Air mist cooling in continuous casting Apr20

Air mist cooling in continuous casting...

Air mist cooling in continuous casting  Continuous casting machines are now required to cast a wide range of steel grades which are ranging from ultra low carbon and low carbon grades to high carbon and high quality pipeline grades. Consistent production of prime quality of these products require increased operational and maintenance flexibility of a casting machine so that the optimum casting parameters can be maintained for each steel grade. This flexibility extends not only to the machine elements and control systems, but also to the secondary cooling system and demands more efficient and reliable spray cooling. Cooling by water plays an important role in extracting heat from both the mold and solidifying liquid steel during the continuous casting of steel. It is characterized by complex boiling phenomena. Heat extraction rates during water cooling, which have strong dependence on the metal surface temperature and it can rapidly change with time as the strand cools down. Hence uncontrolled cooling may cause fluctuations in the temperature gradients inside the solidifying shell of steel and generate tensile thermal stresses at the solidification front that can ultimately lead to the appearance of hot tears/cracks in the final product. The necessity of having a sound quality of cast steel product and increased productivity of continuous casting machine has focused attention on the need for more efficient systems of secondary cooling during continuous casting of liquid steel. Air mist cooling (AMC) in secondary cooling zone of continuous casting machine is a step in this direction.  Air mist nozzles utilize compressed air in combination with water pressure to atomize secondary cooling water. This provides a much wider turn down / control ratio which is necessary in case a product mix covers a wide range of steel grades. Air mist nozzles also...