The effects of welding parameters on penetration and mechanical properties of 316 series austenitic stainless steels

Key Words: GTAW, Fatigue, Mechanical properties, Microstructure, Penetration, Shielding gases, Stainless steel, Welding ParametersIn this study, the effects of the welding parameters such as welding current, types of currents and welding speeds on penetrations, mechanical properties and microstructures of AISI 316 and AISI 316Ti types of austenitic stainless steels by automatic Gas tungsten arc welding (GTAW) methods were investigated. The study has been carried out in two stages. In the first stage, welding has been performed on the surface of the austenitic stainless steels by GTAW with and without using filler materials and then the effects of those parameters on penetrations and microhardness and microstructures were examined. In the second stage, the effect of welding parameters on microhardness, tensile strength, Charpy v notch impact test, fatigue behaviours and microstructures of the two types of austenitic stainless steels by automatic GTAW method at but joined and flat position using ER 316LSi filler materials. Bending test machine were also designed and manufactured to do fatigue tests. Stereo and optical microscopes were used for measuring penetration depts and basic microstructural examinations. Scanning electron microscope (SEM) studies were carried out for examination of fracture surface morphologies of some of samples exposed mechanical tests. Point and linear elemental energy dispersive spectroscopy (EDS) analysis were applied on some of selected samples.The experimental results showed that both welding parameters and chemical compositions of the stainless steels had influences on penetrations. Deeper penetrations were observed in the austenitic stainless steels contained titanium. Dept of penetration increased depending on increasing of welding current. Pulsed current had negative affection on penetration compared with normal current. Besides, welding parameters also affected on microstructure, microhardness, tensile strength, toughness and fatigue behaviours of the weldments. Due to fact that two types of austenitic stainless steels show different mechanical behaviours, the composition of the stainless steels should be taken into account during selection of the welding parameters. Better mechanical properties of the weldments can be obtained with only selection of optimum parameters during welding process.