Abstract

BAO, L. et al. Investigation and modelling of work roll temperature in induction heating by finite element method. J. S. Afr. Inst. Min. Metall. [online]. 2018, vol.118, n.7, pp.735-743. ISSN 2411-9717.  http://dx.doi.org/10.17159/2411-9717/2018/v118n7a7.

An induction coil was designed successfully to heat a work roll online for hot or warm strip rolling. The surface temperature of the work roll was investigated through embedding a developed program into finite element (FE) software. A new model to describe the convective heat transfer coefficient between air and the work roll was proposed and the coefficient was obtained as a function of ambient and surface temperature. The influences of working frequency, source current density, air gap length, and coil distance on the mean and variance value of the surface temperature were investigated using the simulation results. The work roll surface temperature was significantly higher than that of the centre due to the skin effect. A longer induction heating time was beneficial for a more uniform temperature distribution on the work roll surface. The mean temperature increased exponentially with increased working frequency and coil distance. However, the mean temperature decreased with increased air gap between the coil and work roll surface. The mean value increased following a power function with increases in source current density, and increased linearly with induction heating time after the initial heating stage. A new formula was proposed and implemented to predict the mean work roll temperature based on induction heating parameters in order to control the surface temperature. The results predicted by the model agree well with measured values and the model proposed is reliable. Furthermore, the proposed equation is beneficial for calculating and controlling the value of any one influencing parameter, if the other three parameters and the ideal mean temperature of induced heating are known.

Keywords : finite element method; induction heating; temperature; work roll; strip rolling.

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