Abstract
This study aimed to investigate the impact of various shielding gas compositions and welding speeds on the welding quality of S355J2 with normalized structural steel, which was welded using the semi-automatic MAG (Metal Active Gas) welding method. To achieve this, a total of 27 welded parts were produced using 9 different gas mixtures and 3 different welding speeds, and the welding quality was observed and analyzed. Hardness test, bending test, optical microscope, SEM (Scanning Electron Microscope), and EDS (Energy Dispersive Spectrometry) examinations of the samples obtained from the welded parts were carried out. This study shows that as the welding speed increases, the heat input of the weld decreases, and thus, the cooling rate of the HAZ (Heat Affected Zone) increases, which increases the weld metal hardness. The hardness of the weld metal decreases as the amount of carbon dioxide increases, which increases heat input and, thus, cooling time

Key words
MAG welding, metal active gas welding, S355 structural steel, shielding gas composition, automatic welding

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