Investigating Dissimilar Welding Quality of AISI 4340 and ST 36 Carbon Steels via Shielded Metal Arc Welding for Structural Applications

In this paper, the optimization of welding processes for dissimilar materials AISI 4340 and ST 36 is examined, addressing the complexities and challenges associated with such joints. The Taguchi Method is employed to investigate key welding parameters, including electrode type, welding current, joint type, and welding speed. Orthogonal arrays are utilized to manage the experimental data efficiently, facilitating clear conclusions. Sample plates are machined to specific dimensions, and welding is conducted using the Shielded Metal Arc Welding method with various electrode types. Tensile strength is employed as a critical metric for evaluating weld joint performance. The “larger is better” criterion is employed to optimize the welding conditions, focusing on achieving high tensile strength. Results reveal the choice of electrode type remarkably affect s joint strength. Moreover, heat input, influenced by parameters like welding speed, plays a vital role in determining the mechanical properties of the weld. Microstructural analysis sheds light on the intricate changes during welding. The fusion zone exhibits finer grain structures compared with the base metals, owing to the rapid thermal cycle induced by welding. The welding electrode also influences the microstructure by introducing alloying elements and filler material. Additionally, angular distortion, a common issue resulting from welding-induced residual stresses, is addressed. Excessive welding currents contribute to increased angular distortion. These findings provide valuable insights for engineers and welders seeking to optimize welding processes and to ensure the reliability and performance of dissimilar material joints.