U.S. patent application number 10/565219 was filed with the patent office on 2006-09-28 for thin strips or foils of alfesi alloy.
Invention is credited to Bruno Chenal, Armelle Danielou, Jean-Marie Feppon.
Application Number | 20060213590 10/565219 |
Document ID | / |
Family ID | 33560962 |
Filed Date | 2006-09-28 |
United States Patent
Application |
20060213590 |
Kind Code |
A1 |
Danielou; Armelle ; et
al. |
September 28, 2006 |
Thin strips or foils of alfesi alloy
Abstract
The invention relates to a thin strip or foil, having a
thickness of 6 to 200 ?m, preferably, of 6 to 50 ?m, and composed
of an alloy containing (in weight %) Si: 1.0 to 1.5, Fe: 1.0 to
1.5, Cu <0.2, Mn <0.1, other elements <0.05 each up to a
total <0.15, the remainder being Al. The annealed thin strip or
foil has a tensile strength R.sub.m >110 MPa for a thickness
>9 ?m and >100 MPa for a thickness of 6 to 9 ?m, and an
elastic limit R.sub.0.2 >70 MPa. Preferably, said alloy has a
silicon content of 1.1 to 1.3% and an iron content of 1.0 to 1.2%.
The aforementioned thin strips or foils may be used especially for
the production of multilayer composites, overcaps for bottles or
aluminium wrappings.
Inventors: |
Danielou; Armelle; (St.
Alban Layose, FR) ; Feppon; Jean-Marie; (Cornillon,
FR) ; Chenal; Bruno; (Saint-Etienne-de-Crossey,
FR) |
Correspondence
Address: |
CONNOLLY BOVE LODGE & HUTZ LLP
SUITE 800
1990 M STREET NW
WASHINGTON
DC
20036-3425
US
|
Family ID: |
33560962 |
Appl. No.: |
10/565219 |
Filed: |
July 19, 2004 |
PCT Filed: |
July 19, 2004 |
PCT NO: |
PCT/FR04/01902 |
371 Date: |
April 6, 2006 |
Current U.S.
Class: |
148/551 ;
420/537; 420/548 |
Current CPC
Class: |
C22C 21/00 20130101;
C22C 21/02 20130101; C22F 1/043 20130101; C22F 1/04 20130101 |
Class at
Publication: |
148/551 ;
420/537; 420/548 |
International
Class: |
C22C 21/02 20060101
C22C021/02 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 21, 2003 |
FR |
03/08864 |
Claims
1. Thin strip or foil between 6 .mu.m and 200 .mu.m thick, and
preferably between 6 .mu.m and 50 .mu.m thick, of an alloy with the
following composition (% by weight): Si: 1.0-1.5; Fe: 1.0-1.5; Cu
<0.2; Mn <0.1; other elements <0.05 each and <0.15
total, remainder Al, with an ultimate tensile strength R.sub.m in
the annealed temper >110 MPa for thicknesses >9 .mu.m and
>100 MPa for thicknesses between 6 .mu.m and 9 .mu.m.
2. Thin strip or foil according to claim 1, characterized in that
it has an ultimate tensile strength R.sub.m in the annealed temper
>115 MPa for thicknesses >9 .mu.m.
3. Thin strip or foil according claim 1, characterized in that it
has a yield stress R.sub.0.2 >70 MPa.
4. Thin strip or foil according to claim 1, characterized in that
its ultimate elongation A is a function of the thickness, as
follows: TABLE-US-00005 Thickness (.mu.m) A (%) greater than and
preferably than 6-9 3 4 9-15 5 7 15-25 10 15 25-50 18 25 50-200 20
25
5. Thin strip or foil according to claim 1, characterized in that
the alloy has a composition such that Si/Fe .gtoreq.0.95.
6. Thin strip or foil according to claim 1, characterized in that
the silicon content of the alloy is between 1.1% and 1.3% and its
iron content is between 1.0% and 1.2%.
7. Manufacturing process for thin strips thinner than 200 .mu.m
made of an Al--Fe--Si alloy with composition (% by weight): Si:
1.0-1.5; Fe: 1.0-1.5; Cu <0.2; Mn <0.1; other elements
<0.05 each and <0.15 total, remainder Al, including the
preparation of a first strip either by vertical semi-continuous
casting of a plate and hot rolling, or by continuous casting
possibly followed by hot rolling, cold rolling of this first strip
down to the final thickness, possibly with intermediate annealing
at a temperature between 250.degree. C. and 350.degree. C., and
preferably between 280.degree. C. and 340.degree. C., and final
annealing at a temperature between 200.degree. C. and 370.degree.
C.
8. Process according to claim 7, characterized in that the alloy
has a composition such that Si/Fe .gtoreq.0.95.
9. Process according to claim 7, characterized in that the first
strip is subjected to an homogenisation at a temperature between
450 and 500.degree. C. before cold rolling.
10. Process according to claim 7, characterized in that the strip
is prepared by continuous twin-roll casting.
Description
DOMAIN OF THE INVENTION
[0001] This invention concerns thin strips or foils less than 200
.mu.m thick and preferably less than 50 .mu.m thick, made of an
aluminium alloy with iron and with silicon, with substantially low
manganese content, and a process of manufacturing such strips or
foils. These strips may be obtained by semi-continuous casting of
conventional plates or by continuous casting, for example by
twin-belt casting or twin-roll casting.
STATE OF THE ART
[0002] The trend in the thin aluminium alloy foil market is moving
towards a constant reduction in the thicknesses used for a given
application, while demanding high mechanical properties and good
formability.
[0003] Alloys with a very low manganese content are frequently used
for thin foil, for example such as the 8111 alloy with the
following composition (% by weight) registered with the Aluminum
Association:
[0004] Si 0.30-1.1; Fe 0.40-1.0; Cu <0.10; Mn <0.10
[0005] The lack of manganese makes it easy to obtain
recrystallisation during the final annealing, but the ultimate
tensile strength R.sub.m remains insufficient for thicknesses less
than 100 .mu.m.
[0006] Therefore, there is a need to develop new alloys and/or to
optimise transformation procedures to satisfy market demand.
[0007] Manganese is normally added to increase the mechanical
strength, for example as in the 8006 alloy for which the
composition (% by weight) registered with the Aluminum Association
is as follows:
[0008] Si <0.40; Fe: 1.2-2.0; Cu <0.30; Mn: 0.30-1.0; Mg
<0.10
[0009] The result of adding manganese is to harden the material.
The mechanical properties obtained with patent U.S. Pat. No.
6,517,646 belonging to the applicant for an alloy with composition
Si=0.23%; Fe=1.26%; Cu=0.017%; Mn=0.37%; Mg=0.0032%; Ti=0.008%, in
combination with a favourable transformation procedure, gives a
value R.sub.m equal to 103 MPa for a thickness of 6.6 .mu.m.
[0010] The mechanical properties can also be improved by adding a
small quantity of manganese in alloys in the 8000 series containing
iron. Patent application WO 02/64848 (Alcan International)
describes the fabrication of thin strips made of AlFeSi alloy
containing from 1.2% to 1.7% Fe and 0.35% to 0.8% of Si, by
continuous casting. A high mechanical strength is obtained by
adding 0.07% to 0.20% of manganese to the alloy. This addition of
manganese is recognised as being necessary to obtain a small grain
size after final annealing.
[0011] Therefore, manganese appears to be an element capable of
improving the mechanical properties of 8000 alloys. However,
manganese in solid solution or in the form of fine precipitates can
block or delay recrystallisation during final annealing. Therefore,
the precipitation of phases containing manganese needs to be
controlled precisely during each step in the procedure, which is
often difficult. Any drift in the transformation procedure has
non-negligible consequences on the effectiveness of the final
annealing. Therefore, it would be very useful to develop an alloy
that does not contain any manganese, but that does have high
mechanical properties.
[0012] U.S. Pat. No. 5,503,689 (Reynolds Metals) describes a
process for manufacturing a thin strip made of an alloy containing
0.30% to 1.1% Si and 0.40% to 1.0% Fe, less than 0.25% Cu and less
than 0.1% Mn, by continuous casting and cold rolling without
intermediate annealing. The preferred contents of iron and silicon
are between 0.6% and 0.75%.
[0013] U.S. Pat. No. 5,725,695 (Reynolds Metals) describes a
procedure for the same composition, with intermediate annealing
between 400.degree. C. and 440.degree. C. (750.degree.
F.-825.degree. F.) and a final recrystallisation annealing at
288.degree. C. (550.degree. F.). The ratio of the Si and Fe
contents is greater than or equal to 1. In the examples, the
maximum ultimate tensile strength obtained is 90 MPa (13.13 ksi),
the maximum yield stress is 39.1 MPa (5.68 ksi), and the elongation
is 11.37% for thicknesses of 46 .mu.m (0.00185.degree.). These
mechanical properties are still low for some applications.
[0014] For alloys obtained by continuous casting, it is often
necessary to perform a high temperature heat treatment to reduce
the noxiousness of segregations, by resorbing precipitation lumps
and homogenising the structure through the thickness. The effect of
a homogenisation at 600.degree. C. for the 8011 alloy (composition
0.71% Fe; 0.77% Si; 0.038% Cu; 0.006% Mn; 98.45% Al) obtained by
twin-roll casting is described in the article by Y. Birol
"Centerline Segregation in a Twin-Roll Cast AA8011 Alloy",
Aluminium, 74, 1998, pp 318-321. The precipitated phases are
modified and heterogeneities are reduced. The reduction in central
segregation subsequently limits the porosity of very thin foils and
improves their formability.
[0015] It is economically attractive to limit the heat treatment
temperature. For an 8111 alloy with composition 0.7% Fe; 0.7% Si;
Mn <0.02, Zn <0.02; Cu <0.02, a beginning of a
transformation of the phases is observed with total
recrystallisation at 460.degree. C., although annealing at
550.degree. C.-580.degree. C. is necessary to obtain a more
complete transformation (see M. Slamova et al. "Response of AA8006
and AA8111 Strip-Cast Rolled Alloys to High Temperature Annealing",
ICAA-6, 1998). Therefore low temperature homogenisation could be
considered for alloys without manganese.
[0016] Moreover, in the transformation to low thicknesses
subsequent to homogenisation, it is standard practice to add an
intermediate annealing step in order to soften the metal. For
manganese alloys, the intermediate annealing control usually
requires a high temperature heat treatment (at above 400.degree.
C.) so as to obtain recrystallisation.
[0017] For manganese-free 8000 type alloys, it is possible to
envisage a heat treatment at a lower temperature than for 8006 type
alloys.
[0018] Patent application WO 99/23269 (Nippon Light Metal and Alcan
International) describes a process applicable to AlFeSi alloys
containing 0.2% to 1% of Si and 0.3% to 1.2% of Fe, with a Si/Fe
ratio of between 0.4 and 1.2, in which intermediate annealing is
done in two steps, the first between 350.degree. C. and 450.degree.
C., and the second between 200.degree. C. and 330.degree. C. The
purpose of this process is to reduce surface defects in the foil.
Mechanical properties are not mentioned.
[0019] The purpose of the invention is to obtain thin strips or
foils made of an AlFeSi alloy with no added manganese, with a high
mechanical strength while maintaining good formability, with the
most economic industrial manufacturing procedure possible.
SUBJECT MATTER OF THE INVENTION
[0020] The subject matter of the invention is a thin foil between 6
.mu.m and 200 .mu.m thick, and preferably between 6 .mu.m and 50
.mu.m thick, of an alloy with the following composition (% by
weight):
[0021] Si: 1.0-1.5; Fe: 1.0-1.5; Cu <0.2; Mn <0.1; other
elements <0.05 each and <0.15 total, remainder Al, preferably
with the condition Si/Fe .gtoreq.0.95, with an ultimate tensile
strength in the annealed temper R.sub.m >10 MPa for thicknesses
>9 .mu.m and >100 MPa for thicknesses between 6 .mu.m and 9
.mu.m. The yield stress R.sub.0.2 of the thin foil (measured on
sheared test pieces) is preferably >70 MPa. The ultimate
elongation is greater than the following values, as a function of
the thickness of the foil: TABLE-US-00001 Thickness (.mu.m) A (%)
greater than and preferably than 6-9 3 4 9-15 5 7 15-25 10 15 25-50
18 25 50-200 20 25
[0022] The silicon content of the alloy is preferably between 1.1%
and 1.3% and its iron content is between 1.0% and 1.2%.
[0023] Another subject matter of the invention is a manufacturing
process for thin strips thinner than 200 .mu.m made of an
Al--Fe--Si alloy with composition (% by weight):
[0024] Si: 1.0-1.5; Fe: 1.0-1.5; Cu <0.2; Mn <0.1; other
elements <0.05 each and <0.15 total, remainder Al, preferably
with the condition Si/Fe .gtoreq.0.95, including the preparation of
a first strip either by vertical semi-continuous casting of a plate
and hot rolling, or by continuous casting possibly followed by hot
rolling, cold rolling of this first strip down to the final
thickness, possibly with intermediate annealing for between 2 h and
20 h at a temperature between 250.degree. C. and 350.degree. C.,
and preferably between 280.degree. C. and 340.degree. C., and final
annealing at a temperature between 200.degree. C. and 370.degree.
C.
DESCRIPTION OF THE INVENTION
[0025] The thin strips or foils according to the invention are made
from 8000 AlSiFe alloys with almost no manganese, typically less
than 0.1%. Iron and silicon contents are significantly higher than
8011 and 8111 alloys that are the most frequently used
manganese-free AlSiFe alloys for thin foil. One preferred
composition range is an alloy containing 1.1% to 1.3% of silicon
and 1.0% to 1.2% of iron.
[0026] Alloys according to the invention preferably have a
composition such that the Si/Fe ratio of silicon and iron contents
is .gtoreq.0.95. Their mechanical strength in the annealed temper
(O temper) is exceptional for alloys with this composition, with an
ultimate tensile strength R.sub.m >110 MPa or even 115 MPa for
thicknesses >9 .mu.m, and >100 MPa for thicknesses from 6
.mu.m to 9 .mu.m, and a conventional yield stress at 0.2%,
R.sub.0.2 >70 MPa. This high mechanical strength is not obtained
at the expense of formability, since elongations are at least as
high as for 8011 and 8111 alloys, and bursting pressures are
higher.
[0027] These high mechanical properties are obtained equally well
for strips produced from plates obtained by conventional vertical
semi-continuous casting and hot rolled, and for strips derived from
continuous casting, either by belt casting or twin-roll casting.
Continuous belt casting is also following by hot rolling.
[0028] Hot rolled strips, or as-cast strips obtained by continuous
twin-roll casting, may be homogenised at low temperature (between
450.degree. C. and 500.degree. C.) to reduce the central
segregation that may reduce formability to the final thickness.
This low temperature heat treatment is sufficient to resorb any
central segregations in these manganese-free alloys. The strips are
then cold rolled, either down to the final thickness or to an
intermediate thickness between 0.5 mm and 5 mm, at which an
intermediate annealing is performed. Unlike alloys containing
manganese, this intermediate annealing can be done at a relatively
low temperature between 250.degree. C. and 350.degree. C., and
preferably between 280.degree. C. and 340.degree. C., for longer
than 2 hours. Although this temperature range is described in the
literature, particularly in patent application WO 02/064848
mentioned above, it is below the normal range that remains above
400.degree. C.
[0029] The applicant has observed that the application of low
temperature heat treatments to an AlFeSi alloy, more particularly
with a composition such that Si/Fe >0.95, possibly eliminating
the intermediate annealing when technically possible, results in
significantly higher mechanical strength than is possible with
normal intermediate annealing, at least 15% better. This higher
mechanical strength is obtained while improving the formability
measured by the bursting pressure or the dome height according to
standard ISO 2758.
[0030] Final annealing is done at a temperature between 200.degree.
C. and 370.degree. C. for between 1 h and 72 h. Annealing durations
depend on the degreasing quality of the foil. A fine grain
structure is obtained after annealing, with an average grain size
measured by image analysis with a scanning electron microscope
equal to less than 3 .mu.m.
[0031] The combination of low temperature homogenisation or no
homogenisation at all with an intermediate annealing at low
temperature or no intermediate annealing at all, is economically
advantageous but also helps to obtain a fine grain size. The grain
size is about 30% lower than is possible with heat treatments at a
higher temperature, consequently increasing the mechanical
properties R.sub.0.2 and R.sub.m which for small thicknesses are
related to the number of grain joints. This gain is not achieved at
the detriment of elongation, since the increase in the number of
grains in the thickness also limits the risk of local damage in one
or two single grains in the thickness of the foil.
[0032] Thin foils according to the invention are particularly
suitable for applications requiring good mechanical strength and
high formability, for example such as fabrication of multi-layer
composites, particularly for lids for packaging of fresh products,
overcaps or aluminium wrapping.
EXAMPLES
Example 1
[0033] Two 6.1 mm thick strips made of alloy A according to the
invention and alloy B type 8111 with the composition (% by weight)
indicated in table 1 were made by continuous twin-roll casting, in
order to demonstrate the influence of the composition of the alloy:
TABLE-US-00002 TABLE 1 Alloy Si Fe Cu Mn Mg Cr Ti B A 1.17 1.11
0.001 0.003 0.0004 0.0007 0.006 0.0005 B 0.7 0.7 0.001 0.003 0.0005
0.001 0.007 0.0005
[0034] The strips were cold rolled to a thickness of 2 mm and an
intermediate annealing was then carried out on them for 5 hours at
320.degree. C. The strips were then cold rolled in several passes
to the final thickness of 38 .mu.m. A final annealing was then
carried out on them for 40 hours at 270.degree. C.
[0035] The mechanical properties were measured in each case. The
measured values were the ultimate tensile strength R.sub.m (in
MPa), the conventional yield stress at 0.2% R.sub.0.2 and the
ultimate elongation A (in %) according to standard NF-EN 546-2, the
bursting pressure in air Pe (in kPa) measured according to standard
ISO 2758 and the dome height Hd (in mm). The results are given in
table 2: TABLE-US-00003 TABLE 2 Alloy R.sub.m (MPa) R.sub.0.2 (MPa)
A (%) Pe (kPA) Hd A 123 76 30 394 9.2 B 104 54 15.8 284 6.6
[0036] It is found that, unlike the 8111 type alloy B, the ultimate
strength of the alloy A strip is much higher than 110 MPa, and the
yield stress is higher than 70 MPa. The bursting pressure and the
elongation are also higher, such that this alloy is both stronger
and more formable.
Example 2
[0037] A 6.1 mm thick strip made of alloy A described in example 1
was made by continuous twin-roll casting. The strip was then cold
rolled to a thickness of 2 mm. A normal intermediate annealing for
an alloy of this type was then carried out on part of the strip,
for 5 hours at 500.degree. C. An intermediate annealing was carried
out on the other part of the strip, for 5 hours at 320.degree. C.
according to the invention. The two parts of the strip were then
cold rolled in several passes to the final thickness of 10.5 .mu.m.
A final annealing was then carried out on them for 40 hours at
270.degree. C.
[0038] The properties were the same as in example 1, and the values
are shown in table 3: TABLE-US-00004 TABLE 3 Inter. annealing
R.sub.m (MPa) R.sub.0.2 (MPa) A (%) Pe (kPa) Hd (mm) 470.degree. C.
99 63 7.3 71 5.1 320.degree. C. 117 84 8.1 92 5.7
[0039] It is found that the lower temperature of the intermediate
annealing increases the mechanical strength, the elongation, the
bursting strength and the formability.
[0040] The average grain size measured by image analysis with an
SEM, is 3.6 .mu.m for annealing at 470.degree. C., and 2.3 .mu.m
for annealing at 320.degree. C. Therefore the increase in
mechanical properties for low temperature annealing is related to
the reduction in grain size obtained after final annealing.
* * * * *