Predicting Model Of Oxide Inclusions In Steel Based On GA-NN And Irreversible Thermodynamics

The nature of majority of inclusions in steel, in particular the deoxy-generated oxide inclusions directly affect the performance of steel. Under the conditions of existing technology, it is impossible to full remove inclusions in steel. As long as the existence of oxygen in steel, the generation of new inclusions can not be avoid. Therefore, in order to achieve the target of reduction of the harmful effects on performance of steel, the control of inclusions' composition by physical-chemistry methods becomes especially important. In this paper, the thermodynamics and kinetics for controlling inclusions composition are mainly concentrated, based on the invetigation of many domestic and international literatures.The eatablishment of previous mechanism models is investigated firstly in this paper. It finds that these models are based on a lot of assumptions. Due to the simplified architecture of the activity of components, the application fields are always be restricted. At the same time, mechanism models always use linear fitting, least-squares procedure and so on to regress in the methods of calculation. But parameter estimation of these traditional mathmatics methods is not unbiased estimators, the fitting accuracy is often not high. Therefore, this paper takes the method of modeling discrete activity data which is the authority of international and obtained from experiment. By using genetic algorithms(GA) to improve the weights and thresholds of BP neural nets(NN), a general activity model of actual solution is established based on experimental data.By introducing GA-NN model to inclusions systems, the inclusions of MnO-SiO₂,CaO-SiO₂-Al₂O₃ and MnO-SiO₂-Al₂O₃ have been studied in this paper. The control methods in low-melting-point region of these inclusions have been put forword, and the different ways of deoxidization with CaO-SiO₂-Al₂O₃ slag covering are analyzed.Combination of actual production, the control of inclusion components during the process of alloying, refining and calcium treatment is studied. An analysis of the generation and variational mechanism of inclusions at different circumstances is obtained, and a solution is proposed.For there's little study on the kinetics of the inclusions' components variation under non-equilibrium state, and GA-NN model can only be applied to the study of the equilibrium composition and morphology of inclusions, irrevisible thermodynamics is introduced to kinetics calculation of inclusions in this paper. From the aspects of chemical reaction and diffusion, the status of inclusions at different period from generation to refining process is stdudied. The formation of inclusions is described from mechanism and a general kinetics equation for describing the components variation of inclusions is obtained by modeling. By the simulation of LF process under laboratory conditions, the phenomenological coefficients of kinetics equations are obtained, and the feasibility of applying irrevisible thermodymics to inclusions calculation is verified.