Analysis of the influence of preheating on the welding of dissimilar SAE 1020 and SAE 8640 steels using the GMAW process

Abstract

The welding of dissimilar steels is widely used in the industrial field to enhance the process's cost-effectiveness. In this application, the joining of dissimilar SAE 1020 and SAE 8640 steels by the GMAW (Gas Metal Arc Welding) process is noteworthy, being used in the manufacturing of ball mill equipment for processing ceramic raw materials. However, due to the different chemical compositions of these two steels, it is necessary to obtain a controlled thermal cycle to minimize the tendency for the formation of a microstructure with high hardness and low toughness in the region near the weld. This study sought to analyze the influence of preheating on the mechanical and microstructural properties of dissimilar SAE 1020 and SAE 8640 steels joined by the GMAW welding process. Additionally, the best parameters for this joint were defined, aiming to obtain a more resistant welded joint. The dissimilar steels were welded under two conditions: with and without preheating, with both conditions using the same welding parameters. After welding, test specimens were extracted and experimental tests were performed. It should be noted that the welding and tests were conducted based on the AWS D1.1/D1.1M:2020 standard. The results obtained from the tensile, face bend, Vickers microhardness, and metallographic analysis tests were comparatively evaluated between the two welding conditions. The analysis of the results showed that preheating before the welding process had a positive influence, converging to better results when compared to welding without preheating. The latter presented its highest hardness at 548.47 HV, whereas the preheated condition had its highest value at 440.70 HV