Development and prospects of molten steel deoxidation in steelmaking process

In the long traditional process of steelmaking, excess oxygen is blown into the converter, and alloying elements are used for deoxidation. This inevitably results in excessive deoxidation of products remaining within the steel liquid, affecting the cleanliness of the steel. With the increasing requirements for steel performance, reducing the oxygen content in the steel liquid and ensuring its high cleanliness is necessary. After more than a hundred years of development, the total oxygen content in steel has been reduced from approximately 100 × 10⁻⁶ to approximately 10 × 10⁻⁶, and it can be controlled below 5 × 10⁻⁶ in some steel grades. A relatively stable and mature deoxidation technology has been formed, but further reducing the oxygen content in steel is no longer significant for improving steel quality. Our research team developed a deoxidation technology for bearing steel by optimizing the entire conventional process. The technology combines silicon–manganese predeoxidation, ladle furnace diffusion deoxidation, and vacuum final deoxidation. We successfully conducted industrial experiments and produced interstitial-free steel with natural decarbonization predeoxidation. Non-aluminum deoxidation was found to control the oxygen content in bearing steel to between 4 × 10⁻⁶ and 8 × 10⁻⁶, altering the type of inclusions, eliminating large particle Ds-type inclusions, improving the flowability of the steel liquid, and deriving a higher fatigue life. The natural decarbonization predeoxidation of interstitial-free steel reduced aluminum consumption and production costs and significantly improved the quality of cast billets.