US3778237A

US3778237A - Plated copper base alloy article

Info

Publication number: US3778237A
Application number: US00239309A
Authority: US
Inventors: S Shapiro; D Tyler; M Pryor
Original assignee: Olin Corp
Current assignee: Olin Corp
Priority date: 1972-03-29
Filing date: 1972-03-29
Publication date: 1973-12-11
Anticipated expiration: 1990-12-11

Abstract

The instant disclosure teaches an improved article consisting essentially of a white copper base alloy plated with a silver plating. The white copper base alloy substrate consists essentially of a substantially nickel-free alloy containing manganese in an amount from 8 to 16 percent, zinc in an amount from 20 to 31 percent, balance essentially copper. The article of the present invention is particularly desirable for articles of flatware or hollow ware.

Description

United States Patent [1 1 Shapiro et al.

[ Dec. 11, 1973 PLATED COPPER BASE ALLOY ARTICLE [75] Inventors: Stanley Shapiro, New Haven; Derek E. Tyler, Cheshire; Michael J. Pryor, Woodbridge, all of Conn.

[73] Assignee: Olin Corporation, New Haven,

Conn.

[22] Filed: Mar. 29, 1972 [21] Appl. No.: 239,309

Related US. Application Data [63] Continuation-impart of Ser. No. 65,277, Aug. 19, 1970, which is a continuation-in-part of Ser. No. 9,997, Feb. 9, 1970, abandoned.

[52] US. Cl. 29/199 [51] Int. Cl B32b 15/00 [58] Field of Search 29/199 [56] References Cited UNITED STATES PATENTS 2,294,482 9/1942 Siegmund 29/199 2,469,878 5/1949 Hannon 29/199 2,473,712 6/1949 Kinney 29/199 2,359,813 10/1944 Wassermann. 29/199 3,560,172 2/1971 Kench 29/199 Primary Examiner--Hyland Bizot AttorneyRobert H. Bachman et a1.

[57] ABSTRACT 9 Claims, No Drawings ware or hollow ware. l

1 PLATED COPPER BASE ALLOY ARTICLE CROSS REFERENCE TO RELATED APPLICATIONS This application is a continuation-in-part of eopending application Ser. No. 65,277, by Stanley Shapiro, Derek E. Tyler and Michael J. Pryor for Copper Base Alloys, filed Aug. 19, 1970, which in turn is a continuation-in-part of Ser. No. 9,997, by Stanley Shapiro, Derek E. Tyler and Michael J. Pryor for Copper Base Alloys, filed Feb. 9, 1970, now abandoned.

BACKGROUND OF THE INVENTION The nickel-silvers are commonly used for flatware and hollow ware applications. In general, these articles are silver plated and benefit considerably from the white alloy substrate. For example, the shiny white base enhances the luster of the finished product. In addition, should the silver plating wear off, the white alloy exposed at the surface blends with the remaining silver plate.

The nickel-silvers, however, present certain undesirable features. In the first place, it is desirable to develop a material which can be used for these applications which is less expensive than conventionally used nickel-silvers, particularly in view of the high cost of nickel. Furthermore, in addition to the high cost of nickel, the nickel-silvers are difficult to fabricate with respect to hot rolling. The hot rolling temperature range is narrow and high. This is not only expensive processing, but necessitates the use of smaller ingots.

Still further, articles of flatware, for example, are generally formed by rolling to shape and coining to provide the pattern. The finished article is then silver plated. A prime requirement for coinability is low hardness. A fine grain size is essential to provide the bright finish silver plated article. In the nickel-silvers, however, it is not possible to provide a low hardness with the desired fine grain size.

Furthermore, articles of hollow ware, for example, are frequently drawn or stretch formed. Such articles are often made from brass or other nonwhite alloys due to the limited drawability and formability of the low nickel-silvers. Hollow ware articles formed from materials of this type must be nickel plated prior to silver plating, with an attendant increase in cost.

Accordingly, it is a principal object of the present invention to provide an improved silver plated article.

It is a further object of the present invention to provide an improved silver plated article which utilizes a relatively inexpensive white copper base alloy as a substitute for the conventionally used nickel-silvers.

It is a still further object of the present invention to provide an improved silver plated article which may be conveniently and inexpensively used in articles of flat- Further objects and advantages of the present invention will appear hereinafter.

SUMMARY OF THE INVENTION! In accordance with the present invention it has now been found that the foregoing objects and advantages may be readily achieved. The article of the present invention consists essentially of a substantially nickelfree, white copper base alloy plated with a silver plating having a thickness of from 0.0001 to 0.010 inch, wherein the white copper base alloy consists essentially of manganese from 8 to 16 percent, zinc from 20 to 31 percent, balance essentially copper. The white copper base alloy substrate has a grain size less than 0.080 mm and the annealed temper properties are as follows: tensile strength, at least 50,000 psi; yield strength at 0.2 percent offset, at least 20,000 psi; and elongation, at least 38 percent. The article of the present invention is particularly useful in aiticles of flaiware or hollow ware.

In accordance with the present invention, numerous highly significant advantages are achieved. The copper base alloys which are utilized have a desirable white color which enhances the luster of the finished product and, should the silver plating wear off, the white alloy exposed at the surface readily blends with the remaining silver plate. Furthermore, the copper base alloys used herein are particularly desirable as a replacement for the conventionally used nickel-silvers in view of the high cost of nickel and also in view of the fact that the copper base alloys used herein are more readily fabricated than conventional nickel-silvers. These copper alloys have properties comparable to the nickel-silvers and aremore easily fabricated. The articles of the present invention are particularly advantageous in view of the fact that the copper alloy substrate contains little or no nickel and have a lower cost than the commonly used higher nickel containing nickel-silvers.

Further advantageous features of the articles of the present invention will appear hereinafter.

DETAILED DESCRIPTION As is indicated hereinabove, the articles of the present invention consist essentially of the foregoing white copper base alloys plated with a silver plating.

The copper base alloys used herein may be conveniently processed.

The alloys should be cast utilizing a temperature below l000C. The alloys are cast from the molten state at a melt temperature no higher than lO00C, generally at a melt temperature above 870C and preferably at a melt temperature within the range of 925 to 975C. The use of these low casting temperatures is significant. It should be understood that the melt temperature is the temperature of the metal immediately before being subjected to cooling during solidification.

As indicated hereinabove, the copper alloy substrate has the composition: manganese from 8 to 16 percent, zinc from 20 to 31 percent, balance essentially copper. The preferred composition utilizes l0l4% Mn, 22-29 percent zinc and the balance essentially copper. It is preferred to determine the zinc content by the formula Zn K 2/3 Mn, where K varies from 30.5 to 36.25, preferably from 32-35. Some advantageous features of the formula are that adherence thereto prevents too much beta phase from forming at hot rolling temperature and allows attainment of substantially all alpha phase after annealing and cooling to room temperature at a rate over 25F per hour.

Naturally, the copper alloy substrate may contain small amounts of additional alloying ingredients to, for example, improve mechanical properties or corrosion resistance. In general, less than 0.5 percent each of the following materials may be added, and preferably less than 0.3 percent each, in order to avoid undesirable second phases and avoid fabrication problems: aluminum; iron; tin; silicon; cobalt; magnesium; and molybdenum. Phosphorus, arsenic and antimony may be added up to 0.3 percent. As indicated hereinabove, it is especially advantageous that the copper alloy substrate is substantially nickel-free; however, if desired, small amounts of nickel may be added. The nickel added should be less than 0.3 percent and preferably no nickel at all is added. Lead may be added in quantities up to 3 percent in order to improve machinability.

Small amounts of the foregoing alloying additions may be readily used, if desired, for example, 0.001 percent each.

Naturally, the alloys of the present invention may contain common impurities up to 0.05 percent each, total 0.25 percent.

Throughout the instant specification all percentages are weight percentages.

In the casting step it is preferred to submerge the manganese in order to prevent heavy loss of manganese by preferential oxidation. This may be accomplished by following the manganese addition immediately by the addition of more copper.

Following the casting step, the material is hot rolled at low temperatures. Specifically, a starting hot rolling temperature of less than 850C must be used and generally from 700 to 800C, with a preferred starting temperature range of 725 to 775C. The low starting hot rolling temperature range is a significant step in the processing. It is important that hot rolling be terminated at a temperature not less than 400C.

Thus, it will be seen that the copper alloys utilized are readily and conveniently hot rollable in contrast to the nickel-silvers which are hot rollable only over a limited and relatively high temperature range and with poor recovery. In the conventional nickel-silvers, finishing temperatures below 800C lead to edge cracking. This is not so with respect to the present alloys.

After hot rolling, the alloy will be cleaned of mill scale by a variety of conventional techniques, which may include pickling, sanding, milling, and so forth. Thereafter, the alloys are processed by cold rolling with or without intermediate or terminal anneals to the final desired gage. In the case of products having a final thickness in excess of 0.1 inch, it may be desirable to anneal the hot rolled material for structural equilibration. The alloys may be cold rolled between interanneals in excess of 90 percent without edge cracking.

The alloys may be subjected to a final anneal in order to render them in the optimum condition for high formability. The annealing temperature is in the range of 400 to 800C and the preferred range is from 500 to 650C. An annealing time of at least minutes is necessary and the preferred annealing time is one to four hours.

The alloys are preferably cooled from annealing temperature to room temperature at a rate over 25F per hour. Surprisingly, it is possible to attain substantially all alpha phase by cooling at this rate.

It should be understood that after annealing the alloy can be cold rolled to a variety of hard tempers. Typical properties obtainable after 60 percent cold reduction are: tensile strength, 95,000 psi; yield strength at 0.2 percent offset, 85,000 psi; and elongation, 3 percent. Naturally, such similar properties are obtainable when the cold work is put in by deep drawing or other similar cold working operations.

The silver plated article of the present invention may be formed by conventional procedures known in the art. Any convenient or suitable process may be readily employed. Naturally, the exact plating procedure will vary depending upon the particular article to be prepared. The following represents a typical procedure which ma be conveniently utilized.

A typical article for silver plating would be processed from annealed copper alloy strip of the present invention. A blank is first formed, for example, utilizing a punch and die set, roughly in the shape of the final product. The blank may be cross rolled and/or grade rolled to provide any required taper, for example, for an article of flatware. An annealing step may be interposed between the two rolling operations, if desired. The profile or exact shape of the article may then be cut from the blank, which step may be followed by an annealing operation, if desired. The final forming operation may then be performed, including the application of pattern. The article is then trimmed, buffed and/or polished preparatory to plating. Also, a variety of cleaning and rinsing procedures may obviously be utilized prior to plating.

After cleaning and prior to electroplating with silver, the article should be struck with silver. This is basically a mild or extremely thin electroplating operation. The articles may also be struck with nickel prior to the silver strike. A typical silver striking bath includes silver cyanide and potassium cyanide, with optional additives, such as potassium carbonate and copper cyanide. A typical nickel striking bath includes nickel chloride, NiCl- '6H O and hydrochloric acid.

Articles of the type of the present invention are then commonly electroplated with silver to the desired plating thickness from a cyanide bath. The baths utilize a silver anode and may contain brighteners, such as carbon disulfide or ammonium thiosulfate. Typical plating procedures utilize temperatures from to F and current densities in the range of 5 to amps per square foot. The resultant plated article may then be polished as desired.

A particular advantage of the silver plated articles of the present invention is found in flatware and hollow ware applications. As a result of the surprising characteristics of the copper base alloys which are used herein, it is possible to achieve both a fine grain size and a low hardness and thus provide a superior substrate for silver plated flatware articles. In articles of hollow ware, the present invention overcomes the disadvantage of conventionally used brass or other nonwhite alloys which must be nickel plated prior to silver plating. The copper alloys used herein provide a white alloy which exhibits drawability and formability equivalent or superior to brass. It is, therefore, possible to produce articles of silver plated hollow ware at a greatly reduced cost.

Although the present invention is particularly useful in preparing silver plated flatware and hollow ware articles, the present invention finds application in any silver plated article in view of the surprising characteristics thereof as described hereinabove.

The present invention and improvements resulting therefrom will be more readily understandable from a consideration of the following illustrative examples.

EXAMPLE I Conventional nickel-silvers were prepared using DC casting of 5-% inches 28-3/4 inches X 25 feet dimensions with a pouring temperature of 1 100C. The casting was done under a charcoal cover and the alloy had the following composition: nickel 12 percent, zinc 29 percent, balance copper. The 25 foot long bars were cut in half prior to hot rolling to form two short bars which were then hot rolled from 925C down to 850C from 5.25 inches to 0.360 inch thickness in eleven passes.

In view of the use of smaller bars, there were no signs of edge cracking. When the bars were not cut in half prior to hot rolling there was significant edge cracking during hot rolling which necessitated edge trimming after hot rolling in order to avoid severe edge cracking of the cold rolled sheet. The hot rolled material was milled and cold rolled in two passes down to a gage 0.10 inch. The alloys were then annealed for one hour at various temperaturesThe mechanical properties are given in Tables A and B, below.

TABLE A Annealed Properties 1 hour Tensile Yield Elonga- Hard- Grain at Strength Strength tion ness Size Temp. (ksi) (0.2% ksi) (R (mm) 550C 69 39 4O 65 0.010 600C 62 29 47 56 0.020 660C 57 21 49 42 0.060

TABLE B Cold Rolled Properties Cold Tensile Yield Elonga- Hard- Grain Re- Strength Strength tion ness Size duction (ksi) (0.2% ksi) (R (mm) 20 78 70 18 89 0.030 40 97 89 4 92 60 1 105 l 98 EXAMPLE Il Alloys were'prepared in a manner after Example I using a pouring temperature of 950C. The alloy had the following composition: manganese 12 percent, zinc 24.5 percent, balance essentially copper. The alloy prepared was processed in the following manner. The alloy was hot rolled starting at 775C from 5.25 inches to 0.360 inch thickness in eleven passes. The alloy was then milled and cold rolled to 0.10 inch thickness in two passes. There were no signs of edge cracking in the cold rolled sheet. The alloy was then annealed at various temperatures for one hour. The mechanical properties are given in Tables C and D, below.

EXAMPLE Ill The alloy prepared in Example 11 was processed in a manner after Example 11 in the following manner. The alloy was hot rolled from 5.25 inches to 0.400 inch from 775C and coil milled to 0.365 inch. The material was cold rolled to approximately 0.185 inch and annealed for one hour at 625C, further cold rolled to approximately 0.100 inch and finally annealed at 625C for one hour. The Rockwell B hardness of the annealed strip was 40 and the finish grain size was approximately 0.030 mm.

EXAMPLE IV A spoon was manufactured from the alloy strip as prepared in Example 111 in the following manner. A blank was formed utilizing a punch and die such that the blank was roughly in the shape of the final product but had a rectangular bowl. The bowl portion of the spoon was cross rolled approximately 20 percent to-a thickness approximately 0.080 inch. The bowl section was then grade rolled to provide a taper varying from a thickness of 0.080 inch to approximately 0.040 inch. Following this the exact shape of the spoon was cut out. Next thebowl was formed and a pattern was struck on the handle. The unplated spoon was trimmed, cleaned and buffed preparatory to plating.

EXAMPLE v The spoon blank as prepared in Example IV was processed for electroplating by striking with silver using an aqueous striking bath containing :silver cyanide in an amount of 0.9 oz. per gallon and potassium cyanide in an amount of 10.0 oz. per gallon. A temperature of F was utilized at a current density of 30 amps per square foot and less than six volts. A steel anode was employed. The blank was immersed in the bath for a period of time of less than one minute.

EXAMPLE VI The spoon blank bearing the silver strike as prepared according to Example V was then electroplated with silver utilizing an aqueous silver plating bath containing the following ingredients: silver cyanide, 4.8 oz. per gallon; potassium cyanide, 8.0 oz. per gallon; potassium carbonate, 6.0 oz. per gallon; and carbon disulfide, 0.0001 02. per gallon. A silver anode was employed, the temperature was maintained in the range of 75 F and the current density in the range of 5 15 amps per square foot and less than six volts. The plating time was adjusted so that the final plating thickness was approximately 0.001 inch. The plated article was f1- nally polished in the conventional manner.

This invention may be embodied in other forms or carried out in other ways without departing from the spirit or essential characteristics thereof. The present embodiment is therefore to be considered as in all respects illustrative and not restrictive, the scope of the invention being indicated by the appended claims, and all changes which come within the meaning and range of equivalency are intended to be embraced therein.

What is claimed is:

1. An article consisting essentially of a white substantially nickel-free copper base alloy plated with a silver plating having a thickness of from 0.0001 to 0.010 inch, wherein the white copper base alloy consists essentially of manganese from 8 to 16 percent, zinc from 20 to 31 percent, balance copper.

2. An article according to claim 1 wherein said article is an article of flatware.

3. An article according to claim 2 including a pattern coined thereon.

4. An article according to claim 1 wherein said article is an article of hollow ware.

5. An article according to claim 1 wherein said copper alloy contains impurities in an amount up to 0.05 percent each, tota1-0.25 percent.

6. An article according to claim 1 wherein said copper alloy contains zinc in an amount from 22 to 29 percent.

7. An article according to claim 1 wherein said copper alloy contains manganese in an amount from 10 to 14 percent.

8. An article consisting essentially of a white substantially nickel-free copper base alloy plated with a silver plating having a thickness of from 0.000] to 0.010 inch, wherein the white copper base alloy consists essentially of manganese from 8 to 16 percent, zinc from 20 to 31 percent, from 0.001 to 0.3 percent of a matenum and mixtures thereof, balance copper.

Claims

2. An article according to claim 1 wherein said article is an article of flatware.
3. An article according to claim 2 including a pattern coined thereon.
4. An article according to claim 1 wherein said article is an article of hollow ware.
5. An article according to claim 1 wherein said copper alloy contains impurities in an amount up to 0.05 percent each, total 0.25 percent.
6. An article according to claim 1 wherein said copper alloy contains zinc in an amount from 22 to 29 percent.
7. An article according to claim 1 wherein said copper alloy contains manganese in an amount from 10 to 14 percent.
8. An article consisting essentially of a white substantially nickel-free copper base alloy plated with a silver plating having a thickness of from 0.0001 to 0.010 inch, wherein the white copper base alloy consists essentially of manganese from 8 to 16 percent, zinc from 20 to 31 percent, from 0.001 to 0.3 percent of a material selected from the group consisting of phosphorus, arsenic and antimony, balance copper.
9. An article consisting essentially of a white substantially nickel-free copper base alloy plated with a silver plating having a thickness of from 0.0001 to 0.010 inch, wherein the white copper base alloy consists essentially of manganese from 8 to 16 percent, zinc from 20 to 31 percent, from 0.001 to 0.3 percent of at least one material selected from the group consisting of aluminum, iron, tin, silicon, cobalt, magnesium, molybdenum and mixtures thereof, balance copper.