Specialized metallurgical processes – compositions for use therei – Processes – Electrothermic processes
Patent
1981-03-06
1982-12-14
Rutledge, L. Dewayne
Specialized metallurgical processes, compositions for use therei
Processes
Electrothermic processes
75 89, 75 90R, 420434, C22B 4700, C22C 2800
Patent
active
043636578
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a process for obtaining manganese- and silicon-based alloys by silico-thermia.
It is known to manufacture manganese-based alloys such as ferromanganeses having a low carbon content of from 0.02 to 2% (so-called "overrefined" and "refined" ferromanganeses) by a silico-thermal reaction between a liquid phase, obtained by the reducing fusion of a manganese ore and lime, and a silico-manganese containing from 10 to 45% of silicon. Although the manufacture of these silico-manganeses having an average silicon content is relatively simple, their use is accompanied by several disadvantages. In particular, if the silico-manganese is manufactured in advance and stored in the solid state, for example during periods of the year when hydro-electric power is abundant, it is necessary to remelt from 1.2 to 9 tons of ballast constituted by the alloying elements (iron+manganese) per tons of useful silicon at the time of use.
A process for the silico-thermal reduction of manganese ore has been described, in particular, in U.S. Pat. No. 3,347,664 (assigned to Union Carbide). In that process, and in numerous similar processes in which a molten mixture of manganese ore and lime is treated with a silicon-based reducing agent, a non-exhausted slag whose manganese content can be as high as from 20 to 25% if carrying out silico-thermia and from 30 to 35% if carbonized ferro-manganese (containing from 6 to 8% of C) is produced by carbothermia, is obtained in addition to the metal. At present, these slags are cooled in ingot-molds, stored are retreated by electric furnace carbothermia at a later stage, giving an almost exhausted slag (less than 6% of Mn) and a silico-manganese whose Si content can range from 10 to 45% and which is reintroduced into a silico-thermia cycle. However, the substantial amount of heat contained in the liquid slag rich in Mn is all lost in this procedure and, moreover, a special furnace has to be set aside for the carbo-thermal exhaustion of this slag.
The main object of the process forming the subject of the present invention is to recover the manganese present in non-exhausted slags and to obtain a manganese-based alloy containing at least 60% and preferably at least 70% of manganese, the remainder being iron, silicon in a content of between 5 and 40% and preferably between 10 and 35% and the normal impurities: aluminum, calcium, carbon, sulphur, phosphorus in a total content not exceeding 5% and usually far below this value.
This process involves the following stages: usually from 20 to 35%, of manganese in oxide form, having a valency of approximately 2. more than 70% of silicon is added to the liquid slag. agitation. hand, and a metal having a manganese content of at least 60% and usually above 70% and a silicon content of between 5 and 40% and preferably between 10 and 35%, on the other hand, are separated by decantation.
The liquid slag may originate, in particular, from the reaction between a molten mixture of manganese ore and lime on the one hand and a silicon-based reducing alloy on the other hand, this alloy generally being a silico-manganese containing from 10 to 45% of silicon. The liquid slag which is generally called "non-exhausted slag" can contain from 10 to 40% and usually from 20 to 35% of manganese in a form similar to MnO. The other constituents of the slag are, in addition to the lime added as flux, alumina, silica and usually magnesia. The following typical composition can be given as a non-limiting example:
The silicon content of the reducing alloy should be at least 60% and preferably at least 70%. It can be as high as 98 to 99% in some cases. The remainder can be constituted essentially by iron, in which case it is a "ferrosilicon" or by manganese, in which case it is a so-called high-grade "silico-manganese". A silico-manganese having a high silicon content of this type can be obtained by various known methods and, in particular, by simultaneous fusion or mixing in the molten state of at least two metals or alloys which provide the elements needed
REFERENCES:
patent: 2810639 (1957-10-01), Kessler
patent: 3329497 (1967-07-01), Deadrick et al.
patent: 3347664 (1965-03-01), Bauer, Jr. et al.
Boscaro Louis
Bucher Jean-Philippe
Demange Michel
Dubrous Francis
Septier Louis
Hey David A.
Rutledge L. Dewayne
Societe Francaise d'Electrometallurgie "Sofrem"
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