New steelmaking process based on clean deoxidation technology

Abstract

After the converter steelmaking process, a considerable number of ferroalloys are needed to remove dissolved oxygen from the molten steel, but it also forms a lot of oxide inclusions that cannot be completely removed. At the same time, it increases the carbon emissions in the steel production process. After years of research, our team have developed a series of clean deoxidation technologies, including carbon deoxidation, hydrogen deoxidation, and waste plastic deoxidation of molten steel to address the aforementioned issues. In this study, thermodynamic calculations and laboratory experiments were employed to verify that carbon and hydrogen can reduce the total oxygen content in the molten steel melt to below 5 × 10⁻⁶ and 10 × 10⁻⁶, respectively. An analysis of the deoxidation mechanisms and effects of polyethylene and polypropylene was also conducted. In addition, the applications of carbon deoxidation technology in different steels with the hot-state experiment and industrial production were discussed carefully. The carbon deoxidation experimental results of different steels were as follows: (1) the oxygen content of bearing steel was effectively controlled at 6.3 × 10⁻⁶ and the inclusion number density was lowered by 74.73% compared to aluminum deoxidized bearing steel; (2) the oxygen content in gear steel was reduced to 7.7 × 10⁻⁶ and a 54.49% reduction of inclusion number density was achieved with almost no inclusions larger than 5 µm from the average level of industry gear steels; (3) a total oxygen content of M2 high-speed steel was as low as 3.7 × 10⁻⁶. In industrial production practice, carbon deoxidation technique was applied in the final deoxidation stage for non-aluminum deoxidized bearing steel, and it yielded excellent results that the oxygen content was reduced to below 8 × 10⁻⁶ and the oxide inclusions in the steel mainly consist of silicates, along with small amounts of spinel and calcium aluminate.

Keywords

clean deoxidation / carbon deoxidation / hydrogen deoxidation / waste plastics deoxidation

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