Measurement prediction and control of steel flows in the casting nozzle and mould

Continuous casting is the dominating process to cast steel. Liquid steel is continuously fed from a tundish to a mould through a casting nozzle. The flow conditions in the mould are influenced by the flow pattern inside the casting nozzle as well as the level of steel in the tundish. The flow into the mould is regulated by a stopper rod or a slide gate. The surface of the strand solidifies quickly in the mould and it is important to maintain a constant level of steel to avoid surface defects. A new physical model that simulates continuous casting has been developed. A physical model of this type is unique. The scale of the model is a commonly used full-scale casting machine at slab casters, except the dimension of the tundish. It is possible to generate different types of flow conditions at simulation in the model. Water and liquid steel has similar kinematic viscosity and water is therefore often used for simulation of the continuous casting process. This simulation has been performed using an alloy with a low melting point. The alloy has besides the low melting point, similar physical properties as steel. Measurements with a compact laser vibrometer have been performed to examine the possibility to quantify the volumetric flow of alloy in the model. The compact laser vibrometer measures the vibrations on the surface of the casting nozzle as the alloy flows through during simulation. The flow of alloy in the model is determined by the velocity of the pump. A calibration of the pump was done to specify the volumetric flow at a specific pumping velocity. This provides the possibility to examine the signal from the sensor during controlled circumstances. The investigation was performed during simulation at specific single phase flows. It was found that the compact laser vibrometer shows a trend of increasing frequency at higher flow rates. A background noise was created by the engine of the pump and measurements were done to be able to exclude this type of disturbance.Validerat; 20101217 (root