Study On Modelling For Secondary Cooling Process In Continuous Casting And Intelligent Optimization For Cooling Water

With the development of continuous casting technique, improving output and quality of products becomes an important problem in continuous casting research. Quality of billets is related to the solidifying process and casting billets solidify completely in secondary cooling zone, so the reaserch of solidifying in secondary cooling zone is significant to understand solidification behavior and insure the products quality. For many years, people study continuous casting by means of experiments, measurement and numerical simulating. With the development of computing tecnique, numerical simulating has become an important method for continuous casting study.Firstly, for heat transfer process in billets continuous casting, this paper studies heat transfer model and develops 2D moving-slice model combining the practice of NanGang steel plant. Using enthalpy to deal with latent heat of solidification the numerical model is solved by finite element method, and a steady temperature field can be obtained under a certain condition. Accuracy and reliability of numerical model are validated by comparing measuring data with model computing data. Furthermore, casting speed, superheat and cooling water's effects on steady temperature field are analyzed in this paper.Secondly, temperature transition speciality is studied through developing and solving 3D transient heat transfer model. In practice, beillets temperature field is always in a long transition, which shows that solidification in continuous casting is an inertial system. Temperature transition is almost not considered in previous study on continuous casting, and products quality can't be insured with control method that ignores temperature transition. Especially, when production setting varies frequently, billets surface temperature will undulate greatly, even appears "pinnacle". This phenomenon impacts products quality strongly. Temperature field dynamic response to the saltation of casting speed, superheat and cooling water is investigated in this paper based on a lot of simulation computing. "Effective casting speed" is adopted and measured speed is filtered in order to avoid appearing "pinnacle" during cooling water saltation, which can reduce disadvantages to billets quality.Thirdly, to optimizng quantificationally secondary cooling system in continuous casting, optimization method besed on metallurgy criterion function is studied. Based on the relation among multiobjective functions, a general objective function for secondary cooling is formulated. Moreover, swarm intillegenec-based search algorithm-particle swarm algorithm is investigated,and a new hybrid evolutionary-based method combining particle swarm algorithm and the chaotic search is proposed in order to improve search efficiency in optimizing secondary cooling water. With the aid of cooling water optimization offline, a new dynamic control model based on optimized relation among speed, superheat and cooling water is obtained considering superheat's effects on temperature field.Lastly, software for solving 2D, 3D heat transfer model is developed combining MATLAB and C. Based on intillegence search algorithms, a simulating platform for secondary cooling water optimization in continuous casting is established in order to realize inputing parameters, outputing parameters, showing temperature field data and displaying optimization results by friendly interface.