Continuous casting is one of the most important innovations in the steel industry due to its high yield, high product quality, energy savings, less pollution, lower cost, as well as better working conditions. Over 96% of crude steel in the world was cast by continuous caster. As a very important functional material, mold flux works as several roles in the continuous casting process. It protects liquid steel from oxidation, insulates it from freezing, and absorbs inclusions, when floating on the top of liquid steel; whereas it lubricates the shell and moderates the heat transfer in the mold, when it infiltrates into the mold/shell channel. Therefore, the quality of final cast product is greatly determined by the performance of mold flux. Improper properties may lead to defects in the bloom, slab or billet, such as severe oscillation marks, cracks, inclusions and slag entrapment, improper solidification structure distribution, and even breakout.

In order to meet the new requirements from the development of advanced steels and green manufacturing, the special issue for Journal of Iron and Steel Research International focused on “Mold Flux: Melt Structure, Properties, Performances”. Nine articles were included in this special issue related to the topics on: (1) Melt structure of silicate, aluminate, etc. based mold flux; (2) Relationship between melt structure and properties of mold flux; (3) Fundamentals of mold flux crystallization; (4) Mechanism of mold flux heat transfer; (5) Interface behavior between molten steel and slag; (6) Thermodynamics and kinetics for the reaction between molten steel and slag; (7) Model between components and performances of mold flux; (8) Development of new type mold flux for advanced steel; Fluoride-free mold flux; and (9) Mold flux performances and its related casting product quality.