| Abstract: | A model is presented to predict the decarburization rate of electrical steels during reactive annealing. In a first step, the warm annealing atmosphere composition is calculated as function of the composition of the cold gas containing N2‐H2‐H2O‐CO‐CO2‐CH4‐O2. In a second step, the decarburization kinetics, which is controlled both by the surface reaction and by the diffusion of carbon towards the surface, is calculated. The model is then used to study the balance between surface reaction and the diffusion control of the decarburization process. We could conclude that for low sheet thickness and/or low H2O/H2 ratio in the annealing atmosphere, the decarburization is surface reaction controlled, while for commercial thicknesses and industrially applied dew points, the process is diffusion controlled. Furthermore, we looked at the difference in decarburization between complex N2‐H2‐H2O‐CO‐CO2 atmospheres used in industrial application, and N2‐H2‐H2O atmospheres typically used in lab annealing. We could conclude that the decarburization rate is influenced by the addition of CO and CO2 and that the final carbon level is increased if CO and CO2 are added to the gas. |
