US3722073A

US3722073A - Production of products directly from nickel cathodes

Info

Publication number: US3722073A
Application number: US00185716A
Authority: US
Inventors: F Larson
Original assignee: International Nickel Co Inc
Current assignee: Huntington Alloys Corp
Priority date: 1971-10-01
Filing date: 1971-10-01
Publication date: 1973-03-27
Anticipated expiration: 1990-03-27

Abstract

A method of producing a unitary piece from a pack of nickel cathodes, comprising hot working said pack to reduce its thickness by about 75 percent or more. Preferably, the hot working is carried out on such cathode packs heated to about 1600*F. to 2200*F. or higher, reductions of 92 percent or 96 percent or more being desirable. Certain embodiments permit the unitary piece to be cold worked and annealed to low hardness at temperatures as low as about 950*F., while various other embodiments permit annealing of the cold worked material at higher temperatures even up to 1800*F., or higher, with substantially no blistering. The present method lends itself to producing nickel strip, such as that suitable for coinage manufacture, from cathode nickel without melting.

Description

Unite States Patent 1 Larson, Jr.

[ Mar. 27, 1973 PRODUCTION OF PRODUCTS 3,648,353 3/1972 Anderson ..29/497.5

DIRECTLY FROM NICKEL CATHODES Primary Examiner-J. Spencer Overholser [75] Inventor Floyg fig Larson Assistant ExaminerRichard Bernard Lazarus woo Attorney-Maurice L. Pinel [73] Assignee: The International Nickel Company,

Inc., New York, NY. ABSTRACT 22 Filed; Oct 1 1971 A method of producing a unitary piece from a pack of nickel cathodes, comprising hot working said pack to [21] P 185,716 reduce its thickness by about 75 percent or more. Preferably, the hot working is carried out on such 52 US. Cl. ..29/472.3, 29/487, 29/4975 caflmde Packs heated to about 1600? to ZZWF- 29/498 148/115 R 148/127 higher, reductions of 92 percent or 96 percent or [51] Int. Cl. ..B2 3k 31/02 more being desirable Certain embodiments permit the [58] Field hi Search ..14s/1 1.5 R 127- 29/471.1 unitary Piece to be wmked and annealed 29/472 3 475 480 1, 5 hardness at temperatures as low as about 950F., while various other embodiments permit annealing of the cold worked material at higher temperatures even up [56] References to 1800F., or higher, with substantially no blistering. UNITED STATES PATENTS The present method lends itself [0 producing nickel I strip, such as that suitable for coinage manufacture, P1111161 et al. from athode nickel ithout melting 3,164,884 1/1965 Noble et 3,359,142 12/1967 Ward, Jr ..148/11.5 R 7 Claims, 1 Drawing Figure D 6 7O Cum 5A 2, 6O Chews/3 i g 50 4o i3 8 Q 30 20 l l 1 l l l 0 200 400 600 800 moo /200 M00 zeoo PRODUCTION OF PRODUCTS DIRECTLY FROM NICKEL CATHODES The present invention relates to a method of producing wrought metal products and particularly to producing such products (e.g., flat products such as sheet or strip) from electrolytically deposited nickel.

It has long been desired to produce wrought sheet or strip directly from electrolytically-produced metals (such as cathodes of nickel or cobalt, for example) since such materials are of high purity, and, therefore, desirable as a raw material for a number of applications, including the direct manufacture of coinage strip and coins. Commercially produced, such cathodes of nickel generally have dimensions of about 28 by 38 by b inches and weigh about 200 pounds, their method of production being well-known to the art (see, for example, US. Pat. No. 2,394,874 to Renzoni).

Briefly, in the production of nickel cathodes, there is employed a compartmented electrorefining cell that is divided into anode and cathode compartments by means of a permeable diaphragm and the electrolyte employed is a sulfate-chloride electrolyte. The impure anode in the anode compartment is electrolytically corroded and substantially pure cathode nickel is deposited at a cathode in the cathode compartment as a result of electrolysis. The impure anolyte is removed from the anode compartment at a steady rate and is subjected to purification treatments to remove therefrom impurities such as iron, copper, lead, arsenic, etc. The purified electrolyte is then introduced at a steady rate into the cathode compartment and nickel of high purity is plated therefrom. A slight hydrostatic head is maintained in the cathode compartment, allowing purified catholyte partly depleted in nickel to flow through the diaphragm into the anode compartment, thus preventing migration of unwanted ions from the impure anolyte in the anode compartment to the purified catholyte in the cathode compartment. As the process proceeds, nickel and impurities are dissolved from the anode. The impure anolyte is removed from the tanks, purified, and finally returned as purified catholyte to each cathode compartment for the deposition of pure nickel at each cathode.

Prior art attempts have been made to work nickel cathodes, e.g., by hot or cold rolling them individually, and it has been found necessary to anneal the wrought nickel cathode material after cold working to a desired shape, e.g., sheet, strip or some other form that is suitable for an intended use. Such annealing serves to improve the workability of the cold-worked product, thereby facilitating subsequent shaping operations. However, the prior art has experienced a problem of blistering at the surface of these cold-worked cathodes, particularly where the annealing temperatures are about 1400F. or higher, these blisters usually being in the form of sub-surface cavities. This blistering problem is especially severe where the annealing of such cold worked products is done in hydrogen or in a hydrogen-containing atmosphere. As a result of such blistering and because individual cathodes are so small as to render handling of individual cathodes an expensive and inconvenient matter, it has heretofore been considered not to be commercially feasible to produce a wrought annealed product directly from a nickel cathode.

Another problem encountered in prior art attempts to convert nickel cathodes into stripsby cold-rolling the cathodes was the separation, during the cold rolling operation, of the electrolytically deposited nickel from the cathode starter sheet of nickel. Such starter sheets are known to the art, they being provided in the electrolytic deposition tank and serving as a substrate on which the nickel is electrolytically deposited from the bath.

Accordingly, it has been the commercial practice to melt the cathodes and cast them into ingots weighing several hundreds or thousands of pounds. Such ingots can then be rolled or otherwise processed in a manner that is commercially practical.

The present invention enables the production of a unitary metal piece or product of relatively large size and quantity directly from a number of such cathodes, without the necessity of melting the cathodes and casting the molten metal.

As used with respect to the present invention, the term cathode includes both whole cathodes as well as cathode portions.

It is an object of the present invention to provide a method whereby a plurality of nickel or cobalt cathodes (especially nickel) can be converted, without melting, to mill products of sufficient quantity and size to meet standard commercial requirements.

It is a further object of the invention to provide directly from nickel cathode, flat shapes which can be annealed at relatively low temperatures so as to avoid, or at least reduce, the possibility of blistering while achieving low annealed hardness therein.

A still further object of the invention is to provide, in preferred embodiments, annealing of the wrought products produced from nickel cathodes at temperatures of 1800F. or higher with substantially no blistering.

Other objects and advantages of the invention will become apparent from the following description and accompanying drawing which comprises a plot of the hardness of wrought nickel strip products versus annealing temperature, Curve A depicting the hardness of such annealed nickel strip produced from nickel cathodes hot rolled and cold rolled according to the present invention and Curve B depicting the hardness of such nickel strip annealed after only cold rolling.

Generally speaking, the present invention is directed to a process for producing flat-rolled metal products using as a starting material electrolytically-produced metal cathodes of nickel or cobalt, which process comprises assembling or stacking, a plurality of v such cathodes in substantially face-to-face relation to form a pack, heating said pack to a temperature of about l600F. or higher and hot reducing, e.g., hot rolling, said pack under correlated conditions of heating temperature and hot reduction such that, at about 1600F. and l800F., the hot reductions are at least about 92 and percent, respectively, to provide a unitary bonded metal piece which preferably is of sufficient size to permit handling on usual production rolling mills employed in rolling ingots of commercial size and which has a relatively low recrystallization temperature after cold working thereof.

A substantially blister-free cold worked and annealed product can be produced from the hot-reduced unitary product by maintaining the annealing temperature at about 950F. to about llF. where the hot reduction of the cathode pack is 75 percent or more at 1800F. and at about 950F. to about 1200F. where such hot reduction is about 92 percent or more at l600F.

The initial pack can, and preferably does, contain a large number of cathodes, e.g., or or more in height, in total amount of up to one hundred or even more, with the total number of cathodes being limited only by practical handling considerations. It is an advantage to employ as thick a pack as possible as this practice facilitates the desired large amount of hot reduction. Multiple cathode lengths in the pack are also desirable.

In general, it is preferred that the amount of reduction accomplished in at least the initial hot rolling pass be as high as possible (e.g., about 30 percent or more and preferably at least about 50 percent) to ensure the formation of a sufficiently strong bond between the cathodes after the first rolling pass so that the cathodes of the pack do not become separated upon exit from the rolls or during subsequent processing.

Heating and hot-rolling are conducted in air, or, if desired, in a protective or other atmosphere. More preferably, for nickel cathodes, to which the present invention is especially suitable, the reduction in thickness on hot rolling is at least about 75 percent and even more preferably at least about 85 or 90 or 92 percent and the temperature of the cathode stack at the beginning of the rolling process is, more preferably, about from 1800F. to 2400F. However, for optimum results, a hot reduction of about 96 percent or greater and a hot rolling temperature of at least about 2000F. is most preferred.

After a plurality of such nickel cathodes is packrolled according to the invention such that the individual cathodes are consolidated into a single (unitary) piece, the resulting single piece can be air cooled and subsequently, further hot worked or cold worked and annealed, and further processed, as by blanking, stamping, etc.

Among its advantages, the present invention allows the manufacture of unitary products of commercially satisfactory quantity and size directly from cathodes, these products being further processable into finished products of various shapes (flat products, etc.) in equipment of commercial scale. There is essentially no limit on the size or weight of the single piece, or unitary product, producible by the present invention, aside from the mechanical limitations of the rolling mill or other manufacturing apparatus employed, since it is possible to stack a very large number of cathodes in various ways, as described below, and then produce a unitary product therefrom.

Furthermore, the bonding of the cathodes to each other is substantially complete, i.e., about 95 percent or more of the mating surfaces of adjacent cathodes is bonded, at the end of the hot-working operation, so that the strength of the bonds in the unitary product is sufficient for commercial processing, there being no need for subsequent heat treatment to increase the bond strength. Still further, the present invention provides products that can be cold-rolled without separation being encountered along planes corresponding to the original starter sheet within the nickel cathode.

Aside from the foregoing commercial advantages derived from the present invention, hot-rolling stacked nickel cathodes at a temperature of at least about 1800F., e.g., about 2000F. to about 2400F., so as to achieve thickness reductions of about percent or more, or at a temperature of at least about 1600F. so as to achieve thickness reduction of about 92 percent or more (e.g., 96 percent), provides the further benefit of lowering the softening, or recrystallization, temperature the unitary product upon annealing of subsequently cold-worked material. Thus, such hot rolled products subsequently cold reduced as little as 2 percent can be annealed to a hardness below about 40 as measured by the Rockwell30-T scale, using annealing temperatures as low as about 950F. Greater amounts of cold reduction provide even lower hardnesses after such annealing and it has been found that a cold reduction of approximately 25 percent or more will consistently provide a 30-T annealed hardness of 30 or below.

The effect of hot working stacked nickel cathodes on the recrystallization characteristics of the final product is shown in the drawing, where the hardness of the various wrought nickel products derived from the nickel cathodes is plotted against annealing temperature.

Referring to the drawing, the curve (curve A) for the hot-rolled strip produced from a pack of nickel cathodes at an initial cathode heating temperature of about 2200F. to reduce the stack thickness by about 96 per cent, air cooled, and cold-rolled to achieve a reduction of about 52 per cent, followed by a 20 minute anneal in a dry hydrogen atmosphere at the various indicated temperatures, shows that a hardness level of less than 30 (e.g., about 25) on the Rockwell 30-1 scale can be achieved by heating for 20 minutes at temperatures of about 950F. or greater. On the other hand, single nickel cathodes subjected only to coldrolling of about 37 percent, an intermediate anneal at about 1200F. for 6 hours, and a further cold reduction of about 20 percent and thereafter annealed in the same manner as the hotrolled cathodes, were not softened below about 40 Rockwell 30 T, even after annealing at a temperature of about l700F. for 20 minutes, as depicted by Curve B. It is felt that the intermediate anneal at 1200F. in the case of the coldworked cathode nickel did not substantially affect recrystallization behavior and therefore, that the specimens depicted by curves A and B were in essentially the same cold worked state (total cold work about 52 percent) before final annealing.

A comparison of the curves for the hot-and-coldrolled cathodes and those cathodes subjected only to cold rolling shows the significant reduction in the softening temperatures, viz., a reduction of up to more than 700F. in softening temperature, brought about by the hot-working process.

The low annealing temperatures which may be employed for softening to low hardness values nickel material derived from cathode nickel subjected to a hot rolling and cold rolling schedule as contemplated by the invention, are an outstanding advantage since annealing temperatures below about 1100F or 1200F., as the case may be, may be employed successfully-and the possibility of blistering during annealing can thereby be greatly reduced or entirely avoided. The possibility of blistering in products hot reduced at least cent, with a minimum hot working temperature of about l600F., for the reason that such a level of hot reduction provides, in addition to the foregoing benefits, a nickel product that can be cold-worked and annealed with substantially no evident blistering being encountered at annealing temperatures exceeding the range of 950F. to l200F. or even l400F., e.g., 1800F. or higher, in a hydrogen-containing atmosphere. With hot reductions of less than about 96 percent, e.g., about 92 percent to about 96 percent, it is preferred, in order to minimize the possibility of blistering, that the annealing temperatures employed in treating subsequently cold worked material be correspondingly lower than l400F., e.g., an annealing temperature of about 950F. to about 1200F.

To illustrate and explain the present invention more specifically, the following examples are provided.

EXAMPLE I Groups of ten pieces each of electrolytic nickel were cut from conventionally-produced nickel cathodes, these pieces having respective dimensions of about 4 by 4 inches and a thickness of about three eighths inch. The respective surfaces of the pieces were ground to remove pronounced asperities and the pieces arranged in various packs respectively comprising single stacks of these cathode pieces, each stack having a total thickness of about 4 inches. The pieces of each stack were then tack welded to one another (using a manual metal-arc flux-coated nickel welding electrode) at two opposite edges.

The stacks were heated in air to about 2200F. and soaked for 1 hour thereat, after which each one of the welded stacks was individually hot rolled (in air) so that the pieces of each stack were bonded together substantially completely to form a unitary piece, or strip, and then air cooled. Each resulting strip, or unitary piece, was about one-eighth inch thick (i.e., a thickness reduction of about 96 percent), the hot-rolling operation employing six passes and the thickness reduction schedule being 4 to 2 k to l k to 1 to one-half to onefourth to one-eighth inches. The A; inch thick strips so produced were then sandblasted to clean their surfaces and the strips thereafter cold rolled to various final thicknesses; viz., either 0.056 or 0.030 inch, representing cold reductions of about 55 and 76 percent, respectively. Thereafter, samples from the various strips were annealed in dry hydrogen for 20 minutes at various temperatures of 1600", l700 or 1800F. The cold worked and annealed strips produced from these stacks that were initially hot reduced by about 96 percent exhibited no visually detectable blistering.

EXAMPLE 11 Further nickel strips were prepared in the following manner from pieces taken from conventionally produced nickel cathodes, these pieces being similar in dimension to those described in Example I but not being given any special surface preparation, such as grinding or sand blasting. Further groups of such pieces were arranged in various stacks (i.e., packs) having individual thicknesses of about 4 inches. The pieces constituting one of such stacks were tack welded to one another at two opposite edges. The stacked pieces of another such set were welded such that the weld beads extended along the respective peripheries of each pair of adjacent such pieces to almost completely enclose the spaces therebetween, so as to protect the interior surfaces from atmospheric contamination (e.g., oxidation) during heating. A small part of the peripheries of the welds were left open to provide weep holes in the trailing edge of the pack during rolling. All of the nickel cathode stacks of this example were heated to 2200F. and soaked for one hour, hot-rolled to 1% inch plates in three passes, reheated to 2200F. and then hot-rolled to rt; inch sheets. The sheets were sandblasted and coldrolled to 0.056 inch strips, which were annealed at l400, l600, and l800F. in dry hydrogen for 20 minutes.

In the case of those stacks whose component pieces were welded almost completely at their peripheries, there was no detectable blistering, thus indicating that satisfactory results are achievable under the present invention without any special surface preparation of the cathode nickel, the cathode material being hot-workable and hot-bondable when stacked with the surfaces in the as-received condition.

In those stacks whose component (cathode) pieces were only tack welded, there was, once again, no detectable blistering of the cold-rolled, annealed material, indicating the dispensibility of special surface preparation of the workpieces. It was also demonstrated that protection of the workpiece surfaces in the interior of the pack from oxidation during heating in air prior to hot working or during hot working, was not necessary to attain the benefits of the present invention. These test results indicated there was no need for special measures, e.g., grinding or otherwise leveling the cathode surfaces to get a relatively close fit therebetween or to weld the cathodes of the pack at their peripheries, so as to reduce the accessibility of air to the spaces between adjacent cathode surfaces in a pack during heating prior to rolling. The'tests also demonstrated that the use of non-oxidizing atmospheres (e.g., hydrogen) during the processing, to reduce blistering in the cold rolled, annealed product or for other purposes was unnecessary.

In another experiment, stacked cathodes that were hot'rolled at about 2200F. to achieve a percent thickness reduction and cold-rolled by about 52 percent were softened to a Rockwell 30-T hardness of about 23 after annealing for 20 minutes at l400F. This material exhibited some blistering after the l400F. anneal.

While the present invention has been specifically described with respect to electrolytically produced nickel, to which it most advantageously applies, it is also applicable to other electrolytically produced materials, such as cobalt, for example. Also, the present invention can be applied to electrolytically produced metal bodies of different thicknesses which bodies can be stacked and pack rolled, so that a unitary piece is produced.

Hot working techniques other than hot rolling, e.g., hot pressing or hot forging, can be used to bond the nickel cathodes together. Also, though it is not necessary, the surfaces of the various cathodes can be leveled prior to stacking to reduce surface irregularities and promote a close fit therebetween as by light cold rolling passes or by cold pressing a stack of cathodes. Com binations of hot pressing, forging, and rolling can be employed, if desired, to obtain the necessary bonding and hot reduction.

Further, where it is not desired to weld together the several cathodes of a pack before hot rolling, these cathodes can be held together by other suitable means, such as by metal bands, etc.

One approach to producing coins that can be followed and to which the present invention readily lends itself, involves producing a nickel sheet by hot-rolling a pack of nickel cathodes at, for example, an initial cathode heating temperature of about l600F. or

higher, e.g., l800F. and a hot reduction of at least about 92 percent, and, more preferably, an initial heating temperature of 2200F. and a hot reduction of 96 percent to produce therefrom a greatly elongated unitary piece having the desired thickness (e.g., a thickness of about 0.125 inch); cooling the resulting nickel hot band, preferably in air; annealing, optionally, the hot band at a temperature of about l300F. to about 1500F.; pickling the hot band to remove surface oxides; cold-rolling the hot band to reduce its thickness to produce coinage strip of the desired thickness and to increase the hardness of the nickel, the thickness reduction preferably being about 25 percent and up to about 70 percent, and even about 90 percent or higher (e.g., a cold reduction of about 50 percent, which can provide a hardness of about 90 to 95RB), such hardness increase serving, inter alia, to avoid burr formation on blanking; blanking the coldrolled coinage strip to produce coin blanks therefrom; edge-upsetting the coin blanks; bright annealing the blanks in a hydrogen-containing atmosphere (e.g., at about 950F. to 1200F., where the hot reduction is between 92 and 96 percent, and up to about l400F., 1800F., or higher where the hot reduction exceeds 96 percent, for 20 minutes to produce an annealed hardness of less than as measured on the Rockwell 30T" scale as required for embossing); and embossing the blanks to produce coins. As a possible alternative, the cold-rolled sheet can be annealed and, thereafter, the annealed sheet can be blanked and the coin blanks subsequently edge-upset and embossed.

Bend ductility tests were performed on embossed coin-shaped pieces that were produced, generally, by hot rolling a pack of nickel cathodes to achieve about 96 percent reduction, at an initial cathode heating'temperature of about 2200F.; surface grinding or pickling to remove oxide scale; cold rolling the hot-rolled sheet by about 50 percent; blanking the cold-rolled sheet, annealing the blanks at 1600F. in dry hydrogen for 20 minutes, and then, embossing. These embossed pieces could be bent 180 around their own thickness of about 0.051 inch, without any detectable cracking or delamination.

Metallographic examination, at diameters, of a transverse section of such cold-rolled, annealed nickel strip, indicated the structure to be homogeneous with no evidence of the original cathode interfaces.

It will be appreciated that when the initial stack contains sufficient material, the hot band resulting from the initial hot rolling operation can be coiled and then annealed and pickled, sandblasted, or otherwise surface-cleaned in conventional equipment designed for handling coils. The cold rolling operation can also then be performed in a rolling mill adapted for handling coils thereby providing for a high production rate. Also, the hot band just described can be annealed before the cold rolling operation to facilitate this operation, such annealing becoming more desirable with lower finishing temperatures of the hot rolling operation, an exemplary annealing condition being l500F. for 20 minutes.

In another preferred embodiment of the present invention, a stack comprising a number of nickel cathodes is assembled between two outer sheets or plates of wrought nickel (e.g., k inch thick plates of commercially pure nickel) to form a pack and the resulting pack is hot rolled in the manner described above. The cathodes intermediate the plates (or sheets) can be stacked so that the edges are vertically aligned or so that their edges are staggered and overlap, to provide a multiple cathode length. Where the external flat pieces of wrought nickel of the pack are substantially larger than the individual nickel cathodes, these nickel cathodes can be arranged in one or more vertical columns (edges aligned or staggered) between the flat pieces so that the top and bottom surface areas of the pack is larger than that of an individual cathode. In this way, the single piece produced by hot rolling will have an external skin of the wrought nickel material and an interior comprising the nickel cathode material. Such a single piece or product generally will have a smoother hot rolled surface finish, which lends to the producibility of smoother products (e.g., strip) therefrom with greater facility. Also, the presence of the wrought nickel at the outer surfaces of products made from the single piece is believed further to reduce the possibility of blistering therein upon cold working and annealing at relatively high temperatures (e.g., l400F. or 1800F. or higher).

As a further advantage of the invention, it is found that pack rolling of stacked cathodes can be used to compensate for thickness variations which occur in production-run cathodes.

It is pointed out that the conditions recited and claimed herein for producing wrought products from nickel cathodes, viz., the specified hot-reduction and hot-working temperatures, along with the various specified values for cold reduction, annealing temperatures, etc., are deemed to be optimum for commercial nickel cathodes that are generally available presently, but that deviations from these recited conditions, as well as modifications to the presently disclosed methods, can be made where the condition or quality, e.g., the impurity content and/or metallographic struc ture, of nickel cathodes is changed from those presently available. Also, as a further example, there above, is thought to be achievable by careful control of the electrorefining operation, possibly in relation to control of electrolyte PH and/or temperature and/or purity or by high rates of electrolyte circulation in and through the tank, for instance.

Although the present invention has been described in conjunction with preferred embodiments, it is to be understood that modifications and variations may be resorted to without departing from the spirit and scope of the invention as those skilled in the art will readily understand. Such modifications and variations are considered to be within the purview and scope of the invention and appended claims.

I claim:

1. A method of producing a unitary product from a plurality of nickel cathodes, comprising:

a. stacking electrolytically produced nickel cathode sheets so as to produce a pack; hot deforming said pack at a temperature of about l600F. to about 2400F. such that the hot reduction is at least about 92 percent when said temperature is about 1600F. and is at least 75 percent when said temperature is about l800F. to bond the cathodes of said pack substantially completely and to produce a unitary product;

c. cold working said unitary product to provide therein a cold reduction sufficient to achieve a low hardness upon subsequent annealing; and

d. annealing said cold worked product at a temperature of at least about 950F. to a low hardness and without substantial blistering such that products hot reduced about 75 percent are annealed in the range of about 950F. to about ll0OF. and products hot reduced about 92 percent are annealed in the temperature range of about 950F. to about 1200F.

2. The method defined in claim 1, wherein said hot deforming comprises hot-rolling said pack so that said pack is subjected to at least an initial hot-rolling pass wherein the thickness of said pack is reduced by about 30 percent or more, thereby imparting to said pack sufficient strength to withstand further handling.

3. The method defined in claim 1, wherein said hot deformation of said pack is conducted at a temperature of at least about 2000F. and said hot reduction is at least about 96 percent.

4. A method of producing flat nickel strip suitable for coinage from a plurality of nickel cathodes, comprismg:

a. providing a stack of electrolytically produced nickel cathode sheets;

b. hot-rolling said electrolytically produced nickel cathode sheets at an initial cathode heating temperature of at least about l600F. to achieve a thickness reduction therein of at least about 92 percent, thereby producing a unitary nickel strip;

0. air cooling said nickel strip;

. cold-rolling said nickel strip to achieve a thickness reduction therein of about 25 percent or more;

and then annealing said nickel strip at a temperature of at least about 950F. to provide a hardness of less than 30 Rockwell 30-T therein, with the proviso that the annealing temperature does not exceed 1200F. when the hot reduction does not exceed 92 percent.

5. The method defined in claim 4, wherein said annealing is conducted in an atmosphere comprising hydrogen.

6. The method defined in claim 4, wherein said hotrolling is conducted to achieve a thickness reduction of at least about 96 percent.

7. A method of producing a unitary product from electrolytically produced metal cathodes, comprising:

a. stacking a plurality of said cathodes so as to produce a pack, said cathodes being made of a metal selected from the group consisting essentially of nickel and cobalt;

. hot deforming said pack at a temperature of about 1600F. to about 2400F. such that the hot reduction is at least about 92 percent when said temperature is about l600F. and is at least percent when said temperature is about 1800F. to bond the cathodes of said pack substantially completely and to produce a unitary product;

0. cold working said unitary product; and

. annealing said cold worked product at a temperature of at least about 950F. to a low hardness and without substantial blistering such that products hot reduced about 75 percent are annealed in the range of about 950F. to about 1100F. and products hot reduced about 92 percent are annealed in the temperature range of about 950F. to about l200F.

Claims

2. The method defined in claim 1, wherein said hot deforming comprises hot-rolling said pack so that said pack is subjected to at least an initial hot-rolling pass wherein the thickness of said pack is reduced by about 30 percent or more, thereby imparting to said pack sufficient strength to withstand further handling.
3. The method defined in claim 1, wherein said hot deformation of said pack is conducted at a temperature of at least about 2000*F. and said hot reduction is at least about 96 percent.
4. A method of producing flat nickel strip suitable foR coinage from a plurality of nickel cathodes, comprising: a. providing a stack of electrolytically produced nickel cathode sheets; b. hot-rolling said electrolytically produced nickel cathode sheets at an initial cathode heating temperature of at least about 1600*F. to achieve a thickness reduction therein of at least about 92 percent, thereby producing a unitary nickel strip; c. air cooling said nickel strip; d. cold-rolling said nickel strip to achieve a thickness reduction therein of about 25 percent or more; and then e. annealing said nickel strip at a temperature of at least about 950*F. to provide a hardness of less than 30 Rockwell 30-T therein, with the proviso that the annealing temperature does not exceed 1200*F. when the hot reduction does not exceed 92 percent.
5. The method defined in claim 4, wherein said annealing is conducted in an atmosphere comprising hydrogen.
6. The method defined in claim 4, wherein said hot-rolling is conducted to achieve a thickness reduction of at least about 96 percent.
7. A method of producing a unitary product from electrolytically produced metal cathodes, comprising: a. stacking a plurality of said cathodes so as to produce a pack, said cathodes being made of a metal selected from the group consisting essentially of nickel and cobalt; b. hot deforming said pack at a temperature of about 1600*F. to about 2400*F. such that the hot reduction is at least about 92 percent when said temperature is about 1600*F. and is at least 75 percent when said temperature is about 1800*F. to bond the cathodes of said pack substantially completely and to produce a unitary product; c. cold working said unitary product; and d. annealing said cold worked product at a temperature of at least about 950*F. to a low hardness and without substantial blistering such that products hot reduced about 75 percent are annealed in the range of about 950*F. to about 1100*F. and products hot reduced about 92 percent are annealed in the temperature range of about 950*F. to about 1200*F.