Experimental Study On Heat Transfer Coefficient And Thermophysical Properties Of Continuous Casting Slab And Simulation Analysis Of Solidification Process

The effect of the secondary cooling in continuous casting is directly related to the quality and yield of ingot blanks.Improper cooling will result in surface cracks and internal cracks as well as the defect of bulge in ingot blanks.The heat transfer coefficient is the key of the water distribution in secondary cooling zone.The process design,equipment design and control design are all based on the thermo-physical property of a given steel grade.So it is of great importance to research the heat transfer coefficient of ingot blanks and the thermo-physical properties of high temperature.The thesis is aimed at researching the heat transfer property of the air-mist nozzle in the secondary cooling process in continuous casting.Based on the basic theories of heat transfer and the results of cooling process simulation of a test piece,an experimental device is designed to measure the heat transfer property of the air-mist nozzle.Temperature signals were gained using a DH5922 N dynamic signal analyzer system,a program is designed using VB6.0 in order to determine the convective heat transfer coefficient.The property of the nozzle in secondary cooling zone is measured through test,the relevant parameters and the relation of surface temperature of the specimen and heat transfer coefficient were obtained.By STA449 C thermal analyzer and GLEEBLE 3500 thermal simulated test machine,we obtain the data of thermophysical and high temperature mechanical properties of Q345 C at the temperature from 800? to 1200?.The data includes the stress-strain relationships,young's modulus,yield limit,toughness,the phase change temperature and specific heat of Q345 C.The necessary high temperature parameters for the design of continuous casting machine were provided.By proper assumption and simplification,the mathematic model of heat transfer process for solidification process of round billet is obtained.The temperature distribution of the heat transfer process for solidification process of round billet is simulated by ANSYS,a base for a proper adjustment of cooling regime in the secondary cooling zone is provided.