Note: Descriptions are shown in the official language in which they were submitted.
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HIGHLY FORMABLE AND INTERCRYSTALLINE CORROSION-RESISTANT AL1VIG
STRIP
The invention relates to a cold-rolled aluminium alloy strip composed of an
AlMg aluminium
alloy and a method for the production thereof. Furthermore, corresponding
components produced
from the aluminium alloy strips will be proposed.
Aluminium-magnesium-(A1Mg+alloys of the AA 5xxx type are used in the form of
sheets or
plates or strips for the construction of welded or joined structures in ship,
automotive and aircraft
construction. They are characterised by high strength which increases as the
magnesium content
rises. AlMg-alloys of the AA 5xxx type with Mg contents of more than 3%, in
particular more
than 4%, have an increasing tendency towards intercrystalline corrosion, when
exposed to high
temperatures. At temperatures of 70 - 200 C, 13-A15Mg3 phases precipitate
along the grain
boundaries, which are referred to as 13-particles and in the presence of a
corrosive medium can be
selectively dissolved. The result of this is that the AA 5182-type aluminium
alloy (Al 4.5% Mg
0.4% Mn) having very good strength properties and very good formability in
particular cannot be
used in heat-stressed areas, where the presence of a corrosive medium such as
water in the form
of moisture must be contended with. This concerns in particular the components
of a motor
vehicle which normally undergo cathode dip painting (CDP) and are then dried
in a stoving
process, as already due to this stoving process, normal aluminium alloy strips
can become
susceptible to intercrystalline corrosion. Furthermore, for use in the
automotive sector, forming
during the manufacture of a component and subsequent operational stressing of
the component
must be taken into consideration.
The susceptibility to intercrystalline corrosion is normally checked in a
standard test (NAMLT
test) according to ASTM G67, during which the specimens are exposed to nitric
acid and the
mass loss due to the intercrystalline corrosion is measured. According to ASTM
G67, the mass
loss of materials which are not resistant to intercrystalline corrosion, is
more than 15 mg/cm2.
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Sheet metal for the automotive industry, e.g. for internal door parts, must
have very good
formability. Here, the requirements are essentially determined by the
stiffness of the component
concerned, with the strength of the material playing only a subordinate role.
The components
often undergo multi-stage forming processes, such as for example doors with
integrated window
frame areas.
So, apart from the corrosion properties, the formability of the AlMg aluminium
alloy also has a
major influence on the usage possibilities for this material. For example, the
materials known so
far have meant that it is not possible for the side walls of a motor vehicle
to be deep-drawn from
a single sheet, making not only reconstruction of the side wall but also
additional process steps
for providing the side wall of a motor vehicle necessary.
The forming behaviour can, for example, be measured in a stretch drawing trial
by an Erichsen m
cupping test (DIN EN ISO 20482), in which a test piece is pushed against the
sheet, resulting in
cold forming. During the cold forming, the force and the force displacement of
the test piece are
measured, until a load drop occurs, caused by the formation of a crack. The
SZ32 stretch
drawing measurements quoted in the application were performed with a punch
head diameter of
32 mm and a die diameter of 35.4 mm with the help of a TeflonTm deep-drawing
film to reduce
friction. Further measurements of the deep drawability were performed using
the so-called plane-
strain-cupping test using a Nakajima geometry according to DIN EN ISO 12004
with a punch
diameter of 100 mm. For this, specimens with a specific geometry underwent
drawing tests until
a crack appeared, with the depth until cracking being used as a measure of the
formability of the
material.
From JP 2011-052290 A, an aluminium alloy strip for can lids is known, which
is preferably
load-resistant despite its small thickness. Here, the strip has a
recrystallized microstructure.
Further, from EP 2 302 087 A1, a chassis part is known made from an aluminium
composite
material, which has aluminium alloy layers as outer layers. Due to the
alloying constituents, the
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Al composite material is characterized by excellent strength values with a
high corrosion
resistance at low weight.
Composite material solutions composed of AA5xxx aluminium alloys with a high
Mg content
and outer aluminium alloy layers to protect against corrosion, however, have
the disadvantages
that manufacture is complex and additionally at joining points where the
aluminium composite
material joins to other parts, for example at cutting edges, drill-holes and
breakouts, there is
furthermore an increased danger of corrosion.
The present invention is therefore concerned with single-layer aluminium
materials. On this
basis, the object of the invention is to provide a single-layer aluminium
alloy strip, having
sufficient resistance to intercrystalline corrosion but nevertheless having
good formability, so
that large-area, deep-drawn parts, such as interior parts of motor vehicles
doors, with sufficient
strength can be provided. Furthermore, a method will be indicated with which
single-layer
aluminium alloy strips can be produced. Finally, components produced from the
aluminium alloy
strips according to the invention will be indicated.
According to a first teaching of the present invention, the object indicatedl
is achieved by a cold-
rolled aluminium alloy strip composed of an AlMg aluminium alloy, wherein the
aluminium
alloy has the following alloying elements:
Si 5_ 0.2 wt.%.
Fe 0.35 wt.%,
Cu 0.15 wt.%,
0.2 wt.% Mn 0.35 wt.%,
4.1 wt.% Mg 4.5 wt.%,
Cr 0.1 wt.%,
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Zn 0.25 wt.%,
Ti < 0.1 wt.%,
the remainder being Al and inevitable impurities, amounting to a maximum of
0.05 wt.%
individually and a maximum of 0.15 wt.% in total, wherein the aluminium alloy
strip has a
recrystallized microstructure, the average grain size of the structure ranges
from 15 um to 30 um,
preferably from 15 urn to 25 pm and the final soft annealing of the aluminium
alloy strip is
carried out in a continuous furnace.
It has been found that within the specification of the AA5182-type aluminium
alloy, there is a
specific, narrow, alloying range which offers sufficient resistance to
intercrystalline corrosion
and at the same time, by taking into account certain constraints, such as for
example the average
grain size and the type of final soft annealing, results in an exceptional
forming behaviour. In
particular, the combination of the average grain size with the claimed
alloying elements of the
aluminium alloy of the aluminium alloy strip means that degrees of formability
can be achieved
allowing the production of large-area design, deep-drawn sheet aluminium
products with
sufficient strength. In particular it has been found that the use of a
continuous furnace rather than
the normal coil annealing performed in a chamber furnace provides a further
significant increase
in formability.
According to a first configuration of the aluminium alloy strip, the aluminium
alloy also has one
or more of the following restrictions to the contents of alloying elements:
0.03 wt.% Si 5_ 0.10 wt.%,
Cu 5_ 0.1% preferably 0.04% Cu 0.08%,
Cr 0.05 wt.%,
Zn 0.05 wt.%,
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0.01 wt.% Ti 5_ 0.05 wt.%
Restricting the alloying content for copper to a maximum of 0.1 wt.% leads to
an improvement
in the corrosion resistance of the aluminium alloy strip. A Cu content of 0.04
wt.% to 0.08 wt.%
ensures that the copper contributes to an increase in strength, but that
nevertheless the corrosion
resistance is not reduced too sharply. Silicon, chromium, zinc and titanium
contents higher than
the values indicated lead to a worsening of the formability of the aluminium
alloy. The amount
of silicon present in the alloy of 0.03 to 0.1 wt.%, in combination with the
iron and manganese
components in the stated quantities, in particular leads to relatively evenly
distributed, compact
particles of the quaternary a-Al(Fe,Mn)Si-phase, increasing the strength of
the aluminium alloy,
without negatively influencing other properties such as the formability or
corrosion behaviour.
Titanium is normally added during continuous casting of the aluminium alloy as
a grain refiner,
for example in the form of titanium boride wire or rods. Therefore in a
further embodiment the
aluminium alloy has a Ti content of at least 0.01 wt.%.
A further improvement in the corrosion behaviour and the formability of the
aluminium alloy
strip can be achieved by the aluminium alloy also having one or more of the
following
restrictions to the contents of alloying elements:
Cr 0.02 wt.%,
Zn 5. 0.02 wt.%
It has been found that chromium in contents below the contamination threshold
of 0.05 wt.%
significantly influences the formability of the aluminium alloy strip and
therefore should be
contained in the smallest possible proportions in the aluminium alloy of the
aluminium alloy
strip according to the invention. The zinc content is set at below the
contamination threshold of
0.05 wt.%, in order not to impair the general corrosion behaviour of the
aluminium alloy strip.
It has furthermore been found that iron within the values permitted according
to the AA5182-
type aluminium alloy in conjunction with silicon and manganese contents as
described above has
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an effect on the formability. In combination with silicon and manganese, iron
contributes to the
thermal stability of the aluminium alloy strip, so that preferably the Fe-
content of the aluminium
alloy strip according to a next configuration is 0.1 wt.% to 0.25 wt.% or 0.10
wt.% to 0.20 wt.%.
The same also applies to the Mn content of a further configuration of the
aluminium alloy strip,
which should preferably be limited to 0.20 wt.% to 0.30 wt.%, in order to
achieve optimum
formability of the aluminium alloy strip.
An especially good compromise between the provision of high strength
properties, good
corrosion resistance to intercrystalline corrosion and improved forming
properties can be
achieved according to a further configuration of the aluminium alloy strip
with an Mg content of
4.2 wt.% to 4.4 wt.%.
In order to provide the strength properties necessary for the areas of
application, the aluminium
alloy strip according to a next embodiment has a thickness of 0.5 mm to 4 mm.
The thickness is
preferably 1 mm to 2.5 mm, since most of the areas of application of the
aluminium alloy strip
fall within this range.
Finally, in the automotive sector the aluminium alloy strip according to the
invention allows
areas of application wherein the altuninium alloy strip in the soft state has
a yield point R0.2 of at
least 110 MPa and a tensile strength R,,, of at least 255 M Pa. It has been
found that aluminium
alloy strips with such yield points and tensile strengths especially are
particularly well-suited for
use in the automotive sector.
According to a second teaching of the present invention the object shown above
is achieved by a
method for producing an aluminium alloy strip according to the embodiments
described above,
wherein the method comprises the following process steps:
- casting a rolling ingot preferably in the DC continuous casting process;
- homogenisation of the rolling ingot at 480 C to 550 C for at least 0.5
hours;
- hot rolling of the rolling ingot at a temperature of 280 C to 500 C;
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- cold rolling of the aluminium alloy strip to the final thickness with a
degree of rolling of
40% to 70% or 50% to 60%; and
- soft annealing of the finished rolled aluminium alloy strip at 300 C to
500 C in a
continuous furnace.
It has been found that with the indicated parameters in conjunction with the
stated aluminium
alloying components an aluminium alloy strip with average grain sizes of 15
lam ¨ 30 lam can be
produced, having sufficient resistance to intercrystalline corrosion,
providing sufficient strength
properties and also having very good forming properties, so that large-area,
deep-drawn sheet
metal parts can be produced. Homogenisation of the rolling ingot ensures a
homogenous
structure and a homogenous distribution of the alloying elements in the hot
rolling ingots to be
rolled. The hot rolling at temperatures of 280 C - 500 C allows
recrystallization throughout
during hot rolling, wherein the hot rolling typically is performed up to a
thickness of 2.8 mm - 8
mm. The final cold-rolling step is restricted to a degree of rolling of 40% to
70% or 50% to 60%,
in both cases in order to ensure recrystallization throughout the aluminium
alloy strip during soft
annealing. The higher the degree of rolling of the aluminium alloy strip, the
lower the average
grain sizes become, wherein it has been found that above a 70% degree of
rolling in the final soft
annealing an average grain size can result that is too low. At a degree of
rolling below 40%
during soft annealing the average grain sizes are on the other hand too large,
so that despite the
resistance to intercrystalline corrosion increasing, the formability is
nevertheless reduced. Soft
annealing of the finish-rolled aluminium alloy strip takes place in a
continuous furnace, which
will normally have a heat-up rate of 1 - 10 C/second and so unlike a chamber
furnace, in which
an entire coil is heated, because of the rapid heating will have a marked
effect on the later
properties of the structure of the aluminium alloy strip. In particular, it
has been possible to
establish that during soft annealing in the continuous furnace an improved
formability of the strip
compared to variants annealed in the chamber furnace is achieved.
Alternatively, according to a further embodiment of the method, the aluminium
alloy strip can
also be produced with an intermediate annealing. According to this alternative
variant after hot
rolling alternatively the following process steps are performed:
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cold rolling of the hot-rolled aluminium alloy strip to an intermediate
thickness which is
determined in such a way that the final degree of cold rolling to the final
thickness is 40%
to 70% or 50% to 60%;
- intermediate annealing of the aluminium alloy strip at 300 C to 500 C;
- cold rolling of the aluminium alloy strip to the final thickness with a
degree of rolling of
40% to 70% or 50% to 60%;
- soft annealing of the finish-rolled aluminium alloy strip at 300 C to 500
C in a
continuous furnace.
The intermediate annealing of the aluminium alloy strip can take place both in
the chamber
furnace and in the continuous furnace. An effect on formability could not be
determined. The
decisive factors here are the degree of rolling achieved in cold rolling to
the final thickness and if
the soft annealing of the strip takes place in the continuous furnace. This
determines the
formability and corrosion resistance in conjunction with the alloying
composition, irrespective of
the type of intermediate annealing.
In order to prevent a further change in the microstructural state in the
coiled condition following
soft annealing, the aluminium alloy strip according to a further configuration
of the method is
cooled after soft annealing to a maximum temperature of 100 C, preferably a
maximum of 70 C
and then coiled.
As already stated above, the intermediate annealing can be carried out in a
further configuration
of the method in a batch furnace or in a continuous furnace.
If the aluminium alloy strip is cold-rolled to a final thickness of 0.5 mm - 4
mm, preferably to a
final thickness of 1 mm ¨ 2.5 mm, this provides the typical areas of
application, in particular
automotive construction, with sheet metal with very good formability, and
which can be deep=
-
drawn with large surface areas and at the same time provide high strength
properties together
with sufficient corrosion resistance to intercrystalline corrosion.
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The soft annealing is preferably performed in the continuous furnace at a
metal temperature of
350 C - 550 C, preferably at 400 C - 450 C for 10 seconds to 5 minutes,
preferably 20 seconds
to 1 minute. This allows the cold rolled strip to recrystallize sufficiently
thoroughly and the
corresponding properties with regard to the very good formability and the
average grain size to
be achieved reliably and economically.
Finally, the object indicated above is achieved by a component for a motor
vehicle, composed of
the aluminium alloy strip according to the invention. The components are
characterised in that,
as already stated, they can be deep-drawn with a large surface area and
therefore for example
large-area components for automotive construction can be provided.
Furthermore, because of the
strength properties provided these also have the necessary stiffness and the
corrosion resistance
required for use in automotive construction.
It is conceivable, for example, for the component according to a further
configuration to be a
motor vehicle body part or body accessory, which apart from being subject to
high strength
requirements is also heat-stressed. Preferably, the body-in-white parts such
as an internal door
part or an internal tailgate part, are made from the aluminium alloy strip
according to the
invention.
The invention is explained in more detail below with the help of the drawing.
The drawing
shows as follows:
Fig. 1 a schematic flow diagram of an embodiment of the production method
of the
aluminium alloy strip;
Fig. 2a a top view of the specimen geometry for the plane-strain cupping
test according to
DIN EN ISO 12004;
Fig. 2b a side-view of the schematic test set-up for the plane-strain
cupping test according
to DIN EN ISO 12004;
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Fig. 3 a sectional view of the test setup for the SZ32 stretch drawing
measurements in
the Erichsen cupping test according to DIN EN ISO 20482; and
Fig. 4 a typical embodiment of a large-area, deep-drawn sheet metal part
according to
the present invention.
Fig. 1 shows the sequence of embodiments for the production of aluminium
strips. The flow
diagram of Fig. 1 is a schematic representation of the various process steps
of the production
process of the aluminium alloy strip according to the invention.
In step 1, a rolling ingot of an AlMg aluminium alloy with the following
alloying elements is
cast, for example in DC continuous casting:
Si 0.2 wt.%,
Fe 0.35 wt.%,
Cu 0.15 wt.%,
0.2 wt.% Mn 0.35 wt.%
4.1 wt.% Mg 4.5 wt.%,
Cr 0.1 wt.%,
Zn 0.25 wt.%,
Ti 0.1 wt.%,
the remainder being Al and inevitable impurities, amounting to a maximum of
0.05 wt.%
individually and a maximum of 0.15 wt.% in total.
Then the rolling ingot in process step 2 undergoes homogenisation, which can
be performed in
one or more stages. During homogenisation, temperatures of the rolling ingot
of 480 to 550 C
are reached for at least 0.5 hours. In process step 3 the rolling ingot is
then hot rolled, wherein
typically temperatures of 280 C to 500 C are reached. The final thicknesses of
the hot-rolled
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strip are for example 2.8 to 8 mm. The hot-rolled strip thickness can be
selected such that after
hot rolling only a single cold rolling step 4 takes place, in which the hot-
rolled strip, with a
degree of rolling of 40% to 70%, preferably 50% to 60%, has its thickness
reduced to the final
thickness.
Then the aluminium alloy strip that has been cold-rolled to its final
thickness undergoes soft
annealing. According to the invention the soft annealing is performed in a
continuous furnace. In
the embodiments shown in Table 1, the second route was applied with an
intermediate annealing.
For this, the hot-rolled strip after hot rolling according to process step 3
is passed for cold rolling
4a, in which the aluminium alloy strip is cold rolled to an intermediate
thickness, which is
determined in such a way that the final degree of cold rolling to the final
thickness is 40% to
70% or 50% to 60%. In a subsequent intermediate annealing the aluminium alloy
strip preferably
recrystallizes throughout. The intermediate annealing was carried out in the
embodiments either
in the continuous furnace at 400 C to 450 C or in the chamber furnace at 330 C
to 380 C.
The intermediate annealing is shown in Fig. 1 by process step 4b. In process
step 4c according to
Fig. 1 the intermediately-annealed aluminium alloy strip is finally passed for
cold rolling to the
final thickness, wherein the degree of rolling in process step 4c is between
40% and 70%,
preferably between 50% and 60%. Then the aluminium alloy strip is again
converted to the soft
state by soft annealing in step 5, wherein according to the invention the soft
annealing is carried
out in the continuous furnace at 400 C to 450 C. The annealings of the
comparative examples in
table 4 were carried out in the chamber furnace (KO) at 330 C to 380 C. During
the various
trials, apart from the different aluminium alloys various degrees of rolling
after the intermediate
annealing were set. The values for the degree of rolling after the
intermediate annealing are
likewise shown in Tables 1 and 4. The average grain size of the soft-annealed
aluminium alloy
strip was also measured. To this end, longitudinal sections were anodised
according to the Barker
method and then measured under the microscope according to ASTM E1382 and the
average
grain size determined from the average grain diameter.
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The aluminium alloy strips manufactured in this way had their mechanical
characteristics
determined, in particular the yield point R0.2, the tensile strength Rm, the
uniform elongation Ag
and the elongation at rupture Agomm, Tables 2, 5. Apart from the mechanical
characteristics of the
aluminium alloy strips measured according to EN 1 0002- 1 or ISO 6892 in
addition the average
grain sizes according to ASTM E1382 in p.m are given. Furthermore, the
corrosion resistance to
intercrystalline corrosion in accordance with ASTM G67 was measured, and in
fact without
additional heat treatment in the initial state (at Oh). In order to simulate
use in a motor vehicle,
the aluminium alloy strips, prior to the corrosion test, furthermore underwent
various heat
treatments. A first heat treatment consisted of storage of the aluminium
strips for 20 minutes at
185 C, in order to model the CDP cycle.
In a further series of measurements the aluminium alloy strips were also
stored for 200 hours or
500 hours at 80 C and then underwent the corrosion test. Since the forming of
aluminium alloy
strips or sheets can also affect the corrosion resistance, the aluminium alloy
strips were stretched
in a further trial by approximately 15%, and underwent heat treatment or
storage at raised
temperature and then a test for intercrystalline corrosion according to ASTM
G67, during which
the mass loss was measured.
Table 1 gives the alloying contents of a total of four different aluminium
alloys, which fall
within the specification of the AA5182-type aluminium alloy. The reference
alloy is constituted
by the material used to date and is shown in comparison to variants 1, 2 and
3. Table 1 also
contains details of the type of final annealing, the final degree of rolling
and the measured
average grain size (grain size diameter) in p.m. Variants 1 and 2 differ here
merely in terms of
final degree of rolling, which leads to the formation of a different grain
size. Thus variant 2
differs from variant I irrespective of the almost identical alloying elements
essentially in terms
of the final degree of rolling of 57% at identical continuous furnace
conditions. The result was
that variant 2 had an average grain size of 18 p.m compared to 33 [tm for
variant I. The strips in
Table 1 were heated in the continuous furnace for 20 seconds to I minute to a
temperature of
400 C to 450 C, then cooled and coiled at less than 100 C. The specimens taken
were then, as
indicated in Table 2, measured according to the corresponding DIN EN ISO
standards.
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It is clear from Table 2 that variant 1 in terms of the yield point does not
reliably reach the value
of 110 MPa and in the diagonal measurement, identified by the D symbol, has a
value of less
than 110 MPa. The measurement in the direction of rolling L and transversally
to the direction of
rolling Q showed, however, that variant 1 actually reached a yield point R0.2
of 110 MPa. The
reference and variants 2 and 3 were significantly above this lower limit for
the yield point. The
embodiment according to the invention in variant 2 reliably achieved the yield
point value of 110
M Pa in all tensile directions. It is clear to see that variant 3 with the
highest Mg content of 4.95
wt.% achieves the highest yield point and tensile strength figures. It can
also be seen that the
different degree of rolling between variants 1 and 2 not only markedly
influences the grain size,
but in particular raises the yield point to a value of significantly higher
than 110 MPa.
In particular the alloy according to the invention in variant 2 has a lower
anisotropy compared to
the reference, reflected in lower values of the planar anisotropy Ar. Here,
the planar anisotropy
Ar is defined as 1/2*(11 +4)-2 rD), wherein 4,, 4) and rD correspond to the r-
values in the
longitudinal, traversal and/or diagonal direction. Here, the average r-value
7, calculated from
1/4*(4 +4)+2rD), does not differ significantly from that of the reference
material.
Table 3 gives the measured values recorded in relation to the resistance to
intercrystalline
corrosion. It can be seen that variant 2 according to the invention in terms
of the measured values
of the reference, in particular in respect of the long-time stressing, has
comparable values both in
the stretched state and in the unstretched state. Here variant 2 and the
reference are almost
identical. Variant 3, which despite the having the highest yield point values
and tensile strength
values, nevertheless in the corrosion test demonstrated that an excessive Mg
content results in an
excessive mass loss, in particular in the long-time tests, which apart from a
short temperature
cycle of 20 minutes at 185 C also include long-time stressing of 200 hours at
80 C.
With regard to the measured values in Table 3 regarding the formability it can
be seen that in
particular variant 2 was superior in terms of the stretch forming properties
in the SZ32 cupping
test and in the plane-strain cupping test to the reference alloy. The clear
improvement in forming
behaviour of the aluminium alloy strip according to variant 2 compared to the
reference
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aluminium alloy strip shows that even with a reduced Mg content comparable
yield point values
and tensile strength vales could be achieved with the reference alloy, without
major losses in
resistance to intercrystalline corrosion. This was demonstrated in particular
by the mass loss
measurement performed according to ASTM G67 in the NAML test. Significantly,
with variant
2 an improvement in the deep drawing behaviour in the Erichsen cupping test by
7% and in the
plane-strain cupping tests by approximately 10% was found, demonstrating the
additional
forming potential of the aluminium alloy strip according to the invention.
This additional
forming potential can be used to produce deep-drawn, large-area sheet metal
parts, for example
internal door parts of a motor car.
A brief explanation of the test setup for the "SZ32 cupping" test according to
DIN EN ISO
20482 and the plane-strain cupping test with Nakajima geometry according to
DIN EN ISO
12004 is provided below.
Fig. 2a shows the geometry of test piece 201. From a circular sheet metal cut-
out the tapered test
piece 201 is cut such that the web 204 has a width of 100 mm and the radii 202
at the waisted
parts are 20 mm. Dimension 203, which is 100 mm, represents the diameter of
the punch. Fig. 2b
shows the test piece 201 clamped between two holders 205, 206. The test piece
201, which was
placed on a mount 208 and via the holders 205, 206 pushed against the support,
is pulled with a
punch 207, having a semi-circular tip with a radius of 100 mm, in the
direction of the arrow. The
holders also have entry radii R of 5 or 10 mm on their side facing the mount
208. The force with
which the cupping test is performed is measured during the forming and a
sudden drop in load,
signalling the formation of a crack, leads to the measurement of the
corresponding punching
depth.
The "SZ32 cupping" test according to Erichsen has a similar setup, but no
waisted test pieces are
used, however. Ilere, a test piece 309 is simply held between a holder 310 and
a support 311 and
drawn with a punch 312 until likewise a drop is measured in the load of the
drawing force. Then,
again, the corresponding position of the punch is measured. The opening of the
dies in Fig. 3 was
35.4 mm and the punch diameter 32 mm, meaning that the punch radius was 16 mm.
A Teflon
deep-drawing film was also used to reduce friction in the SZ32 deep-drawing
test.
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In Tables 4 and 5, further embodiments and comparative examples were created
and measured
according to their mechanical characteristics and their resistance to
intercrystalline corrosion. It
can be seen that the combination of using the continuous furnace and a
specifically selected grain
size of 15 pm - 30 p.m, preferably of 151.tm - 25 p.m results in a good
compromise between
corrosion resistance and mechanical measured values. Thus, for example, the
embodiments
according to the invention Nos. 3, 4, 7 and 11 have a satisfactory resistance
to intercrystalline
corrosion and also exhibit the mechanical measured values R0.2 and R,õ
necessary for use in the
automotive sector, so that these are ideal for the provision of large-area,
deep-drawn
components.
Fig. 4 shows as an example a corresponding body-in-white part in the form of
an interior part of
a door, which by using the aluminium alloy strip of the present invention can
be produced from a
single deep-drawn sheet. Here, the sheet thickness is preferably 1.0 ¨ 2.5 mm.
Furthermore, other
parts of a motor vehicle are conceivable in sheet metal shell construction,
such as the interior
parts of tailgates, bonnets, and components in the vehicle structure, which
are subject to stringent
requirements in terms of formability and intercrystalline corrosion.
'I
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Table 1
Material Si Fe Cu Mn Mg Cr Zn Ti Impurities Final
Final degree of Grain
lwt.%1 annealing
rolling(cold sizelu
rolling)
ml
min 0.20 4.0 Individually max.
. AA 5182 max. 0.20 0.35 0.15 0.50 5.0 0.10 0.25 0.10 0.05 in total max.
0.15
,
Reference 0.07 0.24 0.036 0.3 4.570.005 0.007 0.016
0.05
0.15 BDLO
46 15
Var. 1 0.06 0.16 0.004 0.27 4.37 0.008 0.002 0.013
0.05
0.15 BDLO
21 33
Var. 2 0.06 0.16 0.004 0.27 4.38 0.008 0.003 0.013
0.05
0.15 BDLO
57 18
Var. 3 0.05 0.17 0.023 0.26 4.95 0.008 0.003- 0.026
0.05
0.15 BDLO
57 17
Table 2
Test piece Pos. Rol Rm Ag Ag Ason,õ,A80,,m(Hand Z- n-
value r- Ar F
(elong) ) value value
_
N/mm N/mm % % % % %
2 2
Ref. L 137 284 21.3 20.7 24.5 25.2 69
0.316 0.827. 0.197 0.754
- T 133 276 22.i 21.4 25.2 25.8 72
0.306 0.704
D 133 277 21.9 21.6 25.5 26.3 71
0.305 0.779
Var.1 L 110 262 21.2 21.9 k 25.9 26.4
71 0.335 0.668 - 0.779
0.363
T 107 256 24.7 23.0 27.7 28.7 72
0.338 0.870
D 1 1 1 259 22.0 21.2 24.6 25.7
65 0.332 0.708
Var.2 L 128 266 23.2 22.7 26.8 27.7 67
0.332 0.724 0.035 0.693
T 127 261 23.1 22.2 26.2 27.0 67
0.332 0.685
D 128 262 23.9 22.5 26.5 27.6 66
0.333 0.681
Var.3 L 141 29024.1 23.5 28.4
29.1 70 0.335 0.697 -0.12 0.710
T 140 286 22.6 - 23.4 27.6 27.8
68 0.336 0.740
_
.
- D 141 286 22.6 23.3 27.1 27.7 65
0.335 0.663
DIN EN ISO 6892-1:2009 DIN EN ISO
DIN EN ISO 10113:2009
10275:2009
CA 02882614 2015-02-20
- 17 -
Table 3
IK-mass losses Formability
SZ32 cupping Plane-strain
Variant Not 20 min. 20 min 17h 15% 15%stretched
cupping
thermall 185 C 185 C plus 130 C stretched 20 20
min. [mm]
y treated 200 h 80 C min. 185 C 185 C plus
[mm]
200h 80 C
Limit 2.0 4.0 35.0 50.0 15.0 45.0
Reference 1.2 2.1 29.8 48.8 10.4 42.1 14.2 27.9
Var. 1.2 1.7 10.4 21.3 4.4 12.9 14.5 30.3
1(comp.)
Var. 2 1.2 2.4 33.7 42.2 13.5 40.1 14.6 30.7
(inv.)
1.3 5.3 41.7 55.0 30.4 53.5 14.6 31.6
Var. 3
(comp.)
]
CA 02882614 2015-02-20
- 18 -
,
Table 4
Alloy Degree Final Gra
No of anneali in Si Fe Cu Mn Mg Cr Zn Ti
size
rolling ng
1Ftnal
1%1
1 III 46 KO 16 0.0 0.2 0.04 0.3
4.5 0.00 0.00 0.01
7 4 0 0 0 5
7 6
3 II 57 BOLO 18 0.0 0.1 0.00 0.2
4.3 0.00 0.00 0.01
6 6 4 7 5 8
2 3
_
4 I 45 BOLO 18 0.0 0.1 0.00 0.2
4.1 0.00 0.00 0.02
3 3 2 5 5 1
4 1
6 I 45 KO 21 0.0 0.1 0.00 0.2
4.1 0.00 0.00 0.02
3 3 2 5 5 1
4 1
7 III 30 BOLO 22 0.0 0.2 0.04 0.3
4.5 0.00 0.00 0.01
7 4 0 0 o 5
7 6
1 III 25 BOLO 27 0.0 0.2 0.04 0.3 4.5 0.00 0.00 0.01
1 7 4 0 0 o 5
7 6
1 I 32 BOLO 29 0.0 0.1 0.00 0.2
4.1 0.00 0.00 0.02
3 3 3 2 5 5 1
4 1
15 III 30 KO 30 0.0 0.2 0.04 0.3 4.5 0.00 0.00 0.01
7 4 0 0 0 5
7 6
-
16 I 25 BOLO 31 0.0 0.1 0.00 0.2
4.1 0.00 0.00 0.02
3 3 2 5 5 1
4 1
1 II _ 21 BOLO 33 0.0- 0.1 0.00 0.2 4.3
0.00 0.00 0.01
8 6 6 4 7 5 8
2 3
-
20 I 20 BOLO 34 0.0 0.1 0.00 0.2
4.1 0.00 0.00 0.02
3 3 2 5 5 1
4 1
'1
CA 02882614 2015-02-20
- 19 -
Table 5
IK-mass loss, IK-mass loss, 15% Mechanical
characteristics, soft
unstretched** stretched ** state
_
20 Min. 20Min. 20 Min.
No Start 20 min. 185 C
185 C 20 Min. 185 C Result
(Oh) 185 ( 185 C R02 Rm Ag A)on,.
+ 200 h + 500 h +200h =
1 III 15.4 ' 16.6 25.7 26.9 18.8 33.6 135
279 20.7 25.2 Comparison
3 11 1.2 2.4 33.7 36.7 13.5 40.1 128 262 23.9 26.5 Invention
4 1 1.3 ' 1.9 17.8 22.2 1.6 20.1 -
117 258 22.8 25.3 Invention
6 1 8.2 10.8 18.6 22.1 9.6 20.7 106 250 23.8 26.7 Comparison
7 III 1.1 1.7 18.0 24.5 3.3 25.1 119 276
20.3 24.9 Invention
11 III 1.1 1.6 14.3 17.7 2.8 19.8 116
275 20.2 24.4 Invention
13 1 1.1 1.2 13.3 16.7 2.1 17.4 104 251
22.2 24.8 Comparison
_
15 III 2.8 3.0 7.9 10.9 6.4 18.0 125 281
19.5 23.6 Comparison
16 l' 1.1 1.3 10.8 13.1 1.9 14.2 103 252
21.6 26.1 Comparison
18 11 1.2 1.7 10.4 12.5 4.4 12.9 109 259
22.0 24.6 Comparison
20 1 1.1 1.2 8.3 11.1 1.7 12.4 101 251 20.8
25.1 Comparison
,
