Especially deep desulphurization of cast iron by magnesium mono-injection in ladles of different size

The article is devoted to the development and industrial mastering of technological processes of particularly deep desulphurization of cast iron (sulphur content ≤ 0.002 %) by magnesium mono-injection in ladles of various sizes. The paper presents the results of research on the development of technologies for extra deep desulphurization of cast iron by mono-injection of granular magnesium, which was carried out at modern automated cast iron desulphurization and slag rolling complexes. The work was carried out jointly by Ukrainian and Chinese specialists in China at Wuhan Steel Plant No. 1 using 110-ton ladles and in Taiwan at CSC Steel Plant No. 2 using 300-ton ladles. The proven technological parameters of the cast iron desulphurization processes using granular magnesium injection with tuyeres with evaporation chambers at Steel Plant No. 1 of Wuhan Steel and double-nozzle tuyeres at Steel Plant No. 2 of CSC Concern ensured the required processing cycles, reliable and technological magnesium injection and its absorption efficiency. It was found that the degree of desulphurization of cast iron is up to 99 % of treatments and the final sulphur content in cast iron is up to 0.0002 %, with the total estimated degree of magnesium absorption into sulphur, residual magnesium and deoxidation of cast iron being ~95 %. It has been established that an important technological technique that increases the stability of the achieved processing parameters is the adjustment of the ladle slag composition, which was carried out by adding waste granular lime in the amount of 1.0-2.0 kg/t of cast iron and did not require significant costs. The results of industrial cast iron treatments were analysed and nomograms of the dependence of specific magnesium consumption on the initial sulphur content for tuyeres of various designs were constructed. The developed processes are economically justified for use in the practice of preparing cast iron for conversion.