Abstract: 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.

Key words: nozzle port angle, flow field in mold, high temperature measurement, numerical simulation, surface velocity