An Analysis of the Effect of SMAW Welding Current on the Tensile Mechanical Properties of ST40 Low-Carbon Steel

Welding is one of the most widely used metal joining processes in manufacturing and construction industries. Low carbon steel ST40 is commonly applied because of its good mechanical properties, adequate strength, and excellent weldability. However, the quality and performance of welded joints are highly dependent on welding parameters, especially the welding current. Improper current selection may lead to welding defects, insufficient penetration, excessive heat input, and reduced mechanical strength of the joint. Therefore, controlling the welding current is essential to ensure reliable and high-quality welds. This study aims to analyze the effect of welding current variation in the Shielded Metal Arc Welding (SMAW) process on the mechanical properties, particularly the tensile strength, of ST40 low carbon steel. An experimental method was employed in this research, The material used was ST40 steel plate with dimensions of 260 mm 20 mm x 5 mm, prepared with a single V-groove joint at a groove angle of 35°. The welding process was performed using an E6013 electrode with a diameter of 2.0 mm, DC+ polarity, and a horizontal welding position. Welding current variations of 60 A, 70 A, and 80 A were applied. After welding, the specimens were machined according to the ASTM E8 standard and tested using a universal tensile testing machine. The results show that welding current variations significantly influence tensile strength, yield strength, strain, and modulus of elasticity of the welded ST40 steel. A welding current that is too low results in unstable are conditions and poor penetration, while an excessively high current causes excessive heat input and potential weld defects. Among the three current variations, the 80A current produces the most optimal mechanical properties.