Impact of different welding techniques on the structural integrity and microstructure of high-carbon steel

In demanding applications such as cutting tools, springs, and high-performance bearings, high-carbon steel with a carbon content of 0.6% to 1.5% is frequently utilized due to its remarkable strength, hardness, and wear resistance. The performance of this kind of steel can be greatly impacted by welding, though, depending on the conditions and welding technique employed. This work investigates the impact of varying current levels on the mechanical characteristics and microstructure of high-carbon steel during shielded metal arc welding (SMAW) and gas metal arc welding (GMAW). The results demonstrate that SMAW typically yielded stronger and more dependable welds. The sample that was SMAW welded at 140 A had the highest ultimate tensile strength (495 N/m²) and the highest elongation (15%), suggesting that strength and ductility were well-balanced. By contrast, the GMAW sample welded at 120 A had a lower elongation (10.5%) and tensile strength (424 N/m²). A tensile strength of 317 N/m² and an elongation of 7.5% were the results of the weld region developing coarser grains when the GMAW current was raised to 140 A. This is due primarily to the production of martensite and other hard phases during cooling. Hardness testing revealed that all weld zones became harder than the base metal. By employing scanning electron microscopy to examine the microstructure, ferrite, pearlite, martensite, and bainitic ferrite emerged. GMAW tended to develop bainitic ferrite, whereas SMAW produced finer lath martensitic structures. For high-carbon steel applications that need durability, SMAW often showed superior mechanical strength and structural stability.

Keywords: High carbon steel; SMAW; GMAW; Tensile test; Hardness test; Percentage elongation; Microstructure.

Dr. Taoreed Adesola Adegbola is a Mechanical Engineer specializing in material science characterization relating to mechanical properties in Mechanical Engineering. He holds a DTech in Mechanical Engineering from Tshwane University of Technology. He also holds an MSc in Systems Engineering from the University of Lagos. Dr Adegbola is currently working as a Lecturer at the Tshwane University of Technology where he is also conducting research in the material science field and guiding young researchers in the field of study.