Solving Inverse Heat Conduction Problem In Secondary Cooling Of Continuous Casting Based On Tikhonov Regularization Method

Continous casting process include transport device,tundish,casting mould,casting mould vibration device,dummy bar,secondary cooling device,tension leveller,cutting device etc.Compared with traditional die casting method,it has obvious advantages such as shorter process flow,higher metal yield,better slab quality,energy saving and consumption reduction,and easy to realize mechanical automation.With the increasing demand for steel quality in production and life,secondary cooling process of continuous casting is an efficient and economical entry point to improve steel quality.Surface heat transfer coefficient and temperature field distribution of billet are important parameters for optimizing nozzle operating parameters and billet casting speed in secondary cooling process.It is difficult to directly determine the temperature or surface heat flux(heat transfer coefficient)of the billet due to the high temperature,violent vibration and large temperature gradient,the inverse problem solving method brings a new way to solve the problem.Taking the temperature of several measurable temperature measuring points in the billet as the input condition,the surface heat transfer coefficient and temperature distribution can be obtained by solving the inverse problem.The main works and conclusions of this paper include the following aspects:Introduced the industrial background and research status of the inverse heat conduction problem.After analysis,calculation and reasonable simplification,the physical model and mathematical model of the experimental platform for dynamic heat transfer in secondary cooling of high efficient continuous casting were determined,which were qualitatively regarded as the inverse heat conduction problem with periodic stepped boundary conditions.The advantages of Tikhonov regularization method and sequential function specification method in this paper are analyzed.Using Tikhonov regularization method,numerical examples similar to experimental problems are processed to verify the irrelevance of the inversion grid.Theeffects of the location of measurement points,the time steps,the form of stabilization function and the size of random errors on the calculation accuracy are discussed.The results show that the closer the position of the measured points are to the surface where the inverted parameters are located,the more accurate the calculation results are the greater the influence of measurement errors;the longer the time step is,the better the stability of the calculation results and the worse the ability to track the inverted parameters;when solving inverse heat conduction problems by Tikhonov regularization method,the form of stability functional should be chosen as the form sensitive to the regularization coefficient.For Tikhonov regularization method,considering the accuracy and stability of calculation results,a slope method is proposed to select regularization coefficients.The thermal physical model proposed in this paper is verified by numerical simulation experiments.The influence of regularization coefficient on calculation accuracy is discussed when measurement error is unavoidable.The method is applied to the experimental datas,and the calculated results are in good agreement with the expectations.The results show that the method can balance the accuracy and stability of the understanding,and can effectively solve the ill-posed problem of the inverse heat conduction problem.Based on the analysis of experimental data from Tikhonov regularization post-treatment results,the secondary cooling process of continuous casting is divided into three zones:air-mist jet zone,parallel flow zone and air cooling-radiation heat transfer zone based on space;and film boiling,transition boiling and nuclear boiling zone based on time.A more intuitive understanding of the temperature drop process of secondary cooling billet in continuous casting has been obtained,which provides theoretical support for the cooling characteristics in the process of continuous casting.