Abstract
In this paper, the effects of the width of the mold on the surface velocity, flow field pattern, turbulent kinetic energy distribution, and surface-level fluctuation in the mold were studied with measurement of the flow velocity near the surface of the mold at high temperature with the rod deflection method and numerical calculation with the standard k-ε model coupled with the discrete-phase model (DPM) model for automobile exposed panel production. Under the conditions of low fixed steel throughput of 2.2 ton/min, a nozzle immersion depth of 140 mm, and an argon gas flow rate of 4 L/min, as the width of the mold increases from 880 mm to 1050 mm and 1300 mm, the flow velocity near the surface of the mold decreases. The flow direction changes from the positive velocity with the mold widths of 880 mm and 1050 mm to the unstable velocity with the mold width of 1300 mm. The calculated results are in good agreement with the measured results. The turbulent kinetic energy near the submerged entry nozzle (SEN) gradually increases, and the risk of slag entrainment increases. Under the conditions of high fixed steel throughput of 3.5 ton/min, the SEN immersion depth of 160 mm, and the argon gas flow rate of 10 L/min, as the width of the mold increases from 1600 mm to 1800 mm and 2000 mm, the velocity near the mold surface decreases. The flow velocity at 1/4 of the surface of the mold is positive with the mold width of 1600 mm, while the velocities are negative with the widths of 1800 mm and 2000 mm. The calculated results are basically consistent with the measured results. The high turbulent kinetic energy area near the nozzle expands to a narrow wall, and the risk of slag entrainment is significantly increased. In both cases of low and high fixed steel throughput, the change rules of the flow field in the mold with the width are basically the same. The argon gas flow rate and the immersion depth of SEN should be adjusted reasonably to optimize the flow field in the mold with different widths under the same fixed steel throughput in the practical production.
Highlights
In the production process of automobile exposed panels, improper control of the flow field in the slab continuous-casting mold tends to bring about mold flux entrainment, large inclusions, and bubble-type inclusions in the continuous-casting slab, which may result in linear defects on the hot-dip-galvanized automobile exposed panel, giving rise to serious surface quality problems [1]
Under fixed steel throughput, no papers reported the effect of mold width on the mold flow field assisted with the quantitative measurement of mold surface velocity at high temperature, which is beneficial for improving the industrial operation of continuous casting and obtaining knowledge for the scientific community
The numerical calculation is conducted by use of the standard k-ε model coupled with the discrete-phase model model, and the calculation and measurement results are compared and analyzed
Summary
In the production process of automobile exposed panels, improper control of the flow field in the slab continuous-casting mold tends to bring about mold flux entrainment, large inclusions, and bubble-type inclusions in the continuous-casting slab, which may result in linear defects on the hot-dip-galvanized automobile exposed panel, giving rise to serious surface quality problems [1]. With regard to the influence of the casting speed, the argon gas flow rate and the immersion depth of the SEN on the mold flow field, Zhang [11] used numerical simulation to study the fluctuation of molten steel on the mold surface at different casting speeds. Under fixed steel throughput, no papers reported the effect of mold width on the mold flow field assisted with the quantitative measurement of mold surface velocity at high temperature, which is beneficial for improving the industrial operation of continuous casting and obtaining knowledge for the scientific community. The influence of mold width on the surface velocity, flow field pattern, turbulent kinetic energy, and surface fluctuation of molten steel in the mold is clarified, which will provide technical guidance for improving the surface quality of automobile exposed panels with different widths
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