**1. Introduction**

High-cleanliness steel has been developed from advanced steel materials with the rapid expansion of transportation, national defense and marine engineering [1,2]. The number of oxide inclusions in molten steel is directly proportional to the total oxygen content of molten steel, which is usually treated as an indicator to evaluate the number of oxide inclusions. Although the purity of molten steel can be greatly improved by the refining of ladle [3–5], abundant oxide inclusions will produce and deteriorate the purity of molten steel if the protective casting is poor.

In the field of steel production, argon as a protective gas has been widely used in the process of continuous casting. The application of argon in ladle stirring [6–10], RH [11,12], the argon bubbling curtain [13,14] in tundish, and submerged entry nozzle [15–18] has provided a great protective effect on removing inclusions and alleviating the clogging of SEN (Submerged Entry Nozzle). However, the secondary oxidation of molten steel cannot be avoided in the early casting stage of the first ladle after baking tundish due to the untimely melt of protective slag. Argon blown into tundish from pipes installed on the tundish cover, as a kind of important protective casting process, plays an important role in decreasing the secondary oxidation of molten steel and improving its cleanliness. During the initial casting period after baking tundish, blowing argon into tundish and

**Citation:** Li, Y.; Wu, C.; Xie, X.; Chen, L.; Chen, J.; Yang, X.; Ma, X. Numerical Simulation and Application of Tundish Cover Argon Blowing for a Two-Strand Slab Continuous Casting Machine. *Metals* **2022**, *12*, 1801. https://doi.org/ 10.3390/met12111801

Academic Editor: Noé Cheung

Received: 19 September 2022 Accepted: 19 October 2022 Published: 24 October 2022

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discharging air may prevent the molten steel from being reoxidized before the protective slag is fully melted. Wang [19] conducted a plant trial in Tang steel and found that the protective casting effect can be greatly improved when the residual oxygen volume fraction in tundish is less than 1%. Story [20] found that the loss of aluminum in molten steel may be decreased by 87.5% with argon blowing into tundish during the whole period of continuous casting. Considering the advantages of the process, some plants in Europe and Japan have been applied in industrial production and shown good effects [21]. For example, the defect rate of IF steel in Corus decreased by 38%, and the quantity of inclusions along the casting direction in POSCO significantly decreased after applying this process. Some plants in China have also adopted this process. Han Steel reported the average content of inclusions in low-carbon steel decreased from 0.47% to 0.32%. Gao [22] found the surface defect production rate of deep-drawing steel decreased from 7.78% to 2.62% as the diameter of argon blowing pipe increased from 20 mm to 34 mm.

Although ABTC has been applied in some plants, the numerical investigation and application assessment of ABTC has rarely been reported in the literature. Therefore, the current study aims to investigate the feasibility and evaluate the protective casting effect of ABTC during a continuous casting period. Firstly, a three-dimensional numerical model based on the practical two-strand slab tundish of the Pangang Group was built to investigate the behavior of oxygen volume fraction under different sealing schemes and argon flow rates during a period of empty tundish and normal casting. Then, plant trials based on the numerical simulation results and steel grade of M3A35 were carried out, where the increased nitrogen content and the loss of titanium and aluminum at the end of the RH process and tundish were tested to evaluate the protective casting effect.
