| Development and application of continuous casting technology is a major technological revolution to the steel industry. With the social development and progress, further optimization for the continuous casting process is needed for accelerating productivity and ensuring the quality of the slab. Casting secondary cooling process is an important part of the continuous casting process, the merits of the aerosol jet billet quality play a crucial role to the quality of slab. The key of improving technology in secondary cooling of continuous casting lies in the understanding of the mechanism of heat transfer on the mobile slab surface by mist cooling, thereby achieving the purpose of optimizing the process by adjusting the process parameters.There are three main features of billet in secondary cooling of continuous casting. First, the billet has liquid core. Second, the moved billet goes through the cooling boundary periodic. Third, the cooling nozzle angle has the regular change. In the research on continuous casting secondary cooling, these three characteristics are the key to simulate the cooling process of hot billet realistically. In this paper, a experimental platform has been designed and built independently for the research of heat conduction in secondary cooling of high efficient continuous casting. The platform consider the periodic heat condition of jet area, convective heat transfer area and dry area which is composed of aerosol jet system and thermal simulation and testing system. It can simulate main characteristics in secondary cooling of continuous casting. This study has inversed the surface temperatures and surface heat flux density by the temperatures that measured by the thermocouples placed in the cylinder. A two-dimensional unsteady inverse heat conduction mathematical model has been built in the cylindrical coordinate. Using Matlab compile the code and verify the accuracy of the inverse heat conduction problem, the mean of the relative error is on10-14level.The results show that the periodic characteristics of heat transfer are found in the mist cooling process, simulation of secondary cooling of continuous casting billet sample cooling process in laboratory has been achieved; the movement speed of cylinder has a strong influence on surface heat transfer forms, there are great differences with the static spraying. The movement of cylinder has different influences on the different surface heat transfer form, such as moving film boiling, transition boiling, nucleate boiling and forced convection. A dissymmetry of the heat transfer is observed upstream and downstream jet. In the boiling heat transfer stage, heat flux of above the area of jet upstream region is higher than above the area of jet downstream region, heat flux of the below area the area of jet downstream region is higher than the below area of jet upstream region. In the heat transfer and convection stage, heat flux of jet upstream region is higher than downstream region. The maximum value of heat flux is not located on the cylinder surface right below jet but located in range of [π/12, π/3] from the jet center in the jet upstream region with higher probability. In the boiling heat transfer stage, the minimum value of heat flux is located in range of [2π/3,3π/4] from the jet center in the upstream region with higher probability. In the heat convection transfer stage, the minimum value of heat flux is located in5π/6in the jet downstream from the jet center with higher probability. The location of maximum and minimum value of the heat flux is changed throughout the cooling process. In this paper, the research method and results can provide a reference for the optimization of the nozzle arrangement secondary cooling of continuous casting. |
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