Numerical Simulation Of Continuous Casting Process In Jumbo Square Casting Mold

With the improvement of continuous casting technology,the demand for casting slab increases,and requirements for large cross section and large scare slab are more and more stringent.Casting mold design is a dispensable part in production process while casting cooling also needs to match the requirement,which the cooling of casting mold is the most critical part in the process.Along with the large-scare industrial development of casting mold,there is more possibility to produce jumbo square casting billet.The casting mold design and technology selection has ensured the product quality.Because of the large section of the ultra-thick jumbo square billet,the continuous casting mold has several technical difficulties,which mainly are: 1,There are large volume of liquid steel and large heat capacity inside of the casting mold,and complex liquid steel flow,which are easily cause internal quality problem of the slab.2,How to fast and effectively transfer the heat out of the slab under the premise of ensuring the safety of the casting mold as well as the quality of the slab when out of the casting mold.We made the following studies to address these problems.First,this paper analyzed the flow characteristics of molten steel,considering the molten steel as incompressible fluid,and according to the basic theory of numerical simulation,we chose RANS simulation and large eddy simulation method to make analysis and analyzed the advantage and disadvantage of these two simulations.Because these two simulation equation are very similar,we combined these two simulation by the length characteristics according to the characteristics of the mathematical model of the molten steel in the casting mold,which was turbulent numerical simulation equations on the basis of standard k-ε equation.In this way,it not only solved the problem of large amount of calculation,also improved the accuracy of the simulation.The combination of the simulation equations provided a theoretical reference of the molten steel analysis in casting mold.Second,when calculating simulation on molten steel,we firstly determined the init-ial and boundary conditions of the molten steel,and secondly took turbulent numerical simulation equation which are based on the standard simulation equation as the control equation,and thirdly made the finite element analysis through changing the nozzle structure,immersion depth of the nozzle as well as the flow speed of the molten steel,and finally obtained the flow field distribution under different parameters.The analysis verified the reliability of the composite simulation equations,and provided a new way of molten steel flow of the billet in side of the casting mold.Third,we made analysis on molten steel solidification of the billet.According to the heat transfer and thermodynamic theory,we took use of the boundary condition of heat transfer,reversely calculated the heat flux which would be the boundary condition in the simulation of the temperature variation process of the slab solidification,and made comparison of the slab solidification at different area of the casting mold.Simultaneously,we made analysis of the solidification,shrinkage and hot deformation behavior of the copper mold.Combined with these two kinds of deformation behavior to calculate the inverted taper of the mold,during to the large size of the casting mold,we chose multi taper as the ideal choice of inverted taper.Finally,we machining the continuous casting slab into a test specimen,by using of the Gleeble-3500 Simulator to make experience of high temperature mechanical properties.The result simulated the mechanical properties of the specimen under different temperature.According to the experimental data,we analyzed the safe thickness of the billet,which thickness is the critical safety thickness,and then analyzed corrected value according to the experimental data.Because it easily appears corner crack defects,we analyzed the reason that may cause the defects,and according to the experimental data of high temperature mechanical materials,we deal with corner chamber of the casting mold,and with different proportion of billet size to modify the mold corner size to ensure the high temperature mechanical properties of the casting mold.