Specialized metallurgical processes – compositions for use therei – Processes – Producing or treating free metal
Patent
1995-12-14
1997-12-30
Andrews, Melvyn
Specialized metallurgical processes, compositions for use therei
Processes
Producing or treating free metal
75503, 75540, 75623, 75708, 420116, C21B 1500, C21C 700, C22B 404, C22B 900
Patent
active
057025029
ABSTRACT:
A three-stage process for obtaining metallic Cr units insitu during the production of stainless steel. Raw chromite ore or a concentrate produced from chromite ore is mixed with a carbonaceous reductant and slagging agents are added to an iron bath (24) for smelting and refining in a refining reactor (10). During the first stage, partially metallized chromite is smelted by carbon in the reactor that is top-and bottom-blown with oxygen and oxygen-containing gases respectively to produce a chromium alloy bath having a carbon content well below saturation. In the second stage, the alloy bath is decarburized by being bottom stirred with the oxygen-containing gas to the final bath carbon specification. In the third stage, the alloy bath is reduced by a metalloid reductant such as silicon or aluminum and again bottom stirred but with a non-oxidizing gas to achieve a high chromium yield. The reactor includes a top lance (18) extending through a throat (14) with a lower portion (20) of the lance extending to a point just above the bath and means (22) such as a tuyere or porous plug mounted at or near a bottom (16) and extending through a refractory lining (12) for stirring the iron bath containing dissolved carbon. Lance (18) includes a central passage (34) for injecting a compact, focused jet oxygen gas (30) that can penetrate through a slag layer (26) for decarburization of the iron bath and an outer passage (32) for discharging an oxygen gas (28) above the bath for post-combustion of CO to CO.sub.2. Passage (32) includes a plurality of evenly spaced annular diverging nozzles (33). The lance also includes a pair of concentric conduits (36) and (38) for conducting a coolant.
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Kundrat David M.
Smillie Allan M.
Sussman Richard C.
Andrews Melvyn
Armco Inc.
Bunyard Robert J.
Fillnow Larry A.
Lorengo J. A.
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