Microstructural Analysis of 304 Stainless Steel by TIG Welding

Abstract

Gas tungsten arc welding is the process repairing and widely used in heavy engineering for joining metal. It can be uses for various type of metal and application. The aim of this project is to study the effects of 304 stainless steel with 3 mm thickness on mechanical properties and its microstructure analysis towards gas tungsten arc welding method. The variables set up in this project were current, gas flow rate and welding direction upon rolling direction of stainless steel sheet. Three current setup were used which is 60 A, 80 A and 100 A Type of filler metal used in this project was ER 308L with 1.6 diameter. Two set up for gas flow rate were used which is 8 l/m and 12 l/m. Testing that carried out were tensile test, Vickers macro hardness test with 10 kgf load and microstructure analysis by using optical microscope. The effects of microstructure in austenitic stainless steel welds is discussed. From the mechanical properties procedures, the strength of the weld metal was obtain. For hardness testing, the most important zone to be focused were heat-affected zone (HAZ) and weld metal (WM). The integrity of the welding tested by using tensile test and hardness test with different amount of current and gas flow rate. Keywords: Mechanical properties, microstructural analysis, 304 stainless steel, TIG welding. IntroductionGas tungsten arc welding (GTAW) were widely used in steel fabrication and joining metal process [1]. Commonly, the application were applied in heavy engineering field such as aircraft frames, automobile parts, railway wagon and many more [2]. The product from welding application exhibit good mechanical properties and manufacturing characteristic. This allowed the welding process done in different environment including in open air and under water. Furthermore, there were also joining of welding by dissimilar metal such as steel and aluminium to increase the strength of the joining metal [3]. The underwater welding normally associated by using stainless steel as it's good in corrosion viewpoint relatively and has extensive lifetime due its composition. The usage of stainless steel is small compared to carbon steels but exhibits a steady growth. The important thing about welding a stainless steel were the quantity of ferrite in the welds must be minimized or controlled to avoid degradation during its lifetime service [2]. However, there are several factors that will change the behavior of the welding strength when some welding parameters were being altered. Hence, this study were cope for several parameters such as current, welding towards rolling direction of stainless steel plate and gas flow rate for argon. Suit with the objectives of this study to determine the welding joint integrity by altering the welding parameters. The different setup in each parameters will produce a different result and the optimum or the best result was analyzed. The objectives of this paper is to study mechanical properties and microstructure of 304 stainless steel by TIG welding.