US1354490A - Production of ferromanganese - Google Patents

Description

Josnrr-r JOHNSON, $131., OF NEW YORK, N. "5. DEARGARET HILLES JOHNSON EXECU- TRIX 01 SAID JOSEPH E. JOHNSON, 31%., DECEASED.

PRODUCTION OF FEBBOMANGANESE.

To all w ham it may concern:

Be it known that l, JosnrirE. JoHNsoN,

Jr., a citizen of the United States, residing at New York, in the county of New York,

State of New York, have invented certain new and useful Improvements in Production of Ferromanganese; and I do hereby declare the following to be a full, ,clear, and exact description of the invention, such aswill enable others skilled in the art to which it ap aertains to make and use the same.

l erro-manganese alloys are used in large quantities in the manufacture of steel. it is desirable to have them high in manganese and low in carbon for two reasons, to wit 1 First, the lower the percentage of manganose in the ferro-manganese alloy, the more troublesome and expensive is its employment as an addition in-the manufacture of steel; for the reason that as the percentage of manganese in the ferro-manganese alloy declines, the total amount of the other constituents of the alloy increases, thereby introducin into the steel a correspondingly increase proportion of these other constituents 'of the alloy, with proportionate disadvantage. v

Secondly, it is found that the presence of a relatively large amount of carbon, in proportion to the manganese, in ferro-manganese alloys containing both iron and carbon, lowers the availability of such alloys in the manufacture of steel for many uses. For instance, in order to introduce into'a bath of molten iron or steel a sufficient quan tity of manganese, it is, in many cases, not feasible to employ, for that purpose, spiegeleisen, even though the spiegeleisen may have as high as 20%of manganese; for the reason that spiegeleisen having that content of manganese contains about 5% of carbon, so that to add to the steel a sufficient amount of spiegeleisen to give the steel the desired manganese content would involve, in many cases, the simultaneous introduction of an amount ofcarbon beyond the permissible limit. On the other hand, the carbon content of a manganese alloy containing both iron and carbon rises but slowly with increasing proportions of manganese in the alloy, so that a ferro-manganese alloy containing as high as 80% of manganese contains only 6 to 63 of carbon, for which reason, by the use of such an alloy, the op- ,Specification of Letters lPate iit.

Patented 1918. Serial No. 246,345.

erator is enabled to give to the steel the desired manganese content while restricting the amount of carbon simultaneously introduced to a feasible and acceptable minimum.

F or the foregoing reasons, standard ferroinanganese containing 80% of manganese had, for most uses, previous to the scarcity of manganese brought about by the present war, driven out commercially the use of low manganese alloys, even in the manufacture of high carbon steels.

The high grade manganese ores required, in accordance witn the methods practised in the art at the present time, to make the standard ferro-manganese alloy containing 80% of manganese occur in the United States in very limited amounts, whereas low grade manganese ores (that is to say, ores low in manganese) occur in much greater quantities.

Ferro-manganese alloys may be produced either in the electric furnace or in the iron blast furnace. Both of these methods, as at present practised, are open to serious objection. F or instance, in the electric furnace,.

the consumption of power is high, running from 6,000 to 10,000 kilowatt hours perton of manganese. The cost of this power, in many localities, exceeds, at present, the normal selling price. obtained for the manganese alloy in times of peace, so that the production of ferro-manganese alloys in the electrio furnace is, under present conditions, only feasible if an extremely high price can be obtained for the product, or where by reason of peculiarly favorable local condi tions, low costelectric power is available.

On the other hand, the production of ferro-manganese alloys in the ordinary iron blast furnace is accompanied with very considerable losses of manganese, due to the fact first, that the manganese has a greater affinity for silica and unites with it to form silicate of manganese, which passes out into slag, and secondly, that the manganese'is volatilized in very considerable amounts and passes out of the top of the furnace as a fume, which has been found to be practically irrecoverable. In the electric furnace, it is possible to greatly reduce the slagging loss and at the same time to have a relatively small loss from fume, bymaintaining the hearth temperature of the furnace sufficiently high. So also, the slagging loss of manganese may be reduced by increasing the heat in the smelting zone or hearth of the existing blast furnace, but this cannot be done in ordinary blast furnace practice without materially increasing the heat in the furnace shaft, and this increase in heat in the furnace shaft (where the normal temperaturejis, in any event, -unduly high) is found to increase the hearth in comparison with the amount "of low temperature heat simultaneously produced and which is only useful in the shaft.

In the case of the iron blast furnace, this i compensated to a'considerable extentby the fact that iron ore is reducible to a very large extent by the carbon monoxid gas generated in the hearth, and therefore, a large percentage of the total work of the iron blast furnace is done in the shaft by the reducing action of the carbon monoxidgas rising through it.

Different conditions, however, prevail in the reduction of manganese in manganese blast furnace practice. Carbon monoxid reduces manganese oxid to a much smaller eX- tent than it does iron oxid, and, therefore,'a much smaller portion of the total work of reduction takes place in the shaft, the far larger proportion of the reduction being effected in the hearth and by the direct action of carbon instead of by the action of carbon monoxid. Consequently, the requirements of heat in the hearth of the manganese blast furnace are greatly increased, whereas the requirements of heat in the shaft of the manganese blast furnace are relatively small. Consequently, blast furnaces for the production of ferro-manganese use about three times the amount of fuel per'ton of metal that is used in blast furnaces for. the production ofiron, although the amount of heat required for 'reduction'is but slightly greater than in the case of iron. sults in an enormous excess of heat in the shaft of the manganese blast furnacepas above indicated, and this excess of heat is accompanied by atrcmendous volume of gas, both of which conditions tend greatly to promote the volatilization of the manganese.

Furthermore, the conditions of high temperature, greater gas volume, and the pres ence of large quantities of manganese oxid fume have a violent destructive effect on the lining of the furnace, so that the life of the lining of a blast furnace for the production of ferro-manganese is but a fraction of the life of the same furnace when pro- This reof fuel that it canburn in the hearth, and.

any cause which leads to an increased consumption of fuel per ton of metal, reduces the metal output by a more than proportional amount. Consequently, inasmuch the fuel consumption in ferromanganese blast furnace practice is about three times as high as the fuel consumption in pig iron production, the metal output of ferro-manganese blast furnaces is only about one-third or lesstthan that of the same furnaces when used in the production in pig iron. This low output, together with the short life of the furnace lining, and the high cost for re-lining, increases very considerably the cost of making ferro-m anganese, over that of making pig iron, entirely apart from the cost of ferro-manganese ore.

A further consideration of importance is that lean ores require more fuel for their smelting than richer ones, so that as the ores ofmanganese become leaner, the fuel requirements rise still further, which adds to all of the unfavorable conditions hereinbefore described I have found that the difficulties described as existing in the production of ferromanganese in the blast furnace can be enormously diminished by a procedure which essentially and radically changes the heat conditions prevailing in the furnace, and particularly by a procedure which permits the operator'to proportion the amount of shaft heat and of hearth heat to one another according to their respective requirements.

Thus, I have ascertained that if the nitrogen introduced as a constituent of the air in the ordinary ferro-nianganese blast furnace practice is substantially diminished, or greatly reduced, so that the blast employed is rich in oxygen, it is possible to so radically alter the furnace conditions as to practically revolutionize the mode of operation of the furnace and the results obtained.

In the practice of the invention, I lower the relative amount of nitrogen and increase the relative amount of oxygen in the blast until I obtain an adjustment of the composition appropriate to the proportionate amount of hearth heat and of'shaft heat desired. The elimination of the nitrogen has the cumulative effect of increasing the amount of high temperature heat obtainable per unit of fuel and of reducing to an enormous extent the amount of gas which by its physical heat-carrying capacity serves to carry the heat out of the stack, Where it is necessa and desirable u into the W a P tionate reduction of the amount of gas per pound of metal passing out of the hearth.

In practice, I find that, by the practice of the'invention, I am able to reduce the amount of fuel to less than half of that now required in ferro-manganese blast furnace practice. So also, I very considerably reduce the manganese loss for the reason, first, that the reduction of the silica in the charge, due to the reduction of it in the coke, combined with the increased temperature in the hearth lessens the manganese loss in the slag so as to bring it down to a small percentage ofits present proportions, and, secondly, because the enormous reduction in the amount and temperature of the gas in the shaft of the furnace cuts down the loss of manganese by volatilization to a highly important extent.

Furthermore, the practice of the invention permits an important reduction in the expense for lining, maintenance, etc., for the reason that the reduced volume and temperature of thegases and the reduction of their content of manganese fume decreases the wear on the lining of the furnace to a fraction of its present amount. Furthermore,

because of the much smaller amount of fuel required and the smaller proportionate amount of gas evolved per pound of fuel, it is feasible to reduce the size of the furnace required for a given 011tput,t0 a fraction of the present size. The increased life of the lining, and the smaller size of the furnace required reduces the expense for refractories and for maintenance and overhead, to a fraction of their present amounts.

In addition'to the hereinbefore described advantages of the invention, it permits me to introduce certain other features not commercially practicable in the ordinary ferromanganese blast furnace practice. Thus,

.withthe increased hearth heat available, I

can reduce a considerable percentage of silicon and cause it to unite with the ferro-man- 'ganese with the result of forcing down the carbon contents of the alloy.

' I can, if so desired, add a further step to the process, by subjecting the alloy, while still in the liquid condition, but after it has been tapped off into a separate vessel, to the action of oxid of iron or oxid of manganese, or both, with the result that these oxids attack the silicon of the alloy and reduce it to silica, which, uniting with a portion of the oxid unreduced, passes ofi as slag, the metal reduced from the oxid entering the ri e w.)

ores which are excluded in the present practice.

lVhat I claim is:

l. The method of producing in a blast furnace, alloys of iron, high in manganese. which comprises blowing the furnace charge (containing carbon, iron and manganese) with a blast richer in oxygen and poorer in nitrogen than the atmosphere, the relative oxygen and nitrogen content of the blast being so proportioned that an increase in hearth temperature is produced sullicient to obtain the desired high manganese content in the alloy, with accompanying decrease in the amount and temperature of the gases traversing the shaft of the furnace, whereby manganese losses are diminished, and a saving of fuel per unit of alloy output is effected; substantially as described.

2. The method of producing in. a blast furnace, alloys of iron, high in manganese, and low in silicon and carbon, which comprises blowing the furnace charge (containing carbon, iron, manganese and silicon) with a blast richer in oxygen-and poorer in nitrogen than the atmosphere, the relative oxygen and nitrogen content of the blast be- .ing so proportioned that an increase in hearth temperature is produced sui'licie'nt to obtain the desired high manganese content in the alloy and'to likewise increase the content of silicon at the expense of the carbon content of the alloy and with accompanying decrease in the amount and temperature of i the gases traversing the shaft of the furnace, and then treating the resultant alloy product while still in a liquid condition with a silicon-oxidizing sla thereby lowering the proportion of silicon in the final alloy product; substantially as described.

3. The methodof producing in a blast v furnace, alloys of iron, high in manganese and low in silicon and carbon, which,com prises blowing the furnace charge (containing carbon, iron, manganese and silicon) with a blast richer in oxygen and poorer in nitrogen than the atmosphere, the relative oxygen and nitrogen content of the blast being so proportioned that an increase in hearth temperature is produced suiiicient to obtain the desired high manganese content in the alloy and to likewise increase the connace, and then treating the resultant alloy product While still in a liquid condition with a silicon-oxidizingslag comprising at least one of the oxids ot' the constituent metals of the alloy other than silicon, thereby loweringthe proportion of silicon in the final alloy product and introducing therein an additional proportion of the metal of the reduced oxid; substantially as described.

4. The method of producing in a blast furnace, alloys of iron, high in manganese, and low in silicon and carbon, which comprises blowing the furnace charge (containing carbon, iron, manganese and silicon) with a blast richer in oxygen and poorer in nitrogen than the atmosphere, the relative oxygen and nitrogen content of the blast bein so proportioned that an increase in hearth temperature is produced sulficientto obtain the desired higlrmanganese content inthe alloy and-to likewise increase the content of silicon at the expense of the carbon content of the alloy and with accompanying decrease in the amount and temperature oi the gases traversing the shaft of the furnace, and then treating the resultant alloy product while still in a liquid condition with a silicon-oxidizing slag, comprising oxid of manganese, thereby lowering the proportion of silicon in the final alloy product and raising the proportion of manganese therein; substantially as described.

In testimony whereof I attix my signature.

JOSEPH E. JOHNSQN, JR,