Abstract
In order to enhance the liquid surface activity in ultra-wide slab mould with a cross-sectional dimension of 2920 mm × 150 mm (with a width-to-thickness ratio of nearly 20), this study established a two-phase flow model for steel and liquid slag, comparing and analysing the effect of submerged entry nozzle (SEN) inclination angle on both the flow field and temperature field within the mould. The primary findings indicated that at a nozzle angle of 15°, the upward reflux was weak, resulting in a liquid surface velocity below 0.23 m/s, slow renewal of molten steel, which were not conducive to the melting of the mould flux. To improve both liquid surface activity and the melting and flow of the mould flux, the nozzle angle was reduced from 15° to 10°. This adjustment allowed the maximum liquid surface flow velocity to reach 0.35 m/s, thereby enhancing liquid surface activity and facilitating greater energy transfer to the liquid surface. The uniform distribution of heat-flux density around the mould further demonstrated that reducing the nozzle angle significantly enhances liquid surface activity. However, when the nozzle angle was further decreased to 5°, strong upward reflux was observed, resulting in the adjacent slag layer being washed away to one-quarter of the mould's width, which increased the risk of slag entrapment and exposure at the corners. Given the large width-to-thickness ratio of the ultra-wide slab mould, the flow jet from the submerged nozzle was prone to early collided with the wide surface during its movement towards the narrow surface. This interaction leaded to a reduction in kinetic energy, weaker upward reflux, lower heat flux near the liquid surface, and larger fluctuations in heat flow distribution along the mould's width. This study illustrates that appropriately reducing the nozzle angle can mitigate these adverse conditions and provides a theoretical foundation for selecting SENs for ultra-wide slab moulds.
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