US1769986A - Process of refining (degasifying and deoxidizing) of copper - Google Patents

Description

i (cathodes) by absorption from the gases Patented July '8, 1930 UNITED; STATES PATENT OFFICE MICHAEL GEORGE CORSON, ,OF JACKSON HEIGHTS, NEW YORK PROCESS OF REFINING (DEGASIFYING AND DEOXIDIZING) OF COPPER No Drawing. Application filed April 26, 1927, SerialNo. 186,821.

The present day practice of refining cop-- usually being an unavoidable component of such gases. While'the theoretical amount of oxygen required for the oxidation of this sulfur ought not to be larger than the amount of sulfur itself, the practical amount of oxygen permitted to combine with copper in the oxidation process runs, however, beyond 0.5% and sometimes up to 1.0% of the total weight of the metal. In other Words, an excess of oxygen amounting to 1000-2000% is considered necessary for the complete removal of sulfur.

v This large amount of oxy en calls in its turn for a prolonged period of poling and for a considerable consumption of wooden poles. Again, the operation of poling has to be closel v watched, since the overpoled material will contain absorbed hydrogen and the ingots cast of it will be gassed.

I have-found that neither the excessive oxidation, nor the prolonged poling are really necessary. I have found that the process of oxidation pertains only to copper and not to sulfur, since there is always enough oxygen in the copper during its sojourn in the. furnace to take care of the sulfur by forming S0 gas. The oxidation is only a secondary phenomenon to the blowing away of the low pressure layer of sulfur dioxide gas coveringthe surface of the molten metal. This blowing away ofisulfur dioxide destroys the equilibrium between the sulfur dioxide on the one a hand and sulfur plus oxygen on the other, as

dissolved in copper, and as a consequence a continuous evaporation of sulfur dioxide takes place.

k I have discovered thatthe removal of sulfur, i. e., sulfur dioxide, will take place with- Renewed November 12, 1929.

out over-oxidizing copper if the molten metal is kept under vacuum. lVith thetotal gas pressure over the molten copper maintained at say 1+5 of'mercury, a rapid and prac-' tically complete removal vofsulfur'dioxide takes place and the moltenmetal can be made to contain not more than 0.10% oxygen.

My invention also includes the removalof the oxygen from the molten copper. While poling may be retained for the elimination of the bulk of oxygen, it cannot result in a sound metal, unless about 0.04% of oxygen are allowed to remain in the metal. This amount of oxygen produces about 9% by volume of a copper-copper-monoxide eutectic and the latter causes av large number of troubles in various industrial applications of copper.

All other methodsof a complete deoxida' tion of copper proposed and used until the present, consist in the introduction of some reducing agent, which for the sake of efliclent use must be soluble in copper. The

amount of this reducing substance cannot be strictly calculated and has to be introduced in a considerable excess. This results either in the formation of a solid solution (in case of' phosphorus, SlgllCOIl and manganese) or of a secondary constituenta compound of copper-with the 'reducingfageilt (in the case of magnesium, calcium, cerium). Inthe first case the electric conductivity is impaired, in

the second the metal is likely to be dirty and to cause troubles in its future uses. I

Other reducing agents, for instance boron suboxide and calcium carbide have been suggested and actually used. These substances remain, however, solid at the melting point of copper and float upon the latters surface, whence their reducing action may not be efficientandreliable.

I have found that calcium carbide may form a cheap and highly efficient reducing agent provided it is present-in a liquid form. For this purpose I dissolve calcium carbide in some molten fluoride or a mixture of fluor ides. Among these sodium'fluoride, calcium fluoride, aluminum-sodium fluoride. (cryolite) represent good solvents for calcium car- In general, my process of refining copper may be presented as follows: Cathode or native copper is continuously melted in the usual type of reverberatory furnace and amounts of the molten metal are withdrawn periodically and placed in an auxiliary furnace of some kind, which is so arranged as to make it possible to close it reasonably airtight so enabling a strong vacuum pump to produce a vacuum with a remaining'pressure of 15.". In a few minutes the total amount of sulfur is eliminated as sulfur dioxide. Next the molten metal is covered with a roughly powdered mixture of fluorides-and calcium carbide, though it is also possible to introduce this mixture in a liquefied form. A violent reaction startsimmediately and after a few minutes the layer of the reducing mixture becomes quiet which indicates the end of reduction (deoxid ation) the metal is immediately ready for pouring, and no contamination of any kind results. This process of deoxidizing with the aid of a liquid layer of a mixture of fluorides and I calcium carbide is not limited to use in conjunction with the removal of sulfur. dioxide by the application of a vacuum. It can be as well applied to-the molten oxidized copper resulting from the process of removing sulfur by oxidation as is usually done in the refineries. It can also be used as a supplenot, therefore, become oxidized and no film of any oxide may be found in alloys manu factured in this way.

Claims: 1; A process of purifying copper which comprises forming a bath of metal, oxidizing any sulfur present to sulfur dioxide, and then lowering the pressure upon the surface of the bath to a point substantially below atmospheric and maintaining such condition until the sulfur dioxide has been removed.

2. A process of purifying copper which comprises forming a bath of metal, oxidizing bide at .the temperature of the molten metal to deoxidize the same. I j

3. A process of deoxidizing copper which comprises treating the oxygen-containing metal while molten with a mixture of calcium carbide and fluorides capable of dissolving the carbide at the temperature of the molten metal.

4. A process of deoxidizing copper which comprises treating the oxygen-containing metal while molten with a mixture comprising calcium carbide and sodium fluoride.

5. A process of deoxidizing copper which comprises placing a'mixture of calcium carbide and fluorides upon the surface of a bath of copper, the fluorides being so chosen and present in such amount as to insure the dissolution of thev calcium carbide in the fluorides under the influence of the heat of the bath, and maintaining. the bath fluid until the copper has become substantially deoxidized. 6. A process of deoxidizing a copper-containing bath which comprises forming a layer of molten fluorides upon the bath, dissolving calcium carbide therein, and maintaining the bath fluid until it has become substantially deoxidized.

7. A process of deoxidizing copper which.

comprises treating the oxygen-containing metal while molten with a mixture compris ing calcium carbide and cryolite.

Signed at 8108 Polk Ave. Jackson Heights in the count-y of Queens and State of New York this twenty-third day of April A. D.

MICHAEL GEORGE CORSON.

1 any sulfur present to sulfur dioxide, then lowering the pressure upon the surface of the bath to a point substantially below atmos pheric and maintaining such condition until the sulfur dioxide has been removed, and then treating with a mixture of calcium carbide and fluorides capable of dissolving the car-