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GB1558803A - Coins and similarly discshaped articles - Google Patents

Coins and similarly discshaped articles Download PDF

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Publication number
GB1558803A
GB1558803A GB3421976A GB3421976A GB1558803A GB 1558803 A GB1558803 A GB 1558803A GB 3421976 A GB3421976 A GB 3421976A GB 3421976 A GB3421976 A GB 3421976A GB 1558803 A GB1558803 A GB 1558803A
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GB
United Kingdom
Prior art keywords
coating
copper
core
blank
steel core
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
GB3421976A
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Viridian Inc Canada
Original Assignee
Sherritt Gordon Mines Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Sherritt Gordon Mines Ltd filed Critical Sherritt Gordon Mines Ltd
Priority to GB3421976A priority Critical patent/GB1558803A/en
Publication of GB1558803A publication Critical patent/GB1558803A/en
Expired legal-status Critical Current

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Classifications

    • CCHEMISTRY; METALLURGY
    • C25ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25DPROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D7/00Electroplating characterised by the article coated
    • C25D7/005Jewels; Clockworks; Coins

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Electroplating Methods And Accessories (AREA)

Description

(54) COINS AND SIMILARLY DISC-SHAPED ARTICLES (71) We, SHERRITT GORDON MINES LIMITED, a company organised under the laws of the Province of Ontario, of 2800 Commerce Court West, Toronto, Ontario, Canada, do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed to be particularly described in and by the following statement:- This invention relates to coins and similarly disc-shaped articles, such as medals, or medallions.
The metallic composition of coins has varied over the years owing to the escalating cost of the metals or alloys from which coins have conventionally been made. For example, gold coins are now virtually extinct, and silver coins may frequently contain copper and/or other metals to reduce the metallic value of the coin compared to its face value, while still giving it a silver-like appearance. Another kind of coinage in frequent use is copper coinage, which is made of copper or a copper alloy.
As compared to silver and gold coinage, of course, copper coinage is usually used for coins of lower value in a monetary svstem.
With the increasing cost of metals, the value of the metal of which a coin is made may increase so much that it approaches or even exceeds the face value of the coin, with the result that it can be advantageous to melt down such coins and obtain the current price of their contained metals. It is primarily for this reason that, for example, coins made of silver have now been replaced by coins made of other metals or alloys of similar appearance and lower intrinsic values, such as nickel or nickel alloys.
Until now, this problem has not become particularly significant with respect to copper coinage, since the value of the copper or copper alloy of which the coins are made has remained small compared to the face value of the coins. However, with the escalating cost of copper and its alloys, this problem has now become relevant with respect to copper coinage, with the result that it is now desirable to find some alternative composition or construction for copper coins. Because most countries are reluctant to change the appearance of their coins, it is at the same time necessary to preserve the copper-like appearance of such coins, as was done in the case of silver coins, where the silver-like appearance of the coins was preserved by a suitable choice of metal or alloy for at least the faces of the coin.
According to one aspect of the present invention there is provided a blank suitable for minting to form a coin or similarly discshaped article comprising an appropriately disc-shaped steel core completely encased by a copper coating electroplated thereon.
According to a second aspect of the present invention there is provided a method of producing a blank suitable for minting to form a coin or similarly disc-shaped article, including electroplating a copper coating onto an appropriately disc-shaped steel core such that the copper coating completely encases the steel core.
Such a blank can be subsequently minted bv applying the required insignia to one or both faces of the blank by means of an appropriately designed die or dies. Where a coin is to be produced, the size of the core and the thickness of the copper coating will of course be such as to produce a blank of the same size as a conventional copper coin which it is intended that the coin produced from the blank embodying the present invention should replace.
Steel is considerably less expensive than copper and the metallic value of a coin produced from a blank embodying the present invention is considerably less than the metallic value of a conventional copper coin of the same size and made entirely of copper and/or copper alloy. Also, the seigniorage of a coin produced from a blank embodying the invention, that is to say the difference between the face value of the coin and the cost t.f producing it (including the cost of raw materials), is sufficient to constitute an attractive alternative process for producing coins of copper-like appearance. Further, since the exterior of the coin is copper, its appearance will resemble that of a conventional copper coin, and will not become substantially different therefrom over a period of time.If desired. alloy elements may be included in the copper coating to increase wear or corrosion resistance.
In order to produce a coin of satisfactory hardness and wear resistance for the usage which a coin experiences, while at the same time permitting the blank to be readily imprintable with the required insignia by means of an appropriately designed die or dies, the steel is preferably a low carbon steel. Advantageously, the carbon content of the steel is less than about 0.05%, a preferred value being of the order of 0.01%.
Many coins have raised rims around the peripheries of opposed faces, and these raised rims, if required, are preferably formed on the steel cores before the electroplating step.
Advantageously, the electroplating step includes loading a plurality of cores into a perforated container, placing the container in an electroplating bath, and electroplating the copper coating onto the cores while moving the container angularly about a horizontal axis.
An intermediate coating of another metal, such as nickel or zinc, may be electroplated directly onto the steel core, with the copper coating then being electroplated directly onto the intermediate metal coating. The intermediate metal coating may also be electroplated onto the cores by use of a perforated container in an electroplating bath, as mentioned above in connection with the copper coating.
The copper coating preferably has a thickness of at least 0.05 mm on each opposed face of the core, and a thickness on the peripheral edge of the core measured radially in the range of from about 2 to about 4 times the face thickness. The intermediate metal coating preferably has a thickness in the range of at least about 0.005 mm on each opposed face and the thickness on the peripheral edge of the core measured radially in the range of from about 2 to about 4 times the face thickness.
After the copper coating has been electroplated onto the core, the blank is preferably heated to form a layer of interdiffused copper and steel with consequent metallurgical bonding of the copper coating to the core. Where an intermediate metal coating is provided, such heating is caused to form a layer of interdiffused copper and intermediate metal and also a layer of intermediate metal and iron with consequent metallurgical bonding of the copper coating to the intermediate coating and of the intermediate coating to the core.
The heating step may also be used to decrease the hardness of the steel core to a value more suitable for minting, for example, less than about 65, and preferablv less than about 45, on the Rockwell 30T hardness scale.
In one embodiment of the invention, a batch of coinage cores was made of low carbon steel, namely steel manufactured bv Dofasco and sold by them as ASTM A424 tvpe I. the maximum carbon content of such steel being 0.01% by weight. The circular steel cores of appropriate diameter were punched out of steel strip of appropriate thickness, namely about 1.2 mm, and were given a raised rim around the periphery of both faces by an upsetting operation. The steel cores were loaded, as a 60 kg batch, into a perforated barrel made of polypropylene 91 cm long and 46 cm in diameter. This 60 kg batch of cores contained about 13,000 cores.
The steel cores were then put through a cleaning cycle by lowering the barrel into successive baths providing rinses of 5% neutral detergent solution, hot water, cold water, 10% HCL and cold water, respectively. In each instance, the barrel was immersed in the bath with its longitudinal axis horizontal, and was oscillated over nearly 1800 about its longitudinal axis at about six to and fro cycles per minute. The barrel was then immersed in a nickel sulphamate plating bath containing about 98 grams per litre nickel, and oscillated as before. The temperature of the nickel plating bath was maintained at about 55"C. and the pH was maintained at about 2. Flexible cathode rods were mounted within the barrel, and baskets containing nickel anode pieces were supported in the plating bath externally of the barrel.A voltage of 12V was applied, giving a current of 290A.
After 1.5 h, a 2.8 kg sample of nickelplated cores was withdrawn from the barrel and rinsed in water. The thickness of nickel coating on the faces of these cores was found to be 0.003 mm. After a further 1.5 h, a 3.8 kg sample of nickel-plated cores was withdrawn from the barrel, and the nickel coating thickness was found to be 0.006 mm on the core faces and 0.02 mm on the circumferential rims. Laboratory test show that the nickel coating thickness of 0.003 mm on the first sample of cores was inadequate for subsequent copper plating.
The second sample of nickel plated cores was then placed in a smaller barrel having a length of 30 cm and a diameter of 15 cm.
The second barrel was then immersed in an acid copper sulphate plating bath containing 45 prams per litre copper qnd the barrel was continuouslv rotated at 6 r.p.m. Flexible cathode rods were mounted within the barrel.
and baskets containing copper anode pieces were supported in the bath externally of the barrel.
This plating bath was maintained at a temperature of 40"C. and a pH of 1. The nickel plated cores were plated with copper for 13.5 h at a voltage of 3V and a current of 40A and, after this time, a copper coating of 0.06 mm was deposited on the nickel-plated core faces, with a copper coating of 0.14 mm hav mg been deposited on the circumferential rims. After the copper plating, the resultant blanks were rinsed and dried.
The blanks were then annealed in a pure hydrogen atmosphere at a temperature of 800"C. for 30 min, and allowed to cool in the same atmosphere. An analysis of the annealed blanks is shown in Table 1.
TABLE 1
Nickel Copper Fe % Thick- Plate on Plate on Cu Ni (by dif- Weight Diameter ness Hardness Face Face % % ference) (g) (mm) (mm) R-30T (mm) (rim) 14.4 1.7 83.9 5.44 24.81 1.35 42 0.006 0.060 Metallography showed the plating of the cores to be free from any significant defects, with there being good adhesion between the copper and nickel coatings and between the nickel coating and the steel core.
Some of the blanks were minted, by applying appropriate insignia to both faces of the blanks by means of dies, and excellent results were achieved. To provide a coin of high lustre, it may be advantageous to burnish the blanks before minting, for example, by burnishing in a soap solution containing metallic media.
The barrel in the copper plating bath may be oscillated, as was the barrel in the nickel plating bath, rather than continuously rotated.
It will be understood that the invention is applicable to the production of other discshaped articles, as well as coin blanks. Medals and medallions are examples of other discshaped articles to which the invention is applicable. Also, such articles may not necessarily have a circular periphery and may not necessarily be imperforate.
Other embodiments within the scope of the invention will be apparent to a person skilled in the art, the scope of the invention being defined in the appended claims.
WHAT WE CLAIM IS: 1. A blank suitable for minting to form a coin or similarly disc-shaped article comprising an appropriately disc-shaped steel core completely encased by a copper coating electroplated thereon.
2. A blank according to claim 1 wherein the steel core has a carbon content less than 0.05 by weight.
3. A blank according to claim 2 wherein the steel core has a carbon content of about 0.0l' by weight.
4. A blank according to any one of the preceding claims wherein the copper coating has a thickness of at least about 0.05 mm on each opposed face of the core, and a thickness on the peripheral edge of the core mea sured radially in the range of from 2 to 4 times the face thickness.
5. A blank according to any one of the preceding claims wherein the copper coating is metallurgically bonded to the steel core by a layer of interdiffused copper and iron.
6. A blank according to any one of the preceding claims wherein an intermediate coating of another metal is electroplated directly onto the steel core, and the copper coating is electroplated directly onto the intermediate metal coating.
7. A blank according to claim 6 wherein the intermediate coating is a nickel coating.
8. A blank according to claim 6 wherein the intermediate coating is a zinc coating.
9. A blank according to any one of claims 6 to 8 wherein the intermediate metal coating has a thickness of at least 0.005 mm on each opposed face of the core, and a thickness on the peripheral edge of the core measured radially in the range of from 2 to 4 times the face thickness.
10. A blank according to any one of the preceding claims having a raised rim extending around the periphery of each opposed face.
11. A blank according to claim 6 wherein the copper coating is metallurgically bonded to the intermediate metal coating by a layer of interdiffused copper and other metal, and the intermediate coating is metallurgically bonded to the steel core by a layer of interdiffused other metal and iron.
12. A blank according to any one of the preceding claims wherein the steel core has a hardness value less than about 65 on the Rockwell 30T hardness scale.
**WARNING** end of DESC field may overlap start of CLMS **.

Claims (32)

**WARNING** start of CLMS field may overlap end of DESC **. and baskets containing copper anode pieces were supported in the bath externally of the barrel. This plating bath was maintained at a temperature of 40"C. and a pH of 1. The nickel plated cores were plated with copper for 13.5 h at a voltage of 3V and a current of 40A and, after this time, a copper coating of 0.06 mm was deposited on the nickel-plated core faces, with a copper coating of 0.14 mm hav mg been deposited on the circumferential rims. After the copper plating, the resultant blanks were rinsed and dried. The blanks were then annealed in a pure hydrogen atmosphere at a temperature of 800"C. for 30 min, and allowed to cool in the same atmosphere. An analysis of the annealed blanks is shown in Table 1. TABLE 1 Nickel Copper Fe % Thick- Plate on Plate on Cu Ni (by dif- Weight Diameter ness Hardness Face Face % % ference) (g) (mm) (mm) R-30T (mm) (rim) 14.4 1.7 83.9 5.44 24.81 1.35 42 0.006 0.060 Metallography showed the plating of the cores to be free from any significant defects, with there being good adhesion between the copper and nickel coatings and between the nickel coating and the steel core. Some of the blanks were minted, by applying appropriate insignia to both faces of the blanks by means of dies, and excellent results were achieved. To provide a coin of high lustre, it may be advantageous to burnish the blanks before minting, for example, by burnishing in a soap solution containing metallic media. The barrel in the copper plating bath may be oscillated, as was the barrel in the nickel plating bath, rather than continuously rotated. It will be understood that the invention is applicable to the production of other discshaped articles, as well as coin blanks. Medals and medallions are examples of other discshaped articles to which the invention is applicable. Also, such articles may not necessarily have a circular periphery and may not necessarily be imperforate. Other embodiments within the scope of the invention will be apparent to a person skilled in the art, the scope of the invention being defined in the appended claims. WHAT WE CLAIM IS:
1. A blank suitable for minting to form a coin or similarly disc-shaped article comprising an appropriately disc-shaped steel core completely encased by a copper coating electroplated thereon.
2. A blank according to claim 1 wherein the steel core has a carbon content less than 0.05 by weight.
3. A blank according to claim 2 wherein the steel core has a carbon content of about 0.0l' by weight.
4. A blank according to any one of the preceding claims wherein the copper coating has a thickness of at least about 0.05 mm on each opposed face of the core, and a thickness on the peripheral edge of the core mea sured radially in the range of from 2 to 4 times the face thickness.
5. A blank according to any one of the preceding claims wherein the copper coating is metallurgically bonded to the steel core by a layer of interdiffused copper and iron.
6. A blank according to any one of the preceding claims wherein an intermediate coating of another metal is electroplated directly onto the steel core, and the copper coating is electroplated directly onto the intermediate metal coating.
7. A blank according to claim 6 wherein the intermediate coating is a nickel coating.
8. A blank according to claim 6 wherein the intermediate coating is a zinc coating.
9. A blank according to any one of claims 6 to 8 wherein the intermediate metal coating has a thickness of at least 0.005 mm on each opposed face of the core, and a thickness on the peripheral edge of the core measured radially in the range of from 2 to 4 times the face thickness.
10. A blank according to any one of the preceding claims having a raised rim extending around the periphery of each opposed face.
11. A blank according to claim 6 wherein the copper coating is metallurgically bonded to the intermediate metal coating by a layer of interdiffused copper and other metal, and the intermediate coating is metallurgically bonded to the steel core by a layer of interdiffused other metal and iron.
12. A blank according to any one of the preceding claims wherein the steel core has a hardness value less than about 65 on the Rockwell 30T hardness scale.
13. A blank according to claim 12 wherein
the steel core has a hardness value of less than about 45 on the Rockwell 30T hardness scale.
14. A method for producing a blank suit able for minting to form a coin or similarly disc-shaped article, including electroplating a copper coating onto an appropriatelv discshaped steel core such that the copper coating completely encases the steel core.
15. A method accordin to claim 14 including forming raised rims around the peripheries of the opposed faces of the steel cores before the electroplating step.
16. A method according to claim 14 or claim 15 wherein the electroplating step includes loading a plurality of appropriately disc-shaped steel cores into a perforated con- tainer, placing the container in a copper electroplating bath and electroplating a copper coating onto the cores while moving the container angularly about a horizontal axis.
17. A method according to any one of claims 14 to 16 wherein an intermediate coating of another metal is electroplated directly onto the steel core and the copper coating is electroplated directly onto the intermediate metal coating.
18. A method according to claim 17 wherein the intermediate coating is a nickel coating.
19. A method according to claim 17 wherein the intermediate coating is a zinc coating.
20. A method according to any one of claims 17 to 19 wherein the intermediate coating is electroplated onto the cores by loading a plurality of appropriately disc-shaped cores into a perforated container, placing the container in an intermediate metal electroplating bath, and electroplating the intermediate metal coating onto the cores while moving the container angularly about a horizontal axis.
21. A method according to claim 14 wherein the steel core has a carbon content of less than 0.05 by weight.
22. A method according to claim 21 wherein the steel core has a carbon content of about 0.01e-t by weight
23. A method according to any one of claims 14 to 22 wherein the copper coating is electroplated onto the steel core until the copper coating has a thickness of at least 0.05 mm on each opposed face of the core, and a thickness on the peripheral edge of the core measured radially in the range of from 2 to 4 times the base thickness.
24. A method according to claim 23, when dependent on any one of claims 17 to 20, wherein the intermediate metal coating is electroplated onto the steel core until the intermediate metal coating has a thickness of at least 0.005 mm on each opposed face of the core, and a thickness on the peripheral edge of the core measured radially in the range of from 2 to 4 times the face thickness.
25. A method according to any one of claims 14 to 24 wherein the blank is heated, after the copper coating has been electroplated onto the core, to form a layer of interdiffused copper and steel with consequent metallurgical bonding of the copper coating to the core.
26. A method according to any one of claims 17 to 20, or any one of claims 21 to 25 when dependent on any one of claims 17 to 20, wherein the blank is heated, after the copper coating has been electroplated onto the core, to form a layer of interdiffused copper and intermediate metal and a laver of interdiffused intermediate metal and steel with consequent metallurgical bonding of the copper coating to the intermediate metal coating and of the intermediate metal coating to the steel core.
27. A method according to claim 25 or claim 26 wherein the heating step also results in a decrease in hardness of the steel core to less than about 65 on the Rockwell 30T hardness scale.
28. A method according to claim 27 wherein the heating step results in a decrease in hardness of the steel core to less than about 45 on the Rockwell 30T hardness scale.
29. A blank according to claim 1 and substantially as herein described.
30. A method according to claim 14 and substantially as herein described.
31. A coin minted from a blank as claimed in any one of claims 1 to 13.
32. A coin minted from a blank made bv a method as claimed in any one of claims 14 to 28.
GB3421976A 1977-07-20 1977-07-20 Coins and similarly discshaped articles Expired GB1558803A (en)

Priority Applications (1)

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GB3421976A GB1558803A (en) 1977-07-20 1977-07-20 Coins and similarly discshaped articles

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GB3421976A GB1558803A (en) 1977-07-20 1977-07-20 Coins and similarly discshaped articles

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0163419A3 (en) * 1984-05-01 1986-05-28 Sherritt Gordon Mines Limited Aureate coins, medallions and tokens and method for the production thereof
DE3940244A1 (en) * 1989-12-05 1991-06-06 Ver Deutsche Nickel Werke Ag V Plated composite material for coinage use - has base roll plated followed by thin electroplating layer
DE4035738A1 (en) * 1990-11-09 1992-05-14 Deutsche Nickel Ag METHOD FOR PRODUCING TWO-PIECE COIN BLANKS AND LIKE COIN BLANK

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0163419A3 (en) * 1984-05-01 1986-05-28 Sherritt Gordon Mines Limited Aureate coins, medallions and tokens and method for the production thereof
DE3940244A1 (en) * 1989-12-05 1991-06-06 Ver Deutsche Nickel Werke Ag V Plated composite material for coinage use - has base roll plated followed by thin electroplating layer
DE4035738A1 (en) * 1990-11-09 1992-05-14 Deutsche Nickel Ag METHOD FOR PRODUCING TWO-PIECE COIN BLANKS AND LIKE COIN BLANK

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