ALLIAGE FER-NICKEL

IRON-NICKEL ALLOY

Abrégé français

L'invention concerne un alliage fer-nickel ayant la composition suivante (en pourcentage en masse) : C 0,05 à 0,5 %, Cr 0,2 à 2,0 %, Ni 33 à 42 %, Mn < 0,1 %, Si < 0,1 %, Mo 1,5 à 4,0 %, Nb 0,01 à 0,5 %, Al 0,1 à 0,8 %, Mg 0,001 à 0,01 %, V max. 0,1 %, W 0,1 à 1,5 %, Co max. 2,0 %, le reste étant constitué de Fe et d'impuretés résultant de la fabrication.

Abrégé anglais

The invention relates to a wire for a wire for a power line comprising an iron-
nickel alloy
having in mass %:
C > 0.1 to 0.4%
Cr > 0.6 to < 1.2%
Ni 35 to < 38%
Mn < 0.08%
Si <0.08%
Mo 2.1 to 2.8%
Nb 0.05 to 0.3%
Al 0.2 to 0.4%
Mg > 0.001 to 0.01%
V .ltoreqØ1%
W 0.25 to 1.0%
Co 0 to < 0.5%
Fe remainder and constituents resulting from a production process, wherein:
the sum, in
mass%, of Mo + W is between 2.2 and 3.5%, the sum, in mass%, of Cr + W is
between 1.0
and 2.0%, the sum, in mass%, of Si + Mn is < 0.1%, and the alloy has a thermal
expansion
coefficient of < 4 x 10 -6/K in the temperature range between 20 and
200°C.

Revendications

6
CLAIMS:
1. A wire for a power line comprising an iron-nickel alloy consisting
of, in mass
%:
C > 0.1 to 0.4%
Cr > 0.6 to < 1.2%
Ni 35 to < 38%
Mn < 0.08%
Si < 0.08%
Mo 2.1 to 2.8%
Nb 0.05 to 0.3%
Al 0.2 to 0.4%
Mg > 0.001 to 0.01%
V .ltoreqØ1%
W 0.25 to 1.0%
Co 0 to < 0.5%
Zr 0 to < 0.2%
B 0 to 0.01%
Fe remainder and constituents resulting from a production process,
wherein:
the sum, in mass%, of Mo + W is between 2.2 and 3.5%,

7
the sum, in mass%, of Cr + W is between 1.0 and 2.0%,
the sum, in mass%, of Si + Mn is < 0.1%, and
the alloy has a thermal expansion coefficient of < 4 x 10-6/K in the
temperature range
between 20 and 200°C.
2. The wire in accordance with claim 1, wherein the alloy has in mass %:
C > 0.15 to < 0.4%
W 0.25 to 1.0%.
3. The wire in accordance with claim 1 or 2, wherein the alloy has in mass
%:
Zr > 0 to < 0.2% and/or
B > 0-0.01%.
4. The wire in accordance with any one of claims 1 to 3, wherein for the
alloy the
ratio (Mo + W + Cr)/C is 13.5 ¨ 15.5.
5. The wire in accordance with any one of claims 1 to 4, wherein for the
alloy the
element W is substituted for some of the element Mo.
6. The wire in accordance with any one of claims 1 to 5, wherein the alloy
has a
thermal expansion coefficient of 3.5 x 10-6/K in the temperature range between
20 and 200°C.
7. A method for producing the wire in accordance with any one of claims 1
to 6,
comprising: casting a melt of the alloy into blocks; rolling the blocks to
create billets;
drawing the billets to create a pre-product wire with a pre-specified
diameter; aluminizing the
pre-product wire; and drawing the pre-product wire to a final dimension.
8. The method is accordance with claim 7, wherein between individual
drawing
steps there is an annealing process.

8
9. A use
of the wire as defined in any one of claims 1 to 6, as a core wire for a
power line.

Description

1 CA 02725206 2012-12-14
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Iron-Nickel Alloy
The invention relates to an iron-nickel alloy having a low thermal expansion
coefficient and
special mechanical properties.
It is known that iron-based alloys having approximately 36% nickel have low
thermal expansion
coefficients in the temperature range between 20 and 100 C. Those alloys have
therefore been
used for several decades wherever constant lengths are required, even with
changes in
temperature, such as for instance in precision instruments, clocks, bimetals,
and shadow masks
for color televisions and computer monitors.
KR 100261678 BI is an invar alloy wire and a method for producing it. The
invar alloy has the
following composition (in mass %): 33 to 38% nickel, 0.5 to 1.0% cobalt, 0.01
to 1.3% niobium,
0.5 to 4% molybdenum, 0.2 to 1.5% chromium, 0.05 to 0.35% carbon, 0.1 to 1.2%
silicon, 0.1 to
0.9% manganese, max. 0.1% magnesium, max. 0.1% titanium, and the remainder
iron, the sum
of Mo + Cr being between 1.2 and 5.0% and the sum of niobium and carbon being
between 0.1
and 0.6%.
KR 1020000042608 discloses a high-strength invar alloy wire and a method for
producing it.
The alloy used contains (in mass %): no more than 0.1% nitrogen, 0.01 to 0.2%
niobium, 0.3 to
0.4% carbon, 33 to 38% nickel, 0.5 to 4% molybdenum, 0.210 1.5% chromium, 0.1
to 1.2%
silicon, 0.1 to 0.9% manganese, 1.0 to 10% cobalt, and, as needed, additions
of up to 0.1% each
Al, Mg, and Ti, and the remainder iron.
Both publications provide method parameters for cold drawing and hot drawing
and annealing
within defined temperature ranges.
The invention relates to a creep-resistant iron-nickel alloy having
a low thermal expansion coefficient and special mechanical properties.
Moreover, a production

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process for wire-like components made of this alloy is provided. It is
possible to employ the
material for specific uses, and the alloy has a low thermal expansion
coefficient.
This is attained using an iron-nickel alloy having the following composition:
C 0.05 to 0.5%
Cr 0.2 to 2.0%
Ni 33 to 42%
Mn < 0.1%
Si < 0.1%
Mo 1.5 to 4.0%
Nb 0.01 to 0.5%
Al 0.1 to 0.8%
Mg 0.001 to 0.01%
V Max. 0.1%
W 0.1 to 1.5%
Co Max 2.0%
Fe remainder and constituents resulting from the production process.
In one aspect, the invention relates to a wire for a power line comprising an
iron-nickel alloy
consisting of, in mass %:
C > 0.1 to 0.4%
Cr >0.6 to < 1.2%

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2a
Ni 35 to < 38%
Mn <0.08%
Si <0.08%
Mo 2.1 to 2.8%
Nb 0.05 to 0.3%
Al 0.2 to 0.4%
Mg > 0.001 to 0.01%
V
W 0.25 to 1.0%
Co 0 to < 0.5%
Zr 0 to < 0.2%
B 0 to 0.01%
Fe remainder and constituents resulting from a production process,
wherein: the sum, in
mass%, of Mo + W is between 2.2 and 3.5%, the sum, in mass%, of Cr + W is
between 1.0
and 2.0%, the sum, in mass%, of Si + Mn is <0.1%, and the alloy has a thermal
expansion
coefficient of < 4 x 10-6/K in the temperature range between 20 and 200 C.
One preferred variant of the inventive iron-nickel alloy is provided as
follows (in mass %):
C 0.1 to 0.4%
Cr 0.5 to 1.5%
Ni 34 to 40%
Mn < 0.08%

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2b
Si <0.08%
Mo > 2.0 to < 3.5%
Nb 0.05 to 0.4%

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Al 0.2 to 0.5%
Mg 0.001 to < 0.01%
V Max. 0.1%
W 0.2 to < 1.0%
Co 0 to 0.5%
Fe Remainder and constituents resulting from the production process.
Another variant is formed by (in mass %):
C > 0.15 to < 0.4%
Cr 0.6 to max. 1.2%
Ni 35 to 40%
Mn <0.08%
Si <0.08%
Mo > 2.0 to < 3.0%
Nb 0.05 to 0.3%
Al > 0.1 to < 0.5%
Mg > 0.001 to <0.01%
V Max. 0.1%
W 0.25 to 1.0%
Co 0 to max 0.5%
Fe Remainder and constituents resulting from the production process.
The inventive composition of the alloy is distinguished from the prior art in
that the Si and Mn
contents are kept as small as technically possible. It is known that there is
a strong relationship
between the elements silicon and manganese with respect to the thermal
expansion coefficient.
On the other hand, these elements are metallurgically necessary in order to
ensure adequate
processability. This relates in particular to hot shaping to create billets
and wire rods.
Thus, using the inventive chemical composition it is possible to use the
smallest possible
amounts of the elements silicon and manganese so that the negative effects
these elements have

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on the theme expansion coefficient can be avoided and at the same time the
alloy is easy to
process. For this reason the sum of Mn + Si should not exceed 0.2% (in mass
%). The sum of
Mn + Si should be <0.1% where this is technically feasible.
It is of particular advantage when the inventive alloy has a nickel content
between 35 and 38%, a
chromium content of > 0.6 to < 1.2%, a molybdenum content between 2.1 and
2.8%, an
aluminum content between 0.2 and 0.4%, and a tungsten content of > 0.25 to <
1.0%.
If necessary, the element zirconium may also be added in contents > 0 to <
0.2% and/or the
element B may be added in contents > 0 ¨ 0.01% of the inventive alloy.
B + Zr individually or together improve the hot formability of the alloy.
Moreover, it is advantageous when the awn of the elements Mo + W is between
2.0 and 4.0%.
It is likewise advantageous for the mechanical properties when the sum of the
elements Cr + W
is between 1.0 and 2.0%.
According to another thought of the invention, the element W may be
substituted for some of the
element Mo.
It is significant that the alloy elements Mo, W, Cr, and C are available in
sufficient quantities and
that the ratio of (Mo + W + Cr)IC is selected such that it is possible to
achieve a balanced mix of
carbide strengthening, mixed crystal hardening, and cold hardening in the
final product. An
optimum ratio is considered to be in the range between 13.5 and 14.5, e.g. 14
and 15.
According to another thought of the invention, the W;Cr:Mo ratio should be
approximately
1:2:5. However, the portion of the aforesaid elements in the inventive alloy
must be specified
such that the thermal expansion coefficient sought is not exceeded.

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In the temperature range between 20 and 200 C the inventive alloy has a
thermal expansion
coefficient of < 4 x 10-61K, especially < 3.5 x 10-6/K.
Furthermore, the invention relates to a method for producing components from
the inventive
alloy in an arc furnace, an induction furnace, or a vacuum furnace (where
necessary with
5 VOD treatment), with subsequent ingot casting, hot rolling (or forging)
to create billets and
wire rods on wire of a pre-specifiable thickness, and subsequent drawing to
create wire-
shaped pre-products with a pre-specifiable diameter, annealing processes
occurring when
necessary between individual drawing steps. Since the degree of cold
strengthening is critical
for the usage properties, both with regard to the thermal expansion
coefficient and with regard
to strength, the wire rod diameter must be adjusted such that adequate cold
forming can be
performed prior to and after intermediate annealing, which may take place in
multiple stages.
In one method aspect, the invention relates to a method for producing a wire-
shaped
component from the alloy in accordance with any one of claims 1 to 18,
comprising: casting a
melt of the alloy into blocks; rolling the blocks to create billets; drawing
the billets to create a
pre-product wire with a pre-specified diameter; a luminizing pre-product wire;
and drawing
the pre-product wire to a final dimension.
According to another thought of the invention, the inventive alloy may be used
as wire for
power lines, especially as the core wire for power lines.
The inventive alloy may moreover be advantageously used for:
-- Lead frames
-- Shaped parts, especially carbon fiber molded parts
-- Components in chip production.
For the preferred uses the inventive alloy may be present in the form of
sheet, bar, strip, or
wire material.