Development And Application Of Heat Tracking Model For Continuously Cast Wide-Thick Slab

As an effective way to eliminate the centerline segregation and porosity,soft reduction technology and heavy reduction technology have been widely carried out in steel continuous casting process.Both the soft reduction and the reduction are carried out under the region of solidification end,and the determination of the final solidification point is a prerequisite to implement reduction,and the main method for determining the position is the on-line calculation of heat tracking model in many steel mills of our country.Therefore,improving the accuracy of the model is of great significance to optimizing the reduction process and improving the quality of the billet.Taking the slab production process as the research object,this paper used the independent programming to study the micro solidification model and to establish the macro and micro coupling model of two-dimensional solidification heat transfer based on physical parameters.On this basis,an on-line calculation of heat tracking model is established,and the influence of continuous casting process parameters on the model is discussed,and the influence of the solute macrosegregation is studied.The model is applied to the control system of the dynamic heavy reduction on the casting machine,and the model is verified.The main conclusions can be summarized as follows:(1)The change of phase composition during molten steel solidification has an important influence on physical parameters.The micro solidification model was established to simulate the phase composition changes and solute segregation behavior during solidification.And the calculation process of physical parameters,such as phase fraction and thermal conductivity,was accomplished by the model.(2)The macro and micro coupling model of slab solidification heat transfer was established.In the continuous casting process,the uneven distribution of the billet surface was caused by uneven heating.And through the study of heat,the heat dissipation of its wide face centerline along the width direction accounts for about 4%of the total heat dissipation.According to the pin-shooting experimental results and the pressure feedback value in the production process,the macro and micro coupling model of solidification heat transfer is more accurate and reasonable than the conventional model.(3)An on-line thermal tracking model based on physical parameters is established.The physical parameters obtained from the micro solidification model are saved to the database,and the temperature field is calculated by reading the corresponding physical parameters from the database.By comparing the model,the online thermal tracking model can be used to simulate the solidification state of the slab wide center position.(4)In the casting speed 0.7-1.0 interval,the position of the solidification end of every 0.1 increase of casting speed is about 3 m.Under the condition of casting speed 0.83 and casting temperature of 1540?,the positions of solidification ends in strong cold,medium cold an weak cold were respectively 22.9m,23.34m,23.85m.T he segregation of elements causes the solidification end to move backwards,and the influence of carbon element segregation is much larger than that of phosphorus and sulfur element segregation.(5)The average error of the shell thickness and measured using the fixed carbon composition calculated value is 5.65%,and the average error using the shell thickness detection of carbon component calculation is 4.3%,so the use of carbon components to detect the results calculated more accurate.The deviation between the calculated surface temperature and the measured temperature is within 10? and the calculated results are accurate.The dynamic heavy reduction system effectively improves the quality of the billet,and indirectly shows that the on-line thermal tracking model has good practicability.