| The temperature and composition of the molten steel is the key process control parameters in the steelmaking process. Accurate control of molten steel temperature is an important factor to ensure the continuous casting smooth,and precise control over the component of the liquid steel is the guarantee of qualified molten steel and high quality product.The component and temperature control precision of the liquid steel during LF directly affect the smooth production of continuous casting and the qualified rate of finished steel,as it is an important control means of the temperature and composition between converter and continuous casting. Therefore,the establishment of molten steel composition and temperature precise control model for LF, and the realization of the intelligent control of the refining process based on the model has very important practical significance of improving the production efficiency and reducing the production costs.In this paper, the refining process of 135 ton ladle furnace has been studied through the theoretical analysis calculation and on-line debugging based on the statistical analysis of production data.Molten steel composition and temperature control model for the refining process was established.The main research work and results are as follows:(1) According to the the inbound and the target component of the molten steel,the kind of alloy that should be added into the steel to tune the composition and the addition amount of the alloy are calculated,and at the same time,the endpoint components are forecasted. Electrode heating of LF refining process will lead to an increase of the carbon component,and the amount of increasing carbon is mainly determined by the effects of submerged arc and the stability of the current.According to the experimental results,when the submerged arc is well, the average raised carbon was 0.0386%/h.On the contrary,the average raised carbon was 0.0831%/h.The manganese could back to steel during the refining process, and the amount of these manganese related to the initial aluminum content in steel through the equation of ?w[Mn]=0.02054-0.5985.·w[Als]+4.64985·(w[Als])2.(2) Through the analysis of LF refining process energy balance,the calculation model of mathematics of the ladle heat transfer process was established.Taking the first testing temperature at the LF treatment position as the starting point,calculated the change of the molten steel temperature caused by the liner cooling.The result shows that:there is about a 10? difference of molten steel temperature drop within 30min of refining process between online ladle and new ladle;The higher the inbound temperature of molten steel is,the greater the temperature gradient is,and the faster the rate of temperature drop of liquid steel is;During the LF heating process,it has an increasing trend that liquid steel temperature drop caused by liner cooling;during the non-heating process, it has a decreasing trend.(3) The automatic selection of heating grade and heating time during LF refining process was realized.And the heating time could be automatic correction at three minutes before the end of the heating time.(4) Molten steel composition and temperature control model for the refining process was established, and made an online verification of accuracy of alloy calculation,calculation of the heating time,the prediction of ending component and temperature. The results show that:the molten steel component of C,Si,Mn,Ti predicated by the model is almost close to the real component tested and the hit rate has achieved more than 90% when the relative error within 0.02%; the molten steel temperature predicated by the model is almost close to the real temperature tested and the hit rate has achieved 87.5% and 95% when the relative error within ±5? and ±10?.The accuracy can fully meet the field production requirements,and finally realize the intelligent control of the refining process. |
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