The fuzzy logic optimization technique has been used for selection of optimal flux for making low carbon steel welds of high quality. The response surface methodology has been opted and binary, ternary phase diagrams of steels has been used for design of fluxes. The heat affected area affects the properties of base metal so it becomes of utmost importance to select it as a response. It is very important in SAW. The important weld mechanical properties are ultimate tensile strength, hardness and impact strength. The flux composition is very important in deciding the weld metal properties so efforts should be made for desifn, manufacturing and selection of optimal flux for the required joint properties. In this case hardness and HAZ area has been considered as main parameters as output .The optimal flux contains CaF2 5%, FeMn 8% and NiO 5% The results obtained in this experimental study have been verified by doing confirmatory tests.