Research On Optimization And Control Of The Casting Speed For The Billet Caster

The billet quality is closely related to the secondary cooling water distribution, and casting speed is a main factor, which impact on the secondary cooling water in the continuous casting process. Therefore, the optimum control of casting speed is particularly important for the billet quality in the secondary cooling process, the control system of which is based on the casting speed feed forward. In this thesis, combining with practical production, the continuous caster machine of small billet is taken as the research object, and the research objects are the optimal control model of casting speed, which is based on the superheat, and the virtual casting speed model, and the optimum model of water distribution in the secondary cooling process.In the thesis, the numerical simulation of heat transform and solidification model is used, to analysis the change surface temperature and thickness of the billet, which caused by the process parameters. and the process parameter is given by working field. After analyze the related curve generated by the data, the conclusion is easily got that the casting speed and secondary cooling water and superheat are important parameters for the solidification process of billet.The casting speed is frequent fluctuations when the production condition is under a non-stable state. and the casting speed will produce a negative impact on the surface temperature and internal quality. In this thesis a virtual casting speed model is offered, which is based on the dynamic track of billet unit, and the amount of water distribution is calculated by the virtual casting speed instead of the real casting speed. At last, the program is simulated by the PLC to achieve the control of virtual casting speed. After analyze the dynamic heat transfer model, it is found that the change of billet surface temperature is more reasonable, when the instance casting speed change abruptly.In the thesis, the superheat is taken as a related factor in the optimal control of casting speed, when the mold liquid level is controlled by the stopper in the continuous casting system. The billet shell thickness are simulated by the heat transfer model under different superheat, to meet the security of shell thickness. The optimal relation between casting speed and superheat is defined by the heat transfer model, and programmed by the PLC to achieve the control of casting speed based on the superheat. After the optimal control model is used in the working field, it is found that the casting speed can change with the superheat as the derived optimal relation of them, and the optimal control model of casting speed can reduce billet quality influence caused by the superheat. The superheat and casting speed is taken as a main factor determined the billet quality, and build a control model of water distribution based on the superheat. The billet temperature at the base superheat is taken as a standard point, when the superheat change, the compensation amount of water is simulated by the heat transfer model to reach the standard temperature. Through the analysis of simulated data, the relation between superheat and the compensation amount is derived. After compare the different curve of slab temperature before and after water compensation, the discipline is found:the change of water distribution based on the superheat and casting speed model, can reduce temperature change of the billet in the secondary cooling.