Inverse Problem On Mould Heat Transfer And Lubrication For Slab Continuous Casting

The mould is the core component of continuous caster. Understanding the status of heat transfer, solidification and lubrication within the mould exactly in real-time is very important for improving the slab’s quality. At present, there have been many researches about the heat transfer and lubrication behaviors in the mould, but most of them are studied under the idea condition, the calculated results of which are uniform and can’t reflect the real casting condition. With appearance of the conceptions of visualization and intellectualization in continuous casting, the’accuracy’and’real-time’of numerical simulation are more important at production field.In this paper, the mould of continuous slab caster is taken as the research object. Based on the measured data of mould temperature, an inverse problem model is established to analyze the mould heat transfer and the strand solidification. And combining the parallel technology of OpenMP, the conflict of accuracy results and quick computation will be resolved. Corresponding software is developed and applied to different plant and caster for off-line simulation and on-line detection, in order to verify the feasibility and validity of the model. Then the mathematical model of thermal state of slag lubrication is built to study the distribution of slag film and lubrication states, and the influence of process condition and physical properties of powder is also discussed. At last, the relative root mean square (rRMS) and the shell growth rate are presented to investigate the non-uniform characteristic of mould heat transfer and lubrication state.Based on the measured temperature data and OpenMP, an inverse problem model combining the parallel technology is developed, which is assigned to4CPU for parallel computing after domain decomposition of mould and strand. The results show that there is good agreement between the calculated temperature and the measured temperature, which could reflect the exact situation of heat transfer in the mould. And the computing time reduces three-quarters by using the parallel technology, basically meeting the velocity desire of on-line calculation. Now the software is applied in plants and it preliminarily realizes on-line visualization of the temperature, heat flux and strand solidification within mould, which could predict the generation of strand surface crack and optimize the process condition.The slag lubrication model is developed on the basis of temperature field to calculate the distribution of slag film and air-gap. The calculation results of peritectic steel in this paper show that the distributions of liquid slag film and strand surface temperature share similar characteristics. The liquid slag film at the upper part of the mould is thicker, the order of magnitude of which thickness is0.1mm. The liquid slag film disappears gradually when the strand surface temperature decreases. The thickness of solid slag film is about0.5mm, while it reaches1mm at the mould outlet. The status of slag film is affected obviously by the slag melting point and viscosity, and the liquid slag film thickness decreases when the casting speed increased. Furthermore, this paper proposes another method to analyze the air-gap between mould and strand.Non-uniformity and shell growth rate presenting in this paper are all defined to study the non-uniform behaviors in the mould. It shows that the non-uniformity of shell thickness near meniscus fluctuates severely, and the shell growth rate changes abruptly and reaches the maximum in the region of0-200mm below meniscus. The non-uniformity of mould temperature, heat flux, shell thickness and the liquid slag film increases with casting speed, as well as the fluctuation of shell growth rate.