Research On Solidification Heat Transfer And Reduction Process Of Continuous Casting Extra-thick Slabs

With the rapid development of national economy,the demand for extra-thick plates in military industry,aerospace,nuclear power,water conservancy and hydropower,shipbuilding,construction machinery and other neighborhoods has increased sharply.As the base material of rolling extra-thick steel plate,the quality of extra-thick slab determines the quality of plate products.Because of the large cross section of extra-thick slab and the poor degree of central deformation during rolling,the quality defects such as segregation and looseness of extra-thick slab have become the current research hotspot.The central segregation and looseness can be improved and the central quality can be improved by applying a large amount of reduction to the solidification end of extra-thick slab.The key technology is how to determine the reduction position and the reduction area.In this paper,according to the characteristics of extra-thick slab continuous casting,through numerical simulation method,under the heavy reduction of the solidification end of extra-thick slab,determine the position of the reduction and the reduction area,the specific research content is as follows:(1)The model of reduction at solidification end of extra-thick slab was adopted,and the model was simulated by computer and verified.The finite element model of solidification heat transfer was established according to the actual production situation.Through solving the heat transfer model,the reduction position was determined,the thermal coupling model was used at the reduction inlet and the high temperature mechanical properties of the casting billet were determined.The results show that the error between the simulated temperature and the measured temperature is 3.4 %,1.42 %,1.44 % and 4.41 % respectively,the errors are all within 5 %,meeting the requirements of calculation accuracy.(2)The influence of process parameters on temperature field was studied.The heat transfer model of extra-thick slab continuous casting process was established.the effects of superheat on temperature field,casting speed on temperature field and intensity of secondary cooling on temperature field were studied.The results show that when the superheat decreases by 10 ? or increases by 10 ?,it has little effect on the temperature distribution of the slab at the reduction inlet.When the casting speed decreased by 0.1 m /min or increased by 0.1 m / min,the casting temperature distribution at the reduction inlet was greatly affected.When the intensity of secondary cooling decreases by 10 % or increases by 10 %,the billet temperature changes greatly at the reduction inlet.(3)The stress-strain field of reduction is studied.The thermo-mechanical coupling model of continuous casting process is adopted.The simulation results show that: three reduction systems of 6mm,10 mm and 20 mm are adopted,the core strain was 0.02476 and the core strain accounted for 30.49 % of the surface strain when 20 mm was reduced.the center looseness of extra-thick slab was improved better.