Govender, Dhurasha2023-04-112023-04-112022https://hdl.handle.net/10539/34975A dissertation submitted in partial fulfilment of the requirements for the degree of Master of Science in Engineering to the Faculty of Engineering and Built Environment, School of Chemical and Metallurgical Engineering, University of the Witwatersrand, Johannesburg, 2022The 3CR12 ferritic stainless-steel alloy was first developed as a cost-effective alternative to AISI 409 ferritic stainless steel, with good weldability and affordability for mildly corrosive environments. The ferritic stainless-steel is used widely in wagon manufacturing, in which welding of the material, makes up a large portion of the costs relating to welding wire, shielding gases and the time taken to weld. The welding process and consumables are crucial elements in producing quality welds during wagon manufacturing. In South Africa, 3CR12 stainless steel is used in the fabrication of wagon’s due to its high strength, excellent impact, corrosion, and abrasion resistance. The welding electrode that is currently used in the welding of wagons is the ER309L welding wire which has proven to be compatible in chemical composition. Aside from the high cost, there are no historical welding problems related to ER309L welding wire, however, companies are looking at various ways to manufacture wagons cost effectively. The aim of this research was to find a material and consumable combination that will decrease the manufacturing costs of the wagons. Welding wire ER308L was found to be a suitable candidate after observation of previous findings. The objectives of this study were to then experiment with various shielding gases and different gas ratios of these gases to obtain optimum weld properties. Eight sets of 3CR12 plates were welded using a different shielding gas ratio per set. The shielding gases contained combinations of argon (Ar), helium (He), oxygen (O2) and carbon dioxide (CO2) gases. The experiment entailed the welding and non-destructive inspection of 6 mm thick 3CR12 plates, V- butt welded via gas metal arc welding and laboratory testing including hardness, tensile, Charpy impact and microscopy. It was found that the gas ratios containing, 73% Ar, 2% CO2, 25% He and, 75% Ar and 25% He respectively, provided the best mechanical and metallurgical results. Impact values in the range of 74 and 99J and yield strengths of 337-362 MPa, were achieved during these tests together with low ferrite content and the absence of sensitisation. Due to a better root penetration of the 73% Ar, 2% CO2, 25% He gas, it was concluded that this would be the gas recommended to produce wagons as the 75% Ar, 25% He may result in lack of penetration at the root of the weld.enThesis