水口倾角大范围变化对宽板坯连铸结晶器流场的影响

Effect of nozzle port angle with wide range change on flow field in slab continuous casting mold with large width

采用棒偏转法对断面宽度为2 000 mm,水口倾角分别为15°、20°和45°时的连铸结晶器表面流速进行了测量,并结合数值计算分析了水口倾角大范围变化对结晶器内钢液流场的影响。随着水口倾角由15°增加至20°、45°,结晶器表面流速由0.4 m/s减小至0.25 m/s和-0.1 m/s,测量结果与计算结果吻合良好。水口倾角为15°和20°时,形成双循环流,水口倾角为大倾角45°时,流场形态转变为中间流,卷渣风险显著增大。水口倾角为20°时,表面流速处于合理值,有利于抑制卷渣风险。随着水口倾角的增大,钢液射流冲击窄面的冲击位点下移,水口倾角由20°增大至45°,冲击位点下移尤为明显,不利于夹杂物上浮。水口倾角为15°时强烈的双循环流导致液面水口附近波动增高;水口倾角为45°时,宽度1/4位置液面波动加剧,水口附近湍动能明显增大;水口倾角为20°时液面波动最为平缓,有利于抑制卷渣缺陷。

The velocity near the mold surface was measured with the rod deflection method under the condition cross-section width of 2 000 mm and the angle of nozzle of 15°, 20° and 45° respectively. The influence of nozzle port angle on the flow field of molten steel in the mold was also analyzed by numerical calculation. With increasing the nozzle port angle from 15° to 20° and 45°, the velocity near the mold surface decreased from 0.4 m/s to 0.25 m/s and-0.1 m/s. The measured results are in good agreement with the calculated ones. When the angle of nozzle is 15° and 20°, the double roll flow is formed. When the angle of nozzle is 45°, the flow field in the mold changes to intermediate flow and the risk of slag entrainment increases significantly. When the nozzle angle is 20°, the surface velocity has a reasonable value, which is conducive to reduce the risk of slag entrainment. With increasing nozzle port angle, the impact point of molten steel jet impinging on the narrow surface moves down. When the nozzle angle is increased from 20° to 45°, the impact point moves down so seriously that makes the inclusions difficult to float up. When the nozzle angle is 15°, the strong double roll flow leads to the increase of the fluctuation near the nozzle. When the nozzle angle is 45°, the fluctuation of the mold level at 1/4 of the width increases, and the turbulent kinetic energy near the nozzle increases obviously. When the nozzle angle is 20°, the fluctuation of liquid level is the smallest, which is beneficial to restrain slag entrainment.