US2181092A - Metallurgical process and apparatus - Google Patents

Description

, 1936 3 Sheets-Sheet l v H. J. NESS METALLURGICAL PROCESS AND APPARATUS Original Filed March 6 Nov. 21, 1939.

lNvE NTQR Harald AKA 925.5

BY 1, wmiw ATdORNE/K Nov. 21, 1939. H. J. NESS 2.l81,092

METALLURGICAL PROCESS AND APPARATUS Original Filed March 6, 1936 3 Sheets$heet 2 INVENTCR Harold J/Vass I F 'i'Tb EY Nov. 21, 1939. H. J. NESS METALLURGICAL PROCESS AND APPARATUS Original Filed March 6, -1936 3 Sheets-Sheet 3 Patented Nov. 21, 1939 METALLURGICAL PROCESS AND APPARATUS Harold J. Ness, Bloomfield, N. J., assignor to Nesaloy Products, Inc., New York, N. Y., a corporation of New Jersey Application March 6, 1936, Serial No. 67,547 Renewed October 18, 1939 21 Claims.

This invention relates to metallurgical operations and more particularly to apparatus for and a method of producing and maintaining a metallic vapor containing atmosphere and in the carrying-out of metallurgical operations in such atmosphere.

It is the present practice to carry out many metallurgical processes in an atmosphere of hydrogen gas to reduce the oxides of the metals undergoing treatment or to prevent oxidation thereof. The use of hydrogen as a reducing atmosphere is attended with considerable danger, however, due to the explosive nature of hydrogen and oxygen mixtures, particularly at the temperatures attained in many heat treating processes and in the presence of other combustible gases. Moreover, in many instances hydrogen detrimentally affects the physical properties of the metals undergoing treatment. Its use has, therefore,

been restricted to operations wherein a reducing atmosphere is essential and in which the resultant product is not thereby detrimentally affected.

It is one of the objects of the present invention to produce a reducing atmosphere for chemical and metallurgical processes which will be safe, economical 'and highly active chemically.

It is known that certain metals, such as the alkali and alkaline earth metals, when combined in small proportions with various other metals and alloys, impart beneficial properties thereto,

but no satisfactory method has been found heretofore for introducing and maintaining such highly volatile metals in metals of high melting point, such as copper, steel, iron and alloys thereof.

It is a further object, therefore, to provide a method of introducing such highly volatile metals into the more refractory metals and maintaining the same therein, in suiiicient proportions to im- 4 part the desired improved properties to the metals being treated.

Another object is to provide an atmosphere containing a metallic vapor which may be absorbed into the material being treated to react internally therewith 'in addition to providing an A further object is to provide a furnace for metallurgical processes which is not detrimentally affected by the metallic vapors.

A still further object is to regulate the rate of introduction of the metallic treating agent into 5 the furnace.

Still another object is to provide a method of and means for introducing and maintaining lithium inmolten metals during treatment of such metals.

A still further object is to provide a method of producing oxygen free metals such as copper, steel, and alloys thereof, etc.

Another object is to produce satisfactory lithium copper.

Other objects and advantages will hereinafter appear.

It has been proposed heretofore to treat certain metals with lithium and other alkali or alkaline earth metals by introducing the same directly 20 into the molten charge, but due to the highly volatile nature of such metals, they are quickly vaporized from the charge and either pass oil or are consumed by the furnace lining. As a consequence, such processes have not been satisfac- 5 tory due to the non-uniformity of the treated metals resulting therefrom, and such processes have largely gone into disuse. Moreover, such metals as lithium attack the usual furnace linings and the life of such furnace linings is therefore relatively short.

In accordance with the present invention, these difiiculties are avoided by producing within the furnace an atmosphere containing the treating metal, maintaining such atmosphere throughout the process, and providing a lining material which is resistant to the disintegrating effect of the lithium or other active vapor employed. By maintaining such an atmosphere, the treating metal lost by vaporization from the molten mass is replaced, at least in part, by ab sorption from the surrounding metallic vapor containing atmosphere. Some of the metallic vapor of the atmosphere is necessarily lost from the furnace, and it is essential in order to mainmain such atmosphere that additional amounts of the metal contained in the treating atmosphere be supplied as the process continues. This may be accomplished by generating a vapor from a supply of the treating metal within the furnace or by introduction from the outside.

I have discovered that such metal containing atmosphere may be produced and maintained by employing a. furnace lining which is capable of u absorbing large quantities of the treating metal and of liberating the same slowly during the treating process. For use with lithium a furnace lining composed largely of silicon oxide has been found to be suitable. It is desirable, however, to condition the lining before use by heating the lining, either before or after assembly in the furnaceflwlth lithium vapor, preferably at a high temperature of say 2000 F. The conditioned lining is capable at the high temperatures attained in the melting of copper and other metals of liberating lithium slowly and of maintaining continuously within the furnace-a lithium containing atmosphere for a long period of time, as can readily be determined by spectroscopic inspection of the furnace atmosphere. The lining may be reconditioned from time to time as required. However, when lithium in sufficient quantity is also added directly to the molten mass, the lin ings maintaintheir effectiveness continuously due apparently to the lithium vaporized from the mass being absorbed in part by the linings.

In many processes it is not necessary to add any lithium to the charge, a sufficient amount thereof to accomplish the desired effect being absorbedinto the mass from the lithiated atmosphere created by the heating of the furnace lining. In such cases, however, the lining if not replenished with lithium gradually loses its effectiveness and must be reconditioned. I prefer to replenish the lining continuously during the process. This may be done as stated, by vaporizing lithium from the charge, or it may be 'done by vaporizing lithium from a supplemental mass of lithium apart from the charge. A very effective way I have found of supplementing the lithium lost during the process is to introduce small amounts thereof into the furnace such as with the air or fuel. In whatever manner the lithium is supplied, whether by vaporization from the charge or other body within the furnace or by introduction from the outside of the furnace, the silica lining is capable of absorbing the excess lithium over that required for producing the desired lithium atmosphere at the time of introduction or at least a portion thereof and of re-- liberating it during the heating process at a slow and more or less uniform rate, thereby serving as a storage medium whereby a uniform lithium vapor condition is maintained within the furnace at all times during the treating process.

It is to be understood, however, that when the treating metal is introduced into the furnace in small, substantially uniform amounts, as for instance, mixed with the air of combustion or the fuel, is not necessary to employ a furnace lining which absorbs and liberates the treating metal. However, the lining used should be resistant to the chemical action of the treating metal or neutral thereto and incapable of absorbing the same to such an extent as to preclude the maintenance of the desired metallic containing atmosphere within the furnace. For instance, among linings which are resistant to the action of the lithium vapor may be mentioned sillimanite and chromium oxide.

When treating molten metals, such as copper and copper alloys, in a lithium containing atmosphere in a furnace, having a lining, such as silicon oxide, which is acid with respect to lithium, it is desirable to employ a container for the molten metal which is either neutral or basic, as for instance, graphite, chromium oxide, or sillimanite (A1zOa2S1O2). This container may take the form of a crucible or pot or it may comprise that portion of the furnace lining below the liquid level of the molten charge, the lining above the level of the molten metal, if desired being composed of silicon oxide or equivalent material.

In addition to treating molten metals with alkali or alkaline earth metals by absorption of such metals therein from the atmosphere produced in the furnace, the metallic containing atmosphere may be used in the heat treating of solid metals, where it is desired to prevent oxidation such as in hardening, normalizing and annealing of brass, copper, steel, and the heating of steel for forging, pressing or piercing, etc., or in certain welding operations, as for instance, in copper welding and in the uniting of certain bimetals in which the metals are clamped together and heated in the metal containing atmosphere until an alloy bond is produced thercbetween.

The invention will be more fully understood by reference to the accompanying drawings, in which:

Fig. 1 is a vertical section of a gas fired furnace suitable for the practice of the present invention;

Fig. 2 is a vertical section of an induction furnace provided with means for introducing the treating metal into the furnace;

Fig. 3 is an elevation, partly in section, of the burner and fuel feeding equipment of an oil fired furnace, showing means for introducing the treating metal in the oil line;

Fig. 4 is a vertical sectional view of apparatus for introducing the treating metal into the furnace in a vaporous state; and

Fig. 5 is a vertical sectional view of apparatus for introducing the treating metal into the fur-- nace in a liquid state.

In the following specific embodiments, lithium is recited as the particular treating metal, althought it is to be understood that the inventiontion is not limited to lithium, since the apparatus, or suitable modifications thereof, may be employed for producing and maintaining other metallic vapor containing atmospheres.

Referring to Fig. 1, I have shown a gas fired crucible furnace of conventional construction, suitable for the production of lithium copper. The furnace has a refractory lining l0 within which is contained a crucible l I. As stated heretofore, if the furnace lining used is acid to lithium, the crucible II should be composed of a material which is either neutral or basic as graphite, chromium oxide or sillimanite As shown the crucible may be composed of graphite, coated on the interior with sillimanite or other neutral or basic refractory material. A refractory cover plate l2 having a suitable gas vent I3 is provided. Gas and air are admitted through a burner ring l4 surrounding the furnace. the gas being supplied through a conduit l5 and the air through a conduit IS. A blower l1 and valve 18 control the amount of air and gas supplied.

In order to assist in maintaining an adequate supply of lithium vapor in the furnace above and around the crucible, the incoming air is caused to flow through a chamber l9 containing solid lithium particles 20 contained between metal screens 2|. A drip oil cup 22 maintains a protective oil vapor in the chamber I9. A bypass valve 23 permits air to be introduced independently of the lithium containing chamber is, if desired. It is to be understood, of course, that the chamber l9 may be between the blower and manner, as by a small electric motor.

furnace, if desired. Sufficient lithium is carried into the furnace with the air and vaporized therein, to produce strong lithium line when the gases escaping from.the furnace are viewed with a spectroscope.

The furnace lining l0 should be composed of a material with which the lithium does not react deleteriously, as for instance, sillimanite, chromium oxide or silicon oxide. A lining which I have found suitable consists of silica 65%, alumina and the remainder volatile constituents and small percentages of iron, titanium, lime and magnesium. Aluminum oxide in the quantity specified, even though it reacts somewhat with lithium, does not appear to materially affect the action of the lining in absorbing and liberating lithium.

Since the silicon oxide absorbs large quantities of lithium before a state is reached at which it both liberates and absorbs, it is necessary to condition the lining to bring it to a state of saturation or near saturation with lithium before introducing the copper or copper alloy in the furnace.

This conditioning may be accomplished by heating the furnace to about 2000 F. and then adding lithium thereto as a charge, through the top thereof, although sufllcient lithium can be carried into the furnace with the air flowing through the chamber l9 to effectively saturate the lining. After being so conditioned, the lining is capable of liberating lithium in appreciable amounts at temperatures above about 1850 F.

In adapting an old furnace to the present process, I prefer to completely reline the same since otherwise a much more severe and prolonged conditioning is required to cleanse and treat the lining.

The condition of the furnace lining improves with continued use of the furnace under lithiating conditions, and as a consequence, a better product is ordinarily obtained from a furnace in which several heats have been previously run.-

In the production of lithium copper it is only necessary to place the copper to be treated in the crucible l I, and bring the temperature of the copper up to about 2100 F. during which heating, lithium will be liberated from the lining and/ or introduced with the air in suificient quantity to produce a rich lithium vapor in the furnace atmosphere from which lithium will be absorbed into the charge to act as an alloying agent. If desired, a small percentage of lithium may be added to the copper bath, but ordinarily in a furnace which has been properly conditioned, I find it unnecessary to add lithium to the charge.

In Fig. 2 I have shown an apparatus for introducing measured amounts of lithium into a furnace 3|. The apparatus 30 comprises a chamber 32 having a vertically extending cylindrical passageway 33 into which a stick or bar 34 of lithium may be placed. A weight 35 presses the lithium on to a revolving abrasive wheel 36, such as a steel drum having a roughened or knurled surface. The wheel 36 is secured to a shaft 31 driven at a slow rate in any desired Fixed to the shaft 31 is a gear 38 which meshes with a second gear 39 fixed on a shaft 40 bearing in the side walls of the chamber 32. Obviously the gears 38 and 39 may be external of the chamber 32 if desired. Also fixed to the driven shaft 40, directly below the abrasive wheel 36 is a drum 4| having a series of V-shaped notches in its periphery. A brush 42 engaging the wheel 35 causes the lithium removed from the stick 34 and car ried around with the wheel 38 to drop onto the drum 4|, which in revolving in the direction indicated by the arrow, deposits the lithium particles in the chute 43 terminating in a small aperture Y 44 adjacent the periphery of a wheel 45 driven at a relatively high rate of speed, as by a separate motor. The wheel 45 has a notched periphcry whereby the lithium particles which drop thereon are propelled through the passageway 16 into the furnace 3|.

An electric furnace of the induction type is illustrated by way of example, although obviously the lithium feeding apparatus may be employed with any type of electric, gas or oil fired furnace. The upper part 4'! of the furnace lining, above the liquid level, is composed of a material such as silica which will absorb and liberate the lithium in the manner previously described. The lower part 48 of the lining, starting just above the liquid level, is composed of a refractory material which is neutral or basic, such as graphite, chromium oxide or sillimanite (13120323102) .The upper wall or cover of the furnace is disposed an appreciable distance above the level of the charge in order to provide for a substantial volume of the lithium containing atmosphere, produced in the furnace either from the injected lithium or that liberated from the furnace wall. An oil cup 49 secured to the upper wall of the chamber 32 may be regulated to permit a slow dripping of oil into the chamber 32 whereby to create a protective oil vapor therein.

It is to be understood that the lithium pulverizing and introducing apparatus shown in Fig. 2 may be employed with the crucible furnace of Fig. 1, either to inject the lithium directly into the furnace or into the air line, in place of or in addition to the chamber l3.

In Fig. 3 I have shown an arrangement for introducing lithium into an oil fired furnace, such as an open hearth furnace, the lithium being mixed with the oil. In this modification the lithium pulverizing chamber 32 is disposed above a horizontal run 50 of the oil feed line so as to drop lithium at a steady, uniform rate into the oil line. The lithium is carried by the oil through the oil pump 5| and burner 52. The oil is atomized and mixed with air in the burner 52 in the usual manner and the lithium carried into the furnace 53 with the mixture. The walls 54 of the furnace above the level of the molten charge may be composed largely of silica, to form an equalizing medium for the lithium atmosphere while the walls of the furnace below the liquid level may be composed of a material such as sillimanite or chromium oxide to prevent complex acid formation in the lining which tends to dissolve the same or change its nature.

The furnace 53 may be used for producing lithium copper, copper alloys, alloys of steel, such as stainless steel, or other metals or alloys, or for carrying out any metallurgical process in which the heating is preferably effected in a reducing or non-oxidizing atmosphere, such as annealing, brazing, coating, etc.

In Fig. 4 I have shown means for introducing lithium into a furnace, in vapor form. The lithium 55 is contained within a melting pot of any suitable design, that shown comprising a alundum. A heating coil 62 embedded in refractory material 63 supplies heat to the chamber 56 under control of a rheostat 5. The lithium is heated to a temperature suflicient to produce a substantial pressure of lithium vapor in the chamber and the lithium vapor is conducted by a conduit 65 to a valve chamber 86 and through the valve opening 61 into the furnace 83. The valve 69 regulates the flow of lithium into the furnace. It is to be understood that the conduit 65 and valve chamber 66 may be encased in heat insulating material, if desired, to reduce condensation of the lithium therein.

Fig. 5 shows means for introducing the lithium into a furnace in liquid form. The heating pot I0 is substantially the same as that shown in Fig. 4 excepting that the outlet is at the bottom, through a conduit H and valve chamber 12. The vapor pressure produced above the liquid lithium 13 forces the same through the valve opening I which opening is regulated by the valve 15 to permit a fine spray to be projected into the furnace 16. A suitable pressure valve 11 may be provided for the chamber '10.

It is to be understood that it is not essential to introduce lithium into the furnace continuously throughout the entire process, since the lithiated lining may serve to maintain the lithium vapor in the atmosphere. In some processes, such as in the production of copper lead alloys, it is desirable torestrict the amount of lithium introduced, as indicated by spectroscopic inspection of the atmosphere, in order to obtain the best results.

While lithium has been referred to as the speciflc material introduced into the furnace, it is contemplated that alloys or compounds of lithium or other metals may be used. For instance, in the case of oil burning furnaces, sodium may be introduced into the furnace mixed with the oil.

The term open furnace as used in the appended claims includes any furnace either of the combustion type or electric which is not sealed against the entrance of the atmosphere.

The term average chemical composition of which is such that it is oxidizing towards the metal, as applied to the atmosphere, in the claims, comprehends any atmosphere containing any constituent which in the absence of lithium or other alkali metal in the atmosphere, would be oxidizing towards the metal undergoing heating.

Obviously, the process and apparatus employed therein are not limited to the specific embodiments shown and described herein, but are to be limited only by the following claims.

What is claimed isl. The method of producing lithium copper comprising heating said copper in a molten condition in a furnace and maintaining a. lithium vapor in the furnace atmosphere during said heating of the copper.

2. The method of producing a lithium containing atmosphere in a furnace comprising introducing lithium metal into the furnace, while the furnace is at an elevated temperature, admixed with one of the combustibles.

3. The method of producing a lithium containing atmosphere in a furnace comprising introducing lithium metal into the furnace, while the furnace is at an elevated temperature, admixed with the air of combustion.

4. The method of treating metals which comprises heating said metals in a furnace and continuously generating lithium vapor in the furnace from a lining composed of silica saturated or substantially saturated with lithium.

5. In a furnace, a silica mass therein containing lithium, and subject to the heat generated in the furnace for liberating said lithium.

6. The method of regulating the atmosphere in a furnace which comprises providing lithium in the furnace, absorbing said lithium, at least in part, by the lining of the furnace and subsequently liberating said lithium from said lining at a slow rate.

7. The method of regulating the atmosphere in a furnace which comprises providing lithium in the furnace, absorbing said lithium, at least in part, by an absorbing medium within the furnace and subsequently liberating lithium from said medium at a slow rate.

8. The method of producing oxygen free metals comprising heating the metals in a molten condition in a furnace atmosphere containing lithium vapor in sufiicient quantity to cause absorption of lithium metal into the molten mass to effect a deoxidation thereof.

9. The method of producing lithiated metals comprising heating said metals in an open furnace and maintaining a lithium containing atmosphere or vapor in the furnace during melting of the metal.

10. The method of producing a lithium vapor in an oil burning metallurgical furnace comprising introducing lithium metal into the furnace, while the furnace is at an elevated temperature, admixed with the oil.

11. The method of producing a lithium vapor in an oil burning furnace comprising introducing lithium in finely divided form, into the oil prior to atomization thereof.

12. The method of producing a lithium vapor in a metallurgical furnace, which comprises finely dividing the lithium and injecting said finely divided particles into the furnace while the furnace is at an elevated temperature.

13. The method of producing a lithium vapor in a metallurgical furnace which comprises pulverizing the lithium in an oil vapor and introducing the pulverized lithium into the furnace while the furnace is at an elevated temperature.

14. The method of producing a lithium containing atmosphere in a metallurgical furnace comprising saturating a silica mass, within the furnace, with lithium and heating the mass to a temperature sufficient to liberate appreciable amounts of lithium therefrom.

15. The method of producing a lithium atmosphere in a metallurgical furnace comprising saturating a silica mass, within the furnace, with lithium and heating the mass to above about 1850 F. to liberate lithium therefrom.

16. The process of preventing substantial oxidation of metals in a heated state while maintaining the same throughout the process in the presence of an atmosphere, the average chemical composition of which is such that it is oxidizing towards the metal, which comprises the step of providing an alkali metal in said atmosphere in sufficient amount to prevent oxidation of said metal.

17. The process as defined in claim 16 in which temperature in an atmosphere containing combustion gases and lithium.

20. The method of treating metals comprising heating the same in a furnace containing carbonaceous gases, introducing lithium metal into the furnace during the heating and conducting the heating at a temperature sufliciently high to maintain lithium metal in the iurnace atmosphere.

21. The method of treating metals comprising heating the same in a furnace to the desired treating temperature in the presence of carbonaceous gases and producing an atmosphere in the furnace containing lithium in suflicient 5 amount to produce a lithium spectral color in the furnace gases.

HAROLD J. miss,

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