US2558750A - Production of divided metals - Google Patents

Description

y 1951 e. D. HARRISON 2,558,750

PRODUCTION OF DIVIDED METALS Filed July 19, 1943 2 Sheets-Sheet 1 TA Am I41 0. PO/VP INVENTOR.

6500650. //A R/P/SO/V ATTOIP/VE) y 3, 1951 G. b. HARRISON 2,558,750

PRODUCTION OF DIVIDED METALS Filed July 19, 1943 4 2 Sheets-Sheet 2 COMP/P5850? 45 52 36 'c l con 054st i flj 45 HYDROG'E/V rA/wr j b BALZ- M /LL l atentecl july 3, 195i PRODUCTION OF DIVIDED METALS George D. Harrison, Detroit, Mich., assignor of two-thirds to Walter F. Courtis and Thomas M. Courtis and one-third to Courtis Trust, Detroit, Mich., a trust of Michigan Application July 19, 1943, Serial No. 495,329

1 Claim. (01. 75-28 1 This invention relates to the production of metals or mixtures of metals in divided form.

From the method standpoint, the invention comprises forming a unitary article of particles of divided metal recovered from a metal iodine-' containing solution. This unitary article may be produced by reducing the divided metal recovered from a metal iodine-containing solution to a liquid mass, and then casting the same into ingots or similar articles. The uniform article may be also produced by subjecting the particles of the finely divided metal obtained from a metal iodine-containing solution to a compacting action under prior art pressures, said compacting action being followed by the step of sintering the parti cles of the compacted mass one to the other.

It is desired to point out that the metal particles produced in accordance with the present invention have present a trace of iodine, which may beas much as 135% to .l%, whereby these particles are activated in the presence of the iodine, functioning to confer superior properties upon the unitary articles produced therefrom, as here-- inafter pointed out. In one form of the invention, the metal particles which are obtained from a metal iodine-containing solution are converted to a dendritic form and then subjected to a compacting action, preferably followed by the sintering of the particles one to the other, said compacting action being effected under pressures hitherto used in the art of powder metallurgy or at substantially higher pressures, hereinafter more specifically referred to. In one formof the invention the divided metal particles obtained from a metal iodine-containing solution are subjected to oxidation and then reduction.

In the preferred form of the invention, the divided metal particles may, be obtained by electrolysis of a metal iodine-containing electrolyte, and the resulting metal or metal alloy converted into a shaped article, said article being produced preferably by a briquetting or molding step, at a relatively high pressure, which is herein termed compacting, followed preferably by the sintering of the particles one to the other, 'said sinterin'g step being carried out, in one form of the invention, in the presence of an inert agent such as hydrogen, or, in the alternative form of the invention, in the presence of a carburizing gas, such as carbon monoxide, or any equivalent prior art carburizing gases. Alternatively, the divided metal or mixtures of metals may be obtained by chemical precipitation of the metal or mixtures of the metals from metal iodine-con taining solutions, and the so-procluced divided metal subjected directly to briquetting and sintering, as above set forth, either in the presence of an inert gas or a carburizing gas. If desired, the precipitated metal may .be recovered from the metal iodine-wontaining solution and sub jected to an oxidation and reduction step to convert the metal to dendritic form, said metal during these steps being activated by the presence of iodine or iodine-containing compounds adapted to be volatilized to a substantial extent during the reduction process, some of the iodine or iodine-containing constituent remaining adsorbed or absorbed in the metal or otherwise as a constituent portion of the metal powder, said iodine constituent functioning further during the compacting and/0r sintering of the metal particles to confer upon the unitary article produced superior properties, as hereinafter pointed out.

The present invention also resides in the production of metal particles of extreme fineness, any of the metals or alloys, or mixtures of metals and alloys, hereinafter referred to having present a trace of iodine. These metal particles may have between .05% and .1% of an iodine constituent.

oxidized in the presence of an iodine or an iodine-- containing compound and then reduced in the presence of iodine or an iodine-containing compound, said reduction step preferably producing l a dendritic form of particle.

In accordance with the present invention, therev are produced sponge-like metal particles obtained from metal iodine-containingsolutions, and particularly by electrolyzing. metal iodine-containing electrolytes, said particles of metal exhibiting rounded surfaces inhibiting scoring of the surface in which the metal particles are in contact during the period of the mechanical working thereof Theinvention is also directed to the production of sponge-like metal particles obtained from metal iodine-containing salt solutions, said particles having a compressibility of at least 5% to 10% greater than metal particles of similar size produced from non-iodine-containing solutions of metals, and in many cases compressibility is as much as 10% to 50% greater than the compressibility of particles of similar size obtained from non-iodine-containing solutions.

The invention further resides in the provision; of sponge-like metal particles obtained frommetal iodine-containing salt solutions, said particles having rounded surfaces inhibiting scoring of the surfacerin contact with said par- 3 ticles and on which the metal particles are mechanically worked, said particles being characterized by the further property of having at least 5% to greater compressibility than particles of a similar size obtained from noniodine-containing solutions of a metal.

In accordance with the present invention, the divided metal produced from metal "iodine-containing solutions may be treated to' oxidize less than a predominating quantity of the metal and then the resulting controlled oxidation product, which may be from 2% to or oxidized to-an even greater extent, is subjected to the action of a reducing agent to reduce the oxidized product to metal form. This controlled oxidation step is carried out preferably in the presence of a small proportion of the iodine-containing constituent.

In accordance with the present invention, there is provided a method of treating electrolytically produced iron, said method comprising subjecting the particles of iron powder to an oxidizing atmosphere for a time sufficient to superficially oxidize only surface portions of the particles to condition such surface portions for a change in shape upon subsequent reduction of the oxide so formed while maintaining the iron beneath such oxidized surface portions in an unaltered state, and thereafter reducing the oxide so formed in situ by subjecting the oxidized particles of powder to a reducing atmosphere.

While the present invention is particularly adapted to the production of finely divided iron having the properties herein set forth, the invention may be broadly applied to the production and utilization of many metals, including zinc, manganese, cadmium, cobalt, tin, antimony, vanadium, calcium, magnesium, aluminum, beryllium, chromium, nickel, copper, lead, molybdenum, tungsten, tantalum and platinum.

It has been discovered that divided metals or divided mixtures of metals which are obtained from metal iodine-containing solutions are char-. acterized by the property of imparting to a unitary article produced therefrom increased strength as compared to articles produced from non-metal iodine-containing solutions. Further, it has been discovered that when the divided metals or mixtures of metals obtained from metal iodine-containing solutions are oxidized and reduced, as herein set forth, said particles are characterized by the following properties, which may be advantageously utilized in the production of unitary articles:

1. Each particle has a greater compressibility thana corresponding particle produced from a non-iodine-containi'ng solution, and this may be advantageously utilized in the compacting of the particle.

2. Each particle produces less wear when in contact with a working surface on which the particle or association of particles is mechanicall'y worked, thereby, in one form of mechanical working, inhibiting scoring of the surface in contact with the particle or association of particles on which the latter is being mechanically worked.

3. Each particle is characterized b rounded surfaces, which are a contributing factor in inhibiting scoring'of working surfaces with which thepartiele or particles are in contact, and this is not true of particles produced from non-iodine metal-containing solutions, and particularly those produced by the electrolytic d-isassociation of ferrous chloride or ferrous sulphate solutions. This property maybe attributed to the greater softness of the particles of the powder as com- 1y advantageous, as hereinafter pointed out.

pared to the softness of powders recovered from non-metal-iodine-containing solutions.

4. Divided metal or mixtures of metals which are produced as a result of electrolytic action on metal iodine-containing solutions have present less hydrogen than divided metals or mixtures of metals produced by electrolytic disassociation of a ferrous chloride or sulphate or ammonium ferrous sulphate solution. In connection therewith, it is desired to point out that the more hydrogen the electrolytically precipitated metals contain the more'brittle the metal. The metals produced by the electrolysis of a metal iodine salt are characterized, as stated, by a lesser content of hydrogen, as more fully pointed out hereinafter, and for this reason these divided metals produce unitary articles having properties which it is not possible to obtain with electrolytic metals produced by the electrolysis of non-metal-iodinecontaining solutions, as, for example, ferrous chloride and sulphate.

5. The particles electrolytically precipitatedly, and therefore the particles require less energy to convert them into finely divided form. This looseness of association of individual particles, so characteristic of divided metals obtained by electrolytic disassociation' of metal iodine-containing electrolytes, persists when the particles are oxidized and later reduced to convert the particles to complete or partial dendritic form. Due to the fact that the particles are loosely held together, less milling is necessary and this is high- The particles of metal which are originally produced from a metal iodine-containing solution, or which may be produced from non-metal-iodine-containing solutions and which are processed; or, without processing, worked in the presence of a trace of iodine, which may vary from .05% to .l%, appear to be activated by the iodine, such activation functioning, whatever its mechanism, to confer upon the so-treated particles superior properties, this being especially true when the particles are compacted or are compacted under pressure and then sintered at temperatures below the melting point of the metal.

The present invention will be described in con- T nection with the accompanying drawing, wherein Fig. 1 more or less diagrammatically illustrates the present invention up to the electrolytic production of the divided metal;

Fig. 2 illustrates the further processing of the metal from the time of the electrolytic production thereof to and through the reduction step;

Fig. 3 is a transverse cross-sectional view taken on the line 33 of the cell member shown in Fig. 1; and

Fig. 4 is a sectional view showing a plurality of electrodes in a single cell and a plurality of cells for carrying out the present invention, the electrodes in each cell being in operative electric circuit and the respective cells being connected in parallel, series, or parallel series, or in any desired manner.

As shown, there is provided an electrolytic cell I, of which a plurality may be connected in series or parallel, said cell being provided with an anode 2 and a cathode 3, the electrolyte of the cell being designated by the numeral 4. The electrodes may be supported and positioned in the cell in any suitable manner, as, for example, from the cell walls. The cell is provided with a closed top 5 and an open bottom 6. Positioned below :aeesyzso ..-.the-;bottom is. arcellstray E lxadaptedrto." receive .-.tions may: be accomplished by the following; ar-

rangement:

. r-Awleaching tank: 1 9 is provided in which there is produced the electrolyte l for the cell l. The electrolyte passes: to; the filter. I 0 through a. centrifugal-pump llnand a conduit l2. The filter Loris-fin operative:connectionwitha storage tank .l3-2means of a conduit l4. .provided with a valve J5. :The electrolyte produced in tank 1:9 passes to storage tank l3,-.and then to the cell v.trayi'I-a by .meansof a conduit 16 provided with .a

float.- control valve l'i,.'whichautomatically maintainsthe height ofthe electrolyte in the tray 1. .Connectedto the filter l0 isa conduit 18, providedl-with a valve-19, whereby, when the opera- .tion: of the apparatus.v is .first initiated, the metal electrolyte may be prepared by circulating water through the leach tanks, there having been :firstintroduced into the leach tank}! pieces of iron, .over which there is spread particles of iodine crystals.

- Connected to the cell tby aconduit 2! is a vac- -.uum receiver 28, the-clatter being connected with avacuum pump 22 by the conduit 23. The vac- Mumreceiver-ZB is also connected to the leach -tank:9.by. means of the conduit 2%, a floatlevel control valve 25 being positioned in the line it to .keep the line open-or closed,depending. on the levelof the electrolyteinlthe vacuum receiverfifi. Centrifugal pump-25 is positioned between the vacuum: receiverrzfl and the line 24, whereby the electrolyte .in the vacuum receiver is. transferred through the conduit-M to the leach tank 9 when .the valve25 is open .The. precipitated metal, together with the ad herring solution, is. removed fromathe. cell tray- '5, as-stated, by. means oil/the conveyor 3 and is transfer-red to themill ,2lzfor thepurpose of finely.=dividingandrgrinding the precipitate, and preferably subjecting the precipitate. to controlled oxidation. The conveyorv 8. conveys. the precipi- .tate first to the hopper28 andtheninto the mill 2 1. .The hopper 28 :is provided witha screw feed 3E], working. in a material sealed. conduit-.3 ta. .A waterinlet 29 is. alsoprovicled, sincesometimes itisdesirabie to introduce water into; the mill 2? in-accordance-with the amount of oxidation that iscdesired. The-ball-millil isin.circu-itwith therefluxcondenserjl by. means of a conduit 32 [provided with a cut-off valve 33. Connected with the reflux: condenser 3| bymeans of. a. conduit 36 is arcompressor 35, the latter being in operative connectiombyw-means .of. the conduit 35, with a hydrogen tank 31. The-iconduittt is provi'ded witha valve 340;, and-the conduit 36 is provided with a valve -36a. The hydrogen. tankil'l is provided with a 'valvei3la.

'.Wliile:therelectrolytic material is being ground 'in'theI ball mill Z'I -in the presence' of adhering met'al iodine-containing solution, said mill is heateclf preferably by burner' 38, and the" solution lvaporizes -to produce-steamand iodine, which passesiintotther condenser3 along with a the hy- "drogen-sevolvedtbyrthe' hydrolysis of: the solution :present in themill" 27. The hydrogen .is none'con- Tdensible-tand is removed 'by theicompressor 35=and 'passe'sto the-hydrogen. tank 31. For the purpose of. removing an of thei air from the ball mill? 21 before charging-the ball'smill, there' is; rovided;a

vacuum: pump 39- having: in: circuit therewithria conduit ln; provided with -a valve 4| Thermilled =met'al oralloy'maybe'removed from-the ball mill in anylmanner; :includin'g removal of the'material When'the'solution in the mill 2'! has beencompletely decomposed into hydrogen, iron oxide::and iodine and/or volatile 1 iodine-containing compounds; the iodine collects asa solid in-the walls of the condenser 3 I ,-'andis removed by closing the valve 33,.-opening the valves- 42- and 43 in inlet conduits 4d and 45, introducing-water through the conduit is, and'removingthe iodine crystals-suspended in the water through conduit-45.

It is within the province of the present invention to= oxidize the metal-containing material present the ball mill- 21, asjfor'example, iron, to'any desired extent. For example, the materialmay be oxidized so that the oxygen content of theinaterial varies between about 1 and 30% taken on the Weight "of the oxidized product. However, in the preferred :form-of the invention, the-metal present in' the ball mill- 21, as; for example,=electrolytically=-produced 'ironor precipitated iron, is oxidizedso' that the'oxygen-content o'fthe'oxidized material willvary between 2%and taken on the weight of the oxidizedpro'duct.

In the preferred formof the invention, the material present in the ball mill is dried while itis simultaneously reduced to a finely dividedcondition. In the preferred form-of the invention, the material contains only a trace of moisture, but fairly satisfactory results'can be obtained if the moisture content is reduced to below about 1%. If" the material contains'more than 1%; there is a" tendency to inhibit rapid reduction of the iron oxide-containing.material'when the latter is sub sequently'furnaced in'the presence of'a reducing agent.

The'oxidized' mass present in the mill, which probably consists'of a mixture of ironiiparticl'es and iron oxide, is ground to a sizedepending'upon the ultimate use of the material.

For example, iron-containing particles'may'be reduced in size so that will-pass through a 100. mesh sieve, or, alternatively, it may be ground so that 70% will pass througha lOO-mesh sieve and 30% will passthrough a 325-mesh sieve. The metal particles, including any of the metals which comprise the subject matter of the present invention, may be easily broken up and reduced in size so'that the particles ofvthe metal'areas fine as 1 to 5 microns.

lItiisJdesired to point out that the electrolytic metals. produced from. .a metal iodine-containing solution, and especially those metals produced by the electrolysis of an iodine-containing metal salt, are characterized by the'property of being disintegrated into very fine particles and still maintaining a'crystalline 'form' which is not'fiattened by the milling process. In other words, the metals produced from metal iodine-containing solutions, and especially by electrolytic processes, including thespecific electrolytic process herein disclosed, are characterized by the -'property (Sf'being easily disintegrated into finely divided form'w'ithout being converted'into fiattened particles. -This is one distinguishing feature'betw'een the particles of finely divided metal and especially particles of divided iron produced by the present process and those produced by the electrolysis of chloride or sulphate or equivalent metal, including iron, solutions. The divided metal produced from ferrous chloride and ferrous sulphate solutions is characterized by the property of the particles being toughly attached, or more solidly attached, to each other, so that more energy is required in any reduction process. The divided metal particles produced in accordance with the present invention, and especially those .produced electrolytically from metal iodine-containing salt solutions; are characterized, as stated, by the property of being loosely held together, so that relatively little milling, if any, is required to separate the particles thereof and produce a finely divided powder, the particles of which have not been fiattened; and because so little energy is required, in view of the physical condition of the divided metal, as, for example, iron, copper, zinc, chromium, nickel, and the like, during the milling step or the reducing step, the particles of the metal do not become flattened. In view thereof, when these particles are later formed into articles, as, for example, by compacting, or by compacting and sintering, superior properties are imparted to the compacted or the compacted and 'sintered articles, as hereinafter more fully pointed out. Stated differently, the divided metal, which is taken off the cathode of the electrolytic cell, in itself may be termed a potential powder, requiring very little energy to transform it to the fineness so necessary in the production of articles which are subjected to a compacting, extrusion, forming or shaping operation.

It may be pointed out that copper, zinc and lead are deposited in powder form from electrolytes comprising metal iodine salts, said copper, zinc and lead deposits being distinguishable from copper, lead and zinc which are deposited and electrolyzed from solutions which do not contain an active iodine constituent functioning as a portion of the electrolyte, in that the particles of the metal produced from metal iodine-containing salt solutions are more loosely attached to each other than is true when the particles are pro-' duced from an electrolysis of a non-iodine-con-' taining electrolyte.

The dried, oxidized iron product present in the mill 2.1 is removed therefrom in any suitable man-' ner. For example,,the oxidized product maybe removed by ablast of a gaseous medium such as hydrogen, and the like, and then introduced into the hopper 45. If desired, the material may be blown through exit pipe 21a, directly into the, hopper 45. The oxidized iron-containing product' is then introduced, by means of a screw conveyor 41, onto the hearth 48b enclosed in the mufile 48a. of the furnace 48. This furnace may be of any suitable type, but is preferably of the reciprocat-- ing hearth type, the muffle 58a, of which is in closed circuit with a condenser 5 I, and blower 55, by means of theconduits 52, 55 and 51 respectively. There is introduced into the muflie 4812 any suitable reducing gas, as, for example, hydrogen, natural gas, methane, cracked illuminating gas, cracked ammonia gas, carbon. monoxide, and the like. Many hydrocarbon gases may be decomposed or broken down to yield hydrogen and/ or carbon monoxide, which may be used as a reducing agent in the present process. Prefer- 1 ably, hydrogen is used, and this may be obtained as a by-product of the hydrolysis effected 21, said hydrogen being accumulated in the tank 31. The hydrogen present in the tank 37 is automatically introduced through the conduit 58 into the muffle 48a, as it is needed, the conduit 58 being provided with an automatic pressure controL valve Bllwhich steps down the pressure of the hydrogen gas in tank 31 to accommodate the working pressure of the furnace.

As the oxidized metal product, as, for example, oxidized iron, is passed over the reciprocating hearth 48b and through the closed muflie 48a of the furnace 48, the oxidized iron product is subjected to the reducing action of a reducing medium of the character above set forth or its equivalent, said reducing medium being preferably hydrogen, and the oxygen component of the iron oxide material is thereby caused to combine with the hydrogen to form steam, which passes to the condenser 5| along with any iodinecontaining vapors present, and any unused hydrogen, said transfer of these constituents being assisted by the blower 55. The steam, to a large extent, condenses, as does the iodine content in the vapors, and are removed through the conduit 53, the latter being provided with a valve 54. The uncondensed hydrogen is returned by means of conduits 56 and 51 to the muifie of furnace 48.

The temperature within the muffle 48a, is maintained within such a range as to effect reduction 7 of the oxygen-containing material therein, as, for example, the oxidized iron product, while simultaneously inhibiting the sintering to each other of the metal particles, as, for example, the iron particles. Broadly, this temperature may vary between about 250 F. and 1000 F. and may be regulated according to the requirements of individual metals, as, for example, copper, the oxide of which can be reduced at a comparatively lower temperature than iron, as, for example, 700 F. The reduction temperature, in some cases, may be lower than the temperature at which the oxides of the metals are ordinarily reduced, said lower temperature of reduction being efiected because of the presence of a catalyst capable of permitting reaction between the reducing agent, as, for example, hydrogen, and the oxygen present in the composite metal-- containing material. This catalyst is typified-by platinum or nickel. Any metal which possesses the property of excess adsorption of hydrogen may be used as the catalytic agent. The reaction at lower temperatures may also be promoted by electrolytic influence, such as concentration of hydrogen atoms at a cathode in contact with the oxygen-containing metal compounds which are to be reduced. For example, the hearth 48b of the muffle 48a may function as a cathode in the electric circuit, the particles of the metalcontaining compound being introduced upon said cathode. Cooperating with the cathode hearth .4812, there may be provided a suitable anode. There is, in effect, a gap provided between the hearth electrode 482) and its cooperating anode, across which is applied a high voltage current, varying in voltage depending on the distance between anode and cathode.

When no catalytic or electrolytic arrangement is present, the temperature of reduction for iron oxide will vary between about 600 F. and that temperature where the particles of iron begin to sinter one to the other. In general, this upper temperature limit is about 1000 F., but it is recognized that this may vary considerably in accordance with the character of the iron oxide,

15 the character of the reducing medium, the char produced from scrap iron, it being recognized ithat the general principlesof the invention are applicable, as stated, not only to scrap iron but to the production of various other powdered metals from scrap metals and ores, or compounds containing said metals,

About 2,000 pounds of scrap iron is placed in leaching tank 9, said scrap iron being in the form of lathe turnings, pipe cuttings, odd-shaped pieces, scrap castings, punchings, and the like. Instead of using scrap iron, iron ore may be used, as, for example, hematite. Instead of using scrap iron, scrap iron bearing alloys may be used, as, for example, iron vanadium alloys, iron manganese alloys, iron tungsten alloys, and iron chromium alloys.

On top of and in contact with the scrap iron, there is placed about 400 pounds of crystal iodine. Thereafter, 100 gallons of water is introduced into the tank. This water is continuously and repeatedly circulated by means of the pump II through the filter Ill and then through the leach tank 9, until all of the iodine is dissolved, forming an iron iodine solution the major component of which is ferrous iodide. There is present in the leaching tank an excess of iron. The circulating ferrous iodide solution carries with it in suspension certain impurities, as, for example, suspended oxides and other suspended insolubles, which are removed by the filter I0. When the iodine crystals have been completely dissolved to form the ferrous iodide solution, the valve I is opened and the valve I9 is closed, and the solution then passes through the filter I0 and conduit Hi to the storage tank l3. From the latter the solution is introduced into the cell tray I. When the surface level 8 of the ferrous iodide solution is about half an inch above the bottom of the cell I, the fiow of ferrous iodide to the cell tray I is automatically terminated by means of the float control valve I I.

Suificient vacuum is maintained in the vacuum receiver 2!! by vacuum pump 22 to fill the cell l and to transfer constantly the electrolyte in the cell tray I to the vacuum receiver at a predetermined rate of transfer in gallons per hour. It may be stated that the rate of transfer of electrolyte from the cell I to the vacuum receiver 20 should be such as to inhibit the building up .of any substantial percentage of iodine in the ferrous iodide electrolyte before the removal of the ferrous iodide electrolyte or any other metalcontaining iodide from the cell, it being pointed out that as the electrolysis proceeds, the metal iodide electrolyte, as, for example, the ferrous iodide, is broken down into iron and free iodine in cell I, the iron particles being deposited on cathode 3, while the iodine is deposited on anode 2 and dissolves in the electrolyte. Therefore, the electrolyte must be transferred from the cell to the vacuum receiver at such a rate in gallons per unit of time as to effect the desired result, which is removal of the. free iodine dissolved in the electrolyte of cell I before it has opportunity to form ferrous iodide of the iron deposited at the cathode 3. f It is desired to point out that the level of the electrolyte in the vacuum receiver 20 should be maintained at such a point as to prevent the transfer of said electrolyte to the vacuum pump 22 through conduit-23. It is further desired to point out that as long as the cell I is in operation conduit 2! is filled with electrolyte being trans ferred'to the vacuum receiver. The centrifugal pump 26 is capable of delivering more electrolyte per minute from vacuum receiver 20 than transferred from cell I to vacuum receiver 20 by vacuum pump 22.

The cathode 3 is preferably in the form of stainless steel or chromium plated copper, the surfaces of such cathodes serving to inhibit the deposited iron from adhering thereto. In other words, the iron, as de csited by the constant-current of electricity, will fall onto the conveyor fl passing through the lower portion of the electrolyte in the cell tray 1. The anode is preferably, in the cell herein specifically illustrated, of an insoluble material, such as any metal or combination of metals lower than iron in the electromotive series of the metals, typified by stainless steel or carbon. The cathode 3 may be, in

some cases, subjected to mechanical action, as,

for example, a scraping action, to remove the iron fiakes. The iodine liberated at anode 2 is dissolved in the electrolyte contained in cell I, and the latter is transferred to leaching tank 9, where it combines with the excess iron contained therein to recondition the electrolyte from the cell to ferrous iodide. i

Referring to cell I, there has been set forth merely one set of electrodes, composed of a cathode and an anode. However, it is to be understood in actual operation that there may be a plurality of electrodes interposed or positioned between these cathodes and anodes. It is pre ferred that several of these cells containing a plurality of electrodes be positioned in a single tray and connected by piping to the vacuum receiver. Y

The greatest efiiciency of iron deposited at the cathode with relation to kilowatts of electricity consumed will be derived by an operating voltage as close as possible to the electrode potential of iodine, in proportion to the temperature and concentration of the electrolyte contained in the cell. The current concentration of this cell should be less than a cell employing a soluble metal anode, in which case the efliciency of the quantity of iron deposited at the cathode per kilowatt hour of electricity consumed is increased.

The cell herein set forth may be used for the electrolytic production of other metals from metal iodine-containing solutions, as, for example, copper. Since copper iodide is only slightly soluble in water It is desirable to provide an electrolyte which contains the copper iodide in its most soluble state, and for that purpose a'solution of potassium iodide and water is first made up in the proportions of 1 gram of potassium iodide to each subic centimeter of water used. In this is dissolved free iodine until saturation point is reached, which, at ordinar atmospheric temperatures, is approximately /2 gram for each cubic centimeter of water in solution. This solution can then be used in the leaching tank to dis solve the copper. This example is typical of what may be termed the insoluble metal group, comprising metals such as copper, silver, mercury, lead, tungsten, molybdenum, nickel, chro- :mium; tantalum, and coluinbium'. -When using any cell provided with insoluble anodes and a leachingt-anlr inconnection therewith, and cir- .culation, as shownv in theexample set forth herein; the voltage: between the anode and the oathodeis desirably as close to the potential voltage of iodine aspossible, when, the best efficiency is desired, from the standpoint of kilowatt hours, of electricity consumed per pound of metal precipitated. In the production of copper from copper iodine-containing electrolytes, satisfactory results have been obtainedusing stainless steel anodes. and; leadcathodes. However, obviously, other types of electrodes may be used, as, for example, stainless steel or carbon for both anodes and cathodes. While a solution of potassium iodide: in: water has been set forth as a solvent medium-for the copper, other equivalent solvent mediums may be used. It isv desired to point out that.- the herein set forth iodides: of metals, such as copper, silver, and mercury; are more readily soluble: in. iodide solutions; such; as potassium iodide, sodium iodide, ferrous iodide, etc.

The copper produced the cell of the character herein set forth: or in any other electrolytic cell using electrodes of a different. character may be further conditioned to adapt it for certain predetermined: uses, When the powdered copper is to. be used. for the cold briquetting of parts, previous to. their sintering in a furnace, it is desired tormill, oxidize and-reduce the electrolytic copper in.- a. manner substantially identical with the milling, oxidizing and reduction steps herein set forth. By cold briquetting is meant the shaping of the article under pressure in a fixed die at temperatures. below the melting point of themetal being briquetted, as, for example, copper. The preferred range. varies from about 19 to 12o F. However, the metal powder, including any of the metalpowders herein set forth, may be briquetted at temperatures varying from: about 30 to. 40 F. and below the meltin pointof the. metal. When the electrolytically precipitated divided metal, as,.forexample, copper, is to be used in the production of articles produced by pressure shaping, such as rolling, extruding, and. the like, where extreme density, strength and close tolerance. are not required in the finished product,.then the electrolytically precipitated metal or metals may be washed and dried. under conditions inhibiting the oxidation, and. preferably without milling.

Mercury is aliquid metal. at ordinary temperatures, which may be designated as being between 40 and 100 F., and is in. itself therefore not adaptable for rolling or shaping. However, when the mercury is. mixed with other metal powders, as, for example, those powders which are deposited on the mercury when the latter is used as a cathode, the composite medium, that is, the mercury in admixture with said powders, may be shaped or pressure molded, and then subjected to aheating step. to volatilize the mercury, said heating step, in one form of the invention, being such as to sinter the particles of the metal, as,

for example, iron, one to the other; and, in the other form, the temperatures raised to that degree which will volatilize the mercury, 600 F., but will not sinter the particles of metal together.

It is further desired to point out that when a cathode of mercury is usedthe metals deposited thereon, as, for example, iron, or any of the metals herein set forth, are in powder form and can be separated from the mercury in' said powder form, thus eliminating the necessity of any i2 milling, step. All of-said-powdersmay be oxidized and, reduced as. herein set. forth, although. they maybedirectly usedin some instances.

The readily soluble iodides of metals, such as iron, zinc, manganese, cadmium, cobalt, tin, antimony, and vanadium, may be more, advantar geously electrolyzed for the production of divided metal in accordancewith the specific example herein outlined on iron, it being desired topoint out that the best electrolyte from which to accomplish the deposition. to. produce, the metal as free of hydrogenv as possible is the water soluble iodide of the metal. With relation to. such metals as calcium, magnesium, aluminum, beryllium, and other metals which are, higher inthe electromotive series of the elements than these metals and may be termed alkali metals, it is desired to point out that it is necessary to use a mercury cathode to precipitate these metals in. metallic form, and that the electrolysis of their iodide Water solutions will precipitate them upon. any other metalcathode in the oxide form. It is also desired to point out that they are not readily reduced from the oxide in any furnace by means of hydrogen.

Iodine activated metal powders may be produced by chemical precipitation from metal iodineecontaining solutions of any metal, including iron, zinc, copper, tin, cobalt, and lead. For example, a concentrated solution of ferrous iodide may be treated by steam and oxygen, or oxygen with or without the application of heat, whereupon the iron precipitates as the oxide and/ or hydroxide, which isrecovered in any suitable manner, as, for example, by filtering the solution containing the same. This oxide of iron is thereafter washed, driedand reduced in a reducing furnace, in the manner herein set forth. This produces an. iron powder which contains a trace of: iodine, which apparently has beneficial effects when the iron powder is further processed for the production of iron articles, said processing including cold briquetting and pressure shaping, to. produce articles suchasgears, pinions, ingots, sheet iron, and bar stock.

It is further desired to point out that scrap metals and alloys, as, for example, iron and steel scrap, which includes materials such as stainless steel scrap, cobalt steel scrap, manganese steel scrap, scrapmanganese, and tungsten steei, and, in general, all scrap metals or scrap alloys or steels, may be treated with an iodine-containing agent and the metal content of the resulting solution recovered in the form of a metal powder containing a small proportion of iodine. Not only may chemically precipitated iron be recovered from iodine-containing solutions, but it is within. the. province of the present invention to treat non-ferrous-containing materials, typified by brass, bronze, zinc, skimmings, aluminum skimmings, and their scrap, dross, and waste materials with an iodine-attacking reagent which will bring the. metals in solution, as. metal iodinecontaining compounds.

Where the voltage across the electrodes of the cell employing a metal iodide electrolyte doesnot exceed the voltage across an identical cell employing as an electrolyte any other soluble salt of the metal, including sulphates and chlorides, then the particles of the metal, as, for example, iron particles, deposited from the metal iodide electrolyte are more loosely attached to each other, and the particles have more or less individual identity, in contrast to being a solid mass, whereby the particles, agglomerates thereof, and

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masses thereof, possess the property of being more compressible than particles produced from metal salt solutions which do not contain iodine in combination with the metal, as, for example, solutions of iron chloride or iron sulphate.

The electrolytic particles produced from a metal iodine salt solution, in accordance with the electrolytically in accordance with the present process and before it is oxidized or reduced, may be rolled or extruded in the cold, that is, at a temperature up to 100 or 1 F., and then sintered at a temperature below the melting point of the resulting iron mass, as, for example, 2200 F. Obviously, the rolling or extrusion can also be carried out at temperatures above 120? F.

or below the melting point of iron. Similarly,

other metals may be cold rolled or rolled at a higher temperature, and later, if desired, sintered below the melting point of the metal. During these rolling and extrusion steps, the metals or alloys, or mixture of metals and alloys, may be subjected to pressure such as is well known in the prior art.

Obviously, the electrolytic deposit or precipitate of the metal, as, for example, iron, copper, zinc,

'and lead, may be treated in accordance with the above without milling the product to reduce it to a fine, uniform size.

When it is desired to produce articles which are the equivalent of finely machined parts, such articles possessing close tolerance and maximum hardness, tensile strength and/or elongation elasticity, it is desirable to subject the electrolytic product to a reduction step, or first to an oxida tion step and then to a reduction step, during which the particle shaping and size are controlled.

Instead of using a cell such as set forth in Figs. 1 and 3 to electrolyze an iodine salt solution to produce a metal deposit, there may be employed any of the prior art cells which use a soluble anode or an anode compartment in which the metal is placed. It is well known in the art to use a cell which contains therein a metal anode and a metal cathode, the anode of which is dissolved and deposited at the cathode. In thismanner of employing the iodine metal salt electrolyte, it is not necessary to employ a leaching tank, illustrated herein. It is preferred in this modification, wherein a leaching tank is not employed, to provide a system of circulation through a filter, circulating the electrolyte contained in the cell, and filtering therefrom the suspended impurities, such as silica and carbon, etc., which may be contained in the metals being dissolved in the cell and produced at the cathode of the cell..

It is within the province of this invention to produce metals in divided form at filter l0 when the scrap materials, metals, or ores contained in leach tank 9 are composed of a plurality of metals, such as a scrap material consisting of a mixture of tungsten, molybdenum, chromium, nickel, and iron.

Iron powder produced as herein set forth may be pressure molded under a molding pressure of not less than about 150,000 pounds per square inch, said molding preferably occurring in the cold temperatures of 40 to 120 F., but said molding may be effected at higher temperatures 'erties to the resulting metal powder.

14 below the melting pointof irunythereafter, the pressure molding of the iron powder is sintered at a temperature not above 2200 F. The resulting pressure molded article may then be reduced in size by successive pressure molding treatment steps, in molds which differ from the size of the article being molded by approximately 1/1000 of an inch. This series of moldings to reduce the size of the article serves to increase the density of the article, and that is one of the primary functions of this series of steps, which 'may be termed differential drawing.

Articles produced in this mamierfrom the powdered iron .made as herein set forth exhibit a tensile strength which is exceedingly high and substantially higher than that obtained by electrolytic decomposition of electrolytes which do not contain a metal iodine salt as, for example, iron powder produced by electrolysis of a ferrous chloride or a ferrous sulphate solution.

Further, it is desired to point out that articles which have been molded or briquetted as herein set forth and sintered at temperatures below 2200 F., said articles having been produced by the electrolysis of an iodine salt solution, show an extremely high elongation elasticity. Articles manufactured from powders produced by the electrolysis of ferrous chloride and ferrous sulphate containing solutions do not have an elongation elasticity greater than 12% and the elongation of articles produced in accordance with the present invention is much higher.

Articles which have been pressure shaped from iron powder produced by the electrolysis of iodine salt solutions exhibit a significantly greater elongation elasticity constant.

While it has been stated that the divided metal produced from the metal iodine-containing solution is milled in the presence of only a small proportion of water in ball mill 27, it is within the province of the present invention to mill in the presence of a large quantity of water, so that substantially all of the divided metal is converted to oxide form. Further, the milling or reduction to powder form may be carried out without any oxidation and after the milling step the resulting finely divided metal may then be oxidized and then reduced in accordance with the reducing procedure herein specifically set forth.

- It is also within the province of the present invention to wash the divided metal which is electrolytically precipitated or chemically precipitated from the metal iodine-containing so} iodine-containing compound during the milling step or the oxidation step, or the reduction step, or in all of these steps, imparts superior prop It is within the province of the present invention to im part these superior properties to divided metals obtained from sources other than a metal iodinecontaining solution by electrolytic precipitation .or purely chemical precipitation, or otherwise,

by having present during any of the steps above set forth, or all of them, a small proportion of a volatile iodine-containing compound.

It is within the province of the present invention 'to electrolytically produce divided metal from metal iodine-containing solutions and to chemically precipitate the divided metal from iodine-containing solutions, and then to mix these in any proportions, as, for example, 50% of one to 50% of the other; 25% of one to 75% of the other, or, in fact, to mix them in. any proportion; and thereafter process the mixture in accordance with the disclosure of the present invention. This procedure may be employed in connection with any of the metals set forth and disclosed in my copending application Serial No. 342,797, filed June 27,1940, now abandoned. This procedure is not applicable only to the metals above stated but to any and all metals which are capable of being brought into finely divided form.

A divided metal produced electrolytically or by chemical precipitation from metal iodine-containing solutions may be mixed in any and all proportions with divided metal produced from non-iodine-containing solutions. For example, finely divided iron produced from chloride or sulphate solutions, which have distinctly inferior qualities, and the finely powdered iron produced in accordance with the present invention may be mixed with powdered iron of the present invention produced from metal iodinecontaining solutions in the ratio of 5% to 40% of the chloride iron or the sulphate iron to the finely divided iron produced from metal iodine- .containing solutions. Any or all of the metal mixtures herein set forth when pressure molded may be briquetted or molded at usual prior art pressures which vary from about 100 pounds up to 150,000 tons, but usually do not exceed 150,000

pounds.

It is within the province of the present invention to produce articles or parts by pressure treating of the metal powders herein set forth under such pressures as will insure the production of a porous article. shaped article, which may be pressure briquetted or molded and then sintered, will be determined largely by the pressure employed. These porous articles may be used for many purposes well known in the art, including bearings, which are known as self-lubricating bearings.

In that form of the invention shown in Fig. 4, there is provided a plurality of cells 62 and 63, provided with a plurality of cathodes 64 and a plurality of anodes 65. Cells 62 and 63 project into the electrolyte 66 contained in cell tray 61, through which there passes a conveyor 68.

The production of metals from metal iodinecontaining solutions, as, for example, ferrous iodide, copper iodide, zinc iodide, nickel iodide,

cadmium iodide, and similar iodide or iodate solutions, is highly advantageous, in that the health of workers operating the process is not adversely affected. This is not true in working with chlorine.

In carrying out the present invention, ferrous iodide may be produced as herein set forth or as set forth in my copending application Serial No. 342,797, and the iron recovered therefrom by treatment with zinc scrap. In the preferred form of the invention, the zinc scrap is added in an "amount more than sufiicient to accomplish complete precipitation of all of the iron. The solution of zinc iodide and finely precipitated iron may be recovered from the scrap zinc in any suitable manner, as, for example, in accordance with the disclosure of application Serial No. 342.797.

The present invention may be used for the re- .covery of manganese and iron from manganese The porosity of the steel scrap, the latter varying in manganese content between rather wide limits. Illustratively, but not by way of limitation, the manganese content of the manganese steel may vary between 2 /2 to 15%. Assuming that a given lot of manganese steel contains about 15% of manganese, a ton of steel scrap will then contain 300 pounds of'manganese. The manganese steel scrap may be treated in a treatment vessel of the character previously set forth.

In the preferred form of the invention, 3 tons of 15% manganese steel is introduced into the treatment vessel, and there is added 4,000 pounds of iodine and '500 gallons of water. It is pointed out that it is highly desirable in one form of the invention to have an excess of manganese present, that is, more manganese than is suflicient to combine with the iodine present to thereby insure that all the iodine reacts with the manganese to form manganese iodide, and, moreover, leaves free manganese in excess. The manganese iodide which is formed is soluble in the Water, and, therefore, there is produced as a result of the above operation an aqueous solution of manganese iodides, together with free manganese. Due to the excess of manganese present, if any iron iodine compounds, including the iron iodides, are formed, the manganese will immediately react therewith to form manganese iodide and precipitated iron.

The resulting mass is then filtered to produce a solid component consisting primarily of iron and a filtrate consisting primarily of the manganese iodides. The manganese may 'be recovered from the filtrate by the method used'to recover zinc, and the free iodine returned to the treatment vessel for use again in the process.

A finely precipitated iron, if it is-sufiiciently pure, may be directly utilized or converted to a suitable compoundfor use in the various indusk tries, as, for example, into iron oxide for use as a pigment or into iron powder in the metal form. Such metal powder, which is in an extremely pure form and which has a fineness which is only obtained by a precipitation process, may be utilized in the production of pressed gears, pinions, or the like, or for theproduction of alloys, by pressure molding the packed material while it is maintained in a plastic condition at a high temperature.

It is desired to point out that it is highly advantageous to treat the manganese steel with iodine in the presence of an aqueous component, whereby the iodine attacks the steel, since no contaminating metal or metal compound is introduced into the cycle, thereby simplifying the entire procedure and simultaneously separately producing manganese and iron in an extremely fine powdered form of predetermined standard. The products of the present invention may in a sense be termed intermediates, since they may be converted with great facility into other compounds of very high purity.

While examples have been set forth of the electrolytic production of copper and iron from copper and iron iodine-containing solutions respectively, iodides of any of the metals herein set forth, and, in general, metal iodides, may be electrolyzed to produce, in the preferred form of the invention, non-adhering divided metal.

It is desired to point out that in the electrolytic production of metals, and particularly iron, utilizing the cell herein set forth and insoluble anodes, it is desired to operate as closely as possible to the electrode potentialvoltage of iodine,

17 which desired voltage is .54. Operating at this voltage, there is a great economy in energy used in the production of the metal, as, for example, iron. This will be apparent by comparing it with the electrode voltage necessary when operating cells using chloride and sulphate electrolytes. These cells will require potential operating voltages close to about 1.3. Correspondingly, less of the water contained in the electrolyte is separated into hydrogen and oxygen; and, correspondingly, less hydrogen is plated into the metal at the cathode. While it is desirable to operate as closely as possible to the electrode potential voltage of iodine, it is to be understood that this may be considerably varied and still come within the spirit of the present invention. words, it is not desired to be absolutely limited to this specific iodine electrode potential voltage, since this merely represents the most preferred and most economical method of operating. In A departing from the electrode potential of iodine, it is to be understood that the electrode potential voltage is not to be raised so high as to appreciably dissolve the anodes.

As stated, the present invention may be carried out by using a soluble anode, the latter being composed of the metal present in the electrolyte, as, for example, when electrolyzing an iron iodine salt electrolyte the anode is an iron anode. When an insoluble anode of this character is employed, then the operating voltage may be considerably below the electrode potential voltage of iron, as, for example, in the neighborhood of .2 to .3 of a volt, in which instance the iron deposited at the cathode will contain a trace only of hydrogen, that is, about 1 part in 1,000,000.

It is desired to point out that when using insoluble anodes the iron deposited at the cathode will contain up to 60% less hydrogen than iron deposited from a non-iodine-metal-containing electrolyte. Electrolytic iron deposited at the cathode of an electrolyte containing an iron iodine salt solution contains not more than 60% of the hydrogen which is present in electrolytic iron deposited from a non-metal iodine-containing salt solution. Usually, the electrolytic iron deposited from a metal iodine-containing electrolyte contains 20% to 40 as much hydrogen as electrolytin iron deposited from a non-metal iodine-containing salt electrolyte. It is to be understood that the percentages of hydrogen herein specified are obtained when operating a cell of the character herein set forth and in the manner herein set forth, utilizing the electrode potential voltage of iodine or a voltage approximating the same.

It is further desired to point out that iodine at ordinary temperatures is a solid and that chlorine at ordinary temperatures is a gas. Therefore the iodine remains with the electrolytically deposited metal, including all of the metals herein set forth, and this is in contrast to the chlorine,

which, being a gas, escapes more or less from the interstices of the metal. The loosely adhering condition of the particles of the metal deposited from the metal iodine-containing electrolyte favors the occlusion of a small percentage of iodine in the metal, as, for example, iron, copper, or any of the metals herein set forth, and their equivalents.

While it has been stated that the metal, and particularly iron, may contain from .05% to .1% of iodine, taken on the weight of the metal, the metal, and particularly iron, may contain as little as 5 parts of iodine in 1,000,000 parts of iron, and in many cases there will be present from 5 In other 18 to 50 parts of iodine per 1,000,000 parts of iron.

It may be stated that metals produced in the manner herein set forth, and particularly iron, are free of sulphur, and it is well known that sulphur exerts a detrimental effect upon many metals, and is particularly detrimental when it is present in any appreciable amount, or even in traces, in iron.

In the electrolytic process herein set forth, and particularly operating in cells of the character shown in the drawing, the process is most satisfactorily carried out when the electrodes are spaced not greater than of an inch apart, since such spacing requires less voltage. It is tobe understood that the spacing may be greater or less but that the optimum results, from the standpoint of maximum efficiency, are obtained when the above electrode spacing is used. The voltage may be .54 and the current density may be .1 of an ampere per square inch. Using a ferrous iodide solution as the electrolyte, the specific gravity is maintained preferably around 1.8, although this may vary from 1.2 to 2. Electrolytic metal, and particularly iron, produced by any of the methods herein set forth, may be sprayed into the combustion chamber of a combustion furnace to atomize the particles of metal, and particularly iron, said particles being spher ically shaped. The so-produced particles may be pressure molded and sintered to produce electrical parts, such as magnetic cores having low eddy current properties. It is believed'that the rounded particles are very efficacious in reducing eddy current losses when produced from metal iodine-containing solutions. Metals precipitated from metal iodine-containing solutions may be also treated as above set forth.

What is claimed is:

The method of treating electrolytically produced iron powder which comprises the steps of subjecting the particles of iron powder to an oxidizing atmosphere for a time sufiicient to superficially oxidize only surface portions of the particles to'condition such surface portions for 2 a change in shape upon subsequent reduction of the oxide so formed while maintaining the iron beneath such oxidized surface portions in an unaltered state, and thereafter reducing the oxide so formed in situ by subjecting the oxidized particles of powder to a reducing atmosphere.

GEORGE D. HARRISON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 861,535 Pritchard July 30, 1907 971,252 Clancy Sept. 27, 1910 1,466,793 Eutis et a1 Sept. 4, 1923 1,679,337 Moulden et al July 31, 1928 1,857,664 Schlotter May 10, 1932 2,125,909 Gahl Aug. 9, 1938 2,159,699 Hardy et a1 May 9, 1939 2,200,369 Klinker May 14, 1940 2,237,867 Mann Apr. 8, 1941 2,361,925 Brassert Nov. 7, 1944 FOREIGN PATENTS Number Country Date 507,277 Great Britain June 13, 1939 OTHER REFERENCES Chemical Abstracts, vol. 30, 1936, page 966, Charmetant.

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