Determining the Activity of the Components of the Slag System Formed in the Production of Chromium Alloys

Abstract

nents in the slag system SiO 2 ‐CrO x ‐MgO‐Al 2 O 3 (M/A = 2.00) at 1600 and 1700°C by using Knudsen’s effusion method and measuring the composition of the gas phase on an MS-1301 mass spectrometer. We used double effusion cells made of molybdenum and coated with iridium. The ratio of the area of the sublimation region to the effusion region was greater than 300. A standard specimen with a test element (or elements) of known activity was placed in one part of the effusion cell and the test specimen was placed in the other part of the cell. Temperature was measured to within ±5 K by an EOP-66 optical pyrometer. Slags of the investigated compositions were prepared by mixing SiO 2 or a “master slag” (34.2% SiO 2 , 44.8% MgO, and 21.0% Al 2 O 3 ) with pure oxide components. We introduced Cr 2 O 3 and metallic chromium into the specimens in a mass ratio consistent with the reaction Cr 2 O 3 + Cr = 3CrO. We determined the intensity of the ionic currents of components of the gas phase, which was in equilibrium with the test specimen. The partial pressures of the components above the specimen were found from the expression