US2361925A - Preparation of manganese products - Google Patents

Description

Patented Nov. 7, 1944 UNITED STATES PATENT OFFICE PREPARATION OF MANGANESE PRODUCTS Herman A. Brassert, Washington, and James C. Hartley, Norwalk, Conn., assignors to Minerals and Metals Corporation, New York, N. Y., a

corporation of Delaware No Drawing. Application July 4, 1942, Serial No. 449,786

12 Claims.

. production of substantially pure manganese and its conversion into solids of such density that there is not the usual tendency to disintegrate when exposed to the atmosphere, all without fusion of the manganese and at comparatively low temperatures and pressures.

An important object of the invention is to provide tablets of substantially pure manganese and of predetermined weight which will maintain their purity and structural integrity over long periods of time and thus facilitate the charging of predetermined amounts of manganese into a molten metal bath, either for the purpose of producing manganese steels and other alloys or for the deoxidation of steel or other molten metals.

Other objects of the invention will appear from a consideration of the following description of typical procedures in practicing the process and producing the products of the invention.

In practicing the novel process of the present invention to produce the novel products, manganese ore is first treated to eliminate naturally occurring impurities such, for example, as gangue and earthy or siliceous materials, if such materials be present, and the ore is then treated to recover therefrom oxides of manganese in a substantially pure state. These manganese oxides are then reduced to substantially pure manganese by heating in the presence 4 of reducing agents at a temperature below the fusion temperature of manganese, thus producing a man ganese sponge or powder.

An important feature of the present invention is our discovery that, if this finely divided freshly reduced manganese be consolidated while said manganese is still hot from the reducing operation, is still substantially free of any surface contamination and, therefore, is of higher than ordinary chemical activity at the surface and while it is still maintained in a protective atmosphere, a comparatively dense solid may be produced quickly and with a comparatively low pressure. By thus consolidating the freshly reduced, comparatively pure manganese immediately after reduction, we have been able to obtain tablets of pure manganese of such density and of such compactness and imperviousness of surface that the tendency to oxidize and disintegrate, characteristic of manganese solids produced in other ways, is substantially absent.

One object of the invention, therefore, is to produce substantially pure manganese in tablets, briquettes or other suitable solid shapes, of substantially predetermined weight and specific gravity, which are of such character as to be substantially self-protecting.

In order, however, to make a still more durable manganese solid, facilitating the convenient storage and use thereof, the invention contemplates also providing a protective coating for the improved tablets thus produced, preferably a coating of a substance which prevents oxidation of the tablets before use and which at the same time is either harmless or beneficial to the melt when the tablets are added to a bath of molten metal, such, for example, as molten iron in the production of steel. Although the manganese core of the coated manganese tablet just referred to is preferably prepared in the manner hereinabove set forth, namely, by consolidating the freshly reduced manganese while it is still hot from the reducing operation, is still substantially free of any surface contamination and therefore of higher than ordinary chemical activity at the surface and is in a protective atmosphere, it will be apparent that some of the advantages of the coating feature of the invention may still be obtained, even when pure manganese is consolidated in other ways, as, for example, after cooling and reheating in protective atmospheres. In the latter case, however, it will obviously be more important to apply the protective coating since, unless the consolidation of the reheatedmanganese be effected in some such manner as that set forth in U. S. Patent to H. A. Brassert, No. 2,291,685, granted August 4, 1942, the structure will not have the self-protecting characteristics of that produced in accordance with the preferred method of procedure.

If the manganese ore, as mined, contains a high percentage of gangue, it is crushed and subjected to a cleaning treatment, such, for example, as jigging, flotation, eiectrostatic cleaning, or any other desired process for removing the undesirable components. If the natural ore is of a high degree of purity, this preliminary cleaning step may be omitted.

The cleaned and partially purified ore is then crushed to about 40 mesh size, or even finer, and then may be treated in any of a number of ways to separate the manganese oxide from such other components of the ore as iron oxides. For example, the finely divided ore may be treated in accordance with the known processes disclosed in the Bradley Patents Nos. 1,973,508, 1,951,341 and 2,074,013, in order to produce substantially pure manganese dioxide.

Generally the processes disclosed in the Bradley patents consist of reducing manganese dioxide (MnOz) to manganese oxide (MnO) at about 750 F., this temperature being too low to reduce the iron oxides present in the are below the F6304 state, then leaching out the manganese oxide with ammonium sulfate, thereby leaving the iron oxides unattacked and available for concentration by magnetic separation or other known means of beneficiation. containing manganese sulfate is treated with ammonia gas and aerated to produce manganese dioxide.

Alternatively, if desired, the partially purified manganese ore, ground to the desired degree of fineness, may be treated with chlorine gas or chlorine liberating compounds or other halogens or halogen compounds such as fluorine, bromine and iodine, at temperatures suitable to form the chlorides, fluorides, bromides or iodides of manganese and iron. These halides of iron and manganese may then be separated by a fractional distillation in order to separate and recover substantially pure manganese halide and iron halide. The manganese halide may be oxidized to manganese dioxide and the halogen recovered.

If it is not desired to separate all of the iron from the manganese, for example, when treating manganese ores having such low iron content that the expense of such separation is not Justified, the ore may be treated with an acid such as sulfuric acid to dissolve the manganese and iron. The manganese and iron may then be precipitated from the solution with ammonia gas or by lime or alkali added to the solution or by other leaching methods to recover the manganese and iron as substantially pure oxides.

In accordance with this invention. the substantially pure manganese oxide in a pulverulent state is reudced to metallic manganese by treatment at a temperature sufficiently high to reduce the manganese dioxide to powdered manganese,

but sufficiently low to prevent fusion of the powdered manganese. Suitable methods and apparatuses for treating the manganese dioxide are disclosed in U. S. Letters Patent to Herman A. Brassert Nos. 2,252,697, 2,290,734, 2,277,067 and 2,291,685, and in U. S. Letters Patent to Brassert and Hartley application No. 2,296,498, granted September 22, 1942. In U. S. Letters Patent No. 2,291,685, a method is described of forming cakes or tablets of manganiferousmaterials which are specifically adapt ed to be used as a deoxidizing and/or alloying addition to liquid steel in furnaces or ladies. In the other applications mentioned above. a reduced metallic powder is compacted either con: tinuously as, for example, by extrusion, or by a pressing or ramming process, although in these applications the processes relate more particularly to the treatment of iron sponge or powder. As hereinabove pointed out, we have discovered The leaching solution that if finely divided freshly reduced manganese be consolidated while said manganese is still hot from the reducing operation, is still substantially .self-sustaining, which have a predetermined shape, size and weight and which have a surface density and compactness much greater than hereofore obtainable when it has been attempted to consolidate manganese powder, not freshly reduced and uncontaminated, at much higher pressures. These cakes or tablets, which can conveniently,be formed in the manner and by the means set forth in the application of H. A. Brassert, Serial No. 369,053, filed December 7, 1940,

uct directly from the freshly reduced manganese without further treatment.

Because, however, of the marked tendency of manganese to combine with oxygen, it will often be desirable, particularly when the tablets are of such size that there is a considerable area of exposed surface, further to protect them against oxidation and disintegration. When, therefore, conditions are such that it is desirable to provide further protection for the manganese cakes or tablets, they may be coated by dipping or spraying with a suitable material which will not introduce desirable elements into the finished steel. This coating may be of a volatile nature, such as, for example, an oxygen excluding coating of ammonium chloride. Likewise, other compounds, such as sodium fluoride, nitrates or borates, having a melting point similar to the temperature of a bath of steel, may be used. Fluxing agents, such as desulphurizing agents. which are beneficial in the purification of steel, may be used advantageously. Coatings of organic compounds, such as, for example, cellulose derivatives, also serve to prevent disintegration of the tablets. An oxidation resisting surface can also be provided by treating the surfaces of the tablets with a compound such as a fluoride which will react with the pure manganese to provide the inert compound on the surface of the tablet.

Although the tablet to be coated is preferably prepared in the manner hereinabove set forth, it will be obvious that the coating hereinabove described may be used to advantage with tablets which have not received their full consolidation in the preferred manner hereinabove described, such, for example, as tablets made in accordance with the process described in U. S. Letters Patent to H. A. Brassert No. 8,291,685, granted August 4, 1942.

While it is preferred to form the tablets of substantially pure manganese, alloys of manganese may also be produced by adding the alloying elements to the substantially pure manganese powder prior to compacting or before or after reduction or! the ore. For example, it may-be desired to provide a conveniently usable ferromanganese containing about 80% of manganese.

'Assuming that an iron-manganese ore contains only about 37% of, manganese, the desired ratio may be obtained by, adding to the unreduced or reduced ore, respectively, a sufficient quantity of the purified manganese oxide or manganese to provide the desired iron-manganese ratio. It is feasible to form such alloys by the addition of reducible compounds of the alloying elements in finely divided form to the manganese oxides prior to the reduction of the manganese oxide and reduce these compounds concurrently with the processed manganese oxide. In many cases, such concurrent reduction results in a more favorable thermal balance. For example, in the production of a manganese-copper alloy, the addition of copper oxide, the reduction of which is exothermic, provides a favorable offset to the endothermic reduction of the manganese oxides to metal.

From the foregoing description of typical processes embodying the invention, it will be apparent that we have provided a novel method of obtaining a stable and resistant manganese product and a novel product which has great utility in the production of manganese steels and other alloys and for the deoxidation of steel or other liquid metals. It will be evident that a much more convenient method of adding manganese to a molten steel bath has been provided, because the manganese, being in the form of tablets of known weight, will make it unnecessary to weigh the charge of manganese. Addition of a specified number out tablets will serve to accurately control the manganese concentration. It will be understood also that an economical method of refining and reducing lean manganese ores to substantially pure manganese has been provided, thus making possible the recovery of manganese from large bodies or deposits of ore which hitherto have been disregarded because of their low manganese content.

It should be understood that the process is susceptible to considerable variation, particularly in the methods of purifying and concentrating the manganese values prior to reduction to metal and that, therefore, the examples given above should be considered as illustrative only and not as limiting the scope of the following claims.

This application is a continuation in part of our application Serial No. 327,244, filed April 1, 1940.

What is claimed as new is:

1. The method of preparing substantially pure manganese, comprising reducing manganese oxide in finely divided state to metallic manganese, forthwith directly compacting the finely divided metallic manganese only into dense tablets of predetermined weight while still in its freshly reduced condition and still retaining the residual heat from the reduction operation, and coating the tablets with a substantially impervious materialwhich is inert with respect to the tablet material.

2. A method of preparing substantially pure manganese, comprising reducing finely divided, substantially pure manganese oxides to manganese below fusion temperature, forthwith directly compressing the manganese only into a tablet while in its freshly reduced condition and still heated, and coating the tablet with an oxygen impervious substance which is beneficial to molten iron.

3. A method of preparing substantially pure manganese, comprising reducing finely divided, substantially pure manganese oxides to manganese powder at less than fusion temperature, forthwith directly compressing the freshly reduced powder only into a tablet while still retaining the residual heat from the reduction operation, and coating said tablet with a fluxing agent which will exclude oxygen from said tablet.

4. A method of preparing substantially pure manganese, comprising compressing finely divided. substantially pure freshly reduced manganese only, while still heated from the reduction operation, into a solid tablet of predetermined weight, density and elemental composition, and coating said tablet with a substance excluding oxygen from said tablet.

5. A method of producing a substantially pure manganese, comprising reducing manganese oxides in powdered form to metal at a temperatur below the fusion temperature of manganese, forthwith directly compressing said freshly reduccd metal only into tablets while still heated, and coating said tablets with a non-metallic substance to exclude oxygen from said tablets.

6. A manganese product consisting of a tablet comprising a core of compressed substantially pure manganese powder and an oxygen-excluding surface coating of a substance which is volatile at the melting point of iron or steel.

'7. A manganese product consisting of a tablet comprising a core of independently compressed substantially pure freshly reduced manganese powder and an oxygen-excluding surface coating of a flux.

8. A manganese product consisting of a tablet comprising a core of independently compressed freshly reduced manganiferous powder and a surface coating of a non-metallic material.

9. A manganese product consisting of a tablet comprising a core of independently compressed freshly reduced manganiferous powder and a substantially air-tight surface coating of a salt which is inert with respect to the tablet material.

10. A method of preparing tablets of substantially pure manganese which consists of reducing manganese dioxide to substantially pure metallic manganese at below fusion temperature, forthwith directly compacting said freshly reduced metallic manganese to tablets or cakes, while still retaining the residual heat of the reduction operation and coating said cakes or tablets with a substance which will prevent re-oxidation of said metallic manganese at ordinary temperatures.-

11. A method of preparing tablets of substantially pure manganese which consists of reducing manganese dioxide at below fusion temperature to substantially pure metallic manganese, forthwith directly compacting said freshly reduced metallic manganese to tablets or cakes, while still retaining the residual heat of the reduction operation and coating said cakes or tablets with a substance which will prevent .re-oxidation of said metallic manganese at ordinary temperatures.

12. A method of preparing tablets of manganese alloys comprising reducing manganese oxide in finely divided state to metallic manganese, adding to said metallic manganese in finely divided state and predetermined proportions alloying elements and forthwith compacting the finely divided metallic manganese and said alloying elements while hot into dense coherent tablets of predetermined composition and weight, and coating said tablets with a, material which will substantially protect said alloy from oxidation until such time as it is brought into contact with 'a bath of molten steel or iron.

HERMAN A. BRASSERT. JAMES C. HARTLEY.

cERrIFIcATE or connncrzon.

o November 7 191414. mm A, BRASSER'I', gr AL.

Patent No; 2,361,925.

It is mreby-oer'tified that error appears in the printed specification of the above mmbered patent requiring correction as followe Page 2 first column, lire 35, for rehdced recu -reduced; and second column, line' 28, for desirab e reed, -'-undesireb1e-; 1in e M for"the" before "inert' read. "anline 55, for "No. 8,291,685" read --No. 2,291,685"; and. that the said Lettere-Peteht should be read with ibis correction therein that the same may conform to the record of the case in the Patent Office.

Signed. and sealed. this 16th "d y of January, A. p, 1915..

Leslie Frazer (Seal) Acting Commissioner of Patents.