Influence of Heat Input on Microstructure and Mechanical Properties of Gas Tungsten Arc Welded HSLA S500MC Steel Joints

High-strength low alloy (HSLA) S500MC steel is widely used for chassis components, structural parts, and pressure vessels. In this study, the effects of heat input during automatic gas tungsten arc welding (GTAW) on microstructure mechanical properties thermomechanically controlled processed (TMP) were investigated. A butt joint configuration was used, performed in autogenous mode. Six different levels namely 1.764 kJ/mm, 1.995 2.035 2.132 2.229 2.33 kJ/mm considered. Microstructural investigations revealed a than base metal fusion zone (FZ) all welded joints which most likely due to lath martensitic surrounded by retained austenite. With increased input, amount austenite size packets increased. heat-affected (HAZ), two distinct regions coarse grain (CG-HAZ) fine (FG-HAZ) observed. Due presence carbides HAZ, mostly with smaller packets, compared FZ, formed. By increasing through dissolution carbides, dimension microstructural changes growth, both FZ produced TMP lost these regions. However, failure occurred samples maximum tensile strength 690 MPa. Thus, weld HAZ higher even highest indicating formation good between plates GTAW, regardless input.