A study has been made of the decarburization of electrical steels containing various amounts of Si at temperatures from 700℃ to 950℃ in wet hydrogen atmosphere of dew points from 20℃ to 50℃.
Decarburization occurs principally by the reaction $C+H_2O=CO+H_2$. It was found that the oxidized layer of Si formed during annealing has an effect on the decarburization rate, and that the formation of the oxidized layer depends on the annealing temperature, $P_{H_2O}/P_{H_2}$ ratio, and Si content.
For electrical steels with low Si content (below about 0.5%), the decarburization rate at high temperature(above about 850℃) was more influenced by the change of the diffusion coefficient, which was caused by the phase transformation α→$\gamma$ than by the oxidized layer formed during annealing.
For electrical steels with high Si content (above about 2%), the decarburization rate was mainly influenced by the oxidized layer formed during annealing.
For electrical steels with high Si content (above about 2%), the decarburization rate was mainly influenced by the oxidized layer formed during annealing.
