Research Of Solidification And Heat Transfer Model In Billet Continuous Casting Based On The Measurement Of Heat Transfer Coefficient

As an indispensable process in the production of steel,the Continuous casting technology deeply affects the yield and quality of the products.In order to improve the technology of continuous casting,it is necessary to make a further study of the solidification and heat transfer process in the production process of billet,and the solidification and heat transfer model as a kind of numerical simulation method has become an important means to research the solidification and heat transfer process of billet.In order to obtain a high accuracy heat transfer model,with the 150mm×150mm billet continuous casting machine in Nanjing Iron&Steel Co.,Ltd as the object of study,a method of establishing a solidification and heat transfer model of billet that is based on the experimental measurement of heat transfer coefficient in secondary cooling zone has been proposed.The main contents in this thesis are as the followings:(1)An experimental platform used to test the cold and hot characteristics of nozzles in secondary cooling zone was set up.The COMSOL software was used to simulate and analyze the different thermocouple installation scheme,the nozzles characteristics test experimental scheme was developed,and the nozzle characteristic test experiment was completed.(2)Aiming at three different heat transfer coefficient calculation methods,a virtual experiment method was adopted to analyze these different calculation methods.According to the analysis results,the heat transfer calculation method based on regularization was determined.And the chaos optimization was added on it to further ensure the reliability of the calculation results.By calculating,the heat transfer coefficient on the surface of the specimen under different water pressure was obtained.And then combined with water flow density distribution of the nozzle,the empirical formula of the relationship between the heat transfer coefficient and water flow density was obtained.(3)The heat transfer coefficient calculation formula in secondary cooling zone of the billet continuous casting machine was used as the boundary conditions for solidification and heat transfer model.And the entire cross section of the billet was selected to establish heat transfer model,considering the inhomogeneity of the water flow density distribution.To solve the model,a program was written with VB.NET language.(4)The surface temperature and shell thicknesses measured by the thermal imager and nail shooting was adopted to verify the accuracy of the heat transfer model.The validation results show that the difference of surface temperature between model calculation and measured results is less than 15?,and the difference of shell thicknesses between model calculation and measured results is less than 2mm.