from the conferences organized by TANGER Ltd.
Niobium is a widely used microalloying element in the production of HSLA steels; however, supply-related and cost-related risks justify the investigation of alternative solutions. The aim of this study was to determine whether the complete or partial replacement of niobium with titanium is feasible in EN 10149-2:2013 grade S355MC steel while maintaining the mechanical properties required by the standard. During the study, three alloying concepts were compared under industrial conditions: conventional Nb microalloying, Ti microalloying instead of Nb, and combined Nb+Ti microalloying. Slabs cast from the different heats were hot rolled using several finishing temperatures, and the resulting coils were evaluated based on their mechanical properties and microstructure. The results showed that the upper yield strength and tensile strength of the titanium-microalloyed S355MC steels were lower than those of the niobium-microalloyed reference material, while elongation remained nearly unchanged and impact toughness proved to be more favorable. Despite the scatter of the mechanical test results, the titanium-microalloyed steels remained within the standard limits specified for S355MC in all cases. The findings indicate that this microalloying concept can be industrially applicable; however, the inhomogeneity of the properties requires further technological refinement, especially in ladle metallurgy and in controlling the distribution of microalloying elements. From an economic point of view, the use of titanium may represent a favorable alternative. The thesis indicates that the purchase price of FeTi is significantly lower than that of FeNb, and considerable cost reduction can still be achieved even if approximately twice as much titanium is required to obtain the desired mechanical properties. Based on the results, replacing niobium with titanium appears to be a realistic option in the production of S355MC steel, provided that further optimization of the technological parameters is also carried out while maintaining the standard properties of the steel grade.
Keywords: HSLA steel; microalloying; titanium substitution; niobium replacement; mechanical properties© This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.