Foaming Slag-Practice in Electric Stainless Steelmaking

• Based upon laboratory and industrial scale experiments aspects on foaming slag practice in stainless steelmelting are presented. Fundamentals of foaming and reduction of stainless steel slags are applied on the EAF process in an effort to determine key parameters which are verified in full-scale experiments. Finally, recommendations relating to these key parameters are determined and presented. Millscale injection is taken into special consideration since it is believed to have a benficial effect on foaming and chromium recovery. It is possible to utilize a foaming slag practice with low chromium losses (%Cr2O3 < 3) to the slag by controlled carbon and oxygen injection. The key to a successful operation is thorough process control with respect to the (total reductants)/(total oxygen) - ratio. Chromium oxidation during melt down is critical and should be minimized and C+O2-injection during refining should secure reducing conditions. The dissolved silicon content in the steel should be sufficient to protect chromium from oxidation during melt down and refining and, finally, to secure a slag reduction at tapping. Industrial scale trials also indicate millscale injection into the slag to promote the slag foaming and increase the chromium recovery. Evaluation has shown the operation to be cost effective. The extra chromium recovery is roughly 8 kg/tonne giving a net surplus of 4,5 US$/tonne and additional savings in reduced panel and refractory wear and/or decreased tap-to-tap time of 10-16%.

Ämnesord

TEKNIK OCH TEKNOLOGIER  -- Materialteknik -- Metallurgi och metalliska material (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Materials Engineering -- Metallurgy and Metallic Materials (hsv//eng)

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