Process of copper base product within iron base can

BACKGROUND OF THE INVENTION

The present invention relates to the processing of copper metals, i.e. copper and copper alloys, and, more particularly, to the conditioning and working of copper metals following converting.

Generally, extraction of copper from an ore such as chalcopyrite (which contains the copper primarily as the sulfide) involves: milling the ore to fine particle size; froth flotation by which copper rich particles in an aqueous suspension adhere to gas bubbles that rise to the surface of the suspension where the copper rich particles are collected and concentrated; roasting the concentrate to eliminate water and to oxidize some of the sulfur; smelting to eliminate unwanted residues as slag and to separate the copper therefrom in the form of cuprous sulfide; and converting the cuprous sulfide to metallic copper by oxidizing the sulfur to sulfur dioxide, which becomes separated as a gas. Since sulfur, even in very small concentrations, in copper tends to increase brittleness and reduce conductivity, it mdst be removed completely with the aid of a slight excess of oxygen. The result is copper oxide formation. Oxygen, though not to the same degree as sulfur, tends to have a similar effect but has been relatively expensive to remove and control. The present invention is concerned with the removal or control of such oxygen, and with certain products made feasible thereby.

SUMMARY OF THE DISCLOSURE

The primary object of the present invention is to provide processes for and products of the removal or control of oxygen from a copper metal composition of the foregoing type, in the following manner. The copper metal composition, including any desired non-copper components, is enclosed within a close fitting “can,” i.e. casing. The can characteristically contains iron and is capable of gettering oxygen from the copper metal composition, on heating, in order to render it or optionally its surface oxygen free. The copper metal composition may be mechanically worked while in the can in such a way that, despite deformation of the can along with its contents, removal of the can from its contents at the end of the process is not difficult. In accordance with the present invention, therefor, copper and iron constitute a synergistic pair.

Other objects of the present invention will in part be obvious and will in part appear hereinafter.

For a fuller understanding of the nature and objects of the present invention, references is to be had to the accompanying drawing wherein:

FIG. 1 is a schematic flow diagram illustrating copper deoxidation in accordance with the present invention;

FIG. 2 is a schematic flow diagram illustrating clad copper metal production in accordance with the present invention;

FIG. 3. is a schematic flow diagram illustrating copper powder compacting and sintering in accordance with the present invention;

FIG. 4 is a schematic flow diagram illustrating copper winning and consolidating in accordance with the present invention;

FIG. 5 is a schematic flow diagram illustrating dispersoid strengthening in accordance with the present invention; and

FIG. 6 is a schematic flow diagram illustrating slab consolidating and working in accordance with the present invention.

SPECIFIC DISCLOSURE

The processes described specifically hereinbelow incorporate a combination of two or more of the following steps, insofar as such steps are not inconsistent: (1) enclosing a metallic mass of a copper composition in a metallic can of an iron composition; and/or (2) predeterminedly heating the entire assemblage to a temperature at which oxygen diffuses to the surface of the copper, oxygen is released from the surface of the copper, oxygen migrates to the surface of the iron and oxygen reacts with the iron to form a stable solid; and/or (3) heating the entire assemblage to a temperature at which some chemical or physical change other than copper deoxidation occurs; and/or (4) mechanically working the entire assemblage with the can remaining sealed; and/or (5) removing the can from its contents by chemically dissolving or mechanically stripping. Various examples of combinations of these steps are given in the six examples below, which are illustrated in the six figures of the drawing.

Generally, the copper metals useful in accordance with the present invention include commercial bulk and particulate copper and various copper alloys. Contemplated commercial bulk or particle copper, for example typically includes the following.

(1) Electrolytic tough pitch (ETP) copper which contains by total weight in a remainder of copper: combined oxygen in the form of Cu₂O and dissolved oxygen— 0.04%; and nickel, iron, bismuth, arsenic—trace;

. (2) Lake copper, which contains by total weight in a remainder of copper, from 0.05 to 0.089% silver, in addition to minor proportions of oxygen, nickel, iron, bismuth and arsenic, as specified above in connection with ETP copper;

(3) Oxygen free (OF) copper, containing by total weight in addition to a remainder of copper: iron— 0.0005%; sulfur—0.0025%; silver—0.001 %; nickel— 0.0006%; tin—0.0002%; arsenic—0.0003%; selenium— 0.0002%; tellurium—0.0001%; lead—0.0006%; antimony—0.0002%; manganese—0.0005 %; bismuth— 0.0001%; and oxygen—0.0002%.

When deoxidation is contemplated, the copper alloys are those containing copper as their characteristic ingredient, preferably in excess of 50% by total weight, and

3,474,516 one or more other metals that are less active than iron, namely cadmium, cobalt, nickel, tin, lead, arsenic, rhenium and bismuth. These metals have a lower negative free energy of oxide formation than iron. The physical form of the copper metal is either one or more solid cast cakes or fine particles. When deoxidation is to be avoided, other alloying metals may be employed.

Generally, the iron composition of the can is a low cost metal such as follows. A typical wrought iron composition for the foregoing purpose, by total weight contains: carbon 0.02%; manganese 0.03%; phosphorus 0.12%; sulfur 0.02%; silicon 0.15%; iron—remainder. A typical acid bessemer, mild steel for the foregoing purpose, by total weight, contains: carbon 0.07%; manganese 0.35%; phosphorus 0.10%; sulfur 0.05%; silicon 0.02%; and iron—remainder. A typical open hearth, mild steel for the foregoing purposes by total weight, contains: carbon 0.10%; manganese 0.40%; phosphorus 0.03%; sulfur 0.03%; silicon 0.02%; and iron—remainder. A typical stainless steel for the foregoing purpose, by total weight contains: nickel—18%; chromium—8%; carbon— 0.03%; and iron—remainder.

Preferably the thickness of the iron can, depending upon the size of the assemblage and upon the contents to be deoxidized, ranges from ^J/s inch to one inch or more, a typical thickness being % inch.

Generally, oxygen removal from the copper composition within the can is effected in a vacuum which is produced by exhausting the can through an opening to a pressure as low as conveniently possible, e.g. below 20 mm. Hg, preferably in the range of 0.1 to 1.0 micron mm. Hg, in order to reduce the demands on the gettering agent which is constituted either by the iron can itself or by a large surface iron configration in the can. After evacuation, the opening in the can is sealed and the can is heated, together with its contents, to a temperature within the approximate range 1400 to 1800° F. for the period necessary to effect deoxidation to the degree and depth desired. The gettering process may be enhanced either by a gaseous transfer agent or a solid large surface deoxidizing agent, the former of which may be introduced into the can following evacuation of air and the latter of which may be introduced into available space in the corners or at the edges of the can. A suitable gaseous transfer agent is hydrogen, which may be utilized only when not in too large a concentration, preferably when at a pressure of less than 20 mm. Hg. The arrangement is such that the hydrogen reacts with the oxygen to form water vapor not only with surface oxides but also with copper oxides in the interior of the Cu. Water vapor formed on the surface of the Cu migrates over to the Fe can or getter in the can, reacts with it to form stable iron oxide and hydrogen. Some of the latter diffuses out through the Fe can and is lost; most, however, migrates back to deoxidize more Cu. Water vapor formed in the interior of the Cu causes fissuring of the copper mass. However, if the copper mass is retained within the can during hot rolling, the fissures are welded together. Suitable solid gettering agents, such as finely divided iron powder or steel wool, also, may be employed. The gettering procedure can be continued either to a point at which the surface only of the copper is deoxidized or to a point at which the entire copper mass is deoxidized.

Generally the copper composition contents of the iron composition can may be worked advantageously without separation following deoxidation. The reason for this possibility is that iron is more or less inert to copper, forming no intermetallic compounds therewith and having relatively low solid solubility therein. Thus, if the copper has an appreciable amount of oxygen, the iron will getter it to form brittle iron oxide at the interface, by which the iron later may be easily peeled from the copper and by which solid state diffusion or iron into the copper is blocked. If the copper has no appreciable concentration of oxygen, the largely inert iron simply welds to the copper surface and can be removed by pickling, for example in sulfuric acid. Alternatively, in the latter case, a release barrier may be interposed between the iron and the copper, for example, aluminum oxide powder, may be interposed in order to establish a release interface.

If, as in the case of lake copper, iron oxide particles are present in the copper mass, hydrogen should not be used. Rather iron should be used since it has been discovered that deoxidation by solid iron in a vacuum outside the copper mass will not affect iron oxide within the mass. This is fortunate since if the iron oxide particles were deoxidized, the iron, by virtue of its fine size and intimacy with the copper, would diffuse into the copper mass and thereby reduce the electrical conductivity.

The following non-limiting examples further illustrate the present invention.

Example I—FIG. 1

In a typical process embodying the present invention, an as-cast, unconditioned Lake Copper cake is encased in a steel can 12, an opening 14 being left in the jacket to permit evacuation. As shown in exaggerated fashion, the copper cake has copper oxide imperfections at 16, 18 and 20 and contains iron oxide grains at 21. The can is evacuated through opening 14 to a pressure below about 1 mm. Hg. The opening then is closed as by hammering or bending the pipe shut and welding it completely sealed before disconnecting the vacuum pump. Thereafter the can, is heated to a temperature of approximately 1800° F. This temperature and pressure are maintained for a sufficient period to enable copper oxide to decompose into copper and oxygen and oxygen to migrate through the void separating the copper cake and the steel can to form iron oxide at 22 and 24. Iron oxide particles 21 within the copper cake are unaffected. Optionally this temperature and pressure are maintained for a sufficient period to enable the decomposition of copper oxide particle 20, the diffusion of the resulting oxygen through the copper cake and the migration of oxygen to the steel can where iron oxide forms as at 25. Thereafter, the copper cake, while within jacket 12 is hot rolled to form a steel-copper-steel sandwich at a temperature of 1600° F. Finally the steel jacket is removed by pickling in sulfuric acid. Thereafter further hot and cold rolling are effected to produce copper sheet as at 27.

Example II—FIG. 2

A slab of copper 30 is interposed between two slabs of cupronickel 32, 34, the thicknesses of the three slabs bearing the relationship: cupronickel—15%; copper— 70%; cupronickel—15%. The total slab, approximately 8 inches thick, 2 feet wide and 10 feet long, is enclosed within a Ά inch thick mild steel can 36. The entire assemblage is heated to a temperature ranging from 1000 to 1400° F. while hydrogen is passed throgh the can to reduce all the copper and nickel oxides. The ports 38, 40, which permit the passage of hydrogen through the can, then are closed. The entire assemblage next is heated to hot rolling temperatures of from 1400 to 1800° F. and the entire assemblage is rolled to provide one monolithic metallic blank 39. Next the entire assemblage is cold rolled to about 50% more than final thickness. Then the steel sheath 41, 42 is removed by pickling in sulfuric acid. Finally the cupronickel-copper-cupronickel sandwich is cold rolled to ultimate thickness.

In an optional modification of the present example, the hydrogen deoxidation step is replaced by deoxidation by reaction with the iron of the can.

Example III—FIG. 3

Copper powder 44, approximately 325 mesh in particle size, is placed in a mild steel can 46 that is 10 feet long by 2 feet wide by 6 inches deep and % inch thick. The apparent density of the copper powder is about 0.15 pound per cubic inch. Next the can is evacuated at room

8,474,516 temperature through a port (not shown) and the port is welded shut. The assemblage is heated to a temperature of 1600 to 1800° F. The base 48 of the can supports a pair of thick mild steel blocks 50, 52 for a reason now to become apparent. As a result of the heating, the copper powder sinters together into a compact mass approximately Ά its original volume. Since the inside of the can has been evacuated and since V4 inch mild steel at 1600° F. is not very strong, the top of the can collapses as at 54. Buckling of the edges of the can is prevented by blocks 50, 52. The combination of the box construction of the can and the sintered coherency of the copper powder permits hot rolling the can to a thickness of about Vz inch. The steel sheath now is stripped from the resulting copper sheet and the copper sheet finally is cold rolled to its ultimate thickness.

Example IV—FIG. 4

The dimensions of the can used in the following winning and consolidation process are the same as were the dimensions in Example III. Cu₂O and Cu₂S powders 60, 62 are mixed and placed in a mild steel can in proportions that are stoichiometric with respect to the oxygen and sulfur. Heating at 1700° F. while evacuating is effected in accordance with the formula:

Cu₂S+2Cu₂O-> 6Cu+SO₂

Following evacuation of all SO₂ evolved, the port through which the SO₂ is evacuated is welded shut. Sintering, rolling and stripping then are effected as in Example III.

Example V—FIG. 5

A dispersoid strengthened copper composition is produced in accordance with the present invention as follows. A can of the dimensions specified in Example III is filled with a mixture of copper and aluminum particles. The copper particles contain just enough oxygen as oxides and in solid solution to react with all the aluminum metal in the aluminum powder. Hence the inner surface of the can is rendered inert, as by oxidizing or coating with A1₂O₃, powder so its does not gather the oxygen. Next the can is evacuated and sealed. When the assemblage is heated to 1800° F., several reactions occur. Cu₂O decomposes to Cu and O₂. Al expands more than A1₂O₃but any particles A1₂O₃ coating that thereby cracks is promptly repaired by the O₂ from the Cu₂O, whereby molten Al is prevented from running onto the Cu. The Cu powder sinters together as in Example III. Then the entire assemblage is hot rolled. During the rolling procedure, a thin film of molten Al, from the core of every Al particle which consists of said metallic Al core in an A1₂O₃ coating, is smeared onto the surfaces of the Cu particles. This Al reacts with any Cu₂O on the surface of the Cu particles, and also, by interdiffiusing with the Cu, which contains some dissolved oxygen as well as some discrete particles of Cu₂O, contacts oxygen inside the Cu and reacts to form sub-micron sized A1₂O₃ dispersed particles 68. Removal of the mild steel sheath and cold working then results in dispersoid strengthened copper.

Example VI—FIG. 6

The process of Example I is repeated except that four bulk copper slabs, each of the dimensions of the “total slab” indicated in Example II, are enclosed in superposition, snugly within a can of four times the volume as the can of Example II and with a can wall thickness correspondingly greater, e.g. one inch thick. Deoxidation and working under the conditions specified in Example I result in the consolidation of the slabs into a copper sheet or plate 78, whose overall mass is four times that of a single slab.

CONCLUSIONS

The foregoing disclosure has shown and described various processes involved in enclosing a copper containing assemblage in an iron containing can. The can provides ⁶ a versatile self-contained environment that is useful in effecting de-oxidation to produce oxygen free copper, consolidated particles and slabs that are worked to integrated final products, to win refined copper, on copper whose alloys, from compounds such as copper sulfides and oxides, and copper that is strengthened by dispersoid particles. The iron of the can either participates in a reaction therewithin or is shielded from the reaction by its own composition or by an inner inert coat.

Since certain changes may be made in the foregoing disclosure without departing from the invention herein involved, it is intended that all matter described in the foregoing specification or shown in the accompanying drawings be interpreted in an illustrative and not in a limiting sense.