Abstract
Relatively pure chromite from the South Africa was reduced with graphite powder in the atmospheres of CO, Ar, and a vacuum, and the differences in the reduction behavior were investigated. Then, the reduction with flowing CO gas was also studied to compare with the former.
The results are as follows:
1) The reduction process of the chromite with graphite consisted of the following three stages in every atmosphere used:
(Mg, Fe) (Cr, Al, Fe) 2O4→ (Mg, Fe) (Cr, Al) 2O4→Mg (Cr, Al) 2O4→MgAl2O4+MgO
2) In the 1st and 2nd stages, the reduction rate was about the same for CO and Ar atmospheres, while it was much lower in vacuum. On the contrary, in the 3rd stage the rate was the highest in vacuum, followed by Ar, and finally by CO atmospheres.
3) Below 1100°C, carbon deposition was observed during the reduction with graphite in the CO atmosphere and with flowing CO gas.
4) The amount of carbon dissolved in metal by carburization during the reduction with flowing CO gas increased with temperatures up to 1200°C, but decreased above 1250°C.
5) The reduction with the flowing CO gas was much slower with graphite. The reduction in this process indicated a preference of the iron oxide over the chromic oxide.
