Recovery of Chromium from Scrap.
Hennion-FJ; Debarbadillo-JJ; Ahmad-UMU
U S Pat 4 259 296 1981 Mar; :
Chromium is recovered from superalloy scrap by melting, oxidizing to slag-off the reactive metals, sulfidation, and slow cooling to produce a coarse-grained solid containing chromium predominately as chromium sulfide. The sulfiding agent is elemental sulfur or a metal sulfide. The s content should be twice the stoichiometric amount needed to combine with the chromium, but 20-30 pct of that needed for the entire matte. Thus, 6 kg of a melt containing ni 59 and CO 14.6 pct was held at 1,560 deg c, and 1.875 Kg of nickel sulfide was added. The power was turned off, 1.5 Kg of sulfur briquets was added, and the matte was cooled at 130 deg c/h. The cooled structure consisted of four phases: (1) a chromium sulfide phase containing 40 pct cr; (2) a nickel sulfide phase containing 0.1 pct cr; (3) a heavy-metal sulfide phase containing 3 pct cr; and (4) a metallic phase containing 0.06 pct cr.
U.S. Pat. 4,259,296, Mar. 31, 1981; Chem. Abstr. 94:87,872Y