US2070186A

US2070186A - Metal alloys and processes of making the same

Info

Publication number: US2070186A
Application number: US59690A
Authority: US
Inventors: Gilbert E Seil
Original assignee: BUFFALO ELECTRIC FURNACE CORP
Current assignee: BUFFALO ELECTRIC FURNACE Corp
Priority date: 1935-08-19
Filing date: 1936-01-18
Publication date: 1937-02-09
Anticipated expiration: 1954-02-09

Description

Feb. 9, 1937. G. E. sEIL METAL ALLOYS AND PROCESSES OF MAKING THE-SAME Filed Jan. 18, 1936 2 Sheets-Shea?l l :Snventor GILBERT E. SEIL (Ittorneg Feb. 9, 1937. G, E. sElL METAL ALLOYS AND PROCESSES OF MAKING THE SAME Filed Jan. 18, 1936 2 Sheets-Sheet 2 mn?, mE ws 3E l R E B L G ,i

Gttorneg Patented heb., 9, 1937 f Marat. .enters raoocsses or e 'run s Yon-lf.

amputation .tamtam is, icas, semi No. 59,69@ lin @a August i9, 1935 9 Cla.

A This invention relates to therening of metals, metallic material, or metal alloys. More particularly, it deals with the control of the ultimate content of desirable and undesirable constituents of metals and metal alloys, and the scope of the invention is broad enough to contain Within its purview not only novel processes, but products resulting from practicing such processes and possibly furnace structures in which such processes can be carried out.

The general object of this invention is to refine metallic material and/or metal alloys especially those containing adesirable constituent such as chromium, in a simple and readily controlled manner by which there is facilitated, to an exselective oxidation thereof. I

Another object of this invention is to bring labout this oxidation of impurities under conditions as nearly ideal therefor 'as possible'both as to speed of reaction and eiciency thereof, Anamely with the reactive materials in miscible solution and thoroughly mingled. A further object is to carry out this reacting of materials in solution in the presence of a carbon monoxide superatmospheric pressure to assure absence of air.

And a further very important object of the invention is to form in a heated reaction zone and exteriorly ofthe bath of metallic material to be refined, a highly concentrated oxidizing reagent for use in refining such metallic material. With respect to this reagent whose oxidizing component is a metal-oxide, an object is to effect first the reduction of a quantity of the'metal oxide (which may be in the form of ore) into metal, and second the dissolution in the thus formed metal as a solvent, o a quantity of the oxide present. Another object is to contact globules of the metal solvent With the oxide solute whereby there is exposed to the oxide surrounding the metal globules, abnormally large surfaces' per unit of weightfor thus facilitating the dissolving of the oxide in the metal. And a further object of this invention is to retain or confine and prolong close contact of the reagent forming materials in the reaction zone suiiiciently for the mass of material to be forced to temperatures (l) above which the reducing reactiontakes place to convert some of the metal oxide to metal, and 2) above the melting point of the metal at which the solubility of the oxide in the metal increases to a pointI where a substantial quantity of the oxide goes into solution Vin. the metal. To this end, another object is to vary in some easy manner the ratios or proportions of the reactive and l slag forming components in the zone where the reagent is formed. Still another object is to produce a metal refining oxidizing reagent which can bel sold as such and for other purposes. A still further 4Vobject is to correct the bath so that when the oxidizing reagent is added to the bath, the reagent will selectively oxidize the carbon or other oxidizable impurity in the bath with substantially no net concurrent. oxidation of desirable metal present, such as chromium.

The manner in which this invention may be essentially practiced comprises carrying it out in an electric furnace lhaving a hearth and a hollow electrode or electrodes adapted to have charges or burdens of comminuted reagent forming material, preferably formed into briquettes or cores, forced through the electrode toward the arc end thereof. In the hollow electrode a reducing reaction is caused to take place under controlled conditions for forming a highly concentrated reagent having as its essential components a reduced metal and a metal-oxide uniformly dispersed or dissolved therein. On the furnace hearth there is charged the metallic material or metal alloy to be rened where it is melted into a molten mass or bath whose essential components are a slag, anda metal containing one or more oxidizable impurities ('such as carbon sulphur, silicon, phosphorus, or manganese, or possible combinations thereof) desired to be removed from the metallic material of the molten bath. The reagent which is in liquid form and ls hotter than the molten bath drops repetitively to the bath where the miscibility of -the liquid reagent and the molten bath permits a rapid and extensive dispersion of the reagent throughout the bath. This dispersion results in the oxide of the reagent being reduced by the carbon or other oxidizable impurity in solution in the bath of metal or alloy to be refined. The reduction of the oxide frees the metal of the oxide to be added as increments thereof as metal to the 'molten alloy and the oxidation of the oxidizable impurities converts them into a gas, for instance carbon into carbon monoxide, and oxides such as SiO@ MnO, etc., which may enter the slag. This carbon monoxide gas and the carbon monoxide from the hollow electrode are evolved to such an extent that a super-atmospheric pressure is attained in the furnace for keeping out of the furnace any air. These stepsor reactions can be carried on continuously or repetitively for even though an intensely reducing reaction is taking place in the electrode, and anintensely oxidizing reaction is taking place in the bath on the hearth, and both of these zones are in one furnace, they are independently situated and each is outv of the range of inuence of the other. Correctives may be supplied to and used in the bath on the hearth for changing its reactive characteristics or for assuring the permeability of the slag to the reagent discharging into the bath from the arc end of the electrode. The refined metal or reconstituted alloy is recovered by separating it from its slag in the usual manner. Alloys are readily made by this process because the oxides of diierent metals can be fed to the electrode, or various metals can be melted on the hearth.

:l The formation of the reagent comprising mes -j t'allic oxide uniformly dispersed in metal is effectbeen disseminated into the metal or has gonen.

into solution in the metal: third, controlling the mobility or flowability of the coacting charge in the electrode so that the more fluid coactive material thereof as it becomes molten does not ow away from the unmelted material with which it is desired to have the melted material coact,

' or to discharge from the electrode until the desired disseminating or saturation of the reduced metal with the oxides takes place. This control is effected by feeding to the electrode along with the other starting materials certain substances called herein correctives. Various correctives can be used for this purpose and they may be used either to retard the mobility of the reacting mass within the electrode, or to accelerate it, as the case may be. In the embodiment of the invention shown and described herein, the oxidizing reagent is used for refining a bath of metal on the hearth of the same electric furnace wherein the reagent is formed, but it is possible to form the liquid reagent in one furnace, solidify it by cooling (preferably rapidly) and then use it for refining metal in another furnace by supplying the reagent to the molten bath of metal to be going will be set forth in the following description. In the accompanying drawings there has been illustrated the best embodiment of the invention known at present, but such embodiment is to be regarded as typical only of many possible embodiments, and the invention is not to be limited thereto. In the drawings, Figure 1 shows diagrammatically how the invention may be carried out essentially. Fig. 2 is`a vertical sectional view of a more preferred form of furnace for carrying out this'invention. Fig. 3 shows a vertical sectional view taken along the line 3--3 in Fig. 2.

Fig. 1 is self-explanatory and is intended t0 make visually identiable the various features described herein. In the arrangement shown more completely in Figs. 2 and 3, I0 represents the furnace, having a top II, side walls I2 and a hearth I3 made of suitable refractory material,

the nature of which will vary according to the use to which it is desired to put the furnace. The furnace is desirably heated by means of electrical energy and to this end there is provided an electrode or electrodes Ill which project through the side walls of the furnace in a substantially horizontal position, although the position of the electrodes may be changed. The electrodes are desirably formed with an axial passage or bore therethrough so that the electrode is hollow and thereby is adapted to receive and permit passage therethrough at a predetermined rate of charges or cores or cartridges C of predetermined composition; under predetermined heat conditions; and surrounded by an atmosphere of predetermined nature.

The arc section of the hollow interior or bore I5 of the electrode forms a reaction chamber or reagent forming zone as the electrode itself constitutes an electric furnace since the arc can be used to heat the arc section of the electrode to reaction temperatures. The reagent-forming raw material is preferably in molded form such as cores C and these cores are fed to the electrode` individually. For automatically feeding these cores to the electrode, one after another there is in existencean apparatus which carries out that function. Pairs of abutting electrodes are preferably used which may be of any desired composition such as graphite, carbon, or other suit able refractory material, for thus ecaciously providing the heating and reduction chamber or zone wherein the reagent of this invention is formed. A molten oxidizing material constituting the reagent I I dropping from the electrode is collected on the hearth I3 of the furnace. I6 indicates the molten bath of metallic material or alloy to be rened or reconstituted which is on the hearth I3 and this constitutes the refining zone of this invention. This bath is made up of metal or metallic material I8 having oxidizable impurities such as carbon therein, and slag I9. 20 indicates the furnace tap-hole, 2| indicates a draw-olf oi flue which may be used, if necessary, for conducting gases from the furnace, although it is .normal to maintain a super-pressure in the furnace.

The components of one o1' a group of cores C forcibly supplied to the electrode I4 comprise the reagent-forming materials including reactable reagents, correctives, and a binder for holding the components in core form. The reactable reagents include oxides of one or more metals (which may lbe in the form of ore containing gangue material); and a reducing agent composed of one or more such reagents as carbon, carbonaceous material, silicon, silicon-carbide or the like, the correctives are hereinafter described in detail.

As the charge is forced through the electrode and the heated zone thereof is encountered, the materialsof the charge while confined therein and exposed to a sufficiently high temperature undergo two changes, namely, a chemical reaction takes place between that predetermined amount of reducing agent present and as much of the oxide present as nds its chemical requirement in the reducing agent. That is, it is arranged in advance so that there will be only enough reducing agent present toreduce a portion of the oxide to metal, leaving a quantity of the oxide unreduced. The reaction products are reduced metal and an oxide. Also a physical change occurs, namely, the chemically formed metal fuses or melts and subsequently as increased temperatures are encountered lying above aovaisc the melting point of the reduced metal' the metal becomes an active solvent in which the unreduced oxide dissolves. After reaction between the reducing 'agent and the oxide has occurred, increments of metal are formed or released from the oxide and larger amounts of both oxide and reducing agent will dissolve. So with this in mind, the oxides selected for the reagent forming material fed to the electrode are chosen by considering whether or not these increments of metal released from the oxide to the bath are to be of the same metal or metals of the bath or diierent ones. Oxides usable for Athis purpose either alone or in combination are those oxides which are reducible by carbon such as manganese oxide,

' hromium oxide, iron oxide, silicon oxide and the ire. As the charge is in an openended electrode,

that part of the charge which melts first tends to run out of the electrode, or at least to iiow away from the place of its liquefaction. To overcome this, the presence of 'a corrective material in the charge is effective when it has the property of controlling, such as either retarding or accelerating as the case may be, the rate of flow of the entire mass. If the corrective is for conning or holding in place the components of the mass having lower melting points, as the temperature of the mass is increased, there is no escape of they been realized and the entire mass becomes iluid.

of 3MnO+SiO,+6C practically lno Such a corrective for this purpose might be called an antifiux, and include magnesia, lime. clay, aluminum-oxide, comminuted slag from previous runs, or mixtures of such slags. If the corrective is used for accelerating the mobility of the mass, its function is to maintain the relative positions of the reduced metal and the residue from the cores until a predetermined .temperature is reached, whereupon the mass, as a whole', flows from the electrode. These maybe termed iluxes and may consistv of silica, calcium silicate, iiuorspar; slags,` etc.

For instance, if a unitary charge were made up reduction would take place because the MnO.SiO, has such a low melting point that the manganese silicate would iiow out from the hollow electrode at a temperature below which neither the MnO or the S10, can bereduced with carbon.4 Thus, the tem-- perature at which the mass flows may precludel the reduction of the oxide. However, if one core is fed to the reaction zone made up of 3MnO+4C MnC+3CQ andthen if another `core is fed to the reaction zone made up of Si0,+2C- Si}-*2CO, the reduction takes place as indicated because the temperature at which the mass flows is highr enough to induce reduction of the metal oxide with the carbon. Or, conversely, where highly infusible material is present in the reaction zone, a ux can be added which by lowering the melting point of the refractory material will tend topermit the mass to flow instead of permitting selective flowing of the dierent materials. I

This tendency of some materials to melt and flow prematurely can be anticipated by analyzing the ingredients of the charge and referring to melting points of its various components and their combinations as given in the International Critical Tables. VFrom these tables it can be de? termined readily what ingredient to add and what quantity thereof is necessary to control to the quantity thereof to metal.

desired gure the melting or rather the flow point of the mass as a whole.

The melting of the reduced metal is insufficient to cause the metal oxide to dissolve therein. The temperature of the molten metal must be raised above its melting point to increase the solubility function or 'characteristics thereof to a point where the metal oxide is soluble therein, which is done bythe use of a corrective which controls the point at which the mass in the electrode becomes iiuid and thus detains the molten metal in the heated zone of the electrode until its temperature is raised high enough to permit the metal oxide to dissolve therein, whereupon the liquid mass escapes or ilows from the electrode.

The melting point of the metal to be formed in the electrode is known. It is known that at this temperature, the solvent action of the metal for the oxide is substantially zero. Therefore, depending upon the rate and/or temperature at which the desired reduction and dissolution is to take place. is determined what corrective materials are to be used and fed to the electrode in the cores of starting material. The minimum temperature to which the mass in the electrode must be raised is above that at which carbon or other reducing agent reacts with the other reactive materials such as the oxides to reduce'a The optimum temiperature depends upon the melting point of the metal or alloy being reduced from the metal oxide material and the rate at which dissolution of the oxide in the metal is desired to take place.

It is difficult to state definite temperatures in view of the many variables. It is a case of trial and error because it is impossible to know. precisely what temperature is being attained inthe electrode, the test beingwhether or not the mass rate of feed of the cores is varied until liquid only drops or discharges vfrom the electrode. In general, `the optimum temperature is approximately Anot less than 3200 F. and may go to 3600D F. or even above.

The solubility of the metal oxide in the reduced metal solvent varies at dierent temperatures. So the extent of solubility is the function of the difference between the melting point of the metal and the temperature at which the metal acts as or exhibits characteristics of a solvent. Usuallya temperature of from 400 to 600 F. above the melting point of the reduced metal, orr alloy of metals, is required to have the metal function satisfactorily as a solvent for the metal-oxide present in the electrode or reagent zone. The fact that this' temperature is usually well below the melting point of the metal-oxide is an indication that the oxide does go into solution rather than into suspension, although the uniform dispersion and the formation of the needle-like crystals in the chilled or quickly cooled reagent makes it quite clear that solution has taken place, as was determined in the case of chromium alloys and chromium oxide.

Another phase of operation that is to be controlled is the uniform speed of passage of the reactive materials through the hollow electrode. That is,` it is desirable to use a constant linear speed of the charge through the electrode. Also it becomes necessary to pass a constant weight of starting materials per minute through the electrode. Yet as the cores used contain various components having different specific gravities, it becomes desirable to change or lessen the Weight of ity may be used. A simple method is to use saw` dust as a source of carbon for the reduction reaction as this also lessens the specific gravity of the charge.

So .from the reaction or reagent forming zone of the electrode, there is obtained a highly concentrated reagent formed under conditions favorable to dissolving substantial amounts of metal oxides therein, which reagent comprises a metaloxide or mixtures of metal oxides in solution in a reduced metal or in a mixture of reduced metals in liquid form, and this reagent is prepared exteriorly of the bath I8. It comprises an oxidizing reagent formed while actually reducing metal and when solidified may be sold as an article of commerce to such users thereof as alloy makers or refiners. This reagent I'I is then ready to be used in the refining operation in the rening zone I3. In the refining zone, or hearth I3, there has been previously charged the metal or alloyed metal to be refined, and melted into a bath IIS, which bath consists essentially of the metal or metallic material to be refined and an oxidizable impurity such as carbon, or impurities which are to be removed from the metal. This involves the physical action of melting the metal to a point where its `impurity or undesirable constituent such as carbon goes into liquefaction or solution therein. As can be seen from Fig. 1, the reagent drops a little at a time but continuously from the electrode into this bath. Each drop is believed to comprise a globule of metal surrounded by slag. The reagent and the bath of metal to 'be refined being liquid and miscible permit a rapid and extensive dispersion of the reagent in the bath which results in a molten mixture of metal-oxide, metal, and carbon. Upon this mixing, a chemical reaction takes place between the carbon of the bath and the oxide of the reagent by virtue of which there is formed carbon-monoxide and additional metal. As the electrodes become very hot in the forming therein of the active reagent and the produced reagent is at a very high temperature (usually from .400 F. to 600 F. above the vtemperature of themolten metal of the bath), a violent reaction occurs when the reagent enters the molten bath causing terric turbulence when the carbon monoxide is liberated by the reaction. This turbulence increases the surface contact between the reacting materials. With low carbons, almost all of the carbon reduction can be accounted for through a reaction with the reagent emanating from the electrodes. Thus there is effected in the rening zone,

an intensely oxidizing action. This refining action results in the rearranging or reconstituting of the metal or a metal alloy of the bath to decrease the carbon content thereof. The slag coming into the refining zone with the reagent from the electrode and any -slag I9 rising from the bath I6 floats and the resulting refined metal I8 can be readily separated therefrom by known means.

The significance of this rening step may be explained by showing that for the molten bathv of alloy to be rened on the hearth by treatment with the reagent from the electrode: there can be used scrap or waste metal having an excess of an impurity or undesirable element therein which is oxidizable such as carbon and the like, because the refining reagent having some reducible material therein, in being mingled in liquid phase with the bath having an oxidizable element produces a reaction that oxidizes the undesirable element or impurity which in its combined form with oxygen escapes from the metal mixture. If the thus produced oxide is not a gas but of the type of Si0 P20., and MnO, it may become a component of the slag. If it is a gas of the type of CO, it becomes a part of the atmosphere of the furnace. Such gas, together with the gas generated in the electrode causes a super-atmospheric pressure of substantially pure carbon monoxide in the furnace, and this pressure causes gas leaving the furnace to permeate through the electrode burden and out from the hollow electrode in a direction opposite to that of the core feed. There is substantially no nitrogen and carbon-dioxide in the atmosphere in the furnace.

con or carbon by the use of iron oxide (FeO) in the reagent. Carbon can be decreased in quantity in alloys of iron and manganese by a reagent composed of an iron-manganese alloy having manganese-oxide in solution therein.

v In a furnace embodying this invention, electrodes were used that where 8" in diameter which had a bore of 3%". The cores used were from 2% to 3" in diameter and either 81/2" or 17" long. The cores were fed through the electrode, depending upon the furnace temperature and the material of the cores, at speeds ranging from 2" to 8" per minute. 'I'he 81/2 cores weighed from 3 to 4% pounds depending upon the material from which they are made. The reagent forming zone in this furnace was found to be in the electrodes Within ten inches from the arc end thereof.

The oxidizing reagent of this invention may be made in one furnace and used elsewhere in a refining furnace. In such an event, the reagent must obviously be cooled to solidication so it can be transported from the place of its formation to the place of its use so this invention contemplates such a solidified electric furnace product as an article of commerce. If the reagent of this invention is solidified, it is foundto comprise essentially a metal having uniformly dispersed therein crystals of an oxide of one of the alloyed metals. If a quantity of this reagent is chilled or cooled quickly, the crystals of chromium oxide are found to be needle-like and disposed in the metal in parallel formation or each oriented in the same direction. If however the reagent is cooled slowly the crystals are found to be of varying concentration or non-uniformly distributed inthe metal.

As can be seen from Figs. 1 and 2, the reagent formed in the reaction zone drips or drops into the bath, but in order to get into the bath, the drops of reagent II must pass through or penetrate the iioating oxidizing slag I9. To that end this slag must be maintained in a condition to permit such penetration, for otherwise the slag may be too thick or too rigid or viscous for the free flow of the drops therethrough. Retarda- So, by using4 the control taught by this invention, there can tion of the contact or mixing of the reagent drops 7:

with the metal of the fbath tends to*I produce .a harmful change of temperature and of the constitution of the reagent. That is, this delay in its travel from the electrode outlet to the metal bath may cause a change in the equilibrium in vet the reagent and a disturbance in the value of the metallic components thereof.

Another requirement of the slag is that it shall contain an oxide to insure against the harmful strippingy or removal of the metal oxide from the reagent as it passes through the sl-ag. Accordingly, cores containing correctives for the slag of the bath to correct the physical constants and chemical properties thereof may be either fed through the electrode or added directly to the bath on the furnace hearth. Such correctives include cores either in whole or in part of lime, magnesia, burned dolomite, silica, magnesium silicates, calcium silicates, sodium silicate, nuorspar, feldspar, salts, slags from previous runs, and any mixtures of these correctives, one essential compound being an oxide of a metal, such as iron, manganese or chromium, since it is necessary to have an oxide vi' a metal for oxidizing the carbon.

In connection with the use of these correctives,

it is pointed out that the reaction in the reagent forming zone may require a basic slag while the refining reaction may require an acid slag or vice versa. Therefore, it is possible that one core used for furnishing ferro-chrome to the bath may furnish it with an acid slag while an alternate core may keep alkaline the slag on the bath. For

instance, in order to get a good lyield of ferrochrome from the ore, it is necessary to add sufiicient silica to certain ores to increase the mobility of the mixture in the electrode to release the such as chromite (chromium oxide) and carbon are started through the electrodes to insure at reducing atmosphere ln the furnaces. This prevents the oxidation of any of the values in the charge. So, as soon as CO is generated in the furnace, the metal charge of cold scrap, or other metallic material to be rened, is then added to the furnace hearth. This scrap may be in the form of discarded ingots which failed to meet customers specifications, or in the form of refuse such as strip trimmings, punchings, turnings, etc. The temperature of the furnace and its electrodes is regulated by current input. The rate of core' feed is regulated 'so that the desired reducing and dissolving actions take place in the electrode whereby no non-fluid material issues therefrom, andcores continue to. be fed until the scrap ris entirely melted.

Samples of the slag and molten metal are taken from the bath on the hearth at stated intervals, such as every minutes to determine the condition of the rened metal. For instance in makand the chrome has been raised to the desired.

point. If the carbon has not been reduced sureached the desired analysis, it is tapped into a ladle and is allowed to cool until it has reached a pouring temperature. It is then poured into molds either for ingots or for other purposes. After the material has been cast, the electrodes are partially withdrawn from the furnace and a new charge of scrap is added; the electrodes again put in place and the current turned on and the above described steps are repeated.

For making chrome alloys it should be considered that chrome ore is composed of two com- 'ponents The primary component is the mineral chromite which comprises approximately 80% to 90% of 4the ore and has the following formula:-

In this component the molecular sum of the bases (A+B) is always equal to the molecular sum of the acids (C-l-D). A portion of this component can be reduced at a definite temperature by such reducing agents as carbon or silicon.

The second component of the chrome ore (usually termed the gangue) comprises approximately-% to 10% of the oreand consists of (MgO)X(SiO,) y. lThe proportions of magnesium oxide and silicon dioxide vary between the formulas and (Siog- This second component is not reduced by reducing agents such as carbon or silicon under usual conditions.

Whenthe first component is partially reduced to metal by the process of this invention, the iron oxide of the base and the chromium oxide (Caos) of the acid of lthe primary component are reduced forming an alloy of metallic iron and metallic chromium while in the residual material of the primary component the magnesium oxide and aluminum oxide react and combine with the secondarycomponent magnesium silicate to form spinel and magnesium-aluminum silicate. The spinel, which consists of magnesium alumi- K nate, hasa particularly high melting point, and,

If, however, the melting point is not sufficiently..

high for the reaction and equilibrium which is required in the reagent in the hollow electrode, it is'then possible to add to the electrode as correctives either magnesium oxide or calcium oxide to increase the refractoriness or melting point of -this residual material, Upon the addition of magnesla'or lime the residual material, after the reduction of the iron oxide and chromium to metal, will have a melting point in accordance with predetermined calculations.

At least a part of then carbon in the metal is removed by the reagent formed in the electrode. Probably the percentage of carbon removed by the slag to the percentage removed by the reagent varies inversely with the percentage of carbon in the metallic bath on the furnace hearth. In other words, when the carbon in the metallic bath is relatively high, there is an appreciable reaction between the oxides in the slag and the carbon in the metal. This reaction is a function of the surface contact between the slag and the metal. This surface'contact is increased to a great extent bythe turbulence caused when the dissolved metal-oxides in the reagent drop into the metallic bath and through reaction with the carbon therein, evolve CO.v With low carbons almost all of the carbon decrease can be accounted for through a reaction between the carbon and the reagent emanating from the electrodes.

In considering the reactions between oxides and metals in the bath,` it must be borne in mind that the order of the reactions between the oxides and the metals varies with the temperature. Silicon and manganese are more easily removed by oxidation than carbon when the temperature of the alloy is slightly above the melting point. At higher temperatures, it is more difficult to remove silicon and manganese than carbon. At low temperatures FeO will oxidize metallic chromium from the metal, converting it into Cr,O, which goes into the slag without materially changing the carbon content of the bath. At higher temperatures, the ratio of chromium to carbon removed by FeO favors lthe carbon removal.

The recovery of materials which cannot be comminuted economically such as stainless steels of varying composition can be effected by melting the materials on the hearth of the furnace and correcting this waste material to a predetermined specification as to desirable constituents such as chromium and nickel, and undesirable constituents such as carbon by feeding the cores of proper material through the electrode.

Ercample 1.-'10 make low carbon ferro-manganese three methods may be usedz-l. The low carbon ferro-manganese can be produced by feeding as reagent-forming materials to the electrode cores containing manganese ore, carbon and the proper corrective. The initial material formed in the refining zone will contain carbon in appreciable quantities but as the refining action .progresses and the metal bath increases in mass due to increments thereto of metal released from the reagent as the oxide thereof is reduced to metal by oxidation of the carbon of the bath, the carbon content of the bath will obviously-decrease to an exceedingly low point.l This method requires considerable tima-2. In a furnace vof the type described a charge of high carbon ferromanganese is charged through the door into the hot furnace. Before the metal is charged cores have been fed through the electrodes until the furnace atmosphere is composed of carbon monoxide. This prevents the oxidation of the manganese. If a high manganese product is-desired then cores composed of manganese ore, carbon and corrective material such as lime or magnesia are.sup plied to the electrode until the resulting reagentI from the electrode causes the carbon of the bath to be decreased to the desired point-3; Slags rich in manganese or manganese ore may be melted in the hearth or refining zone of the furnace. Cores composed of SiOy with a theoretical amount of carbon are fed to the electrode to form a reagent containing silicon metal. The silicon of the reagent reduces the manganese in the slag of the bath` on the hearth to a metallic manganese. A metal substantially free from silicon carbon may be obtained if this reaction is stopped at the point where all the manganese is reduced from the slag but no increments of silicon from the reagent have been added to the metal. If Silico-manganese is to be made the silica-carbon cores are fed to the electrode until the desired percentage of silicon is obtained in the `molten metal on the hearth.

Example II-Stainless steels.-1000 lbs. of stainless steel are charged into the heated hearth of the furnace. Power is admitted through the hollow electrode until the charge partially melts. Cores made from chrome ore and the theoretical amount of carbon calculated to bring about a partial reductionof the metallic oxides are fed through the electrodes at the rate of 21/2 per minute until sufcient reagent from the electrodes has caused the chromium content of the bath to reach a predetermined percentage. At this point the carbon is probably reduced to the predetermined percentage. If a furnace sample taken from the bath shows that the carbon is not suiliciently reduced, but that the chromium is high enough, iron oxide cores which have the theoretical amount of carbon are supplied to the electrode at the proper rate until the resulting reagent has caused the carbon to be reduced to the predetermined figure.

In this example it is sometimes necessary, depending upon the composition of the chromium ore from which the cores are made, to add enough silica to the core mixture so that the melting point of the residual gangue in the electrode will be about 3200" F. This can be accomplished by consulting any of the standard melting point curves found in the critical tables. This melting point is not the proper melting point for the slag floating on the metal in the bath and for that reason cores containing silica (SiO,) can be fed to the electrode alternately with the chrome ore cores at a set ratio, whereby the melting point of the slag on the bath can be corrected to a predetermined figuren this case 2850 F. to 2900o F. Although this silica may be added through the door of the furnace, it is preferable to add it through the hollow electrode so that a permeable slag condition will be maintained on the surface of the metal.

Example IIL- Another example for the preparation of stainless steel is to use 1000 lbs. of steel scrap, preferably with low phosphorus content, without paying any attention to inclusions of oxides, sulphur or silicon content, and melting the scrap on the hearth of the furnace. Cores containing chrome ore and the theoretical percenta'ge of carbon for the reduction of the metal-4 lic oxides are fed to the electrodes for causing the oxidizing reagent to drop onto the hearth and into the melted steel scrap until the chrome content of the bath has reached the desired proportion due to increments of chromium to the bath from the reagent and from reaction between the reagent and the carbon of the bath. At this point, if any nickel is to be added, it

may be added through the door of the furnace or by cores through the electrode. When this method for the preparation of stainless steel is.

with careful control of'other impurities in accordance with the specifications of the ilnished product, and insuilicient'carbon to reduce all of the metallic oxide contained inthe ore fed to the electrode. The cores are added to the electrode until the reagent therefrom oxidizes the carbon of the molten scrap until the carbon content has reached the predetermined allowable percentage. Carbon-free iron can also be made by supplying such cores to the electrode and omitting f rom the hearth any starting scrap as the reagent itself-from the electrode will form the reiined metal .on the hearth.

Specifically then, this invention is directed to .the treatment with a novel highly concentrated oxidizing reagent of intermediate metallurgical products, such as pig iron, ferro-silicon, cast iron, high-carbon ferrochrome, high-carbon fer --romanganese, silicon manganese, silicon chromium, and any metallurgical products containing a percentage of either alone or in combination of carbon, silicon, sulfur, phosphorus, and the like oxidizable impurities or undesirable constituents. l

ln this invention the advantages of the undesired presence of these reducing agents in the intermediate metallurgical products is utilized for the reduction of the oxide of the novel reagent by which the metallic alloy is substantially rid of its impurities. l

This patent issues from a patent application which constituted a continuation in part of patent application Ser. No. '724,024 led May 5, 1934 which ln turn was a continuation in part of patent application Ser. No. 597,399 filed March 7, 1932.

li claim:

1. In thereiining of a metal-bearing material made up of a plurality of constituents including at least one metal as a desirable constituent thereof and at least one oxidizable undesirable constituent thereof, the process for modifying the proportion of certain constituents thereof which comprises forming a molten bath of the material to be refined and an oxidizing slag thereon in a carbon monoxide atmosphere, forming an oxidizing reagent composed essentially of metallic oxide and a reduced metall at a temperature in excess of the melting point of the reduced metal while conned in a substantially horizontal hollow electrode, supplying a quantity of reagent to the bath for liquid admixture therewith under conditions for inducing an oxidizing action of the reagent upon the oxidizable undesirable constituent of the molten bath by virtue of which the proportion thereof is decreased through conversion into an omde, and then recovering rened metallic material from the bath.

2. 'I'he process according to claim 1 in which the proportion of the desirable constituent of the metal-bearing material to be refined is increased by supplying an oxide of that constituent as a component of the reagent-forming mixture in the electrode by virtue of reaction taking place in the bath whereby the oxidizable undesirable constitV uent of the bath reduces this oxide to release the reduced metal thereof into the bath.

3. The process according to claim 1 in which the material to be refined may contain as the desirable constituent thereof at least one of the elements chromium, iron, manganese, and silicon.

4. The process according to claim l in which the material to he refined may contain as the undesirable constituent thereof at least one of the elements carbon, manganese, and silicon.

5. The process according to claim 1 in which the reagent is a metallic oxide dissolved in metal` 6. 'Ihe process according to claim l in which the reagent is supplied to the molten bath while at a temperature ranging substantially between 400 F. and 600 F. above the temperature of the bath.

7. The process according to claim 1 with the addition of supplying a substance to the bath to make the slag thereof. readily permeable by said reagent whereby the reagent can pass through the slag and come in contact with Ithe liquid thereunder without substantial change of composition of the reagent.

8. The process of refining metal alloys containing chromium as desirable metal and an oxidizable undesirable constituent such as carbon which comprises dropping from a hollow electrode into a molten bath of the alloy to be rened drops of a liquid reagent containing essentially an oxide of the chromium and a reduced metal, under such conditions that a reaction takes place between the reagent and the molten bath whereby the oxidizable undesirable constituent such as carbon is oxidized and increments of the chromium of the oxide are released into the bath, and recovering the rened and reconstituted alloy from the bath.

9. The metallurgical process which comprises forming a molten bath of metal material to be rened and an oxidizing slag thereon in a carbon monoxide atmosphere, forming an oxidizing agent of metal and a metal oxide heated while held in dispersed contact to a temperature above the melting point of the metal and below the melting point of the oxide, supplying a quantity of the oxidizing agent to the bath for liquid admixture therewith for inducing an oxidizing action of the agent upon oxidizable impurities in the bath, and then recovering the treated metal from the bath.

' GILBERT E. SEIL..

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