PLASMA REDUCTION OF CHROMIUM ORE

摘要

Smelting reduction of chromite ore has been studied in a small scale labortatory Ar-H2 transferred arc plasma furnace. A graphite crucible was used in carbon bearing pellet reduction experiments and the water cooled Cu crucible was used for the controll of C content in hydrogen reduction experiments. The carbon bearing chromium pellet which was prereduced in rotary kiln (Rist) was used in order to reduce the burden of plasma furnace or secondary reduction furnace. In recent years, some metallurgical processes have been studied for the production of alloys with concentration corresponding to the stainless steel range by reduction of chromite ore in iron metal bath. Recently, carbothermic reduction process in Fe-Cr alloy has been widely proposed, because of the much savings of the free energy by the reduction of chromite ore into the carbide form. Several studies have also been made of both the theoretical and practical of pyrometallurgical processes for controlling the chromium to iron ratio of the raw materials. The activity of chromium in Fe-Cr-C alloys which was the most important ternary system of chromium steelmaking was calculated by a thermodynamic data on the behaviors of solute atoms such as C, Cr, Si, Mn, Ni, P, N etc. The object of this study was to check the influence of chromium activity in metal bath by addition of several elements in chromite reduction. The composition of metal bath was controlled by addition of Fe-Si, Fe-Si-Mn, Ni, Cu, Fe-P, N etc. The amount of each composition was adjusted by the 5 steps by increasing form 1 percent to 5 percent. Chromium activities, acr, are decreased a little by increasing the elements Si, Ni, P, N addition, but the acr is on the contrary increased a little by the addition of Cu. Most of all by the addition of carbon in Fe-Cr alloy, acr is considerably decreased by the function of carbon.