Investigation of Decarburization Behavior in RH-reactor and Its Operation Improvement

Abstract

In order to investigate the decarburization behavior in the RH-reactor, the samples of bulk steels and splashed metals were directly taken from the vacuum vessel by the use of a specially designed sampler in addition to the conventional ladle samples.
The analyses of samples have revealed that (i) the carbon content of the bulk steel is uniform throughout the vacuum vessel and (ii) the carbon content of the splashed metal is almost the same as that of the bulk steel. On the basis of the results obtained, several decarburization mechanisms were examined and a new decarburization model has been proposed. In this model, it is assumed that the C-O reaction in the bulk steel is affected by the static pressure of the vessel and also by the evolution pressure of CO bubbles, therefore the reaction gradually decreases with the progress of decarburization. This mechanism covers the reason of low reaction rate in the final stage of decarburization.
Along with the discussions of the mechanisms, a new method to measure the circulation flow rate of molten steel has been established and also a new equation which is able to make more precise estimation of the flow rate has been derived. A few experiments have been made with the 100t RH-reactor in Hirohata Works, NSC to accelerate the decarburization rate. It has been found that the use of oval shape snorkels is effective in the early stage, and that argon blowing from the bottom of vacuum vessel is effective in the final stage of decarburization.