FLAN MONETAIRE

COIN BLANK

Abrégé français

L'invention concerne un flan monétaire. Les pièces de monnaie, constituées d'un noyau d'acier galvaniquement recouvert d'une couche de cuivre, sont utilisées dans le monde entier, comme c'est par exemple le cas pour les pièces de 1, 2 ou 5 centimes d'Euro. Le cuivre a pour inconvénient que plus les pièces circulent, plus une patine matte se forme, les pièces perdant alors leur éclat et leur couleur initiale. L'invention vise à fournir un flan monétaire contenant un noyau d'acier (1) recouvert d'une couche (2) de cuivre/d'un alliage de cuivre, permettant aux pièces de monnaie frappées à partir dudit flan de conserver leur éclat et leur teinte, y compris lorsqu'elles sont utilisées très longtemps. La couche de recouvrement (2) du flan monétaire est, selon l'invention, dopée avec du nickel (3), ce qui permet de garantir que les pièces frappées et en circulation conservent l'éclat de leur couleur cuivrée.

Abrégé anglais

Coins which consist of a steel core having an electrolytic covering layer composed of copper are internationally routine, e.g. the 1, 2 and 5 eurocent coins. Copper has the disadvantage that a matt patina is formed during use of the circulating coin, as a result of which gloss and the original colour are lost. It is an object of the invention to provide a coin blank which contains a steel core (1) having a covering layer (2) which is composed of copper/copper alloy and retains brightness and colour shade in long-term use of the coin minted therefrom. The covering layer (2) of the coin blank is, according to the invention doped with nickel (3), as a result of which copper-coloured brightness and constancy of colour of the minted circulating coins are ensured.

Revendications

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Claims
1) Coin blank with a core of an iron material, which is provided with a
copper
or copper alloy covering layer, characterized in
that the copper or copper alloy covering layer (2) comprises a nickel doping
(3).
2) Coin blank according to claim 1, characterized in
that at the surface of the covering layer (2) the nickel doping (3) is less or
equal to 10 percent by mass with respect to the mass of the covering layer.
3) Coin blank according to claims 1 or 2, characterized in
that the covering layer (2") comprises a copper-zinc-alloy, which comprises
a nickel doping (3).
4) Coin blank according to claims 1 or 2, characterized in
that the covering layer (2") comprises a copper-tin-alloy, which comprises a
nickel doping (3).
5) Coin blank according to one of claims 1 to 4, characterized in
that above the core (1) of iron material or a pre-coated iron material a layer
combination (2'/ 2") is arranged, which comprises a plurality of layers of
copper
and/ or copper alloys, and that the covering layer (2") comprises a nickel
doping
(3)-
6) Coin blank according to one of claims 1 to 5, characterized in
that on the core (1) of iron material a layer combination (2'/ 2") of the type
of Cu/ Cu Zn or Cu/ Cu Sn or Cu Zn/ Cu or Cu Sn/ Cu or Cu Zn/ Cu Sn or Cu Sn/
Cu Zn
is arranged and that the covering layer (2") comprises a nickel doping (3).
7) Method for manufacturing a coin blank with a doped layer, with:
forming a copper or copper alloy covering layer (2) on a core of an iron
material; and
inserting a nickel doping (3) into the covering layer (2).
8) Method according to claim 7, characterized in that the inserting of the
nickel doping (3) into the covering layer (2, 2") comprises the inserting of a
nickel

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layer on the covering layer (2, 2") and a subsequent thermal treatment of the
coin
blank.
9) Method according to claims 7 or 8, characterized in that the inserting
of a
nickel doping (3) comprises the depositing of a homogeneous nickel containing
layer with a thickness of less or equal to 3 µm on the covering layer.

Description

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Description
Coin blank
The present invention relates to a coin blank with a core made of an iron
material,
preferably of steel, with a covering layer made of copper and/or of a copper
alloy.
Coin blanks and coins minted therefrom whose core consists of steel and which
are coated on its surface with a covering layer of an NE-metal, are known and
commonly used. Besides of older mechanical plating procedures in particular
galvanic coating of steel blanks has prevailed in general due to production
orientated and economic reasons. Coating of coin blanks of steel with copper
or
copper alloys serves as corrosion protection of the highly corrosive steel
core as
well as for the coloring of the face value, for example by galvanic covering
layers
of copper or of a copper alloy, for example brass. Well-known examples are the
coins of the 1-, 2- and 5-euro cents presently in circulation, which comprise
a
core of steel, which is galvanically copper-coated. The copper layer has
typically a
thickness of 20 p.m to 30 um or more.
From DE 29 32 229 steel coins are known, which are galvanically nickel-coated
and have a permanent, typical nickel shine. In order to achieve this it is
necessary that the nickel coating has a thickness of greater or equal to 10
um.
From DE 41 20 291 a coin blank is also known, which has a two- or multi-layer
galvanic coating of the steel core with nickel, copper and nickel as most
outer
layer, wherein the thickness of the coating with respect to the weight of the
blank
amounts to 1 % Ni, 4 - 7 % Cu and 1 - 1.5 % Ni. This corresponds to a layer
thickness of more than 10 lam each for the single layers.
Generally, such coins are preferred for circulating that have a steel core
with a
copper-colored galvanic covering layer. By this, a specific coloring of the
coin is
obtained as well as a corrosion protection of the steel core is pursued. A
galvanic
copper layer has, however, the disadvantage that by using the coin frequently
during circulation a matte patina is formed, through which the original shine
of the
copper coin surface is lost relatively fast. By this also the color changes
seriously from the
original copper red to an unsightly reddish brown. Similar effects occur for
galvanic

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covering layers, which are formed from a copper alloy such as CuZn or CuSn.
Also those
surfaces lose their shine and their originally golden color.
Known coins, which consist of a steel core and are galvanically nickel-coated
(DE
29 32 229, DE 41 20 291) are indeed more corrosion stable and keep their
typical
nickel shine while being used as circulating coins, but they are restricted to
the
silver color of nickel.
It is an object of the invention to provide a coin blank with a core of an
iron
material, in particular steel, which is provided with a covering layer of
copper or
of a copper alloy, wherein the covering layer maintains during frequent use of
the
circulating coin minted thereof sufficiently long the original copper shade or
copper alloy shade and its shine and has therefore a high tarnish persistency.
According to the invention the object is solved with the features indicated in
claim
1. Advantageous embodiments of the invention are subject-matter of the
dependent claims. The invention further relates to an object with a covering
layer
of copper or of a copper alloy and a nickel doping in the covering layer. A
coin
blank, which comprises a steel core and which is provided with a covering
layer of
copper or of a copper alloy, is superficially doped with a very thin nickel
coating.
In this process, the covering layer may be formed galvanically. Just as well,
doping may be performed with nickel by an electrochemical or physical
depositing
of a nickel layer. In practice, the nickel doping maintains the intensive
color of
the copper layer and the shine of a circulating coin, which is minted from the
coin
blank according to the invention, is not lost during permanent use. The same
positive
effects regarding color stability and shine result from coins, which are
minted from coin
blanks, whose core contains steel or pre-coated steel, which is coated
galvanically with a
copper alloy such as for example CuZn or CuSn or even with a layer
combination, such as
Cu! CuZn or Cu! CuSn, if the covering layer is doped with nickel according to
the
invention. The nickel doping according to the invention does result in no or
only
in a minimal visual recognizable change of the color of the coin blanks with
respect to undoped coin blanks.
The superficially nickel doped coin blank according to the invention allows
for
minting of circulating coins, which contain a steel core, which is coated
galvanically with copper and/or a copper alloy, in a new quality of coins.
These
coins guarantee a permanent shine and color stability of the respective
covering

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layers of copper, brass (CuZn) or bronze (CuSn) or in terms of color analogous
copper alloys, as for example aluminum bronze (CuAl).
The solution according to the invention does also not exclude blanks for
memorial
coinages, medals and similar special cases of a galvanic coating. Just as well
objects, which have a surface of copper or a copper alloy may be superficially
doped with nickel, in order to make the original shine permanent, if a
tarnishing
caused by aging of the copper surface or the copper alloy is not desired, e.g.
for
fittings, handles, armatures etc.
The invention is detailed in what follows according to two embodiments:
FIG. 1 illustrates the cross section through a coin blank of steel with a
galvanic
copper layer as covering layer with nickel doping according to the invention
1 ¨ steel core
2 ¨ galvanic copper covering layer
3 ¨ nickel doping in the copper layer
The coin blank comprises a core (1) made of an iron material, for example a
low
alloyed steel, such as for example DC04 steel according to the European norm.
The core is covered pore-free with a galvanic copper layer (2) with the usual
thickness in the range of 10 gm to 30 gm. On this covering layer of copper (2)
a
very thin nickel layer of a thickness of 0.5 gm to 3 gm is deposited, which
migrates in form of a doping (3) into the surface of the covering layer (2)
due to a
final thermal treatment of the coin blank in a protective atmosphere, by which
the
permanent copper color of the covering layer as well as corrosion persistency
is
guaranteed. The nickel doping amounts at the surface of the copper layer 1 to
10
percent by mass, for example 2 percent by mass, with respect to copper in the
surface
area and continuous with a declining concentration gradient towards zero
within the
copper layer. If the concentration of nickel in the surface is higher than 10
% by mass, the
color of the coin blank changes. If the concentration of nickel is lower than
1 % by mass,
the tarnish persistency of the coin blank deteriorates.
FIG. 2 illustrates the cross section through a coin blank of steel with a
galvanic layer
combination of copper as intermediate layer and copper-zinc (brass)as covering
layer with
nickel doping

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1' ¨ steel core
2' ¨ galvanic copper intermediate layer
2" ¨ galvanic copper-zinc-alloy (brass) covering layer
3 ¨ nickel doping in the copper-zinc-covering layer
FIG. 3 illustrates the concentration gradient of the nickel doping across the
cross
section of a coin blank with a galvanic covering layer of copper according to
FIG.
1. The galvanic covering layer has for example a layer thickness of 30 um,
which
is deposited on the core (1) of iron material. The covering layer (2)
comprises a
nickel doping (3). At the surface of the coin blank the nickel doping (3) has
a
concentration of approximately 2 percent by mass. The concentration declines
with growing distance to the surface.

Dessin représentatif