INFLUENCE OF OPERATION PARAMETERS ON THE COOLING PERFORMANCE OF WATER-AIR NOZZLES

In the secondary cooling zone of the continuous casting process water-air nozzles are used to cool down the strand. The cooling has to be sufficient enough to ensure a certain shell thickness and finally the complete solidification of the material. Further a controlled and uniform cooling strategy is important to minimize the amount of defects in the solidified steel. For the determination of the water distribution and the cooling characteristic of water-air sprays at defined operation parameters the Nozzle Measuring Stand (NMS) at the Montanuniversitaet Leoben is used. In this work the measuring principle of the NMS is explained and the influence of several nozzle operation parameters on the cooling characteristics of two water-air nozzles is shown. In a first step the water distribution (VVD) at different nozzle distances, water flows and air pressures was determined. Afterwards the heat transfer coefficient (HTC) for every parameter modification was measured. The surface start temperature for all experiments was set at 950 degrees C. In order to show the change in cooling intensity over the width of the spray, HTC measurements were performed at several positions. Finally the results of the experiments and possible links between the operation parameters, water distribution and HTC are discussed.