Study On The Control Of Steelmaking Process And Blowing End-point For Medium-high Carbon Steel Melting By Converter

With the development of "Made in China 2025", the intelligent manufacturing in steel manufacturing process is under discussion, and the intelligent steelmaking would be an important content for realizing intelligent manufacturing in steel production in future. However, the stable and precise control of BOF end-point is one of the difficulties that the intelligent steelmaking has to solve. Due to the disparate development of converter steelmaking technology in China, the BOF without dynamic detection equipment accounts for a certain proportion among the steel workshops. Therefore, according to the technological characteristics of this kind of converters, the study and development of process and end-point control technology plays an important role in improving the control level during BOF steelmaking process.This paper aims at the problem of low hit rate of BOF end-point control and difficult control of process parameters during the melting of medium-high carbon steel by converter, which are without dynamic detection equipment, conducting some relative study on the optimal control of blowing and slagging process of an 80t converter, the process model based on mixing degree in steel bath, the prediction model of latter period phosphorus content and manganese content, and the reblow model for the melting of medium-high carbon steel. Moreover, the control technology of steelmaking process and blowing end-point for medium-high carbon steel melting is developed, which is conducive to fulfill the precise control of end-point composition and temperature of molten steel during the melting of medium-high carbon steel by converter.Through amalgamation of oxygen balance model and statistic model, the integrated model for prediction of the oxygen blowing quantity was established, and the average relative error of the integrated model is less than 1% when it was used to predict the oxygen consumption during BOF steelmaking process. By means of physical modeling, the influence degree of main technological parameters on mixing behavior in combined converter was studied. Meanwhile, the model for the charge of flux was built and the slagging mode was fixed during the blowing process.The concept "mixing degree in steel bath" was redefined, and the process model was established through the combination of traditional three-stage decarburization theory and principle of thermal equilibrium in steel bath. The verification showed that the hit rate of the process model was 72% when predictive errors of carbon content and temperature were within ±0.04% and ±15℃, respectively.By means of analyzing the oxidizing reaction mechanism of phosphorus and manganese in molten steel during the blowing process, the multi-level recursive regression model for the prediction of latter period phosphorus content, and-the BP neural network model based on algorithm optimization for the prediction of latter period manganese content were established through applying the data mining method combined with metallurgical process theory. Furthermore, the hit rate of prediction model for latter period phosphorus content was 73% when the predictive errors of the model were within ±0.004%, and the hit rate of prediction model for latter period manganese content was 84% when the predictive errors of the model were within ±0.025%.An in-depth study on the varation of composition and temperature of liquid steel near blowing end-point for medium-high carbon steel was presented in this paper. Moreover, the reblow model was developed. The test results for real production showed that after application of the solution for reblow operation, not only the end-point composition and temperature of liquid steel all achieved the target value, but also the predictive errors of the model were within ±10℃, ±0.02%, ±0.02%, ±0.003% and ±0.004%; respectively, when it was used to predict the end-point temperature, carbon content, manganese content, phosphorus content and sulfur content of liquid steel. On the basis of above study, the model set of steelmaking process and blowing end-point for medium-high carbon steel melting was developed, and the control technology was preliminarily formed, which helped to fulfill the comparatively precise control of steelmaking process and blowing end-point for medium-high carbon steel melting by converter.