Effects of Both Flux Compositions and Oxidizing Conditions on the Dephosphorization of High-chromium Hot Metal by Using CaO-CaF₂ Based Fluxes

Abstract

Owing to the spread of using coke for melting of stainless steel scrap and smelting reduction of chromium ore in the stainless steel production, it is thought that the development of an inexpensive and effective method of dephosphorization of chromium-containing hot metal is a necessity. In this study, the dephosphorization was investigated by a method of injecting the powder mixtures of lime and fluorspar with the carrier gas containing oxygen into chromium-containing hot metal. The results show clearly that even with about 30 mass% of chromium content, effective dephosphorization is possible. A powder mixing ratio of lime to fluorspar of 1/1 by weight has been found to be favorable, and under optimum oxidation conditions, chromium oxidation loss has been kept at 0.1 mass% or below at the chromium content of about 30 mass%. Finally, from a thermodynamic viewpoint, the oxygen potential of the dephosphorization with high chromium content levels has been considered to be determined by the formation reaction of CaO·Cr₂O₃.