US2026605A - Method for working and treating metals - Google Patents

Description

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Filed Jan. 9, 1955 METHOD FOR WORK-ING AND TREATINF METALS Jan. 7, 1936.

Patented Jan. 7, 1936 vuliu'rlao STATES PATENT ori-ICE METHOD Fon wgll AND TREATING Frank L. Antiseil, Wilkinsburg, Pa., assignor toV Copperweld Steel Company, Glas'sport, Pa., a corporation of .Pennsylvania Application January 9, 193s, serial No.6o,913

9 Claims.

My invention relates to a method for working and treating copper or other similar metals and, in particular, copper or other metal which has been deposited electrolytically upon a base of copper or another metal such as steel, and to the formation of a firm bond between the deposited copper and the base metal, as well as between successive deposited layers.

It is well known that copper of an exceedingly high degree of purity, for example, 99.99 percent, can be obtained by electrode position from com mercial anodes which, themselves, approach a purity of 99.95 percent. The characteristics of electrolytic copper, however, are not those which are most desirable inthe commercial field. Electrolytic copper is characterized by a fairly coarse grain structure, the size of the grains increasing with the thickness of the deposited layer. 'Ihe initially deposited layers are of very flnestructure-but subsequently deposited layers show a marked increase in the grain size. The typical grain structure of electrolytic copper is shown in photomirograph b of a plate opposite page 152 of The Story of Copper by Watson'Davis, published in 1924 by the Century Company, New York, N. Y.

It has not been possible heretofore to improve I the grain structure or physical'characte'ristics of electrolytic copper by hot vor cold working. It has been found, for example, that the coarse structure characteristic of electrolytic copper has remained even after heating in hydrogen and l alternate hot and cold rolling. f The bond heretofore obtained between deposited co'pper and the base metal, furthermore, has not been entirely satisfactory.

I have invented a method for working and treating electrolytic copper'which results ina grain structure entirely different from that of the original electrolytic deposit and which gives rise to numerous desirable physical characteristics, principally, high conductivity, with malleability and ductility. I deposit successive layers of copper on the base metal, and mechanically work the layers as deposited to introduce an amorphous constituent into each layer, andby subsequent heat treatment at comparatively low temperatures, very much below the fusion point,

I cause an intrusion of the amorphous material into the copper deposit and thebase 'metal forming a tight bond or weld with the latter Kand equiaxed 'coppergrain ,structure in the former.

`In accordance with my invention, 1 subject the electrolytic copper to successive cold working operations as -the electrolytic deposit proceeds base which results from (Cl. 14S-11.5)

layer by layer and subsequently heat treat the entire mass of deposited copper at a temperature below the fusion .point to bringabout nally the desired grain structure and permanent bond to the base.

during the growth of the deposit seems to be a compacting of the copper crystals accompanied by a disintegration of the grains, producing a species of electrolytc copper which is subject to improvement as to grain characteristics by heat l0 treatment. Specifically, I provide for depositing electrolytic copper upon a base in the form of a rod or wire which may be steel or copper. I prefer to rotate the base and move it simultaneously through an electrolytic bath. from the bath, I subject the rotating base with a coating of copperthereon, to the action of rolls disposed axially of the base, provided with a slightly blunted or rounded edge. These edged rolls produce a l the copper in the neighborhood of which is subjected to mechanical working under high pressures. 'I'his sequence of electrode position and mechanical working is repeated until the desired thickness of copper lisas base. The coated ba is then ready for heat treatment. I preferably accomplish this b'y heating the coated base-to a final of 1725" F. in a continuous furnace. After heating, the coated base may be rolled at various temperatures vas high as 1000 F., depending on the final temper desired, or it may also be drawn through dies.-

, The increased adherence of the deposit vto the caused, in myopinion, by an intrusive action of the amorphous grain boundary material of the copperinto the intergranular spaces of the base v metal-'In the welding of wrought iron, mild steel, or other metals, an actual fusion of the 0 accompanied by the formaor the equivalent thereof. The results flowing from my invention may probably be explained on the samebasis as the phenomenon of annealing which brings about, at a temperature well below fusion, a grain growth with a corresponding migration or rearrangement of 'grain boundary material. Such changes favor the intrusive action of foreign grain boundary material, and it is found that there is actually an interchange of such material -between 4the copper and the base at temperatures only slightly above the annealing temperature, resulting in an excellent union of the two metals.

In accordance with my invention,

`metals must occur,- tion of a bonding alloy,

The effect of the mechanical working 5 Upon. emergence l5 spiral track on the coated base, 20

been deposited on the 25 temperature the foregoing process is 35 therefore, it M ture produced in the electrolytic copper by the invention; as observed in photomicrographs. In the drawings;

Figure 1 is a diagrammatic illustration of the electrolytic ,coating baths, the working rolls and the continuous furnace by which the electrolytic copper is deposited on a base, wire or rod, subjected to mechanical rolling and finally heat treatment, in position thereon;

Y Figure 1A is a sectional view along the line IA-IA of Figure 1;'

Figure 1B shows generally the appearance of the rod after the first deposit and mechanical working:

Figure 2 is a partial cross section to greatly enlarged scale taken axially through a copperclad rod showing the physical effect of the cold working;

Figure 3 is a conventional representation of a photomicrograph illustrating the effect of the cold working on the grain structure of the deposited layers;

Figure 4 is a similar section showing the ef- `fect of heat treatment of the coated rod pro- 'duced according to the invention, showingthe effect of heat treatment following the mechanical workings;

Figures-5 and 5A are transverse sections showing the effect of the invention on a layer of electrolytic copper deposited on a-cast copper base;

Figure 6 shows diagrammatically the crystalline state of the iron and the copper deposited thereon after the mechanical working; and

Figure 7 is similar to Figure 6 butshows the change in-granular structure brought about by heating to temperatures below fusion.

4Referring in detail to the drawings, I subject a base member I0, which may be a rod or wire of steel or copper, to treatment in electrolytic baths II and I2, each electrolyticaliy deposited layer being subjected to mechanical working in roll stands I3 and Il. After emerging from the last stand of rolls, the coated base passes into a continuous furnace .I5 for heat treatment.

Preferably I provide means for rotating the base during the progress of the coating and heat treating operations. 'I'he coated base may easily be wound upon a reel after treatment and the uncoated base unwound from anotherreel prior to,

introduction into the baths. Both the unwinding and winding-up reels may be rotated by suitably mounting them, and axial rotation of the rod thereby effected.

The construction of the electrolytic baths Il and l2. and the method of subjecting the base' member to treatment therein. are well known and require 'no detailed description.

rolls Il are shaped so asto have a somewhat rounded or blunted edge I'I and the rolls of each stand are positioned in the housings so as to be slightly oifset as illustrated. 'I'he shape of the rolls II is similar to that resulting from placing a pair of truncated cones base to base, The rolls The roll stands Il and Il each comprise a. pair 'of rolls, I mounted in suitable housings. not shown. The

I 6 of each stand are preferably positioned in substantially the same horizontal plane, and are adjusted therein so that the portions of the rolls of greatest diameter are separated by a distance slightly less than the diameter of the coated base. The weight of the coated base thus wedges itv between the rolls and, because of the angular relation of the forces involved. the total pressure exerted on the coated member by the rolls is considerable. 10 Because of the shape of the rolls I t, the unit pressure to which the electrolytic copper is subjected is very high. It will be apparent that substantially the total pressure of the rolls on the coated member is transmitted through two spaced points, as shown in Figure 1A.

Since the rollsv I6 of a single stand are slightly offset in the direction of travel of the base, the result of the cold working in any stand of rolls is to produce helical tracks I8 in the electrolytic 20 layer deposited on the base, as shown in Figure 1B. Succeeding electrolytic treatments, however, cover the helical paths and all other portions of the initially deposited layer and after the second layer is deposited, lthe mechanical work following thereupon again produces helical tracks.

In a particular instance, the dimension of the rolled mark on the wire was .009 inches wide, and the chord of contact 'is .D11-inches, equalling an 30 area of .000099 square inch, or say in round iigures .0001 square inch, or a bearing area of one ten thousandths of a square inch;

The total weight of wire on point contact is 2.2 pounds, and the resolution of force on this wire by reason of the wedge effect is 5 to 1, resulting in a component of pressure of 51/2 pounds, resulting finally in an enormous pressure of 55,000 pounds per square inch on each of the two rollers, thereby compacting the copper completely.

Figure 2 illustrates a half section of a length of the base member I0 having iive electrolytic lay'ers deposited thereon. The first layer, I9, has a well defined helical track I8 therein formed by the cold rolling after the ilrst electrolytic deposit. The second layer 20 also has a helical track Il but it is displaced axially of the base I0 relative to the track in the layer Il. It will be observed that the track I8 formed -in the initial layer Il is repeated to a decreasing extent in the succeeding layers. Repeated rolling and electrolytic deposition finally produce a coated base, the surface of `which is lightly corrugated'. showing a number of helical tracks oneoverlying the other.

' Referring in particular to Figure 3. I shall dis- 55 cuss the effect of the cold working on the grain structure of the deposited layers. As shown byV the publication referred to above. electrolytic copper is ordinarily of comparativelycoarse, col- --umnar grain structure although the layer next e0 the base on which the deposition occurs is usually of nner grain structure than subsequently deposited layers. In Figure 3, I have shown diagrammatically at Il' the grain structure of different portions of the initially deposited layer. a5 This layer, as stated, is of fairly small grain structure but the-effect of the cold working to which the layer is subjected by the rolls I0 is to actual physical deformation of the deposited layer while at li' is shown the effect on the" grain structure. The portions of the initial layer apart from the track I8 formed therein by the rolls I6 are of comparatively coarse grain structure, as indicated in Figure 3. '111e coarseness of the layers subsequently deposited increases gradually as previously pointed out.

As described, the helical tracks traced by successive roll stands, such as I3 and I4, are dis,- placed slightly, axially of the base member, and result in the formationof portions of successive layers having similar grain structure disposed in step-like relation as shown in Figure 3. It will thus be apparent that each electrolytic layer is characterized by a helical band of compacted and refined grain structure adjacent the helical track formed by the rolls I6. 'Ihe remaining band of each layer is of gradually varying grain grain characteristics, it is observed that the grainv structure of the entire deposited layer is quite fine and uni!orm. This result I attribute to the intrusive eiect of the bands of the` deposited layers which have been subjected to cold working. The effect of the axially displaced bands of compacted,' fine grain copper in each successive deposited layer seems to spread through adjacent layers by this intrusive action and thereby produce the uniform, iine grain structiire which is observed after heat treatment. 'Ihis is best illustrated in 'Figure 4 in which it will be observed that the nne grain structure resulting from the cold working of the initial layer in the -rolls I6 has spread from the initial layer through adjacent layers to the outside layer. The uniform grain structure shownin Figure 4, of course, is

highly desirable since it gives rise to the physical characteristics required in commerce, namely..

ductility and malleability, and provides an excellent bond between layers. I .y l

Upon emerging from the furnace, the coated bese maybe subjected to smoothing eenen witnout substantial reduction in area while hot, by means of either rolls, rotary dies,.or other de- `vice that does not subject the coat to a great shearing stress, and may thereupon be subjected to any further manufacturing operations desirable. Since, as explained above, the union is effected by the migration 'of amorphous material, great welding pressures are not necessary or desirabie. /By bringing ythe two metals in contact at high temperature without friction, it is possible to work the composite article by tandem' devices spaced all'ltA S0 that whenwire reaches the second device it can be reduced by about 20% thereby carrying out the two operations oi.' uniting and reducing at no extra cost.

I have also obrved that the intrusive action above mentioned is also effective in the case of, for example, a steel billet having a copper sheath cast thereon, and a second copper sheath deposited electrolytically on the rst. Cast copper, as

well as electrolytic copper, has a very definite and well recognized type of grain structure. By subjecting the electrolytic layer deposited lon a cast copper sheath to combined mechanical working and heat treatment, as above described, however, I am able to convert the grain structure of the electrolytic copper and also that of the cast cop- 5 per sheath to substantially the type shown in Figure 4, resulting in a single homogeneous grain structure throughout the copper layers, demonstrating the remarkable eifects of the intrusive action of the amorphous constituent. Figures 5 10 and 5A show diagrammatically the grain structure of electrolytic and' cast copper before and after subjecting them to the process of my invention.

The effect of the treatment described upon the grain structure of the copper-iron boundary is best shown in Figures 6 and '7. In Figure 6, the iron has a fairly coarse grain structure and the copper has the grain structure illustrated more particularly in Figure 3. The solid circles in Figl ure 6 represent the amorphous constituent as shown in Figure 3 at I 9. In Figure 1, the iron base is unaltered as to grain-orientation. The copper grain structure has become equiaxed. The amorphous constituent has disappeared with an inter-copper penetration' at all grain boundaries of the iron and with interface penetration or, more strictly speaking, inter-crystalline penetration of the Neumann bands that appears to be,

in effect, interface penetration. On heating the composite article to. a temperature between 400 and 800 F., however, the grain structure is converted into that shown in Figure 7. It will be apparent that the grain boundary material of the copper has penetrated into the intergranular spaces of the iron and that, simultaneously, the grain structure of the copper has been consider-l ably reflned. There is an annealing effect upon the iron grain structure characterized by the introduction of Neumann lines. The interlocking grain boundary material, of course, effects a very f strongly adherent union between the copper and the iron. The net effect of the electrodeposition followed by mechanical working and heat treatment at about 800 F., seems to be that a weld between the metals is produced ata temperature much below the fusion point. There appears to be a critical temperature, at about the annealing point, at which this result occurs.

Itwill be apparent from the foregoing description that the invention provides a highly useful method and apparatus for' making electrolytic copper subject `to vheat treatment for improving the physical characteristics thereof, including the bond with the base, whereas heretofore it has been impossible to bring-about any improvement in electrolytic copper by heat treatment. My invention makes itA possible to obtain a marked improvement in the characteristics not only' of elec trolytic copper, but also of other metals of similar properties, by a simple heat treatment and hot working preceded by -the mechanical working after the deposition of each layer, as described above. v

The dimension of the unit of amorphous mao5 terial is of the order of a small multiple of atomic diameters. The ordinary grain boundary is from one to one-hundred thousand times that size and -provides, therefore, a space for many millions of the amorphous units when the metal is below the temperature at which grain growth prevails. 0n e subjecting the metali to temperatures approaching the time-temperature annealing value, the tendency to form solid solutions within the matrix. as

well as the inherent tendency for the amorphous 'I5` maternita-@Mmmm into grain umts.A wm bring the intrusive action Vto an end when the grain ysize becomes larger than the grain bolmdaries of The amorphous constituent may be provided in ways other than that already described. As an example, I may'wash thecoated rod with nickel, arsenic or other solutions as it emerges from the electrolytic baths. thus introducing a foreign constituent of .00l%.

` Although I have illustrated and described herein but one preferred'embodlment of the invention,

' it will be obvious that-many changes may be made in the apparatus and method disclosed herein without departing from the scope of the invention or the spirit of the appended claims.

I claim: v

1. The method of making a copper sheathed wire including the steps of depositing successive layers of copper from an electrolytic solution of copper onto a core wire, intermediate the depositing of successive layers compacting` spaced paths on the layer already deposited leaving uncompacted portions therebetween, and annealing the composite article without reaching the fusion point of the copper layers.

2. A method of making a. coherent, integral mass of metal from a series of layers thereof including the steps of successively ccmpacting portions of each layer to reilne the grain structurethereof, leaving the intermediate portions in their original coarse-grained state to anchor the layers together, and annealing the layers whereby the intrusive eiect of the compacted portions extends to adjacent layers wiping out boundaries therebetween and uniting the layers.

3. The method Ofmaking a composite article,

which comprises electrodepositing successive layersvof metal on a core, compactingspaced portions of each layer and leaving uncompacted portions therebetween before depositing the succeeding layer, and annealing the article to reilne the grain structure and cause the intrusive effect of the compacted portions to extend to adjacent layers.

14. .The method of making 'a composite article, which comprises electrodepositing successive .layeraoi'metalonacore,rotatingtliearticle copper layers.

axially while advancing it longitudinally in contact with compacting rollers to compact spaced.4 portions of'each layer and leaving uncompacted portions therebetween before depositing the succeeding layer, and annealing the article to refine s the grain structure and cause the intrusive effect of the compacted portions to extend to adjacent layers.

5. The method of making a composite article, which comprises electrodepositing successive lay- 10 ers of copper on a steel core, compactin Spiced portions of each deposited layer and leaving uncompactedportions therebetween before depositing the succeeding layer, and annealing the article to reilne the grain structure and cause the l5 intrusive effect ot the compacted portions to extend to adjacent layers.

6. The method of making a composite article which comprises electrolytically depositing a cop- .per layer from a copper solution onto a base 20 metal, compacting spaced paths thereon while leaving uncompacted portions therebetween, thereafter electrodepositing another layer of copper, and annealing the composite article without reaching, the fusion point of the copper 25 layers.

7. The method of making a composite article which comprises passing an elongate core such as a wire as a cathode through an electrolytic bath so as to deposit a copper layer on the core, form- 80 ing compacted spaced paths in the form of helixes on the deposited copper while leaving uncompacted portions therebetween, thereafter ef fecting the electrodeposltion of further copper on the preceding layer, and annealing the composite article without reaching the fusion point of the copper layers.

8. The method of making a copper sheathed wire which comprises passing a core wire as a cathode through an electrolytic bath, rotating 40 the wire axially while advancing'it through the bath, forming compacted helical paths on -the deposited metal while leaving 'uncompacted portions therebetweemthereafter continuing "the -electrodeposition of an additional layer of cop- 5 per, and annealing the composite article without reaching the fusion point of the copper layers.

9. The method of producing a copper sheathed wire including the steps of electrodepositing suc- 5o cessive layers of copper on a core wire, axially rotating the coated wire and while rotating it forming helical depressions or slight groov in the deposited metal and leaving uncompacted portions therebetween before depositing the lucl5 oeeding layer, and annealing the copper sheathed wire without reaching the fusion point of the FRANKLANTIBIIL.

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