Abstract
Studies on the use of various welding methods and equipment (electrode, welding wire, welding powder, etc.) in welding of steels have intensively continued nowadays. Flux-cored arc welding technology is one of the welding methods which have mostly been investigated and applied to different metals in recent years. In this study, the effect of different shielding gases on microstructural and mechanical properties of S275 structural steel joined by flux-cored arc welding was examined. Pure argon (100 % Ar) and a mixed gas (86 % Ar, 12 % CO₂, 2 % O₂) were used as shielding gas in welding processes. A double V groove of 50° was opened on steel sheets. Welding processes were performed horizontally by using a 1.2 mm-diameter rutile flux-cored wire. Tensile, hardness, and bending tests were used to determine mechanical properties of welded samples. In addition, metallographic examinations were performed to determine microstructural properties of weld zones. As a result of the tensile test, the highest mechanical properties were obtained from weld seams by the mixed gas. There were crack and rupture defects in weld zone as a result of bending tests. In all welding parameters, the hardness of weld metal was higher than that of the heat affected zone (HAZ) and base metal. The microstructure studies revealed that grain coarsening occurred in HAZ.

Key words
flux-cored arc welding, shielding gas, argon, mixed gas, mechanical properties, microstructure

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