US2060073A - Copper refining method - Google Patents

Description

Nov. 10, 1936. R.P. HEUER 2,050,073

COPPER REFINING METHOD Filed June 5, 1950 2 Sheets-Sheet 1 PERCENTAGE C151 O O O Q E 3 2 E 9 aavaaunao saaaoao m suruvazdwai NOV. 10, 1936. R H R 2,060,073

COPPER REFINING METHOD Filed June 5, 1939 2 Sheets-Sheet 2.

I I H;

Patented Nov. 10, 1936 UNITED STATES QQPPER REFINING METHOD I Russell P. Heue. Havel-ford, Pa., assignor to The American Metal Com N. Y., a corporation pany Limited, New York,

of New York Application June 5, 1930, Serial N0. 459,300

37 Claims.

My invention relates to methods for refining copper. The apparatus shown-herein is claimed in my application, Serial Number 605,389, filed April 15. 1932, for copper refining apparatus.

A purpose of my invention is to produce commercial copper substantially free from cuprous oxide and at the same time having so few gas cavities as not to interfere with the mechanical working of the copper. I

A further purpose is to reduce by means of carbon the content of copper oxide to a point much below that reached under the present practice.

A further purpose it to crowd carbon into the body of a substantially sulphur-free copper melt in order to reduce the cuprous oxide content to a minimum.

A further purpose is to roast solid copper cathodes to substantially eliminate the sulphur,

melt the cathodes, and reduce any cuprous oxide 20 present in the molten copper by contact with carbon, avoiding blowing and poling, and obtaining an oxide-free copper having no dissolved gaseous impurities except carbon monoxide.

A further purpose is to eliminate sulphur con- 5 tamination from solid copper by reduction with hydrogen, remove any dissolved hydrogen by melting in an oxidizing atmosphere and cast the resulting copper.

A further purpose is to obtain commercial copper castings free from any excess of carbon dioxide, water vapor or hydrogen, and consequently without gas cavities due to the liberation of these impurities during the solidification period of the copper.

A further purpose is to deoxidize copper beyond the point at which it is microscopically oxygen free so that it can be solidified intocastings substantially free from gas cavities and to cast the copper preferably while protecting it from the 40 atmosphere, desirably by carbonmonoxide free,

. from contaminating gases.

Further purposes will appear in the -s 'tion and in the claims.

In the drawings, Figure l is a top plan view of".

an arrangement of furnaces by which methods may be desirably performed.

Figure 2 is an enlarged vertical section of the carbon reducing furnace seen in Figure 1.

Figures 3 to 5 are diagrammatic views useful in explaining my invention.

In the drawings like numerals refer to like parts.

The common practice is to melt copper cathodes in largeintermittent reverberatory furnaces. In such furnaces, the conventional mode of oper purity in the molten copper. Oxygen is also present'in thebath as dissolved cuprous oxide. The blowing, while removing part of the sulphur, increases the oxygen content of the bath and saturates the bath with nitrogen and other gases from the atmosphere.

The primary purpose of the poling operation is to remove the excess of oxygen, present largely in the form of cuprous oxide. In doing so, however, the bath takes up hydrogen, carbon monoxide, carbon dioxide and water vapor from the organic matter.

At times during the poling operation the bath lsprotected by charcoal or coke floating upon the surface. By virtue of its position and its small quantity as compared with the bath, the amount of reduction possible from carbon used in this manner is negligible.

Previous observers have noticed that, when the poling operation is carried too far, the copper is valueless because of the large numbers of gas cavities. As stated by H. O. Hofman (Metallurgy of Copper, McGraw-Hill Book Co., Inc., New York, 1914, page 384) "It is important that some C1120 remain in the copper, as the dissolving power of copper for gasis greatly weakened by 3 its presence." The general feeling has been that in some way. the presence of C1120 decreases the 'solubilityof the copper to gases, and consequently avoids the danger of gascavities. Another explanation. which has been put forward is that the 4 copper would become more highly saturated with reducing gases as poling proceeded farther, and the solubility of the copper for the gases would decrease on cooling, causing them to separate as gas cavities during solidification. It is com'mon- 1y considered bad practice to reduce the content of Cu20 below 0.3%. From physical-chemical studies of the poling operation I have discovered that the commonly accepted explanations of the role of cuprous oxide are incorrect, and that the retention of cuprous oxide in the copper is undesirable and unnecessary. What has been attributed to solubility is really due to reactions which occur whenever cuprous oxide is present. 5

The reduction of cuprous oxide under the conditions of poling takes place according to the following reactions:

I will consider the above reactions in terms of the thermodynamic activities of the reacting components and of the standard free energy changes for each reaction where the activities of the reacting components are referred to arbitrarily chosen standard states for the reacting components in which their activities are unity.

(See Gilbert Newton Lewis and Merle Randall, Thermodynamics and Free Energy of Chemical Substances, McGraw-Kill Book Co., Inc., New York, first edition, 1923, chapters IQIII and XXIV,

andpages 190, 255, and 293.)

Thus for the reaction the relationship between the activities and the standard free energy change would be as follows:

Since at constant temperature the logarithm becomes constant, the expression oi Equation (5) is frequently simplified under the name 0! the law of mass action. When this is done, the

pressures of gases and the molalities of dilute solutions are ordinarily substituted for the activities.

Applying Equation (5) to Reaction (1). and using the same nomenclature, we get:

(A.Cu) =activity of copper (A.CO) =activity of carbon monoxide (A;Cu:0) =activity oi cuprous oxide (A.C) =activity or carbon in the above reaction equilibrium is never reached during poling. It is only attained when the cuprous oxide is practically all removed.

Applying the general form of Equation (5) to Reaction (2), and using the previous nomenclature, we obtain:

--AF=RT In (6) (A.Cu)'(A.CO,) (A.Cu O)(AiCO) (A1302) =activity 01' carbon dioxide It is probable that the bath will become saturated with carbon dioxide during the poling operation,

so that (A.CO2) will be constant. Also, (A.Cu)

is constant as the bath is practically pure copper.

Then Equation (7) becomes:

K AFQ=-RT In MT) (8) where K is a constant i'orthe particular conditions. At constant temperature this expression becomes:

(A.Cuz0) (ACO) =K1 =proper constant Since the activities 01 copperand of water are constant, this equation becomes, at constant temperature:

(A.Cuz0) (A.H2) :m

K2: proper constant Equation (11) has been plotted in Figure 4, using (A.Cua0) values as the abscissae and (A.Ha) values as the ordinates.

The activity of any component is a function of the concentration. Therefore, we may observe the relation between the concentration of carbon monoxide or hydrogen and that of the cuprous oxide by theme of the curves shown in Figures 3 and 4.

For example, with a high cuprous oxide concentration, corresponding to the point a, the concentrations oi! hydrogen and carbon monoxide are low. As the concentration of cuprous oxide falls, as shown progressively at points 11, c, and d, the concentrations of hydrogen and carbon monoxide remain substantially the same.

When the cuprous oxide content reaches a low enough value, as that indicated by e or I, at the knees of the curves, the concentrations of hydrogen and carbon monoxide rise. when the concentration of cuprous oxide is reduced progressively below that represented by the point I, a rapid rise in concentration of hydrogen or carbon monoxide occurs, entirely out oi proportion to the decrease in the concentration of cuprous oxide.

In the practical operation of the refining furnace, poling is stopped at about the point g on the respective curves of Figures 3 and 4, representing a cuprous oxide content of about 0.3%. Previous observers have considered that it is necessary to stop at this point, either because the cuprous oxide reduces the solubility of gases in the copper, as suggested by Hofman, or because the copper will become more highly saturated with reducing gases as the poling proceeds further, and these reducing gases will separate out on cooling. Both of these explanations have been found by me to be erroneous.

As previously stated, it is not the separation of carbon monoxide and hydrogen because of lower solubility in solid than in liquid copper. or because of any other reason, which causes the bulk or the gas cavities, but rather the reactions during solidification of the dissolved carbon monoxide and hydrogen with any remaining cuprous oxide to produce carbon dioxide and water vapor with which copper has been saturated already.

By reference to Reactions (1), (2) and (3) it will be seen that Reaction (1) can hardly take place during the solidification oi the sting, because no carbon is present at that time. However, Reactions (2) and (3) could occur, since both carbon monoxide and hydrogen are present in copper made by the prior art commercial process.

During the solidification of copper containing less than 3.45% oi cuprous oxide, crystals of pure copper will first separate out, thus concentratingv the cuprous oxide in the supernatant liquid along carbon dioxide and/or water vapor.

Thus it will be seen that overpoling and excessive gascavities are due just as much to the presence of cuprous oxide in the copper as they are to the presence of reducing gases, such as hydrogen and carbon monoxide. I propose therefore to eliminate cuprous oxide, thus avoiding --the injury done to the copper from' overpoling and excessive gas release, and by producing copper free from cuprous oxide, I obtain better physical properties and higher electrical conductivity in the product.

The solubility of hydrogen in molten copper is considerably greater than its solubility in solid copper at the freezing temperature. on the other hand,. there is substantially no change in the solubility of carbon monoxide when copper solidifies. Therefore, forgetting for the moment the question of reactions with cuprous oxide, carbon monoxide is a much less undesirable ingredient in molten popper than hydrogen. I avoid the presence of excessive quantities of hydrogen or remove it beforecasting, whether or not cuprous oxide is present. Carbon monoxide, however, is not particularly harmful from the standpoint of change of solubility on solidification, nor of fornation by any reaction possible during solidification, sothat I may even saturate the bath with carbon monoxide as later explained.

Poling is necessitated by blowing, and blowing is required in order to remove sulphur. To eliminate both blowing and poling I propose to eliminate sulphur from the cathodes prior to melting them. rather than to attempt to oxidize sulphur out of the molten ,bath. Having eliminated sul; phur, I melt the cathodes under conditions which prevent any absorption of sulphur.

My low sulphur bath does not require blowing,- and therefore does not have the high oxygen, content due to blowing, and the saturation with other atmospheric gases for which it is respon-.-

sible. The elimination of poling enables me 'to avoid the attendant contamination with hydro-- gen, carbon dioxide and water vapor.

Hydrogen, carbon dioxide and water vapor tend to produce gas as previously explained, but carbon monoxide does not of itself act in this way be.- -cause it is not formed by any of the reactions which occur during cooling, and its solubility.

does not greatly decrease when the -'.copper solidifies.

As a further precaution against the possibility of reactions occurring between hydrogen or carbon monoxide and cuprous oxide during cooling,

I reduce the cuprous oxide in the resultant metal much below any content which has been deemed possible heretofore. The reduction of cuprous :oxide until only a trace is present is best per-.

paratus which might be employed. The roasting or calcining operation to remove sulphur is best performed in the continuous fiue'of a furnace as shown in my Patent, No. 1,914,716, for Copper. melting furnace, granted June 20, 1933, or in Lukens and Heuer Patent, No. 1,733,419, for Continuous copper melting furnace, granted October 29. 1929.

It will be understood. however. that my invention is notrestricted to use with a continuous furnace.

The furnace A of Figure 1 is of the general type shown in my Patent, No. 1,914,716, above referred to. Cold cathodes are charged at 9 by any suitable pusher- Ill on to the continuous hearth ll operating in the flue l2. Thehearth is moved by a motor I! and any suitable connections. In the illustration shown the piles of cathodes ll are carried clockwise to the discharge point l5, where they arepicked up by the fork l6 and carried into the furnace l1 and there dropped. The charging fork I8 is desirably moved in and out through a door l8. 1

In the furnace ii, the bath l9, desirably covered by a suitable protective slag, is heated by products of combustion from burners at 20. I prefer to use oil burners, but it will be understood that any suitable means of heating may be employed. From the furnace II the products of combustion pass through the neck 2|, through which the cathodes are charged, and around the flue in a counter-clockwise direction, finally rising through the stack 22. During normal operation of the furnace,'the products of cumbustion are prevented from taking a clockwise path by the wall 23.

The hearth II in the flue i! may be continuous or may consist of a plurality of cars separately moved about the flue. The continuous mode of operation is much superior, and therefore I indicate the hearth as extending around the flue and being turned by any suitable driving means l3. 7 The preheating and roasting chamber l2 contains a non-reducing atmosphere. The copper sulphate or other sulphur compound adhering to the cathode is calcined, and is decomposed by the products of combustion. The-sulphur is carried off as sulphur dioxide.

During roasting, the cathodes should be heated to about 815 C. to complete the formation of sulphur dioxide. Lower temperatures will suffice, although operation is slower inthat case. Higher temperatures will work satisfactorily provided care is taken not to melt the cathodes in the flue. Melting here is objectionable for various reasons, metallurgically because molten copper gen sulphide. Here also, the presence of molten copper is undesirable for the reason above stated.

Where reduction with hydrogen is employed, I will preferably melt the copper under slightly oxidizing furnace conditions to remove dissolved or from-the fiue gases by a suitable slag.

slag used may be the normal slag forming from oxidation of the copper, or it may-beaspecialslagasdesired.

'- beunderstood that where copperisalreadyfree from sulphur, it maybecharged into charges, thus increasing the economy of operatiomlprefer eveninthatcasetouse a furnace of the type of furnace A. It would of course be possible to preliminarily desulphuriae and intermediately cool the cathodes before llchargingthemintofurnacei'l.

Having melted the sulphur-free copper, I next proceed to reduce by carbon any oxygen present, thus avoiding the possibility of reactions with reducing gases which may be dissolved in the cop- 80 per. No blowing is necessary since the sulphur is already low, andfsince no blowing is required, the copper need not be poled.

In order to reduce the cuprous oxide, I pour the metal from the pool ll of furnace A into furnace 88 B. Furnace B is free from gases of combustion, and is heated electrically or by any other suitable means. In my figure I show electrodes 2| passing through the wall I! of the reducing furnace or deoxidizing vessel, and sealed, to prevent ent 40 trance of-air, by collars 2i and 21. The electrodes are connected to a suitable current source,

not shown. While I show an electric furnace employing carbon electrodes, I need not restrict myself to this particular type of electric furnace,

is and any conventional electric furnace, resistance or induction, may be used as my furnace B. Copper from the bath I! is preferably charged into the inlet opening II of furnace B through a closed trough II heated by a burner 3|. Slag is retained 60 in the furnace ll by a gate ii.

The furnace B is filled, both above and below the level of the copper, with coke or other suitable carbonaceous material which will not contaminate thecopper with hydrogenor water vapor.

Coke is a harmless carbonaceous reducing agent which is forced in through the openings 32 and a near the top, by means of plungers '32 and 33. Theheatinginthefurnaceispartly duetothe electrical resistance of the coke surrounding the electrodes, since the electrodes will not usually be immersed in the bath. The copper bath'fl may be drawn off as desired through the tap opening II and the pouring spout I at the end of the finance. 7

In ordinary operation the level of the pouring spout is slightly above that of the'copper bath 34, so that the furnace must be rotated slightly in order to pour from the'spout. For convenience in rotation I preferably make my furnace B cir- 7 color in cross section. l'br'rotating the furnace r I provide suitable supporting rollers 31 engaging bands ll, and also a gear driving band I! engaged by a rack I which is moved backfand forth by a I screw ll through a, non-rotatable nut l2, secured used to agitate thecopper in contact with the carbon, ifdesired, but I do not consider agitation s necessary to accomplish the reduction of cuprous oxide. v

'l'hereactionstakingplaceinthereducingfur- 'nace during the firststage of reduction are as.

follows; 10 C+Cuz0=2Cu+C0 (12) C0+ClhO=2Cu+COs (it) Carbon monoxide produced in Reaction (12) will dissolve in the copper until the copper becomes saturated. Carbon dioxide formed from Reaction (13) will also tend to saturate the copper. The carbon monoxide is not objectionable because it is not produced by the reaction between any remaining cuprous oxide and the reducing gases during solidification, nor does its solubility change markedly during solidification. But I wish to have the copper bath unsaturated with carbon dioxide to allow for the possible formation of carbon dioxide during the cooling period by oxidation of carbon monoxide. Therefore, I continue the contact between the carbon and the copper until all of the cuprous oxide is reduced. When this has taken place the carbon will reduce carbon dioxide as follows:

c+co==2co (14) In order to reduce carbon dioxide to carbon monoxide, 1 prolong the dioxidation after the cuprous oxide is effectively eliminated. substantial excess of carbon monoxide above that required to saturate the bath will pass oil! at this stage. and the carbon monoxide passing ofl will .protect'the copper from contamination with other gases. Thus I will obtain copper substantially free from cuprous oxide and containing practically no dissolved gas other than carbon monoxide.

The carbon monoxide dissolved in the copper has a "buffer" action in protecting the copper from increase in cuprous oxide content. This carbon monoxide, produced by Reaction (14), is formed from carbon dioxide which wasformerly dissolved in the copper, so that after- Reaction (14) is complete, the carbon dioxide will be removed from the copper, and carbon monoxide produced instead. Notwithstanding that two volumes of carbon monoxide are produced from one volume of carbon dioxide, most of the carbon monoxide resulting from Reaction (14) will remain dissolved in the copper because carbon monoxideis quite soluble in molten copper, while carbon dioxide is only sparingly soluble under the same conditions.

Now, as previously pointed out, it is entirely possible that an effective quantity of oxygen will be introduced into the copper before the copper solidifies, either due to leakage of air into the copper deoxidation furnace or due to contamination with air at the pouring spout or in the mold during casting. By its buffer" action, the 'carbon monoxide will care for a slight contamination with oxygen by reaction with the oxygen to form carbon dioxide. The buffer" action of carbon monoxide is in addition to the ability of carbon monoxide to react with existing cuprous oxide in the supernatant liquid during solidification. Since the copper has been deliberately unsaturated with carbon dioxide, the carbon dioxide resulting from the "buffer" action of carbon monoxide will not oversaturate the copper, and so will not produce gas cavities. It is of course obvious that protection from oxygen is highly important because the quantity of oxygen which may be cared for by the buil'er" action of the carbon monoxide is limited.

While I have shown one furnace B in Figure 1, it will be evident that I may employ any conventional arrangement, using two or more such furnaces in series to treat the molten copper successively, as shown for slagdeoxidation in Lukens and Heuer Patent, No. 1,733,419, granted October 29, 1929.

The reduced copper from furnace B will ordinarily be poured into molds. In Figure 1 I illustrate diagrammatically conventional casting apparatus consisting of a. conventional casting wheel having supporting structure 44 and molds 45, adapted to be moved in either direction to a position registering with the pouring spout 36, when copper may be poured through openings 46 into the molds. In order to minimize contact between the air and the oxide-free copper during casting, and decrease the absorption of oxygen, I pour preferably into vertical molds.' By this method I eliminate the set or oxidized copper surface obtained on horizontal castings. For best results I also surround the stream of pouring copper with a nonoxidizing gas, preferably carbon monoxide, since the copper under ordinary conditions will already be saturated with carbon monoxide, to prevent the absorption of atmospheric gases, especially oxy en. I illustrate at "conventional means for surrounding the stream of pouring,

copper with an atmosphere of carbon monoxide. The molten copper may simply be poured in a chamber containing carbon monoxide.

Thus it will be seen that my process consists of the following steps, desirably in succession: (1)

removing sulphur from the cathodes; (2) melting; (3) reducing cuprous oxide; (4) reducing carbon dioxide; (5) casting. The first step might be eliminated if sulphur-free material could be obtained, and of course the sulphur might less desirably be removed after melting. In the preferred form of my invention the elimination of sulphur is accomplished before melting, but this is not essential, especially if the conventional copper melting reverberatory furnace is to be used, since the copper can be' charged into such a furnace either continuously or intermittently, with or without preheating, can be melted, blown to remove sulphur if desired, poled to remove part of the oxygen content, deoxidized by treatment in the deoxidation furnace'B and cast, preferably with proper protection. The last step, while offering a desirable combination in the practice of my invention, could be dispensed with if it were desired to transfer the copper to a storage furnace, for example.

Independently of the role 01' cuprous oxide, the

7 presence of hydrogen in the copper bath is undeslrable because of its tendency. to form gas cavities due to its decrease in solubility during solidiflcation. Green poles previously used to reduce copper oxide ofcourse introduce a large quantity of hydrogen into the bath in the form of hydrocarbons. By avoiding the use of material rich in hydrogen in the deoxidizing furnace, as by employing charcoal or coke, I avoid introducing excessive quantities of hydrogen into the bath.

It will be understood that my invention could be carried out. entirely in one furnace, where the calcining, melting, and reducing'operations would proceed. This, however, would be slow and less 'ess of manufacture, and not facture.

desirable than the continuous method of operation using two or more furnaces.

It will be evident that the elimination of sulphur is necessary in those cases only where the raw copper material has an excessive sulphur content-which represents the normal condition; also that the elimination of blowing and poling keeps down the amount of cuprous oxide and carbon dioxide present and avoids the necessity for excessive reduction by' carbon to take care of this condition; that the reduction of cuprous oxide and subsequently of carbon dioxide below the saturation point of carbon dioxide is highly essential and is secured most quickly and most effectively by immersion of the carbon within the molten copper bath; and that casting within vertical molds reduces the subsequent air contamination with its increase of cuprous oxide and carbon dioxide within the solid copper.

By my statements that the atmosphere surrounding the copper during deoxidation will contain so little carbon dioxide and hydrogen as not to harmfully affect the copper, I do not mean to imply that any substantial percentage of carbon dioxide or hydrogen is present, as the at- 'mosphere will preferably contain no substantial percentage of carbon dioxide and hydrogen. I merely mean that the quantity of carbon dioxide and hydrogen, if any be present, will not be sufiicient to ailect the copper harmfully.

When I refer herein to complete removal of cuprous oxide present in the copper, to complete deoxidation of the copper, or to any similar thought, I of course wish to indicate that removal of cuprous oxide is complete according to the tests commonly used by the copper metallurgist at the time of filing this application for patent, such as microscopic examination, so that no distinct phase of cuprous oxide is visible in the solid copper. I do not mean to indicate that cuprous oxide which may remain in solid solution in the solid copper, as determined by methods developed subsequently to my date of filing this application, is necessarily absent.

It will be evident that, where reference is made in the specification and claims to a casting or to casting, it is intended to designate a commercial product having the properties such as malleability and ductility of acommercial casting, and its procmerely a laboratory or museum specimen and its process of manu- In view of my invention and disclosure variations and modifications to meet individual whim ,or particular need will doubtless become evident to others skilled in the art, to obtain part or all of the benefits of my invention without copying the structure shown, and I, therefore, claim all such in so far as they fall within'the reasonable spirit and scope of my invention.

Having thus described my invention, what I claim as new and des e to secure by Letters Patent is: Z

1. In the art of, castings substantially free fromfcuprous oxide and gas cavities, the process which consists in desulphurizing copper cathodesin the solid state, in melting them free from contact with sulphur, the melt produced containingcuprous oxide, in reducing dissolved cuprous oxidefin the molten copper bath by large surface contact with carbon in an atmosphere having insuflicient carbon dioxide and hydrogen to harmfully affect the copper and in prolonging the reduction until the harmful content of carbon dioxide in the copper isremoved. a I I preparing copper for making 2. In the art of preparing copper for making castings substantially free from cuprous oxide and gas cavities, the process which consists in removing sulphur from the solid copper charges to avoid the necessity of blowing and consequent poling, in melting the charges free from contact with sulphur, the molten copper containing "cu-' prous oxide and carbon monoxide, and in unsaturating the metal from carbon dioxide in order that it may take up carbon dioxide during solidification without becoming over-saturated with carbon dioxide.

3. The process of purifying copper cathodes, which consists in heating cathodes in the presence of hydrogen to volatilize sulphur as hydrogen sulphide, melting the cathodes free from contamination with sulphur, reducing substantiallyeall of the cuprous oxide present in the copper by contact with carbon in an atmosphere having insuihcient carbon dioxide and hydrogen to harmfully affect the copper and in prolonging the reduction until the content of oxides of carbon in the copper is harmless.

4. The process of making copper castings substantially free from cuprous oxide and objecttionable gas cavities, which consists in reducing sulphur by heating copper cathodes in the presence of hydrogen, melting the cathodes under oxidizing conditions to eliminate dissolved hydrogen while avoiding contamination with sulphur, substantially completely reducing cuprous oxide present in the copper and casting the purifled material.

5. The process of treating copper, which consists in roasting solid copper cathodes to eliminate sulphur, in melting the cathodes free from contamination with sulphur and in treating the molten copper with carbon throughout the body of the copperfor a duration sufficient to render the remainder of the oxides of carbon in the copper harmless, in an atmosphere having so little carbon dioxide and hydrogen as not to harmfully aflect thecopper.

6. In the art of making copper castings substantially free from cuprous oxide and gas cavities, the process which consists in melting substantially sulphur-free copper in a melting furnace under conditions which produce oxygenbearing molten copper, in protecting the copper from contamination with substances rich in hydrogen subsequent to melting, in transierring the molten copper to a deoxidizing vessel, in treating the molten copper in the deoxidizing vessel with carbon submerged throughout the body of the molten copper in an atmosphere substantially free from hydrogen for a time sufllcient to reduce carbon dioxide, in maintaining dissolved carbon monoxide in the molten copper, in transferring the molten copper from the deoxidizing vessel to the point of casting and in subsequently cooling the molten copper to solidify it while free from admixture with carbon throughout the molten copper.

"I. The process of treating copper, which consists in roasting solid copper charges to eliminate sulphur, in melting the charges free from con- .tamination with. sulphur, in treating the molten copper with carbon throughout the body of the copper, in an atmosphere having insufllcient carbon dioxide and hydrogen to harmfully affect the copper, in prolonging the reduction until the harmful content of gas in the copper is removed, in casting the copper and in protecting the copper from air during casting by a harmless gas having a sumciently low partial pressure of oxygen so as not to contaminate the copper with oxygen.

8. In the art of producing copper castings substantially free from gas cavities, using a fuelilred furnace and an electric furnace, the process which consists in preparing oxygen-bearing molten copper in the fuel-fired furnace, in transferring the molten copper to the electric furnace, in eliminating cuprous oxide from the molten copper by carbon reduction in the electric furnace, in continuing the reduction to unsaturate the molten copper with carbon dioxide, in casting the copper and in protecting the copper from excessive contact with air during casting.

9. The process of preparing copper castings practically free from gas cavities and cuprous oxide, which consists in treating molten copper with carbon submerged throughout the copper to reduce the cuprous oxide until too little cuprous oxide remains in the bath to react with impurities in the copper during solidification and liberate carbon dioxide or water vapor from the copper, in reducing carbon dioxide in the molten copper to carbon monoxide, in distributing carbon monoxide in the molten copper, in separating the molten copper from the carbon, in casting the copper in pure condition and in protecting the copper from contact with air during casting.

10. The process of purifying molten copper and of producing the copper in solid form, which consists in reducing dissolved carbon dioxide, present in the molten copper by reason of the reaction between cuprous oxide and carbon monoxide, -to carbon monoxide by contact with carbon maintained submerged throughout the molten copper, in maintaining carbon monoxide inthe molten copper, in separating the molten copper from the carbon and in withdrawing and solidifying the copper in pure condition free from excessive contamination with air.

11. The processof producing copper castings free from excessive gas cavities, which consists in exposing the molten copper to a large surface of carbon submerged throughout the copper free from contamination of substances rich in hydrogen preliminary to casting, in separating the molten copper from the carbon, in casting the copper in pure condition and in protecting the copper from air during casting by surrounding the copper with carbon monoxide free from contamination with substances which will cause the liberation of carbon dioxide, hydrogen or steam in the solidifying copper.

12. The process of producing copper castings free from excessive gas cavities, which consists in deoxidizing the copper, in dissolving carbon monoxide in the copper, in carrying the deoxidation to an extent such that carbon dioxide is removed until the quantity of carbon dioxide left is not objectionable during casting, in casting the copper in pure condition and in protecting the copper from oxidizing gases, during casting, by carbon monoxide free from substances which will cause the liberation of carbon dioxide, hydrogen or steam in the solidifying copper.

13. In the art of producing copper castings free from objectionable gas cavities, the process which consistsin preheating solid copper charges, in melting the charges by fuel combustion while exposed to a bath of molten copper, in transferring the molten copper to a deoxidizing vessel, in deoxidizing the molten copper by the action of carbon monoxide free from substances which will cause hydrogen or steam to be liberated in the copper during solidification, in transferring the molten copper from the deoxidizing vessel to the point of casting and in casting the copper in pure condition while blanketing it with a gas having 'a predominantly reducing component of carbon monoxide and having a sufllciently low partial pressure of oxygen so as not to contaminote the copper with oxygen or its compounds other than carbon monoxide.

14. In the art of producing copper castings free from cuprous oxide and objectionable gas cavities, the process which consistsdn preheating solid copper charges, thereby producing oxygenbearing molten copper, in melting the charges, in deoxidizing the molten copper and removing sumcient of the carbon dioxide in the copper to render the remainder harmless, by carbon in a confined space in an atmosphere low in carbon dioxide and hydrogen and in casting the copper in pure condition while protecting the molten copper from excessive contact casting.

15. In the art of producing copper castings substantially free from objectionable gas cavities, using a fuel-fired melting furnace and a deoxidation furnace, the process which consists in preparing oxygen-bearing molten copper in the fuel-fired furnace, in transferring the molten copper to the deoxidation furnace, removing from the molten copper substantially all of the cuprous oxide and suflicient of the gas in the with air during copper to render the remainder harmless bycarbon reduction in the deoxidation furnace in an atmosphere having insuflicient carbon dioxide and hydrogen to harmfully affect the copper, in casting the copper and in protecting thecopper from excessive contact with air during casting.

16.- The process of purifying molten copper to substantially remove its content of cuprous oxide and make solid copper of high density, which consists in treating molten copper containing cuprous oxide with carbon in a confined space free from contamination with substances which will cause the liberation of carbon dioxide, hydrogen or steam during solidification of the copper, thereby forming carbon monoxide and taking out some cuprous oxide, in treating the molten copper with the carbon monoxide, thereby distributing carbon dioxide in the molten copper and taking out more cuprous oxide, in reducing carbon dioxide in the molten copper to carbon monoxide by contact with the carbon, in maintaining carbon monoxide in the molten copper and in casting the copper in pure condition while blanketing it with carbon monoxide free from substances which cause the liberation of carbon dioxide, hydrogen or steam in the solidifying copper.

17. The method of treating copper to make castings free from cuprous oxide and objectionable gas cavities, which consists in melting the copper while in contact with products of fuel combustion, and in subsequently removing from the molten copper the cuprous oxide and sufficient of its content of dissolved gas to render the remainder harmless by exposing the copper in molten condition to contact with carbon in the absence of contamination with air and with gases of combustion from hydrocarbon fuel.

18. The method of treating copper to make castings free from objectionable gas cavities, which consists in melting the copper by fuel combustion, in oxidizing the copper to remove sulphur, in completely deoxidizing the cuprous oxide present in the molten copper by carbon while protecting the copper from contamination with air and the harmful castings free from a 'oxide and objectionable gas cavities, which containing cuprous oxide,

gaseous products of the fuel combustion, in casting the copper and in shielding the copper during casting from air, oxidizing gaseous products of fuel combustion and hydroen.

19. In the art of producing copper castings substantially free from gas cavities, the process which consists in substantially eliminating the cuprous oxide content of oxygen-bearing molten copper by reduction with carbon in an atmos-- phere having insufllcient carbon dioxide and hydrogen to harmfully affect the copper, in prolonging the reduction until the harmful content of carbon dioxide is reduced to carbon monoxide, in maintaining carbon monoxide in the molten copper, in separating the molten copper from the carbon and in casting the copper in pure condition free from excessive contact with air.

20. In the art of producing copper castings substantially free from gas cavities, using a fuelilred melting furnace and an auxiliary deoxidizing furnace, the process which consists in preparing oxygen-bearing molten copper in the fuelfired melting furnace, in transferring the copper to the auxiliary deoxidizing furnace, in deoxidizing the molten copper by carbon reduction in the deoxidizing furnace in an atmosphere containing so little carbon dioxide and hydrogen as not to harmfully affect the copper, in casting the copper and in protecting the copper from excessive contact with air during casting by a noncontaminating reducing gas.

21. In the art of producing copper in refined form, the process which consists in melting the substantial concentration of carbon monoxide.

22. The process of treating copper to produce distinct phase of cuprous sists in preheating solid copper charges, in melting the copper by fuel combustion, while surrounded by molten copper, to produce a copper melt containing cuprous oxide, in completely deoxidizing the cuprous oxide present in the molten copper by carbon in an atmosphere having so little carbon dioxide and hydrogen as not to harmfully affect the copper, in casting the copper and in protecting the copper during casting from excessive contact with air by a gas having a predominantly reducing component of carbon monoxide and having a sumciently low partial pressure of oxygen so as not to contaminate the copper with oxygen or its compounds other than carbon monoxide.

23. The process of treating copper to produce castings free from a distinct phase of cuprous oxide and objectionable gas cavities, which consists in preheating solid copper charges, in melting the copper, surrounded by molten copper, by fuel combustion to produce a copper melt conin completely deoxidizing the cuprous oxide present in the molten copper by carbon and prolonging the deoxidation w'ith carbon for a time sufficient to render the refrom fuel combustion in so little carbon dioxide conditions of freedom an atmosphere having and hydrogen as not to harmfully affect the copper, in casting the copper and in protecting the copper during casting from excessive contact with air.

,24. The method of treating copper to produce castings free from cuprous oxide and objectionable gas cavities, which consists in melting the copper by fuel combustion in which the gases of combustion are in contact with the molten copper to produce a molten bath containing cuprous oxide and in removing from the copper cuprous oxide and prolonging the deoxidation for a time sufficient to render the remainder of the oxides of carbon harmless, by maintaining .the copper in molten condition in contact with carbon in an atmosphere having so little carbon dioxideand hydrogen as not to harmfully affect the copper.

25. The process of purifying copper, which consists in preparing oxygen-bearing molten copper under fuel-fired conditions in which the molten copper is exposed to the products of fuel combustion, in exposing the molten copper in a confined space to contact with carbon while protecting the copper from air and products of fuel combustion, in agitating the molten copper while it is in contact with the carbon for a time sufficient to completely deoxidize the copper and effect removal of harmful gas from the copper, in transferring the molten copper from the confined space to the point of casting and in subsequently cooling the molten copper to solidify it.

26. The process of producing copper castings, which consists in removing cuprous oxide from molten copper by contact with carbon, in continuing the reduction by carbon to reduce carbon dioxide to carbon monoxide, in agitating the copper while it is in contact with the carbon and in casting the copper while surrounding it with a gas which is harmless to the copper.

2'7. The process of deoxidizing molten copper,

which consists in melting the copper by fuel combustion'in which the gases of combustion are in contact with the molten copper, in exposing it to contact with carbon in a confined space to remove cuprous oxide, in continuing the contact with carbon after the removal of cuprous oxide to change carbon dioxide to carbon monoxide and in producing forced agitation of the molten copper while it is in contact with the carbon.

28. The method of refining metals which readily oxidize upon exposure to air in their molten state, which comprises subjecting the metal to an oxidizing reaction to remove sulphur, melting the metal with fuel heating flames, subjecting the metal in molten condition to a complete reaction with a harmless carbonaceous reducing agent to remove substantially all of the metallic oxides while keeping the metal protected from the air and the contaminating products of combustion of fuel heating flames, and pouring the metal while protecting it from the air and the contaminating products of combustion of fuel heating flames.

29. The method of refining copper, which comprises subjecting the metal to an oxidizing reaction to remove sulphur, melting the metal in a fuel fired reverberatory furnace, subjecting the oxidized metal in molten condition to a complete reaction with a harmless carbonaceous reducing agent to remove substantially all of the metallic oxides while fully protecting the metal from the atmospheric air and the contaminating products of combustion of fuel heating flames, and pouring the metal while protecting it from the air and the contaminating products of combustion of fuel 30. The method of refining copper which comprises, melting the copper in a fuel-fired furnace which tends to oxidize the metal, transferring the metal to a treating vessel and there subjecting it in molten condition to a complete reaction with a harmless carbonaceous reducing agent by bringing all of the metal into thorough contact with the reducing agent while keeping the metal protected from the air and the contaminating products of combustion of fuel heating flames to perform a complete reducing action on the metal, and pouring the oxygen-free copper while protecting it from air by a gas composed principally as to active constituent of carbon monoxide.

, 31. The method of refining copper, which comprises, melting the copper in a fuel fired reverberatory furnace, oxidizing the copper to remove sulphur, subjecting the copper in molten condition to a complete reaction with a harmless carbonaceous reducing agent by bringing all of the metal into thorough and intimate contact with the'reducing agent while keeping the metal protected from the air and the contaminating products of combustion of fuel heating flames to remove substantially all of the metallic oxides, and casting the metal while protecting it from oxidizing influences and the contaminating products of combustion of fuel heating flames.

32. In the art of making castings free from cuprous oxide .and of high density, the process which consists in preheating solid copper charges, in subsequently carrying the charges to a melting furnace and there melting the charges under conditions which produce oxygen-bearing molten copper, in agitating the molten copper in a confined space and a noncontaminating atmosphere in direct contact with carbon for a sufllcient duration to remove enough carbon dioxide to render the remainder harmless to the copper and in cooling the molten copper, in a mold separate from the confined space, to solidify the copper.

33. In the art of preparing copper for making castings free from cuprous oxide and of high density, the process which consists in preheating solid copper charges, in melting the charges while in contact with a bath of molten copper under conditions which produce oxygen-bearing molten copper and in treating the molten copper with carbon for a duration suilicient to render the remainder of the carbon dioxide in the copper harmless, to deoxidi'ze the molten copper in a confined space protected from substances which will cause gas cavities due to liberation of carbon dioxide, hydrogen or steam in the copper during solidification.

34. In the art of making copper castings substantially free from cuprous oxide and excessive gas cavities, the process which consists in treating molten copper containing cuprous oxide with carbon monoxide, thereby taking out cuprous oxide and distributing carbon dioxide in the molten copper, in reducing the carbon dioxide so formed by carbon in contact with the molten copper in a confined space free from substances which cause the liberation of hydrogen or steam in the solidifying copper, in maintaining carbon monoxide in the molten copper, in transferring the molten copper from the confined space to the point of casting and in subsequently cooling the molten copper to solidify it.

35. The process of preparing copper castings practically free from gas cavities and cuprous oxide, starting with electrolytically refined copper, which consists in melting the copper in a fuel-fired melting furnace having the gases of 2,060,078 combustion in contact with the molten copper,

with impurities in the copper during solidification and form gas cavities due to liberation of carbon dioxide or water vapor from the copper, in separating the molten copper from the carbon and in casting the copp r under conditions which maintain a harmless oxygen content in the solidifying copper due .to avoidance of excessive contact with atmospheric gases during casting.

36, The process of preparing copper castings practically free from gas cavities and cuprous oxide, starting with electrolytically refined copper, which consists in melting the copper in a fuel-fired melting furnace having the gases. of combustion in contact with the molten copp r, under melting conditions which produce oxygenbearing molten copper, in transferring the oxygen-bearing molten copper to a separate electrically heated deoxidiz'ing furnace, in there treating the molten copper with carbon until the molten copper is practically completely deoxidized and too little oxygen remains in the molten copper to react with impurities in the copper during solidification and form gas cavities dueto liberation of carbon dioxide or water vapor from the copper, in separating the molten copper from the carbon and in casting the copper under conditions which maintain a harmless oxygen content in the solidifying copper due to avoidance of excessive contact with atmospheric gases during casting.

3'7. The process of preparing copper castings practically free from gas cavities and cuprous oxide, which consists in preheating copper masses in a preheating furnace, in transferring the preheated copper masses to a melting furnace, .in melting the copper masses in a fuel-fired melting furnace under conditions which produce eugenbearing molten copper, in transferring the oxygen-bearing molten copper to a deoxidizing furnace, in there treating the molten copper with carbon until the molten copper is practically completely deoxidized and too little oxygen remains in the molten copper to react with impurities in the copper during solidification and form gas cavities due to liberation of carbon dioxide or water vapor from the copper, in dissolving carbon monoxide in the molten copper, in separating the molten copper from the carbon and in casting the copper under conditions which maintain a harmless oxygen content in the solidifying copper due to avoidance of excessive contact with atmospheric gases during casting.

' RUSSELL P. HEUER.

Certificate of Correction Patent No. 2,060,073.

" RUSSELL P. EEEUER November 10, 1936 It is hereby certified that error appears in the printed specification of the above numbered the equatio patent requiringcorrection as follows: Page 2, first column, line 4, in n, for Cu() read (Yu o; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed 23rd day of February, A. D. 1937.

[can] -HENRY VAN ARSDALE,

Acting Commissioner of Patents.

, 2,060,078 combustion in contact with the molten copper,

with impurities in the copper during solidification and form gas cavities due to liberation of carbon dioxide or water vapor from the copper, in separating the molten copper from the carbon and in casting the copp r under conditions which maintain a harmless oxygen content in the solidifying copper due .to avoidance of excessive contact with atmospheric gases during casting.

36, The process of preparing copper castings practically free from gas cavities and cuprous oxide, starting with electrolytically refined copper, which consists in melting the copper in a fuel-fired melting furnace having the gases. of combustion in contact with the molten copp r, under melting conditions which produce oxygenbearing molten copper, in transferring the oxygen-bearing molten copper to a separate electrically heated deoxidiz'ing furnace, in there treating the molten copper with carbon until the molten copper is practically completely deoxidized and too little oxygen remains in the molten copper to react with impurities in the copper during solidification and form gas cavities dueto liberation of carbon dioxide or water vapor from the copper, in separating the molten copper from the carbon and in casting the copper under conditions which maintain a harmless oxygen content in the solidifying copper due to avoidance of excessive contact with atmospheric gases during casting.

3'7. The process of preparing copper castings practically free from gas cavities and cuprous oxide, which consists in preheating copper masses in a preheating furnace, in transferring the preheated copper masses to a melting furnace, .in melting the copper masses in a fuel-fired melting furnace under conditions which produce eugenbearing molten copper, in transferring the oxygen-bearing molten copper to a deoxidizing furnace, in there treating the molten copper with carbon until the molten copper is practically completely deoxidized and too little oxygen remains in the molten copper to react with impurities in the copper during solidification and form gas cavities due to liberation of carbon dioxide or water vapor from the copper, in dissolving carbon monoxide in the molten copper, in separating the molten copper from the carbon and in casting the copper under conditions which maintain a harmless oxygen content in the solidifying copper due to avoidance of excessive contact with atmospheric gases during casting.

' RUSSELL P. HEUER.

Certificate of Correction Patent No. 2,060,073.

" RUSSELL P. EEEUER November 10, 1936 It is hereby certified that error appears in the printed specification of the above numbered the equatio patent requiringcorrection as follows: Page 2, first column, line 4, in n, for Cu() read (Yu o; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed 23rd day of February, A. D. 1937.

[can] -HENRY VAN ARSDALE,

Acting Commissioner of Patents.

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