Effect of groove shape to the mechanical properties in gas metal arc welding process

Mild steel is a material commonly used in various industrial applications. Mild steel is classified as low carbon steel, has a carbon concentration ranging from 0.16 to 0.29 wt% and melts between 1450 to 1520°C. Gas metal arc welding (GMAW) is widely utilized in various industries due to its numerous advantages. Welding parameters plays a crucial role in ensuring high quality welds. Generally, welding parameters including current, voltage, arc length, contact tip to work distance (CTWD), travel and work angle, welding speed and size of electrode. Groove shape and type of joining in welding also significant influence the mechanical properties of welded joint. The objectives of this final year project are to study the effect of groove shape to the microstructure formation behaviour at weld metal and heat affected zone and to investigate the influence of groove shape on mechanical properties in both single and multi-layer welded joints. In this study, single and multi-layer welding were employed to prepare butt weld joints using V and U grooves in the specimens. The metallographic studies of samples subjected to Nital etching and Le Pera etching were carried out using optical microscopy were proven the influence of groove shape on microstructure and consequential impact on mechanical properties. The evaluation of mechanical properties of samples was conducted using Vicker Hardness Tester and Charpy Impact Tester. Vicker hardness results showed that single layer welding of U groove (SU) exhibited higher hardness than single layer welding of V groove (SV) and in multi-layer welding of V groove (MV) exhibited higher hardness than U groove (MU). Charpy impact test was conducted at three different temperatures (20°C, 0°C and -20°C). For single layer welding, the results showed that no significant difference for both V and U groove tested at 20°C. However, SU showed high impact toughness compared to SV at 0°C while SV slightly advantage SU at -20°C. For multi-layer welding, MV showed high impact toughness across both room temperature and 0°C. However, MU exhibited better impact toughness at -20°C compared to MV.