Original Article

Reaction mechanism between MgO and MgO–C lining refractories and an ultra-low-carbon Al-killed steel

¹ School of Mechanical Engineering, Yanshan University, Qinhuangdao City, Hebei Province 066004, PR China
² School of Mechanical and Materials Engineering, North China University of Technology, Beijing 100144, PR China

^* e-mail: zhanglifeng@ncut.edu.cn

Received: 29 July 2024
Accepted: 28 October 2024

Abstract

In the current study, effects of the carbon in MgO-based refractory rod on the cleanliness of an ultra-low-carbon Al-killed steel and on the corrosion degree of the refractory were investigated using laboratory experiments, thermodynamic calculation and a kinetic modeling. After a 90-minute reaction between the MgO refractory rod and the steel, the penetration of the molten steel into the MgO refractory was quite small and an about 20 µm thick interfacial layer containing the liquid slag phase and the spinel was generated at the interface. The liquid slag phase was mainly composed of Ti₃O₅, CaO, MgO, and Al₂O₃, while the spinel was mainly composed of Al₂O₃ and MgO. The composition of inclusions in the steel varied little due to the dense interfacial layer at the steel/refractory interface hindering the mass transfer between the steel and the MgO refractory. When the steel reacted with the MgO–C refractory for 90 min, the molten steel penetrated 1 mm into the MgO–C refractory through grain boundaries, forming channels due to the graphite consumption. A new 20 µm thick interfacial layer containing CaS and MgO was formed between the steel and the refractory. The formation of CaS was favored at the steel/MgO-C refractory interface and was rarely existed at the ssteel/MgO refractory interface during cooling process. The average content of MgO in inclusions increased from 10.29 wt.% to 46.55 wt.% while that of Al₂O₃ in inclusions decreased from 89.71 wt.% to 53.45 wt.% reacting for 90 min. The experimental result agreed well with the current kinetic model combined with thermodynamic calculation results. The influence of different content of T.O and T.Al in the steel on the composition of the steel and inclusions were also investigated using the current model. It is indicated that the content of MgO in inclusions increased with the decreasing T.O content and the increasing T.Al content in the molten steel.