Safety and exploitation conditions of steel welded structure depend on many factors. The main role of that conditions is connected with materials, welding technology, state of stress and temperature. Because of that very important is good selection of steel and welding method for proper steel structure. For responsible steel structure are used low carbon and low alloy steel, very often with small amount of carbon and the amount of alloy elements such as Ni, Mn, Mo, Cr and V in low alloy steel and their welds. In the terms of the kind of steel it is used a proper welding method and adequate filler materials. In the present paper it was tested and optimized the chemical composition of metal weld deposit on the operational properties of steel welded structures.