US1480267A - Process for the manufacture of manganese or of manganese alloys poor in carbon and silicon - Google Patents

Description

Patented Jan. 8, 1924.

UNITED STATES PATENT OFFICE.

no MICHAEL STURE KALLING AND SVEN DAGOBERT DANIELI, OF TROLLHATTAN,

SWEDEN, ASSIGNOBS TO AKTIEBOLAGET FEB-BOLEGEBINGAR, OF STOCKHOLM, SWEDEN, A LIMITED JOINT STOCK COMPANY.

PROOESS FOR THE MANUFACTURE OF MANGANESE OR OF MANGANESE ALLOYS POOR IN CARBON AND SILICON.

No Drawing,

To all whom it may concern:

Be it known that we, Bo MICHAEL S'rURE KALLING and Swan DAGOBERT DANIELI, subjects of the King of Sweden, residing at Trollhattan, in the Kingdom of Sweden, have invented new and useful Improvements in Processes for the Manufacture of Manganese or of Manganese Alloys Poor in Carbon and Silicon, of which the following is a specification.

The present invention relates to a process for the manufacture of manganese, or manganese alloys, poor in carbon and silicon, especially those with low percentages of phosphorus and iron, from manganese ores, whose principal content of manganese occurs in the form of oxides of manganese, in which the average degree of oxidation of the manganese is higher than is represented by the formula MnO, such for example as manganese ores which contain one or more of the minerals braunite, hausmannite, pyrolusite, polianite, psilomelan, or the like.

It is well known that manganese, or manganese alloys poor in carbon, can be manufactured in the following manner. Substances containing oxides of manganese, may be smelted with, or while in a molten condition brought into contact with silicon, or with alloys which contain silicon--preferably those containing more than 10% Si, as not until this percentage of silicon has been reached will the content of carbon have decreased sufficiently to be regarded as low, for example ferro-silicon,ferro-silicomanganese, ferrosilico-aluminium-manganese, etc.

In order that this method may be usable for the manufacture of manganese alloys, it is indispensable that the reduction with silicon should take place under such conditions that neither the reagents nor the products formed by the reaction shall be capable of absorbing any appreciable quantity of carbon. For obtaining this result one may for instance use an electric furnace, the lining of which does not contain any carbon and in which the heat generation takes place in a free electric are or arcs formed between two or several points of electrodes which are not in contact with the charge (for instance a furnace of the so called Rennerfelt-type). The chemical reactions which may take Application filed February 1, 1922. Serial No. 533,382.

place in the process in question may be expressed schematically by the following formula:

The reaction does not proceed quantitatively, but ceases when the relation between the content of manganous oxide in the sili cate slag formed, on the one hand, and the content of silicon in the manganese alloy formed, on the other hand, has reached a certain value, which value is a function of the content of silicon in the manganese alloy formed, and which relation increases accord ing as the content of silicon in the alloy decreases.

In order that the content of silicon in the alloy obtained shall be low, it is essential that the content of manganous oxide in the silicate slag simultaneously formed, shall be high. Hence it is obvious that the consumption of silicon per unit of weight of reduced manganese will be higher, according as the degree of oxidation of manganese oxide to be reduced increases.

In order that the process of reduction in question maybe carried out with the smallest possible consumption of silicon, and thus with the greatest possible economy, it is desirable that the degree of oxidation in the manganese of the manganese ore used shall be lowered as far as possible before the reduction with silicon is started.

It is conceivable that, inasmuch as it is well known that manganese oxides of a higher average degree of oxidation than MnO can be reduced to MnO with carbon monoxide or other reducing gases, a preparatory reduction of the ore with such gases might be practicable, However, in view of the practical difliculties of carryin out such a process on a large scale, this soIution can scarcely be of any but academic interest.

In accordance with the present invention, the problem is solved in the following manner :Manganese ore, whose content of manganese consists principally of man anese oxides with an average degree of oxidation above Mn(), is smelted with a quantity of reducin carbon sufficient to bind the oxygen which t e manganese oxides of the ore contain beyond the degree of oxidation MnO.

preciable This reducing carbon is in addition to the quantity of reducing carbon that may be combusted with the carbon dioxide and water which may be given off by the ore during the smelting, and which quantity must be ascertained by experimental tests in each individual case. It has in fact been definitely ascertained, that no appreciable reduction of metallic manganese takes place until practically all the manganese in the ore has been reduced to the degree of oxidation which corresponds to the formula MnO.

It is obvious that by the present process a manganese ore admirably adapted for reduction with silicon will be obtained.

As a rule, manganese ores of the kind in question usually contain larger or smaller quantities of metal oxides, which are more easily reducible with carbon than is MnO, for example oxides of iron. In case it is desired that the alloy poor in carbon and silicon shall have the lowest possible content of metals whose oxides are more easily reducible than MnO, it is advisable to increase the quantity of reducing carbon supplied in the smelting process, so that the bulk of the said metal oxides shall be re duced to metal. Curiously enough, no apuantity of manganesewill follow along in tie'reduction.

Certain manganese ores of the kind in question, though otherwise good, contain appreciable quantities of phosphorus. When such ores are reduced with carbon to metal, practically the entire phosphorus content of the ore is obtained in the metal.

If it is desired that the manganese alloy poor in carbon and silicon shall be as far as possible free from phosphorus, it 18 possiblc. by equivalent increase of the admixture of carbon in the preparatory treatment of the ore with reducing carbon in accordance with the present process (in spite of the fact that phosphorus-pent oxide is more difiicult to reduce than MnO) to have the phos horus practicallv speaking. totallv reduced. without entailing the reduction of am appreciable quantities of manganese. provided only that iron in sufficient quantities to bind the phosphorus so reduced is sin nltaneouslv reduced. Should the mannesc ore which, in accordance with the present process. is to be treated with reducing carbon. contain too low a percentage of iron in proportion to that of phosphorus, it is advisable. in smelting the manganese ore with reducing carbon, to add a suitable quantity of oxides of iron, for example iron ore. w

it i also evident from the above that manganese ores which. owing to too high a percentage of iron or too high a perccntaqe of phosphorus. or both. are otherwi e not adapted for the manufacture of manganese alloys, may be converted by the present containing manganese oxides (the manganese ores) should be supplied on the surface of a inolten bath of silicon heated to a suitable temperature, for example in the form of silico-manganese or high-per cent ferrosilicon. In that case, however, the reaction between the silicon ofthe alloy rich in silicon and the oxides of manganese ore can take place only in the surface of contact between the .alloy rich in silicon and the i manganese ore, and therefore the reaction must proceed comparatively slowly, and its speed will necessarily be lowered according as the concentration of silicon in the alloy, or the concentration of manganese in the ore, is lowered. In accordance with the present invention, the mixing of the reagents is effected in the following manner: silicon, for example in the form of silico-manganese or high per cent ferro-silicon, is successively supplied in finely divided form on the surface of a molten bath of the ore previously treated with reducing carbon.

Ever little grain of the silicon, or the alloy rich in silicon, is thus converted (as soon as the reaction between the silicon and the manganous oxide commences) into a little drop of silico-manganese alloy, the specific weight of which increases owing to i the {Qiringmfl' of silicon and the absorption of manganese. so that it becomes heavier than the molten manganese ore, and sinks dow'n through the latter. The surface of contact between the drops of silico-manganese and the molten manganese ore is, of course, comparatively large, and, if the concentrationpf manganous oxide in the molten ore is sufficiently high, and the path which the drop of silico-manganese has to traverse in its downward progress through the ore is sufiiciently long. practically all the silicon will have been oxidized during the fall of the drop. so that. manganese. or a manganese allov poor in carbon and silicon will collect under the cover of molten manganese ore. This result. however. is subiect to the condition that neither the reacting substances nor the reaction products are allowed durinc the process to absorb appreciable ouantifies of carbon.

Owin'r to the reaction of the motel drops with the molten manganese ore. the latter will be continuou ly deprived of manoanous oxide and enriched with silicon dioxid. so that the concentration of manganous oxide therein will eventually approach the limit when silicon is no longer oxidized to a satisfactory extent. The su ply of silicon must then be discontinued and the furnace emptied, whereu on-a new bath of manganese ore previous y reduced by smelting with carbon should be prepared, and the supply of silicon can be recommenced.

As experience has shown that the molten manganese bath need not be very deep, the process can also be performed in the following manner. To a shallow manganese bath (which as a rule remains in the furnace when it is tapped off) is supplied a mixture of unmelted, previously reduced manganese ore, preferably in a finely pulverized state, and finely pulverized silicon, for example in the form of an alloy, a mixture so adjusted that the Mn() concentration of the ore bath, owing to the successive supply of MnO entailed by the melting of the charge, and in spite of the successive absorption of silicon dioxide and reduction of manganese, is kept constant, until the furnace chamber is filled and must be emptied. This latter form of the process has the advantage that it is easier to protect the silicon of the alloy supplied against oxidation with free oxygen, and to prevent the Caking of the small grains of the silicon alloy used for the reduction.

The actual performance of the process can, of course, be carried out in any furnace of suitable construction, but the process may most conveniently be performed in electric furnaces of a suitable type, and in one of the following ways: Either by using a sin gle furnace in which a suitable qmmtity of manganese ore is first preparatorily reduced with carbon, whereupon the silicon is supplied on the surface of the bath of molten ore thus obtained, or else by preparatorily reducing the manganese ore with carbon in onefurnace, and thereu on either discharging it in a molten condition direct into another furnace, in order there to be treated with silicon, or moulding it, after discharge, in suitable receptacles, where it is allowed ts harden, in order to be transferred in a solid state-if desired, after grinding-to the second furnace, where the treatment with silicon is to take place.

Athird combination, in which the same furnace is used alternately for the production of previ'ously reduced manganese ore, which, after discharge, is allowed to harden, and for the reduction, with the aid of silicon, of preparatorily reduced ore, obviously coincides in principle with the latter of the above-mentioned alternatives.

It is obvious that, whichever alternative is selected, the lining of the furnace in which the reduction with silicon takes place, must not contain any appreciable quantity of carbon.

In the reaction between the preparatorily reduced manganese ore and the silicon, there is obtained, as above mentioned, a silicate slag which contains manganous oxide, and whose manganese content must be kept higher according as the silicon content in the manganese alloy poor in carbon is lower. It has, however, been found possible within certain limits to diminish the manganese content in this slag, provided the slag contains other bases. For example, it has been ascertained that two slags, one of which contained MnO and 30% SK), and the other 35% MnO and 30% Ca() as well as 35% Si(),, were in this respect equivalent.

The importance of this discovery lies principally in the fact that, per unit of weight of silicon consumed in the reduction, a smaller quantity of manganese in the form of slag, when lime (or other bases) is supplied to the process during the reduction with silicon is obtained, than when such bases are not supplied.

in the special case wherc a silico-manganese alloy is used as a reducing agent, it is possible to contrive that the slag precipitated as a byproduct shall not contain a larger quantity of manganese than can be entirely utilized for the manufacture of the quantity of silico-mangancse with which lho reduction of the preparatorily reduced inangancsc ore is effected. In the production of silico-nuingauese alloy from such slag, one can as a rule count on an output of manganese of not less than 99%. This entails the advantage that the present process can be employed without the precipitation, as a by-product. of slug which requires to be used for the numufacture "of other mangrancse alloys.

l reduction with silicon (where lime has been added in the process) of the preparatorily reduced manganese ore, it has been found that if the lime has been insuf' iicicntly burned, or, if after the burning it has been allowed to lie for some time before use, part of the silicon supplied will be oxidized by oxidizing gases present in the lime, such as carbon dioxide and water.

it has been found possible to obviate this drawback by supplying lime (or other bases) to the manganese orc simultaneously with the smelting of the latter with carbon. it has in fact been found, curiously enough, that a slag which in the aggregate consists of MnO and (laO as to over 90%, is comparatively easily smelted, while at the same time it does not (in contra-distinction from high-basic calcium silicate slugs) crumble into powder if kept for some length of time.

The fusibility is further increased by the presence of silicon dioxide, the content of which, however, need in no case exceed 15%. The fact that it has been possible to supply bases already in the first stage of the process also entails the advantage that limestone,

and silicon, (A) with the use of the process which is the subject of the present invention, and (B) with previously known processes.

For the sake of completeness, the formulae for the reactions which take place when the silicate slag, rich in manganous oxide, obtainedas a by-product, is worked up into ferro-slhco-manganese, are also appended.

A. Manufacture of ferro-manganese poor in carbon and silicon in accordance with the 7 process which is the subject of the present invention:

1. Preparatory reduction of the manganese ore with carbon.

(manganese ore with circa 6ll% Mn, (quartz) (burnt Fe and 5.5% SiCn) lime) 2. The reduction with silicon in the form of ferro-sihco-manganese of the manganese geducg carbon) 47M110.16CaO.FeO.6SiO, Fe MnC CO (preparatorily reduced Mn ore with (Spiegel iron (escaping MnO and 1.2% Fe) wit l 23% Mn) gases) ore preparatorily reduced with carbon with the addition of lime.

sumo-manganese alloy with 25% Si, M11, 0.8% c

3. The conversion of the silicate slag nese alloy.

(preparetorlly reduced manganese ore) (silicate slag with 33% Mn) (ferro-mnnsanese with 94% Mn 1% Si and 0.5% i.

22MnO.16CaO. i sio 4Si0, FeO 500 2MnO.16Ca0.9SiO Si Mn FeC 4900 (reducing carbon) iron be10nging to ducing carbon) B. Manufacture of term-manganese poor in carbon and 51110011 in accordance w1th previous known processes:

(silicoqnnnaanese alloy with 2 Si, 70% Mn and 0.8 carbon) (Mn-ore with circa 60% Mn, 5% Fe, 5.5%

2. Conversion of the silicate slag richin silico-manganese alloy:

(waste slag with 7% Mn.) (escaping Reduction of the manganese ore with silicon in the form of a silico-manganese alloy.

.20 (silicate slag with 55% Mn) (ferro-rnanganese wit circa 83% Mn, 0.8% C

and 1% Si) manganese, obtained as a by-product, into sa enn sio 14.07Si(),+ asses 57.66

(silicate slag with (quartz) (oxide of iron (reducing 55% Mn) accompanycarbon;

ing quartz and reducing carbon) 1.8a +0.92)Si ,Mn,,.Fe.C+ 154.7900 +5.72Mn +5.69%.

(lerro-silico-manganeso) On comparing the above formulae it will he found that:

(a) 1n the present process about 52% of the manganese content of the ore supplied to the process is recovered in the manganese alloy poor in carbon. while in the previous process merely somewhat over10% is obtained in the reduction with silicon.

(1)) Per unit of weight of manganese ob tained in the form of a manganese alloy poor in carbon, the consumption of reducing silicon is about 90% higher in the latter than in the former case.

(c) The consumption of ore per unit of (escaping gases) weight of manganese obtained in the form of manganese alloy poor in carbon. is in the latter case about 44% higher than in the former.

(d) The manganese content in the alloy poor in carbon obtained is about 10% higher in the former than in the latter case.

(6) The content of carbon in the former case is scarcely more than half as large as in the latter.

(f) In the latter case the silicate siag rich in manganese, obtained as a byproduct, contains so large a' quantity of manganese that it cannot be fully utilized for the manufacture of the equivalent quantity of silicomanganese alloy with which the reduction took place, whence it follows that, when the earlier process is adopted, the manufacture, in order to yield the best possible economic results, must be combined with the manufacture of, for example, ordinary ferro-manganese rich in carbon, or silico-manganese alloys. It should be observed that a manufacturing process which in order to pay, has to be combined with another kind of manufacture, as a rule, diminishes the value of the process.

It is to he understood that Wherever we have used the expression manganese in the specification and claims, this expression is intended to cover not only manganese as such, but also alloys thereof, and where we have used the expression manganese alloy it is intended to cover not only an alloy of manganese, but manganese as metal.

Having thus described our invention we declare that what we claim is:

1. The process of manufacturing manganese poor in carbon and silicon, and having low percentages of phosphorus and iron. which consists in smelting manganese ores in which the principal content of manganese occurs in the form of manganese oxides having an average degree of oxidation of the manganese higher than is represented by the formula MnO in an electric furnace with a quantity of reduction-carbon adapted to reduce the main part of the higher manganese oxides of the ore into manganous oxide a part of the eventually occurring iron oxides to iron and apart of the eventually occurring phosphoric combinations to phosphorus then reducing the prereduced manganese ore in an electric furnace by silicon in the form of alloys preferably having more than 10% of silicon, the latter reduction taking place under such conditions that the metal formed has no opportunity to absorb any appreciable quantity of carbon.

2. The process of manufacturing manganese poor in carbon and silicon, and having low percentages of phosphorus and iron,

which consists in smelting manganese ores in which the principal content of manganese occurs in the form of manganese oxides having an average degree of oxidation of the manganese higher than is represented by the formula MnO in an electric furnace with a quantity of reduction-carbon adapted to reduce the main part of the higher manganese oxides of the ore into manganous oxide a part of the eventually occurring iron oxi es to iron and a part of the eventually'occurring phosphoric combinations to phosphorus, then reducing the prereduced manganese ore in an electric furnace by silicon in the form of alloys preferably having more than 10% of silicon, said silicon being supplied in a finely pulverized state on the surface of a molten bath of prereduced manganese ore, the latter reduction taking place under such conditions that the metal formed has no opportunity to absorb any appreciable quantity of carbon.

3. The process of manufacturing manganese poor in carbon and silicon. and having low percentages of phosphorus and iron, which consists in smelting manganese ores in which the principal content of manga nese occurs in the form of manganese oxides having an average degree of oxidation of the manganese higher than is represented by the formula MnO in an electric furnace with a .quantity of reduction-carbon adapted to reduce the main part of the higher manganese oxides of the ore into manganous oxide, a part of the eventually occurring iron oxides to iron and a part of the eventually occurring phosphoric combinations to phosphorus, then reducing the prercduccd manganese ore in an electric furnace by silicon in the form of alloys preferahl hav iug more than 10); of silicon, the silicon being supplied in a finely pulverized state and mixed with pulverized prerednced manganese ore on the surface of a molten bath of prereduced manganese ore. the latter re duction taking place under such conditions that the metal formed has no opportunity to absorb any appreciable quantity of carbon 4:. The process of manufzu'turing manganese poor in carbon and silicon, and having low percentages of phosphorus and iron,'

which consists in smelting manganese ores in which the principal content of manganese occurs in the form of manganese oxides having an average degree of oxidation of the manganese higher than is represented by the formula llInO in an electric furnace with a quantity of reduction-carbon adapted to reduce the main part of the higher manganese oxides of the ore into manganous oxide, a part of the eventually occurring iron oxides to iron and a part of the eventually occurring phosphoric comhi nations to phosphorus, then reducing the prereduced manganese ore in an electric furnace by silicon in the form of alloys preferably having more than 10% of silicon, said silicon being supplied in a finely pulverized state and mixed with ulverized prereduced manganese ore and asic substances such as lime on the surface of a molten bath of prereduced manganese ore, the latter reduction taking place under such conditions that the metal formed has no opportunity to absorb any appreciable quantity of carbon.

5. The process of manufacturing man anese poor in carbon and silicon, and havmg low percentages of phosphorus and iron, which consists in smelting manganese ores in which the princi al content of manganese occurs in the orm of manganese oxides having an average degree of oxidation of the manganese higher than is represented by the formula M110 in an electric furnace together with lime and a quantity of rcductioncarbon adapted to reduce the main part of the higher manganese oxides of the ore into manganous oxide, a part of the eventually occurring iron oxides to iron and a part of the eventually occurring phosphoric combinations to phosphorus, then reducing the prereduced manganese ore in an electric furnace by silicon in the form of alloys, prc ferably having more than 10% of silicon, the latter reduction taking place under such conditions that the metal formed has no opportunity to absorb any appreciable quantity of carbon.

6. The process of manufacturing manganese poor in carbon and silicon, and having low percentages of phosphorus and iron,

which consists in smelting manganese ores in which the principal content of manganese occurs in the form of manganese oxides having an average degree of oxidation of man ganese higher than is represented by the formula MnO in an electric furnace together with lime and a quantity of reduction-car: bon adapted to reduce the main part of the higher manganese oxides of the ore into manganous oxide. a part of the eventually occurring iron oxides to iron and a part of the eventually occurring phosphoric combinations to phosphorus, then reducing the prereduced manganese ore in an electric furnace by silicon in the form of alloys preferably having more than 10% of silicon, said silicon being supplied in a finely pul; verized state on the surface of a molten bath of prereduced manganese ore, the latter reduction taking place under such conditions that the metal formed has no opportunity to absorb any appreciable quantity of carbon.

e process of manufacturing manganese poor in carbon and silicon, and having low percentages of phosphorus and iron, which consists in smelting manganese ores in which the principal content of manganese occurs in the form of manganese oxides having an average degree of oxidation of the manganese higher than is re resented by the formula Mini) in an electric urnace together with lime and a quantity of reduction'carbon adapted to reduce the main part of the higher manganese oxides of the ore into manganous oxide, a part of the eventually occurring iron oxidcs to iron and a part. of the eventually occurring phosphoric combinations to phosphorus, then reducing the prereduced manganese ore in an electric furnace by silicon in the form of alloys preferably having more than 10% of silicon, said silicon being supplied on the surface of the molten bath of prereduced manganese ore in a finely pulverized state and mixed with pulverized manganese ore, the latter reduction taking place under such conditions that the metal formed has no opportunity to absorb any appreciable quantity of carbon.

8. The process of manufacturing manganese poor in carbon and silicon, and having low percentages of phosphorus and iron, which consists in smelting manganese ores in which the principal content of manganese occurs in the form of manganese oxides having an average degree of oxidation of the manganese higher than is represented by the formulaMnO in an electric furnace togetherwvith lime and a quantity of reduction-carbon adapted to reduce the main part of the higher manganese oxides of the ore into manganous oxide, a part of the eventually occurring iron oxides to iron and a part of the eventually occurring phosphoric combinations to phosphorus, then reducing the prereduced manganese ore in an electric furnace by silicon in the form of alloys preterably having more than 10% of silicon, said silicon being supplied in a finely pulverized state and mixed with pulverized prereduced manganese ore and basic substances such as lime, on the surface of the molten bath of prereduced manganese ore, the latter reduction taking place under such conditions that the metal formed has no opportunity to absorb any appreciable quantity oi carbon.

In testimony whereof We have signed our names to this specification.

B0 MlCllllllL STURE KAhhlNG. SVEN DAGOBEB/l llANIEhl. W'itnesses v AUG. HAGELIN, E. NILON.