Study on Behavior of Slag Rim and Shell Initial Solidification at Meniscus in Continuous Casting Slab Mold

Understanding the formation of a slag rim on the mold meniscus is crucial for controlling surface defects in the initial shell. However, there is a scarcity of quantitative studies on this matter. This study has developed a comprehensive three-dimensional (3D) numerical model for analyzing the meniscus multi-phase flow, heat transfer, and solidification, considering mold oscillation. The 3D morphology of the solidifying shell and the slag rim in the meniscus region were accurately reproduced. The solidification depth (D_IS), solidification length (L_IS) and oscillation mark depth (D_OM) of the initial shell were used to quantify the morphological characteristics of the initial shell. The results confirmed that the formation position difference of the slag rim along the circumferential direction of the mold significantly affects the initial solidification and uniform growth of the shell. In the corner of the mold, the deeper overflow makes the oscillation mark extend 2.8 to 3.2 mm in the direction of casting. In addition, in order to quantitatively investigate the influence of the slag rim, a two-dimensional (2D) model is established with phenomena and parameters considered the same as those of the 3D model. According to the slag rim morphology obtained by the 3D model, in the 2D model, it is proposed to construct three slag rims with the same maximum thickness of 6 mm at 10, 20 and 35 mm above the meniscus (H_Rim). The simulation of initial shell morphology revealed that a lower formation position of the slag rim led to more severe overflow of molten steel from the meniscus, resulting in non-uniform continuous growth of the initial shell. This increases the likelihood of potential blockage in the liquid slag flow towards the slag channel between solidified shell and mold.