Mathematical Simulation and Industrial Application of a Process Control Model for Converter Double-Slag Steelmaking Based on Dephosphorization Slag Discharge and Decarburization Slag Recycling

Converter steelmaking remains the dominant route for global steel production, and the double-slag process is an important refining method that merits further study. In this work, a MATLAB-based mathematical model was developed for the double-slag process under a fixed dephosphorization rate, focusing on slag control during the low-temperature dephosphorization stage (1360–1400 °C) and the subsequent decarburization stage. The model was used to guide industrial trials and analyze the effect of the deslagging ratio (Rds) on slag control and process behavior. The results show that: (1) under a given Rds, the double-slag process can theoretically approach stable slag control and slag volume with increasing decarburization slag recycling cycles; (2) at a fixed dephosphorization rate, changes in Rds affect both the total amount of slag-forming materials and their distribution between refining stages; (3) although the double-slag process reduces slag-forming material consumption compared with the single-slag process and conventional low-slag practice, it does not necessarily guarantee low-slag smelting; and (4) an optimal Rds exists under specific conditions, indicating that a higher deslagging ratio is not always beneficial and must be balanced with effective phosphorus removal. Industrial trials showed that the compliance rate of key slag parameters exceeded 60%, the dephosphorization rate during the dephosphorization stage was above 60%, and the overall dephosphorization rate exceeded 90% on average. The recycling of decarburization slag also showed complex effects on phosphorus removal in subsequent heats, indicating that its influence should be evaluated over multiple cycles rather than from isolated heats. Therefore, ideal stability predicted by the model cannot be fully achieved in industrial practice, and controlled recycling combined with timely slag renewal is required for process optimization.