| Twin-roll casting process is the new technology in the field of metallurgy and material processing.Because of its short process and fast solidified speed,it can not only improve the production efficiency and reduce the manufacturing cost,but also produce the material,which is difficult to get with the conventional process.Besides it can improve the properties of the casting material.However,due to the high matching requirements between casting process parameters,different process parameters can affect the solidified structure of the strip,so a large amount of material and financial resources are required during the experiment.Different casting process parameters affect the temperature distribution of the pool and the roll,so as to determine the formation and development of thin-walled solidified tissue,and thus determine the performance of the products.Therefore,with the computer simulation of the distribution of temperature field and the relationship between process parameters and solidified structure,we can find out the regularities which are of great significance for optimizing process parameters of casting production and improving the quality of strip production process.Based on the characteristics of solidification in the vertical twin roll casting process,the mathematical model of the temperature field of the cast roll and the melt pool is set up.On the basis of previous studies,Cellular Automata method is applied to simulate the growth of solidification structure.The ratio of columnar grains in the process of strip solidification was calculated.According to the experiment,the ratio of columnar grains in the solidified structure at different casting temperatures was obtained to verify the correctness of the temperature field model.The main contents of this paper are as follows:(1)The flow field in the melt pool is reasonably simplified.The mathematical model of two dimensional heat transfer of cast roll and melt pool is studied.According to the geometric characteristics of the cast roll and the molten pool,the polar coordinates of the roll are set up and the rectangular coordinates are set up for the molten pool.The relationship between the two kinds of coordinates is established and the mathematical model of the heat transfer of the cast roll and the molten pool is studied.(2)A growth model of solidification structure based on solute diffusion is established.Combined with cellular automata method,the numerical simulation algorithm of dendritic growth is derived.Numerical algorithm for stochastic nucleation of solidification structure is deduced by using continuous nucleation growth model.(3)The paper study the micro area of synchronous rotation of the casting roll.Macro and micro coupling calculation is carried out for the computation area.The interpolation method is used to calculate the temperature distribution in the micro area,and then the effect of casting rolling parameters on the formation of solidification structure is studied.(4)Based on the mathematical model of temperature field,dendrite growth model and macro and micro coupling algorithm,the temperature field simulation program and solidification nucleation and growth simulation program of casting roller and molten pool are developed by using C language.(5)According to the 3wt%Si simulation program developed using the research of silicon steel casting process parameters(pouring temperature,casting speed and pool height)effects on casting roll and molten pool temperature distribution,as well as on the solidification structure of thin strips in the proportion of columnar crystal zone,the columnar front liquid temperature gradient,the dendrite growth rate,column dendrite spacing and solidification cooling rate effect.(6)The experimental research on strip casting and rolling of 3wt%Si silicon steel has been carried out.The proportion of columnar grain region in the solidified structure obtained from the experiment is compared with that calculated by the program. |
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