US2240313A - Method of making composite metal - Google Patents

Description

April 29, 1941. A H. J. Nl-:ss l 2,240,313

mamon oF MAKING COMPOSITE METAL Filed March l, 1938 imm IllmlNVENTOR TTO EY Patented Apr. 29, 1941 UNITED STATES PATENT OFFICE METHOD or Mame. ooMrosrrE METALl Harold J. Ness, Bloomfield, N. J. Application March 1, 193s, serial Nn. 193,218

8 Claims.

This invention relates to alloys and to the method of producing the same. It is described hereinafter with reference to bearing metal alloys composed primarily of copper and lead but certain features of lthe process described are applicable to the production of alloys of other metals.

The present application is a continuation in part of my earlier applications Serial No. 27,712, filed June 21, 1935, and entitled Alloys Serial No. 56,567, filed December 28, 1935, and entitled Alloy, and Serial No. 79,968, led May 15, 1936, entitled Metallurgical process. Y

In a copending application Serial No. 193,277, iiled on even date herewith, which application also comprises a continuation in part of said above applications, I have described a method of producing copper-lead alloys by the use of lithium. The present invention contemplates the production of such alloy in accordance with the process of said copending application and the applying of said alloy to backing or supporting metals, such as steel.

One of the objects of the present invention is to eliminate the diilculties which have heretofore accompanied the production of copper-lead alloys and the application thereof to steel backing members.

Another object is to provide a method of producing alloys in which agitation of the molten mass is obtained without mechanical stirring up to the time of solidication thereof on the backing member.

Another object is to provide a process of coating a backing metal with a copper-lead alloy of better physical properties than heretofore obtainable on such backing metals.

Another object is to produce steel backed copper-lead alloys having lead contents up to 70%.

Another object is to produce an intimate bond between a supporting metal and an oxygen free alloy of copper and lead.

Another object is to provide a novel and effective method of coating backing metals with copper, copper-lead alloy or other metals or alloys.

Another object is to clean said backing metal and/or to maintain the same in a clean and oxygen free condition prior to and up to the timeof application of the copper-lead alloy or other metal thereto.

Another object is to produce/an alloy bond between the copper-lead alloy and the backing metal.

Another object is to provide means and a method for applying the copper-lead alloy ory other metal to a backing member in the form of a continuous strip.

Another object is to provide a method and apparatus for coating backing metal with a. copperlead alloy or other metal in a non-oxidizing atmphere.

Another object is to produce an oxygen f ree steel backed copper-lead alloy.

Other objects and advantages will hereinafter appear.

'I'he present invention is based, in part. upon the discovery that when lithium is introduced into certain alloys, as for example, a. copperlead alloy, and precautions are observed to maintain some lithium in the alloy, a natural circulation or agitation of the molten mass occurs which enhances the intimate mixing of the alloying ingredients and that such agitation or automatic stirring action continues after it has once started, until actual solidication of the alloy upon cooling. As a consequence, no opportunity is aiorded for the ingredients to segregate. Moreover, the agitation is very rapid,` apparently occurring simultaneously throughout the entire molten mass so that 'a thorough stirring of the molten mass results and, upon solidiflcation thereof, the ingredients of the alloy are retained in an intimate, lmiform and nnely subdivided formi.

'I'he lithium, when maintained in a small-proportion in the copper-lead mixture by regulated conditions oi.' operation, the nature of which will hereinafter appear, producesin the molten mass as the temperature thereof is raised to above a certain critical temperature, a violent agitation which appears to proceed upwardly from the center of the mass, thence radially outwardly toward the sides of the containing .crucible and down the sides of the crucible. This circulatory agitation proceeds in the direction indicated as long as the temperature is retained above the critical temperature, and it is accompanied by considerable surface turbulence and a crackling and simmering sound. As the mass is permitted to cool down to the critical temperature, the turbulence and the rate of circulation decreases until the ",criticall temperature is reached, at which point a reversal in the direction of the circulatory agitation occurs, the movement at the surface then proceeding from the sides of the crucible towards the center thereof at an increasing rate approximating that of the previous surface movement, and thence apparently axially downward into the mass. This latter movement of the mass continues in the radially inward direction at the surface until the critica1" temperature is again reached, at which point the diradial movement at the surface.

The "critical temperature varies with the proportion of the copper and lead in the mixture,

- lying approximately between the limits of 1700' and 1900 F. For a copper-lead-lithlum. alloy containing 35 per cent lead, it is believed to be about 1850 F. It is readily determined, for any particular mixture, from observation of the suxface of the mass, since the transition from outward to inward movement of the mass at the surface thereof is pronounced and unmistakable.

The proportion of lithium required to eifect this stirring or agitating action is very small, very definite and active agitation and uniform and line dispersion of the lead having been obtained in the production of copper-lead alloys, which upon analysis showed as little as 0.000l7% of lithium. Too great a percentage of lithium in the molten mass will, under certain conditions, react so violently as to cause spattering and for this reason it `is preferable to maintain the lithium content of the charge not over about 1 per cent.

The lithium may be introduced into the mixture in a variety of ways. as for example, alloyed with the lead, alloyed with the copper, in a solid metallic state either alone or wrapped in other metals, such as copper, lead, nickel, etc., or as a vapor.

- Various methods of adding .the lithium to the charge are described in my aforesaid copending application but I prefer that it be added as a vapor, merely by creating' a lithium vapor or atmosphere about the crucible, in any suitable manner, as for instance, by liberation of the lithium from the liningof the furnace, which has been previously treated therewith, as will hereinafter appear, or by introducing lithium metal or a compound thereof into the furnace atmosphere. In whatever manner the lithium is introduced into the charge, thereafter the mass is heated .to above the critical temperature at which agitation starts.

- The temperature at which the copper-lead alloy is applied to the backing metal should be above the so-called critical, temperature. It may be applied as soon as 'the critical temperature is reached, although the quality and fineness of dispersion is not affected by continued heating above the "critical temperature for a substantial period, i. e., from half an hour to an hour or more, or the temperature may be alternately raised and lowered above and below the critical temperature, thereby alternating the direction of agitation. This reversal of direction of agitation may be produced at either relatively short intervals or at substantially longer intervals, without materially aecting the resulting castings, as long as the coating is done above the critical temperature.

The molten mass, as it cools on the backing metal, continues its agitation, until'stopped by solidicatlon of the mass. There is, therefore, no opportunity for segregation of either the lead or copper to occur. The molten mass is very dense and therefore there is little or no shrinkage during solidication. It has been found, however, that the mere rection of movement again changes to an outward addition of lithium to the charge in the proportions speciiied, does not result in the stirring action described nor in the production of a finely divided and uniformly distributed structure, but

in addition it is necessary to prevent, at least in part. loss of lithium from the charge or to convduct the process under conditions which will supply additional lithium to the charge as the process continues. In practice it has been found that the linings of the furnaces used,which contain large proportions of silica, unless pretreated react with the lithium of the charge, as a result of which the lithium is very quickly and `completely absorbed from the charge. In order to prevent the loss of the lithium from the charge in this manner and to provide continuously a lithium containing atmosphere about'the crucible during heating of the charge, the lining of the furnace is treated with lithium vapor at a high temperature so Ithat the lining will take up a portion ofthe lithium with which it is treated. 'I'hefurnaceliningsthustreatcdwillremainin a suitable lithiated lcondition for a considerable period, when not in use, and may be used for melting lithium containing copper alloys repeatedly without reconditioning. `This conditioning of the furnace lining, it is believed, re-

suits in a saturation or near saturation of the lining by the lithium or a compound thereof whereby the lining upon subsequent melting of a charge, is not free to readily absorb additional lithium from the charge, but on the contrary liberates lithium to produce a lithium containing atmosphere over and possibly through the crucible, which atmosphere retards the 'escape of lithium from the charge. If desired, this lithium containing atmosphere may comprise the sole means of introducing the lithium into the charge, excellent results being obtainable by merely heating a pure copper and lead mixture in a furnace having a lithium treated lining. Sum- .cient lithium is absorbed into the charge, from the lithium containing atmosphere produced from heating of the lining, to cause pronounced agitation of the molten mass and a line and unlform distribution of the lead in the copper or of the copper in the lead, as desired, upon castins the copper, a condition which produces high` tensile and compressive strength and resistance 'to pounding. The grain structure of the copperlead alloys produced in accordance with the process herein described is entirely diiferent'from copper-lead alloys as heretofore produced, the latter comprising copper and lead in masses of heterogeneous sizes and shapes whereas the copper in the alloy of the present invention assumes the elongated grain structure of oxygen free copper with the lead finely divided and highly dispersed within the individual copper grains, each copper grain including a countless number of separate lead particles. The alloy being produced in a lithium containing atmosphere, it is completely oxygen free and has not only grain formation but physical properties comparable to oxygen free copper.

'I'he number of lead particles appearing in a cross section of` the copper-lead alloy of the present invention is enormous and for an alloy containing 40% lead, it may vary from,vsay. 50.- 000 to several hundred thousand per square inch and the average size of a lead particle may be of the order of magnitude of l-6 square inches or smaller although the present invention is not limited 'to such particle size or distribution range, the foregoing gures being given only by way of example. The tensile strength of a copper-lead alloy containing 65% copper and 35% lead is of the order of magnitude of 14,000 lbs. per square inch, the compressive strength of the same alloy being of the order of 48,000 lbs. per square inch and the elongation approximately 15%. The presence of lithium in the alloy in addition to its dispersing action, toughens and hardens both the copper and lead of the alloy and increases their tensile strength, thereby further enhancing the physical properties of the alloy. Moreover, due to the encasement of the individual lead particles within the copper grains, the lead will not sweat out under operating conditions and temperatures,l a feature which is not present in copper-lead alloys of the prior art. The addition of iron, tin and/or silicon in small percentages serves to harden the alloy, as set forth in detail in my said copending application.

One feature of the alloy of this invention is its capability of being remelted and recast with-` out danger of segregation since a remelt thereof when conducted under the same controlled condition as an original melt evidences the same agitating effect as an original melt. Since remelting results in a continued internal working of the mass, it is possible to remelt and recast worn out bearings Lor to cast the original melts into ingots for subsequent recasting. 'I'he copper-lead alloy may becast onto supporting or backing metal, such as steel, for such uses as bearings, brake-linings, clutch surfaces, piston surfaces, etc.

In order that the invention may be more clear-- Fig. -2'is a vertical section of a furnace andl die for the coating of backing strips with a copper-lead-lithium alloy;

Fig. 3 is a sec-tional view on the line 3-3 of Fig. 2;

Fig. 4 is a sectional View on the line I-l of Fig. 2; v.

Fig. 5 shows means for introducing lithium compounds into the furnace of Fig. l;

Fig.' 6 is a vertical sectional view of the mechanism of Fig. 5, taken on the line B-G of Fig, 5; and

Fig. '1 is a sectional view of a shell to be coated with the copper-lead alloy.

Referring to Fig. 1, I have shown a gas fired furnace of conventional construction having a refractory lining III within which is contained a crucible II, which may be of graphite, preferably lined with a refractory cement such as silimanite to prevent'l reaction of the lithium therewith. A refractory cover plate I2 having a suitable gas vent I3 is provided. Gas and air are admitted throughfa burner ring I4 surrounding the furnace, the gas being supplied through taining an adequate supply of lithium vapor in the furnace above and around the crucible, the

incoming air is caused to ow through a chamber I8 containing solid lithium particles or a powdered compound .of lithium, contained between metal screens I9. A by-pass sleeve 20 permits alr to be introduced independently of the lithium chamber I8, if desired. Sumcient lithium either in elemental or compound form is carried in to the furnace with the air and vaporized therein, to produce a strong lithium spectral line when the gases escaping from the furnace are viewed with a spectroscope, thus denoting the presence of lithium in the furnace gases in an elemental form and in an ionized condition. Experimental data indicates that the presence o f lithium in the elemental form is due. at least in part, to the reducing action of carbon monoxidey gas in the furnace on lithium oxide, under the conditions prevailing in the furnace. A furnace lining which has been found suitable consists of silica 65%, alumina 25%, and the remainder ignition loss, i. e., moisture and other volatile material, and small percentages of iron, titanium, lime and magnesia.

The lining is treated by heating lithium in the furnace for a substantial period at atemper'ature sufllcient to cause formationrof a strong lithium vapor in the furnace as previously described. 'I'he lithium for treating the lining may be introduced into the furnace. as a charge, through the top thereof, although suilicient lithium can be carried into the furnace with the air flowing. through the chamber I8, to effectively treat the lining. The sufficiency of the amount of lithium or lithium compound taken up by the lining can be determined by heating a charge of copper and lead therein. If upon heating of such a charge to a temperature of from about 1700 to 1900 F., an agitation of the mass occurs the lining is suiiiciently treated for a successful carrying out of the present process. If no agitation occurs, it isnecessary to retreat the furnace lining in the'same manner. The treatment can also be effected by applying to the lining a compound of lithium, such as lithium chloride. The compound may be. applied as a water solution or suspended or dissolved in other volatile vehicles, as fully set forth in my copending application Serial No. 112,988, filed November 27, 1936, and entit1ed/,Furnaces.

The direction of the agitation of a nickel fre molten alloy in the crucible is indicated by arrows in Fig. 1, the` plain arrows indicating the apparent direction of the agitation when the charge 2| is heated to above the critical temperature, and the feathered arrows indicating the direction of agitation when the charge is permitted to cool below the critical temperature. With nickel added to the charge in amounts up to the order of magnitude of 9%, the direction of agitation appears always to be that shown by the plain arrows.

In the process of producing copper-lead-lithium alloys in which the 1ithium is introduced into the furnace atmosphere from the lining of the furnace, it is desirable to replace or add to the lithium given off by the walls, by nermitting a .small amount thereof to be carried in by the air flowing through the lithium containing chamber i8, although this is not necessary which has also been treated with lithium. The

lining 22 rests upon a water Jacket 2l having a water inlet 24 and an outlet 2i. Extending downwardly through the lower portion of the will be varied in accordance with the service to be performed by the alloy. For heavy work, asinrailroadrollingetochabearingrichin copper is preferred, as for instance, an alloy containing in theoriginal melt, lead 15%, lithium 0.01 to 0.1% and the remainder copper.

furnace and the water jacket 23 is a cylindrical die block 2B of refractory material'having Va rectangular opening 21 extending therethrough. A graphite receptacle 20 preferably having a lining of siilimanite or other refractory cement resistant to the disintegrating effect of lithium, extends upwardly from the die block, in which receptacle the molten metal is contained. A passageway 20 extends downwardly from the receptacle 2l to the slot 2l. An apertured plate Il closes the furnace and has resting thereon an apertured dome 3|. 'I'he plate Il and dome 8| are slotted in from one side. as indicated at 82 in Fig. 3. A burner ring Il has air inlets 34 and l5 for the admission of gas and air to maintain the alloy in the receptacle 2l in a molten state. Lithium or a compound thereof may be contained in the air inlet I5, if desired, 1n the same manner as shown at il in Fig. 1, but as an alternative. I have provided a refractory tube 38 in the base of the furnace which is packed with lithium and which serves to liberatev lith- A still harder bearing metal` alloy may consist, in theoriginal melt, of lead 10%, tin 0.2 to 2.0%, lithium 0.1% and the remainder copper.

Iron may also be used to harden the alloy, as for instance, a composition consisting in the original melt of lead 30%, iron 0.5%, lithium 0.1% and the remainder copper.

A good bearing metal for general use may consist of an alloy having in the original melt lead 30%, lithium 0.15% and the remainder copl the furnace and extremely fine subdivision and ium vapor slowly throughout the coating process.

in the die block, below the passageway 20, is

somewhat wider than the strip 31, thereby permitting the alloy'to flow from the passageway 29 and into the die block slot in contact with one face of the strip 31. The cooling jacket 23 causes the alloy to solidify as a coating on the strip. v

The lithium vapor generated or released by the furnace lining passes over the receptacle 28, permitting an absorption of lithium into the charge, thereby to maintain the agitation of the mass and consequent high quality of-the alloy coating. The lithium vapor. also passes, with the furnace gases, through the apertured plate Il and dome Il in contact with the upper portion of the strip 3l, and due to its reducing action, prevents oxidation of thesurfaceof the uniform dispersion of the lead in the copper upon casting. yAnalysis of the lithium content of a number of very satisfactory copper-lead-lithium alloys, bythe spectroscopic method, the

proportions of lithium frequently being too small for accurate determination by ordinary chemical analysis methods. is given below, to indicate the range of lithium to be expected in such alloys.

In place of introducing metallic lithium into the furnaces of Figs. 1l and 2, a compound thereof, such as the chloride, fluoride, hydroxide, oxide, or carbonate of lithium, or lithium containing ores such as spodumene or amblygonite, or

' mixtures thereof, may be used. The lithiated heated strip prier 'to ite passage inte me meiten mass. Consequently, due to the extremely clean surface thus produced on the strip and the freeydom of the alloy itself from impurities, due to acteristics of lead and the coated strips may be stamped, bent, machined and otherwiseworked into any desired form.

As previously stated, the compomtion of the Vcopper and lead content of the alloy may vary wiuiin wide limits whiie maintaining the advantages of ilne structure and uniform disperatmosphere may be provided in a gas red furnace, for instance, by introducing a small quantity of a compound of lithium in powdered form. into the air or gas stream leading into the furnace or it may be injected or blown directly into the furnace through an aperture provided in one of the walls thereof. An apparatus for introducing the powdered lithium compounds directly into the furnace or into the air or gas conduit extending thereinto is fully disclosed in my copending application Serial No. 143,410, nled May 19. 1937, and entitled Injecting apparatus." In an oil nred furnace the lithium compounds may be added directly tothe 011,. either as an oil soluble compound or in colloidal sussion. The relative amounts of lead and copper 'lhe amount of lithium compound required to produce the requisite condition of the furnace atmosphere is very small but is not kcritical and may be readily determined by experiment for any particular furnace. The furnace should be operated on the reducing side sothat the'furnace gases will contain a small percentage of carbon monoxide, the purpose of which will hereinafter appear.- The desired rate or frequency of introduction of the lithium compound may be determined by spectroscopic examination of the gases escaping from the furnace.

It has been found when using a salt, such asA lithium carbonate, introduced either continuously or at intervals throughout theprocess, that suitable results may be obtained 'in anew or unseasoned furnace, although with continued use a iiner subdivision of one metal in the other is obtained. l

While I prefer to employ the apparatus shown in my copending application Serial No. 143,410, referred to above, for introducing the powdered compounds into the furnace; I have, for ease of illustration, shown a. simplifiedl Iequipment for this purpose in Figs. and 6 which will now be described.

Gas and air are admitted through the burner ring I4 surrounding the furnace, the gas being supplied through a conduit 40 and the air through a. conduit 4I. A blower 42, shown diagrammatically, and suitable valves (not shown) control the amount of air supplied.

Interposed in the air line 4I is means for introducing lithium compounds into the furnace. 'Ihis means comprises a sleeve 43 threaded into a T 44 in the air line, a piston 45 slidable in the sleeve 43 and a hopper 46 for the lithium compound 41. The piston 45 is provided with an annular recess 48 adapted in theretracted position of the piston to be positioned beneath the hopper so as to receive a charge of the compound and to convey the same into the air line 4| when the piston is moved to the dotted line lithium compound. It is not necessary, however, that the lining be of the particular composition specied heretofore, since linings have been andulusite, and mulllte, analyzing as follows: silposition. The compound thus introduced into the air stream is carried by this air into the furnace where it is highly heated. A cross bar 49 facilitates the manual reciprocating movement of the plunger and a stop 50 limits the outer movement thereof. The end 5| ofthe piston fits closely in thebore of the cylinder and prevents the air under pressure in conduit 4I. from blowing out through the hopper 46.

If desired, the plunger 45 may be reciprocated by a continuously operating crank 52, as shown in Fig. 6, so as to supply the lithium compound in definitely timed increments.

The desired frequency of operation of the plunger may be determined by spectroscopic inspection of the gases escaping from the vent I3, the lithium compound being supplied in vsuch quantities and at such frequency as to maintain a strong lithium line in the spectrum when the furnace gases are viewed through a spectroscopie.

'Ihe lithium compound so introduced is reduced to lithium metal in the furnace and produces in the copper lead charge a natural circulation or agitation of the molten mass in the samemanner as when metallic lithium is-introduced into the furnace. y

The furnace linings, as stated, may` .be ycomposed largely of silicon oxide, and if desired, the lithium compounds may be introduced into the furnace at spaced intervals since the linings servev erage furnace temperature.

ical 38.07%, alumina 56.63%, titanium 1.14%, iron oxide .73%, ignition loss 2.78% and the remainder moisture and other impurities, has been found suitable. This cement may also be used as a coating for the bricks after their assembly in the furnace. In general, cellular insulating brick or moulded or tamped-in linings have 'not been as satisfactory as linings built up from hard burned refractories, apparently due to the high permeability thereof or the reaction of the lithium or one of its compounds with `the binder employed in such moulded linings. Linings, hearths and other `refractory parts of the furnace consisting of'or containing silicon carbide have .beenk found to react detrimentally with the lithium of the atmosphere, due possibly to the nature of the binder commonly employed, causing breakdown of the refractory and to some extent, reduction inthe efiiciency of the lithium containing atmosphere for its intended purpose. m

I prefer to introduce the lithium metal or compound into the furnaces mixed with the air or fuel since this insures that it will pass through the hottest part of the name, which is at a temperature 'several hundred degrees above the av- Hence the lithium or its compound will be more readily converted into a vapor.

Under theconditions prevailing in the furnace the lithium compound, or at least a portion thereof, breaks down liberating free metallic lithium. The reaction is apparently first the formation of lithium oxide which reacts with earbon monoxide as follows:

'I'he lithium is thus freed to combine with the oxygen of the furnace or any oxygen that may be included in the metal being heated and the lithium carbonate of the above reaction is thermally broken down to lithium oxide liberating carbon dioxide. Thereaction is then repeated with the lithium oxide so formed. As will be noted from `the reactions set forth above each particle of lithium present in the furnace goes through the above cycle repeatedly, until it' ultimately escapes with thefurnace gases and it is necessary, therefore, to supply additional lithium or lithium compounds only to replace that so escaping and as a storage and liberating medium whereby the desired atmosphere is maintained within the fur- `that absorbed by the material being heated ordeposited on parts of the furnace.

As the steel or other backing metal 31 passes through the lithium atmosphere in the furnace 22, a layer or coating of a compound of lithium., mainly the oxide or carbonate, condenses thereon and forms a protective coating over the surface, which coating notA only prevents oxidation of the metal but actually reduces oxide formations thereon. It moreover protects the metal from any carburization. decarburizaticn or other deleterious change in structure orcomposition. The lithium compound on the metal strip 31 alsomayactasafluxtoassistinthebonding of the copper, copper alloy or other coating metal thereto. Whatever the action of the lithium atmosphere, it retains the parts free from oxidation, enhances the wetting of the4 strip by the molten metal and causes an actual alloy bond to occur between the backing strip and the coating metal.

While the invention has been described with particular reference to the application of copper-lead alloys to .steel backing strips, for the production of bearlngs,it is to be understood that pure copper or alloys of copper other than copper and lead, as for instance brasses and bronzes. or aluminum and aluminum alloys, may be applied in the same manner to suitable supporting or backing metals in the lithium containing atmosphere. In fact any two metals or alloys may be joined which are capable of bonding with each other when the less refractory thereof is in a fused state and oxygen free and the surface of the solid and more refractory metal is free from oxide formations.

In the case of copper or copper alloys, the copper actually penetrates into the steel `backing member to a considerably greater depth, in the lithium containing atmosphere than can be obtained in hydrogen or other reducing gases, thus indicating extreme cleanliness of `berth the solid and the fused metal.

In place of coating a continuous strip ofbacking metal, the copper-lead alloy may be poured directly into steel shells of cylindrical or other desired shape. In such case the shells are preferably heated in a furnace having a lithiated or other nonfoxidizing atmophere and the copper-lead alloy poured therein directly from the crucible 2i. The shells may be double walled, as shown in Fig. 7, the inner and outer shells Il and 6i being held in spaced relation by radial wires or spacers l1. The'copper lead alloy is poured into the inner shell and permitted to rise between the shells, the inner core and inner shell il being subsequently turned out. By pouring in `this manner. the alloy flows with-less disturbance, between. the inner and outer shells.

'I'he lithium used inthe alloys and in the process described was pure lithium such. for example, as that prepared by the Maywood Chemical Works of Maywood, N. J.. but it is contemplated that less pure lithium or lithium alloyed Vwith other permissible components of the alloy-to be produced or compounds of lithium, the other components of which readily escapeI or are harmless, may be used.

The copper used has been oxygen free copper, known in the art as such, and the leadv has been that known commercially las 99.9 plus per in the composition to produce desirable variations in the physical properties of the alloy and such alloys of copper are intended to be included 'underthe v'term copper," when used in the claims. 4 l

The termfalloy,I is used throughout the speciflcation and in the claims, in a broad sense, to include a solid solution, mechanical' mixture or Iother. form of `combination of the various elements thereof.

` molten alloy, to `coat said article.

` 2. The vmethod of coating metals with a copper-lead alloy which comprises heating the metal to be coated in an atmosphere containing lithium vapor and while subject to said atmosphere depositing t a copper-lead-lithium alloy thereon.V

`3. The method of coating supporting metals with a copper-lead alloy comprising generating lithium vapor in a furnace, heating the copper and lead together in a molten state therein to produce agitation of the alloy. passing the supporting metal through said lithium vapor and depositing a coating ofla copper-lead alloy thereon. l

4. 'I'he method of making steel backed copperlead bearings comprisingheating copper and lead together in a'molten state in the presence of lithium, heating said steel backing in anonoxidizing atmosphere and casting said copperlead alloy onto said steel backing. l

5. The method of coating metals with copper .and alloys ofjcopper comprising heating said `metal in a lithium containing atmosphere and while subject to said atmosphere casting said copper or copper alloy thereon.

6. The method of producing an alloy bond between copper oran alloy of copper and a more refractory backing metal comprising casting said copper lor copper alloy onto said more refractory metal in an atmosphere containing lithium.

7. The method of coating an oxidizable metal with a lower melting point metal or alloy which comprises heating the metal to be coated and the coating metal or alloy, in the presence of a lithium vapor, above the melting point of the lcoating metal `or alloy andy casting said kcoating metal or alloy thereon.

` 8. The methodof coating a metal with a lower melting point metal or alloy which comprises maintaining said coating metal or alloy in a molten condition in a heating chamber containing carbon monoxide. introducing a compound "of lithium into saidchamber in sufllcient quantity to produce a lithium line in the spectrum of the gases `in said chamber. passing the metal to be coated through a portion of said chamber and casting said coating metal or alloy thereon l HAROLD J. NESS.

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