Influence Of Continuous Casting Process Parameters On Solidification Macrostructure And Macrosegregation Of Large Round Billet

In recent years,large-scale continuous casting billets have developed rapidly,and the production process of large-section casting billets still faces many problems,and the relevant theoretical basic research is relatively weak.In this thesis,a physical and mathematical model of tissue growth and macroscopic segregation was established using Φ800mm 42 Cr Mo continuous casting billet as the research object,and the model was verified by field experimental results.The effects of different continuous casting process parameters on solidification structure and macroscopic segregation were studied.In this thesis,Φ800 continuous casting billet was used as the research object,and the physical and mathematical models of tissue growth and macroscopic segregation were established.Based on Pro CAST,a CAFE model combining finite element and cellular automata was established,and the heat transfer and solidification model of continuous casting billet was simulated by the moving boundary method,the solidification and tissue growth processes of different cooling stages were analyzed,and the influence of process parameters such as pouring superheat,mould cooling strength,and casting speed on the characteristics of solidification microstructure was studied.The results show that the low pouring superheat can greatly improve the equiaxed crystal rate and refine the grain.A strong mould heat flux density will make the columnar crystals more developed;Under the condition of keeping the amount of cooling water unchanged,increasing the casting speed can increase the equiaxed crystal rate and refine the grain to a certain extent.At the same time,the change of pouring superheat has the greatest influence on the distribution and size of the coagulated tissue.Based on Fluent,a multiphysics mathematical model of coupled flow,heat transfer and solute transport was established,and the model also considered the role of hot solute convection.The effects of process parameters such as pouring superheat,mould cooling strength and casting speed on macro segregation and central shrinkage of carbon were studied.The results show that the negative segregation at 1/4 radius can be improved significantly by low superheat pouring,and the center positive segregation can also be well reduced.The cooling intensity of the cmould mainly affects the size and position of the negative segregation at 1/4 radius,the larger the cooling intensity of the mould,the more serious the negative segregation at 1/4 radius,and the deeper into the casting billet;The influence of casting speed on macro segregation of carbon elements is not obvious,and the change on carbon range is small.Among many continuous casting process parameters,the casting speed has the greatest influence on the center shrinkage pine,and the lower casting speed can improve the center shrinkage of the casting billet,and the excessive casting speed is generally unfavorable to the improvement of the center shrinkage pine.