S235 fine grained steel alloys are demanded especially in structural components of buildings, factories and mechanical parts of machines where yield strength values close to minimum 235 mega-pascals (MPa) are in concern. These steels are classified in low alloyed steel groups and in consequence of the cheapness of these alloys their consumption is increasing as well. In this work; 15 mm of S235 structural steel plates are submerged arc welded by 2 types of welding fluxes. The first welding flux is selected as SA AB 1 68 AC H5 as basic character with the basicity index of 1.4 while the second flux is SA AR 1 77 AC rutile as low basic character with the basicity index of 0.7 according to TS EN ISO 14174 by both using the same welding wire S2 of 4mm in diameter according to TS EN ISO 14171-A standard. The effects of flux composition on microstructural and mechanical properties of welded S235 steel alloy are examined. Micro-vickers hardness surveys of base metal and heat affected zones with weld metals, transverse tensile tests and micro-structural investigations are applied for comparison of these two types of welding fluxes. The samples joined by basic and rutile flux are both qualified in micro-vickers hardness surveys and transverse tensile tests. Rutile flux transformed the ferriticpearlitic microstructure into needle like view while basic flux maintained it more globular. Whether globular microstructure is desired in case of toughness considerations in industrial applications, basic flux should be preferred.