Nov. 21, 1939. H. J. NESS 2,181,093 HEAT TREATMENT OF Filed Jan. 26, 1938

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UNITED STATES PATENT office 2,181,093 EEAT TREAMNT OF METALS arold J. Ness, Bloomfield, N.J., assignor to Nes alloy Products, inc., New York, N. Y., a corpool ration of New Jersey Application January 26, 1938, serial No. 186,941 2 Claims. (C. 148-16) This invention relates to the of both surface of the part and may be discovered only ferrous and non-ferrous metals and more particul on failure of the part in use. Similar decarburi larly to the provision of an atmosphere for the zation and scaling problems arise in the reheating heating and heat treatment of such metals for of billets and the heating of bars, wire bars and 5 mechanical working, normalizing, , etc. slabs for , piercing, as in tube making, in This application is a continuation in part of the SOaking of ingots, and in the heat treat my applications Serial No. 67,547, fled March 6, ment of finished or partially finished parts for 1936, and entitled "Metallurgical process and ap hardening, normalizing, etc. Troublesome oxide paratus', Serial No. 79,968, filed May 15, 1936, formations also Occur in the heating and heat 0. and entitled 'Metallurgical process', and Serial treatment of such metals as brass, copper and 0 No. 84,413, filed June 6, 1936, and entitled "Pre aluminum, for forging, rolling, drawing, spin vention of scale formation on ferrous metals'. ning, etc. In the forging of steel for the fabrication of It is, therefore, one of the objects of the pres such parts as connecting rods, crank shafts, auto ent invention to eliminate and/or 5 mobile axles, aircraft engine cylinders, gears, Scaling of , and steel parts during heating in 5 cutlery, etc., it is necessary to heat the steel to preparation for the mechanical working thereof, the forging temperature, usually between 2000' F. Or for normalizing or hardening thereof. and 2600° F. During such heating decarburiza Another object is to provide uniformity in tion of the surface of the occurs and a weight and size of parts being heated or treated. 20 heavy layer of scale accumulates on the surface Still another object is to provide a method of 20 thereof, which scale must be removed before preventing carburization, and/or scale formation forging. This is usually accomplished by impact during heating of iron and steel, which method and scraping and by directing a stream of live will be simple, inexpensive and dependable. steam at considerable pressure against the bars Another object is to prevent oxide formation or blanks. These procedures, however, do not On non-ferrous metals, such as copper, brass completely remove the scale, and as a Conse and aluminum, during heating thereof. quence there is a large proportion of rejections Another object is to enable forgings and other of forged parts due to the scale falling into the mechanically worked metal parts of superior qual forging die and being hammered or forced into ity to be obtained. 30 the surface of the forging during the forging Op Another object is to prevent detrimental alter 30 eration. Moreover, due to the abrasive action of ation of the composition or structure of metal, this scale, the life of the forging dies is materially ordinarily resulting from contact with the fur shortened. In the forging of large or complicat nace gases, during the heating thereof. ed parts many operations are required and often Another object is to protect the metal both it is necessary to reheat the parts several times, physically and chemically, against oxidation, de before the forging operation is completed. Each carburization or detrimental alteration of its heating of the metal, of course, causes additional composition or structure, during the heating scale formation, decarburization, etc., and the thereof and during the subsequent Working resultant reduction in size of the part caused and/or cooling thereof. by the removal of the scale or the deepened de A still further object is to degasify metal, im 40 carburization thereof must be allowed for. How prove its grain refinement and enhance its physi ever, the depth of scale formation or decarburi cal properties. zation is variable depending. On the length and Another object is to condition steel to facili temperature of the heating and the composi tate nitriting thereof. 45 tion of the furnace gases and of the metal, and A still further object is to enable the foregoing 45 hence they cannot be accurately compensated for. objects to be accomplished in a furnace of the Therefore, considerable machining of the parts electric, oil or gas fired type. to remove the decarburized surface portion there Other objects and advantages will hereinafter of and to bring the parts to accurate size is usu appear. 50 ally required. Moreover, any scale driven into In accordance with the present invention I the forging in one of the early operations is heat the metal for treatment Or in preparation for Worked deeper into the metal as subsequent op mechanical working, in an atmosphere contain erations are performed thereon and may weaken ing lithium, which in contact with the metal and render the part defective. Such defects are serves to deoxidize or partially deoxidize the same 55 not always detectable by an examination of the and preyent decarburization of the metal or oxide 55 2 2,181,093 formations on the surface thereof. In the pro Oxygen from that required for complete combus duction and maintenance of the required lithium tion so that the furnace gases will contain a Small containing atmosphere in the treating furnace, percentage of carbon monoxide, the purpose of I prefer to employ a lining for the furnace which which will hereinafter appear. The lithium com s does not absorb too great a quantity of the lithium pounds introduced into the furnace results in the or react detrimentally therewith during the heat formation of lithium metal, lithium oxide and ing process. It is desirable to condition the lining lithium carbonate in the furnace atmosphere. before use by heating the lining, either before The lithium metal serves to eliminate free oxygen or after assembly in the furnace, in the presence from the furnace atmosphere with the formation O of a vapor of lithium or compound of lithium, of lithium oxide. The lithium oxide unites with 0. preferably at a temperature of about 2000 F. The carbon monoxide in the furnace atmosphere to treatment can also be effected by applying to the form lithium carbonate and metallic lithium. lining a compound of lithium, such as lithium The lithium carbonate thermally dissociates into chloride. The compound may be applied as a carbon dioxide and lithium oxide. When the 5 water solution or suspended or dissolved in other metal to be heated is placed in the furnace, com 5 volatile vehicles, as fully set forth in my copend pounds of lithium, mainly the Oxide or carbonate ing application Serial No. 112,988, filed November So present in the atmosphere condense thereon 27, 1936, and entitled "Furnaces'. and form a protective coating over the surface, While a furnace lining so treated will give off protecting the same from any oxidation, decar 20 lithium vapor for a considerable period, it is de burization or other detrimental alteration of the 20 sirable, in Order to maintain such atmosphere, composition or structure of the metal that might that additional amounts of lithium be supplied as otherwise occur. This protective coating remains the process continues. This may be accomplished on the metal throughout the heating process and by generating a vapor from a supply of lithium the Subsequent working and/or cooling of the contained in the furnace but I prefer to intro metal, and will remain on the parts during a sub 25 duce it into the furnace from the outside. A very sequent limited heating thereof in a non-lithiated effective way I have found of supplying lithium atmosphere. to the furnace is mixed with the air or fuel either In carrying out the process of the continuously or periodically. When introduced present invention, the furnace is brought up to periodically, the lining serves as a storage and the proper treating temperature and the lithium 30 liberating medium whereby the desired atmos compound is continuously or substantially con phere is maintained within the furnace between tinuously introduced into the furnace or into the the periods of introduction of the lithium. air or fuel stream leading to the furnace in such In place of introducing metallic lithium into quantity as to produce a rich lithium color in the the furnace, a compound thereof, such as the flame. The lithium not only neutralizes the oxi 35 chloride, fluoride, hydroxide, or carbonate of dizing effect of the furnace gases but the metal, as lithium, or lithium containing ores such as stated, immediately becomes coated with a protec spodumene or amblygonite, or mixtures thereof, tive layer composed primarily of lithium com may be used. The lithiated atmosphere may be pounds. At the time the metal is placed in the provided in a gas fired furnace, for instance, by furnace and for a brief interval thereafter, a 40 introducing a small quantity of a compound of copious supply of the lithium compound may be lithium in powdered form, into the air or gas introduced into the furnace, if desired, in order stream leading into the furnace or it may be to promote a rapid formation of the protective injected or blown directly into the furnace coating on the parts to be heated, and thereafter through an aperture provided in the walls thereof. the Supply of the compound may be reduced to An apparatus for introducing the powdered the minimum amount required to maintain the lithium compounds directly into the furnace or coating thereon. The coating tends to vaporize into the air or gas conduit extending thereinto from the parts as the heating continues and by is fully disclosed in my copending application maintaining a small continuous supply of the Serial No. 143,410, filed May 19, 1937, and en Compound to the furnace, this evaporation is 50 titled "Injecting apparatus'. In an oil fired either prevented or additional amounts of the iurnace the lithium compounds may be added compound are deposited on the parts as the directly to the oil, either as an oil soluble com evaporation Occurs, so that the coating is retained pound or in colloidal suspension. A process of intact. treating fuel oil with lithium compounds is dis The invention will be more fully understood by closed in my copending application Serial No. reference to the accompanying drawing in which: 154,203, filed July 17, 1937, and entitled “Promo Figure i is a vertical sectional view of a forging tion of '. In the case of electric fur furnace showing the preferred location of the naces the lithium compounds may be mixed with blanks and a means of producing and maintain 60 powdered carbon, such as graphite, and the mix ing a lithium containing atmosphere or condition 60 ture blown in a fine spray into the furnace in the in the furnace; manner set forth in my copending application Figure 2 is a vertical sectional view of a hearth Serial No. 143,411, filed May 19, 1937, and en type furnace with a modified apparatus for intro titled "Metallurgical process'. ducing lithium compounds thereinto. 65 The amount of lithium compound required to Figure 3 is a photomicrograph of a section of produce the requisite condition of the furnace chrome nickel steel heat treated in a normal un atmosphere is very small but is not critical and lithdated furnace atmosphere; and may be readily determined by experiment for any Figure 4 is a photomicrograph of a similar particular furnace. It should be sufficient to pro specimen heat treated in a lithiated atmosphere. 70 duce a rich scarlet colored flame when the fur Referring first to Figure 1, I have shown a fur 70 nace gases leaving the furnace are viewed with nace of the conventional type having, a refractory the naked eye. Too great a quantity cannot be lining 0, an opening for the burners 2 and used, however, since it tends to extinguish the outlets 3 for the gases. A lining which has been flame. The furnace should be operated on the found suitable for treating temperatures up to 75 reducing side, that is, with a slight deficiency of about 1800 F, analyzes as follows: silica. 65%, 2,181,098 3. alumina 25%, titanium oxide 1.2%, and the re powdered compounds thereof, so as to receive a mainder impurities and volatile constituents. It chargethereof and to convey the same into the is not necessary, however, that the lining be of air and gas line when the piston is moved in this particular composition, since linings have wardly. The charge thus introduced into the been found satisfactory having a silica content of air and gas mixture is carried by the same into about 31% with approximately 62% alumina and the furnace whereupon, as stated, it passes the remainder mainly, iron oxide and titanium through the hottest part of the flame. The pis Oxide. Linings of magnesium oxide, aluminum ton may be operated manually from time to time oxide and chromium oxide may also be employed throughout the process as determined by exper O or the furnace lining may be composed of hard ience or an inspection of the gases escaping from 10 burned brick of low permeability and low porosity the furnace, or if desired the plunger may be containing approximately 50% silica and 4.4% reciprocated by a continuously operating Crank alumina, having a bulk density of about 1.2 oz. or other means, as shown in my aforesaid appli per cu, inch and a fusion point of about 3200' F. cation Ser. No. 79,968, so as to supply the lithium 5 For furnaces operating at temperatures below in definitely timed increments. 5 about 1800 F. a less dense and less refractory The steel bars 20 being heated are positioned brick may be employed. A suitable cement for Cn the floor of the furnace remote from the bonding the bricks, such as sillimanite, cyanite, burners and at a place where the furnace tem andulusite, and mullite may analyse as follows: perature is substantially uniform. The vapor silica. 38.07%, alumina 56.63%, titanium 1.14%, produced by the lithium metal or compound 20 iron oxide.73%, ignition loss 2.78% and the re thereof pervades the entire furnace and prevents mainder moisture and other impurities. This decarburization of the metal and the formation Cement may also be used as a coating for the of oxide scale on the surface of the parts being bricks after their assembly in the furnace. In heated. general, cellular insulating brick or moulded or In Fig. 2 I have shown a modified apparatus for tamped-in linings have not been as satisfactory the continuous introduction of lithium com as linings built up from hard burned refractories, pounds into a furnace. Referring to this figure, apparently due to the high permeability thereof I have shown a conventional furnace O' pro Or the reaction of the lithium or one of its com vided with burners 2 designed to burn gas, al pounds with the binder employed in such moulded though the apparatus may be equally well em 30 linings. Linings, hearths and other refractory ployed with an oil burning furnace. The furnace parts of the furnace consisting of or containing is provided with a supply of a compound of silicon carbide have been found to react detri lithium, such as lithium carbonate, through a mentally with the lithium of the atmosphere, due conduit 2 extending through the wall of the fur possibly to the nature of the binder commonly nace above one of the burners. While the inlet employed, causing breakdown of the refractory 2 has been shown relatively close to the burners, and to Some extent, reduction in the efficiency of it may be imore remotely disposed and in the case the lithium containing atmosphere for its in of a hearth type furnace, as shown, in which the tended purpose. When the lithium or its con burners are below the hearth, it may be disposed pounds are introduced into the furnace through either above or below the hearth. A supply of the burner or at a point adjacent thereto, the lithium compound may be provided by an inject 40 flame should not impinge directly on the refrac ing apparatus of the form shown in the afore tory, particularly in furnaces operated at high Said application Serial No. 143,410. In Fig. 1. I temperatures. In the embodiment shown, the have shown a modified form of such apparatus flame is directed, as indicated, to the rear of the comprising a container 23 consisting of a cylin furnace, the products of combustion being re drical tube 24, preferably of glass, having flanged as flected by the rear Wall towards the front outlets upper and lower closure members 25 and 26 3. As stated the lining to may be precondi respectively, clamped against the ends of the tube tioned, if desired, by introducing lithium or a 24 in any suitable manner, with interposed Compound thereof into the furnace while the fur gaskets 27. Extending axially through the con 50 nace is at an elevated temperature or the lining tainer 23 is a shaft 28, journaled in the closure may be painted with a water solution of a lithium members 25 and 26. The shaft 28 is driven Compound, such as lithium chloride, and the fur through suitable reducing gears 29 by a motor 3. nace brought up to heat. Thereafter the furnace Mounted upon the shaft 28 are several sets of 55 may be used for successive heats by introducing blades 32, adapted to agitate the powdered lith 55 lithium metal or compounds into the furnace iun compound which is contained in the cham either continuously or at such periods as is neces ber 23. A combustible, mixture of air and gas sary to maintain the requisite amount of lithium linder pressure is supplied by a blower 33 also in the atmosphere of the furnace. driven by the motor 3, the air and gas mixture 60 I may introduce the lithium metal or comi being conducted by a tube 34, into the lower wall 60 pound into the furnace mixed with the air or fuel of the container 23 and passing out of the con since this insures that it will pass through the tainer laden with the powdered compound, hottest part of the flame, which is at a tempera through the conduit 2, extending into the fur ture several hundred degrees above the average 3Ce. 65 furnace temperature, Hence, the lithium or its A valve 35 controls the flow of the air and gas 65 compound will be more readily converted into a into the chamber 23 and consequently the amount Vapor. of lithium compound blown into the furnace. I have shown means for introducing measured. In order to prevent fusing of the lithium com amounts of lithium metal or compounds thereof pound as it passes through the tip of the conduit into the furnace, comprising a sleeve 4 threaded 2, I bypass a part of the air and gas mixture 70 into an eblow 5 in the air intake 6. A piston 7 from the blower 33 through a conduit 37, provided slidable in the sleeve 4 is provided With an With a suitable regulating valve 38. The air and annular recess 8 adapted in the retracted posi gas mixture flowing in conduit 37 is conducted tion of the piston to be positioned beneath a throug-il a Venturi tube 39, disposed adjacent the 5 hopper 9, containing comminuted lithium or outlet 40 of the container 23, so as to assist in 75 4. 2,181,098 the withdrawal of the compound laden air and and consequently a lesser amount thereof is re gas from said container. The additional air and quired. It also breaks down to lithium oxide at gas provided through the conduit 37 not only a considerably lower temperature. It is less Cons serves to maintain the terminal of the conduit venient to use, however, due to its extreme caus 2 cool, but is supplied at sufficient pressure to tic nature but where production of the protective blow the powdered compound through the con atmosphere is required with a furnace tempera duit at such speed that fusing thereof to the wall ture as low as about 700 F, the hydroxide or a of the tube adjacent its tip is prevented. By mixture of the hydroxide and the carbonate may supplying a gas and air mixture to the blower, be employed. However, the carbonate is pre O the ratio of gas and air in the furnace is not dis ferred for general use due to its ease of han O turbed by the fluid medium employed to convey dling, and its relatively cheap cost. The amount the powders into the furnace. A flame arrest of any particular lithium compound td be used, ing valve 36 is included in the line 2 extending in order to provide the desired protective coating, into the furnace to prevent back flash through and lithiated atmosphere can be readily deter 5 the line and if desired, a screen or mesh 4f may mined by making One or more test heats Or the 5 be disposed about the end of the conduit 2 to metal being heated can be observed as the heat break up the flame and also to prevent flashback. ing continues to determine if a proper coating In place of the mixture of air and gas, either air is forming thereon. In certain furnaces fired alone or gas alone may be employed to convey the With artificial gas excellent results have been ob powdered compound into the furnace, although tained with the use of as little as about 0.003 the use of air alone tends to create localized hot Ounce of lithium carbonate per cubic foot of gas zones in the furnace and somewhat detracts from but the amount required is not critical and may the efficiency of the action of the lithium comr vary either side of the figure mentioned. Equiva pound in such zones. Excessive moisture in the lent amounts are required in oil burning fur air, such as results from high compression of the naces for equal heat generation. In electric fur same, or in the gas employed, also detrimentally naces I add carbon monoxide to the furnace or effects the action of the lithium compound and a Supply of carbon from which carbon monoxide the maintenance of the proper lithiated atmos may be generated, in order to obtain a reduction phere within the furnace, and should be avoided. of the lithium oxide in accordance with the fore The inlet 2 should preferably be located relative going equation. When the proper lithium con to the parts to be heated so that the lithium dition is obtained in the furnace, the metal to be compound laden gas stream does not inpinge di heated is introduced therein. If desired, the rectly on such parts but that the compound will metal to be heated may be placed on a traveling be first reduced to metallic form and diffused CCnveyor and passed through the furnace at such into the furnace atmosphere, particularly when rate as to complete the heating or heat treatment air is used as the inspirating or carrying medium. during its passage therethrough. The furnace In carrying out the present process the fur may be opened freely during the process, for the nace is brought up to heat and the motor 3 introduction or removal of parts, or it may be started. The valve 35 is then opened to permit, left open continuously, if desired, without danger the inspirating medium to pass through the of Oxidation of the parts. chamber 23. In so doing it picks up some of the The presence of the lithium metal in the fur powdered lithium compound carrying it into the nace gases permits the heating to be carried out furnace f O. Under the conditions prevailing in without the use of protective muffles, and directly the furnace the compound, or at least a portion in the furnace gases without scaling, carburiza is thereof, breaks down liberating free metallic tion, decarburization or other detrimental effect lithium. The reaction is apparently first the On the metal parts being heated. In fact none of formation of lithium oxide which reacts with Car the embrittling effects or other modification of bon monoxide as follows: the grain structure obtained in heating in hy drogen or other reducing gases, are experienced. 2Li2O--CO=Li2CO3--2Li Furthermore, as stated, there is a deposition or The lithium is thus freed to combine with the condensation of the lithium and/or lithium com oxygen of the furnace or of the metal being. pounds which forms very quickly on the parts heated and the lithium carbonate of the above and which physically protects the surfaces there reaction is again thermally broken down to lith of from any contaminating or oxidizing influence ium oxide liberating carbon dioxide. The reac of the furnace atmosphere. As a result of the ion is then repeated with the lithium oxide SO protective atmosphere and this protective coat formed. As will be noted from the reactions Set ing high carbon and alloy steels, including forth above, each particle of lithium present aluminum containing steels may be heated to in the furnace goes through the above cycle gether without oxidation, decarburization or 60 repeatedly, until it ultimately escapes with the other deleterious alteration of the composition furnace gases, and it is necessary, therefore, to thereof. The coating deposits apparently either supply additional lithium or lithium compounds as an oxide or a carbonate of lithium or both and only to replace that so escaping and that de adheres to the parts throughout the heat treat posited on the material being heated or on parts ment and after removal from the furnace, so that 65 of the furnace. when the heating is complete the parts may be 65 The valve 35 should be adjusted So as to cause immediately removed from the furnace and a sufficient flow of the lithium compound into Worked or cooled in the air. Upon cooling the the furnace, to produce a rich lithium color in coating appears to be mostly the carbonate of the furnace gases. The amount of the compound lithium. 70 required varies with the compound used, the type The valve 35 is kept open or partially open 70 and construction of the furnace, the location throughout the process so as to supply the lithium therein of the metal to be heated and the tem compound continuously to the furnace during the perature attained in the furnace. For instance, heating but, of course, if desired, the amount of lithium hydroxide is approximately twice as rich compound may be varied as the heating con 75 in lithium per unit of weight as the carbonate tinues. s 2,181,098. S The nature, appearance and color of the pro preparatory to hot working, reduces this scale to tective coating varies with the type of furnace a greater or less extent depending on the length employed, the location and composition of the of heating, thus eliminating it or converting it parts therein, the amount of lithium compound into a soft powdery form. used, and the temperature and period of heat The heating of metals in the lithium contain ing. In some instances the coating formed is ing atmosphere also serves to refine, the grain, not visible, the parts, however, remaining un presumably by the elimination of impurities or oxidized. In heat treating where the period of by preventing the absorption of impurities into heating is short and the coating thin, it may be the metal during heating. Whatever the cause, O removed during of the parts and in microscopic examination of the metal after be- 0 . any case the coating may be readily removed by ing heated in accordance with the teachings of dipping the parts, either when hot or after cool this invention shows the metal to have a def ing, in a weak acid solution, such as acetic or nitely improved grain structure than that re hydrochloric acid. An inhibitor is preferably sulting from similar heating in the absence of 5 added to the acid to prevent etching of the metal. lithium. As a result the metal has better physi- 18 The parts, after the coating has been dissolved cal properties, greater tensile strength and elon therefrom are bright, the entire process being gation and increased izod, creep and fatigue effected without the removal of any detectable values. amount of metal from the parts. It will be understood, of course, that changes In Fig. 3 I have shown a microphotograph of may be made in the process without departing 20 100X magnification, of a specimen of S. A. E. No. from the invention, and I contemplate all Such 3312 chrome nickel steel, showing the micro changes as are within the scope of the appended structure at the carburized surface thereof after claims. heating at 1500 F. for fifteen minutes in an un What claim is: lithiated normal furnace atmosphere, and Water 1. The method of preventing substantial oxi quenched. It should be noted that the Specimen dation of metals during the heating thereof Com is noticeably decarburized for approximately prising conducting the heating at the required 0.005 inch in depth at the surface 42 and further temperature in an atmosphere containing a that there was a heavy scale on this surface, as lithium compound and carbon monoxide. indicated by the rough and irregular contour 2. The method of producing a lithium "atmos- 80 thereof. Where such a condition exists, it is phere in a metallurgical furnace containing car necessary to turn, mill, grind or otherwise remove bonaceous gases comprising introducing lithium the surface down to the full depth of the decar containing metal or a compound thereof into burization. It will be readily appreciated that the furnace substantially at the point of maxi such operation is expensive, inconvenient and re mum temperature thereof. 35 sults in a considerable loss of metal. 3. The method of producing a lithium contain Fig. 4 shows a similar microphotograph of the ing atmosphere in a furnace heated by car same magnification of an identical specimen bon containing gas or oil flame comprising in showing the micro-structure at the surface there troducing lithium metal or a compound thereof 40 of after heating to the same temperature for into substantially the hottest portion of the 40 thirty minutes in a lithium containing atmos flame. phere maintained by introducing lithium car 4. The method of treating ferrous metals com bonate into the furnace by the apparatus shown prising heating same in a furnace to a tempera in Fig. 2. It will be noted that the surface 43 is ture above 700 F. and generating lithium in 45 entirely free from decarburization or Scale. Such the furnace by reduction of a lithium compound 45 a specimen may be worked to exact size. with carbon monoxide. While the invention has been described with 5. The method of treating metals which com particular reference to the heating of steel for prises heating the same in a furnace containing forging operations, it applies equally well to the a reducing gas, to the desired temperature and 50 heating of iron and steel for normalizing, anneal introducing a lithium compound into the furnace 50 ing or hardening, as for instance for rolling and during said heating. operations as used in prac 6. The method of treating metals which com tice and in the annealing of metal stampings. prises heating the same in a furnace containing The protective atmosphere may also be used in carbonaceous gases, and introducing into the . 55 the heat treatment of non-ferrous metals, as for furnace during the heating a lithium compound 55 instance brasses, bronzes, copper and aluminum, which is decomposable at the temperature at the protective coating forming equally well On tained in the furnace during said heating. any metal and the lithium containing atmos 7. The method of treating metals which com phere and the coating Serving to prevent oxida prises heating the same in a furnace containing 60 tion or contamination thereof. The atmosphere carbonaceous gases and introducing into the fur- 60 is particularly suitable for such Operations as nace during the heating a lithium compound bright annealing of brass. The term "ferrous which is decomposable at the temperature at metals' as used in the claims includes iron, steel tained in the furnace during said heating, in and alloys thereof. sufficient quantity to produce a protective coat 65 The heating of iron and steel in the lithium ing on said parts. 65 containing atmosphere in addition to preventing 8. The method of treating metals which com- . scale formation, also effects a reduction or par prises heating the same in a furnace in the pres tial reduction of any Scale thereOn at the time ence of carbonaceous gases to above about 700° of its introduction into the furnace. For in F. and Supplying a sufficient quantity of lithium 70 stance, hot rolled iron or steel as Ordinarily Sup or a compound thereof in the furnace to pro- to plied by the manufacturer is usually coated with vide said parts with a protective coating of a a layer of mill scale. This scale is hard and lithium salt throughout the heating and subse brittle and in forging, drawing and shearing Op quent cooling of said parts. - erations is injurious to the dies. The heating of 9. The method of preventing oxidation or 75 the metal in the lithium containing atmosphere, decarburization of ferrous metals which com- 75 s 2,181,093 prises heating the same in a furnace containing combustion gases which comprises hatroducing carbonaceous gases to above 00' . and pro into the furnace atmosphere while the furnace widing a lithium containing atmosphere in said is at an elevated temperature, a compound of furnace of such concentration as to cause a lithium which will decompose under the con s deposition of a lithium compound on said parts. ditions and temperature prevailing in the fur lo. The method of treating metals comprising ce . heating the same in a carbon containing gas ... 20. The method of producing a lithium con fired furnace to the required treating temperature taining atmosphere in a furnace containing and introducing lithium carbonate into the fur carbonaceous combustion gases which com 10 nace in an amount of the order of magnitude of prises introducing a decomposable lithium com 10 0.003 ounce per cubic foot of gas consumed. pound into the furnace atmosphere at spaced 11. The method of promoting grain refinement intervals while the furnace is at an elevated tem in metals comprising heating the same in a fur perature. . - nace to the normal grain refining temperature 21. The method of producing a lithium con ls thereof and supplying a sufficient quantity of taining atmosphere in a furnace containing oar 15 lithium or a compound thereof and a car bonaceous combustion gases which comprises in bonaceous gas to said furnace to provide said troducing into the furnace atmosphere while the metal during such heating with a protective coat furnace is at an elevated temperature, measured ing of a lithium compound. amounts of a lithium compound, at a frequency 20 12. The method of preventing Ovidation, or to maintain a lithium line in the spectrum of decarburization, or effecting deoxidation or the atmosphere of the furnace, substantially, con grain refinement of ferrous and non-ferrous tinuously. metals during heating thereof comprising con 22. The method of producing a lithium con ducting said heating in an atmosphere the chem taining atmosphere in a furnace containing car 2sical composition of which substantially through bonaceous combustion gases which comprises out the process is oxidizing towards the metal, producing heat within the furnace above the de and containing lithium or a compound there composition temperature of a lithium halide un of, the heating being conducted at such temper der the conditions prevailing in the furnace and ature, and the lithium or its compound being introducing such lithium halide into the furnace. 80 present in such quantity as to cause a film of a 23. The method of producing a lithium con lithium compound to form on said metals. taining atmosphere in a furnace containing car 13. The method of rendering innocuous to bonaceous combustion gases which comprises heated metals a furnace atmosphere, the chem providing such furnace with a lining composed ical composition of which throughout the proc largely of silicon oxide and introducing a lithium 85 ess is oxidizing towards such metals, which in compound into the furnace atmosphere while the cludes comprising in said atmosphere carbon furnace is in Operation. monoxide and a small percentage of lithium. 24. The method of producing a lithium con .14. In the heating of metals, an atmosphere, taining atmosphere in a furnace containing care the chemical composition of which is oxidizing bonaceous combustion gases which comprises 40 towards the metals, containing carbon monoxide providing such furnace with a lining composed 40 and lithium. of a refractory material which does not react 15. The method of producing a lithium con detrimentally with lithium vapor under the nor taining atmosphere in a furnace containing a mal conditions existing during the operation of carbonaceous gas which comprises introducing the furnace and introducing a lithium compound into the furnace while it is in operation. 45 as nacelithium is atchloride such elevated into the temperature furnace while as theto cause fur 25. The method of producing a lithium con the lithium chloride to become decomposed. taining atmosphere in a furnace containing car 16. The method of treating metals which con bonaceous combustion gases which comprises prises heating said metals in a furnace con providing such furnace with a lining composed taining a carbonaceous gas and introducing a largely of chromium oxide and introducing a lithium compound into the furnace at intervals, lithium compound into the furnace atmosphere during the heating, of Such frequency as to while the furnace is in operation. maintain a continuous lithium containing at 26. The method of producing a lithium con mosphere in the furnace. taining atmosphere in a furnace containing car 17. The method of producing a lithium con bonaceous combustion gases which comprises. 55 taining atmosphere in a furnace containing a providing such furnace with a lining composed 55 carbonaceous gas, which comprises introducing largely of magnesium oxide and introducing a lithium carbonate into the furnace atmosphere lithium compound into the furnace atmosphere while the furnace is operating. while the furnace is in operation. 60 18. The method of treating metals which coma 2. The method of creating an atmosphere prises heating said metals in a furnace contain containing lithium metal in a furnace or the ing a carbonaceous gas and introducing a lithiun like comprising introducing a compound of compound into the furnace during the heating, lithium into the furnace in the presence of car in such quantities as to maintain a lithium con bon monoxide and producing sufficient heat 65 taining atmosphere in the furnace. therein to effect a reduction of said compound 19. The method of producing a protective at to metallic form by said, carbon monoxide. mosphere in a furnace containing carbonaceous BAROD. J. NESS.