EP2888382B2 - Aluminium alloy strip which is resistant to intercrystalline corrosion and method for producing same - Google Patents

Description

Description

The invention relates to an aluminum alloy strip consisting of an aluminum alloy of type AA 5xxx, which, in addition to Al and unavoidable impurities, has a Mg content of at least 4% by weight. In addition, the invention relates to a method for producing the aluminum alloy strip according to the invention and to a component produced from an aluminum alloy strip according to the invention.

Aluminum-magnesium (AlMg) alloys of type AA 5xxx are used in the form of sheets, plates or strips for the construction of welded or joined structures in shipbuilding, automobile construction and aircraft construction. They are characterized in particular by their high strength, which increases with increasing magnesium content.

For example, from the article Development of twin-belt cast AA5XXX series aluminum alloy materials for automotive sheet applications by Zhao et al., an aluminum strip consisting of an AA5182 alloy with a Mg content of 4.65 wt.%, which is suitable for use in automotive construction, is known.

Aluminium alloy strips of type AA5182 with a Mg content of at least 4 wt.% are also known from the paper Semi-Solid Processing of Alloys and Composites by Kang et al. and from the paper Comparison of recrystallization textures in cold-rolled DC and CC AA 5182 aluminum alloys by Liu et al., as well as from the US 2003/0150587 A1 The paper Hot-Tear Susceptibility of Aluminum Wrought Alloys and the Effect of Grain Refining by Lin et al. concerns round bars made of its AA5182 alloy.

The DE 102 31 437 A1 relates to corrosion-resistant aluminium alloy sheets, whereby sufficient resistance to intergranular corrosion is achieved by the addition of Zn in a content of more than 0.4 wt.%.

In addition, the publication reveals GB 2 027 621 A a process for producing an aluminum strip.

AlMg alloys of type AA 5xxx with Mg contents of more than 3%, especially more than 4%, are increasingly prone to intergranular corrosion when exposed to elevated temperatures. At temperatures of 70 - 200°C, β-Al ₅ Mg ₃ phases precipitate along the grain boundaries, which are referred to as β particles and can be selectively dissolved in the presence of a corrosive medium. This means that the aluminum alloy of type AA 5182 (Al 4.5% Mg 0.4% Mn), which has very good strength properties and very good formability, is not used in heat-stressed areas if the presence of a corrosive medium, for example water in the form of moisture, is to be expected. This particularly applies to the components of a motor vehicle, which are usually subjected to cathodic dip painting (KTL) and then dried in a baking process, since this baking process alone can cause sensitization to intergranular corrosion in conventional aluminum alloy strips. In addition, for use in the automotive sector, the deformation during the manufacture of a component and the subsequent operating load of the component must be taken into account.

Susceptibility to intergranular corrosion is usually tested in a standard test according to ASTM G67, in which the samples are exposed to nitric acid and the mass loss due to the release of β-particles is measured. According to ASTM G67, the mass loss for materials that are not resistant to intergranular corrosion is more than 15 mg/cm ² .

Corresponding materials and aluminum strips are therefore not suitable for use in heat-stressed areas.

Based on this, the present invention is based on the object of proposing an aluminum alloy strip made of an AlMg alloy which, despite high strengths and a Mg content of more than 4% by weight, is resistant to intergranular corrosion, in particular even after forming and subsequent exposure to heat. In addition, a manufacturing process is to be specified with which aluminum strips resistant to intergranular corrosion can be produced. Finally, components of a motor vehicle that are resistant to intergranular corrosion, for example body components or body attachments such as doors, hoods and tailgates or other structural parts, but also component parts made of an aluminum alloy of type AA 5xxx, are to be proposed.

und wobei die Aluminiumlegierung des Aluminiumlegierungsbandes folgende Zusammensetzung in Gew.-% aufweist:

• Si ≤ 0,2 %,
• Fe ≤ 0,35 %,
• 0,04 % ≤ Cu ≤ 0,08 %,
• 0,2 % ≤ Mn ≤ 0,5 %,
• 4,35 % ≤ Mg ≤ 4,8 %,
• Cr ≤ 0,1 %,
• Zn ≤ 0,25 %,
• Ti ≤ 0,1 %,

According to a first teaching of the present invention, the above-mentioned object is achieved by an aluminum alloy strip having a recrystallized structure, wherein the grain size (KG) of the structure in µm satisfies the following dependence on the Mg content (c_Mg) in wt.%: $$\mathrm{KG}\ge 22+2*\mathrm{c\_Mg}.$$

and wherein the aluminum alloy of the aluminum alloy strip has the following composition in wt.%:

• Si ≤ 0.2%,
• Fe ≤ 0.35%,
• 0.04% ≤ Cu ≤ 0.08%,
• 0.2% ≤ Mn ≤ 0.5%,
• 4.35% ≤ Mg ≤ 4.8%,
• Cr ≤ 0.1%,
• Zn ≤ 0.25 %,
• Ti ≤ 0.1%,

Remainder Al and unavoidable impurities individually maximum 0.05 wt.%, in total maximum 0.15 wt.%, wherein the aluminium alloy strip is cold rolled and annealed and the aluminium alloy strip has a yield strength Rp0.2 of more than 120 MPa and a tensile strength Rm of more than 260 MPa.

With a Cu content of 0.04 wt.% to 0.08 wt.%, copper contributes to an increase in strength, but does not reduce corrosion resistance too much. In addition, by limiting the Mg range to 4.35 wt.% to 4.8 wt.%, very good strength can be achieved with a moderate grain size. Resistance to intergranular corrosion can therefore also be achieved with particularly reliable processing, since the necessary grain sizes of the structure can be reliably achieved in the process.

An aluminum alloy strip with a recrystallized structure can be provided by hot strips or annealed cold strips. Extensive studies have shown that there is a relationship between grain size, magnesium content and resistance to intergranular corrosion. Since the grain size of a material is always in the form of a distribution, all information provided on grain size refers to the average grain size. The average grain size can be determined according to ASTM E1382. With a sufficiently large grain size, i.e. if the grain size is greater than or equal to the lower limit of the grain size according to the invention in relation to the Mg content of the aluminum alloy strip, resistance to intergranular corrosion can be achieved so that the mass loss in the ASTM G67 test drops to below 15 mg/cm ^2. Corresponding aluminum strips can therefore be described as resistant to intergranular corrosion. This was demonstrated for the above-mentioned aluminum strips in the undeformed state after a simulated cathodic dip-painting cycle and after a simulated cathodic dip-painting cycle including a subsequent operating load of a maximum of 500 hours at 80°C. The resistance to intergranular corrosion was also demonstrated for the above-mentioned strips when the material is stretched by 15% before the cathodic dip-painting cycle and the operating load in order to simulate the formation into a component. As a result, the aluminum alloy strip according to the invention provides high strengths and yield points due to its relatively high Mg content and is also resistant to intergranular corrosion. It is therefore very suitable for use in heat-stressed areas in automotive construction.

• mit KG in µm und c_Mg in Gew.-%,
• kann sichergestellt werden, dass die Streckgrenze R_p0,2 des Aluminiumlegierungsbandes größer als 110 MPa ist. Die Zugfestigkeit des Bandes liegt dabei üblicherweise oberhalb von 255 MPa.

According to a next embodiment of the aluminum alloy strip according to the invention, the grain size additionally satisfies the following condition: $$\mathrm{KG}<{\left(253/\left(265-50*\mathrm{<figure-callout\; id="2"\; label="c\_Mg"\; filenames="imgf0001.png"\; state="\{\{state\}\}">c\_Mg</figure-callout>}\right)\right)}^2$$

• with KG in µm and c_Mg in wt.%,
• It can be ensured that the yield strength R _p0.2 of the aluminum alloy strip is greater than 110 MPa. The tensile strength of the strip is usually above 255 MPa.

• Si ≤ 0,2 %,
• Fe ≤ 0,35 %,
• 0,04 % ≤ Cu ≤ 0,08 %,
• 0,2 % ≤ Mn ≤ 0,5 %,
• 4,45 % ≤ Mg ≤ 4,8 %,
• Cr ≤ 0,1 %,
• Zn ≤ 0,25 %,
• Ti ≤ 0,1 %,

A further advantageous embodiment of the aluminium alloy strip is achieved in that the aluminium alloy of the aluminium alloy strip has the following composition in % by weight:

• Si ≤ 0.2%,
• Fe ≤ 0.35%,
• 0.04% ≤ Cu ≤ 0.08%,
• 0.2% ≤ Mn ≤ 0.5%,
• 4.45% ≤ Mg ≤ 4.8%,
• Cr ≤ 0.1%,
• Zn ≤ 0.25 %,
• Ti ≤ 0.1%,

The remainder Al and unavoidable impurities individually maximum 0.05 wt.%, in total maximum 0.15 wt.%. By limiting the Mg range to 4.45 wt.% to 4.8 wt.%, a very good strength is also achieved. with moderate grain size.

According to a further embodiment of the aluminum alloy strip according to the invention, the maximum grain size is 50 µm, since the process reliability decreases when producing aluminum strips with grain sizes of more than 50 µm from an aluminum alloy of type AA 5xxx with a Mg content of at least 4% by weight. A maximum grain size of 50 µm, on the other hand, can be achieved with process stability. The process stability for producing structures with controlled grain size increases with decreasing grain size. The production of an aluminum alloy strip with a maximum grain size of 45 µm, preferably a maximum of 40 µm, is therefore associated with increasing process stability.

According to a further embodiment of the aluminum alloy strip according to the invention, it has a thickness of 0.5 mm - 5 mm and is therefore ideally suited for most applications, for example in automobile construction.

The aluminum alloy strip according to the invention is cold rolled and then soft annealed. Recrystallizing soft annealing usually takes place at temperatures of 300°C - 500°C and makes it possible to eliminate the hardening introduced during the rolling process and to ensure good formability of the aluminum alloy strip. In addition, cold rolled, soft annealed and therefore recrystallized strips can be used to provide lower final thicknesses than recrystallized hot strips.

Finally, the aluminum alloy strip according to the invention has a yield strength R _p0.2 of more than 120 MPa and a tensile strength R _m of more than 260 MPa. The aluminum alloy strip according to the invention, which is resistant to intergranular corrosion, thus also exceeds the strength properties of an aluminum alloy of type AA5182 required by DIN485-2. The elongation values with a uniform elongation A _g of at least 19% and an elongation at break A _80mm of at least 22% also far exceed the values required by DIN485-2.

• Gießen eines Walzbarrens bestehend aus einer erfindungsgemäßen Aluminiumlegierungszusammensetzung,
• Homogenisieren des Walzbarrens bei 480 °C bis 550 °C für mindestens 0,5 h,
• Warmwalzen des Walzbarrens bei einer Temperatur von 280 °C bis 500 °C,
• Kaltwalzen des Aluminiumlegierungsbandes an Enddicke mit einem Abwalzgrad von weniger als 40%, bevorzugt maximal 30 %, besonders bevorzugt maximal 25%,
• Weichglühen des fertig gewalzten Aluminiumlegierungsbandes bei 300 °C bis 500 °C.

According to a second teaching of the present invention, the above-mentioned object is achieved by a method for producing an aluminum alloy strip comprising the following method steps:

• Casting a rolling ingot consisting of an aluminum alloy composition according to the invention,
• Homogenizing the rolling ingot at 480 °C to 550 °C for at least 0.5 h,
• Hot rolling of the rolling ingot at a temperature of 280 °C to 500 °C,
• Cold rolling of the aluminium alloy strip to final thickness with a rolling degree of less than 40%, preferably a maximum of 30%, particularly preferably a maximum of 25%,
• Annealing of the finished rolled aluminium alloy strip at 300 °C to 500 °C.

The process steps listed result in a grain size after annealing that satisfies the dependency on the Mg content listed above, due to the low degree of rolling during cold rolling of the aluminum alloy strip to the final thickness. The degree of rolling to the final thickness is used to set the hardening of the strip before annealing, which determines the resulting grain size. As the degree of rolling decreases from less than 40%, to a maximum of 30% and a maximum of 25%, different grain sizes are set, which can be adjusted to the alloy composition. In this respect, an aluminum alloy strip can be produced that is resistant to intergranular corrosion.

• Kaltwalzen des warmgewalzten Aluminiumlegierungsbandes mit einem Abwalzgrad von mindestens 30 %, vorzugsweise mindestens 50 %,
• Zwischenglühen des Aluminiumlegierungsbandes bei 300 °C bis 500 °C,
• anschließendes Kaltwalzen an Enddicke mit einem Abwalzgrad von weniger als 40%, bevorzugt maximal 30 %, besonders bevorzugt maximal 25%,
• Weichglühen des fertig gewalzten Aluminiumlegierungsbandes bei 300 °C bis 500 °C.

According to a further embodiment of the method according to the invention, the following process steps are alternatively carried out after hot rolling:

• Cold rolling of the hot-rolled aluminium alloy strip with a rolling degree of at least 30%, preferably at least 50%,
• Intermediate annealing of the aluminium alloy strip at 300 °C to 500 °C,
• subsequent cold rolling to final thickness with a rolling degree of less than 40%, preferably a maximum of 30%, particularly preferably a maximum of 25%,
• Annealing of the finished rolled aluminium alloy strip at 300 °C to 500 °C.

Both of the above-mentioned processes have in common that the degree of rolling before annealing, i.e. the degree of rolling of the final thickness during cold rolling, is limited to less than 40%, preferably a maximum of 30%, particularly preferably a maximum of 25%. In the second embodiment of the process according to the invention, an additional cold rolling step takes place after an intermediate annealing at 300°C - 500°C. During the intermediate annealing, the aluminum alloy strip, which has been strongly hardened by cold rolling, is recrystallized and converted back into a formable state. The subsequent cold rolling step with a degree of rolling of less than 40%, preferably a maximum of 30%, particularly preferably a maximum of 25%, means that, in conjunction with the Mg content of the aluminum alloy used, the grain size can be adjusted to the required ratio. As a result, in the annealed state A strip can be produced which is both resistant to intergranular corrosion and has the necessary forming and strength properties.

According to a further embodiment of the method according to the invention, the soft annealing and/or the intermediate annealings take place in a batch furnace, in particular a chamber furnace, or a continuous furnace. Both furnaces provide a sufficiently coarse grain structure, which ensures resistance to intergranular corrosion. Batch furnaces are usually not as expensive to operate and purchase as continuous furnaces.

According to a third teaching of the present invention, the above-mentioned object is achieved by a component for a motor vehicle which consists at least partially of an aluminum alloy strip according to the invention. The component is usually subjected to painting, preferably cathodic dip painting. Nevertheless, there are also possible uses for unpainted components made from the aluminum alloy strip according to the invention.

As already stated above, the aluminum alloy strip has excellent properties in terms of strength, forming properties and resistance to intergranular corrosion, so that the heat load during painting, a baking process that typically takes 20 minutes at around 185°C, has little influence on the resistance of the component to intergranular corrosion. Forming into a component, which was simulated by stretching by 15% transverse to the original rolling direction, also has only a minor influence on the resistance to intergranular corrosion. Even after 15% stretching, the values for the mass loss according to ASTM G67 are less than 15 mg/cm ² . Furthermore, operation in temperature-stressed areas, which was simulated by a heat load of 200 or 500 hours at 80°C, only has a minor influence on the resistance to intergranular corrosion. The mass loss values according to ASTM G67 are less than 15 mg/cm ² even after corresponding temperature stress.

A component is particularly advantageous if it is designed as a body or body attachment part of a motor vehicle. Typical body parts are the fender or parts of the floor assembly, the roof, etc. Body attachment parts are generally doors and tailgates, etc. that are not firmly connected to the motor vehicle. Invisible body components or body attachment parts are preferably made from the aluminum alloy strip according to the invention. These are, for example, inner door parts or inner parts of tailgates, but also floor panels, etc. A typical heat load for such components of a motor vehicle, for example inner door parts, is caused, for example, by sunlight during operation of a motor vehicle. In addition, body or body attachment parts of a motor vehicle are generally exposed to moisture, for example in the form of splash water or condensation, so that resistance to intergranular corrosion must be required. The body or body attachment parts according to the invention, made from an aluminum alloy strip according to the present invention, meet these conditions and also ensure a weight advantage over the steel structures used to date.

Fig. 1

ein schematisches Ablaufschema für ein Ausführungsbeispiele eines Herstellverfahrens,

Fig. 2

in einem Diagramm die Korngröße in Abhängigkeit vom Magnesiumgehalt der Ausführungsbeispiele und

Fig. 3

ein Bauteil für ein Kraftfahrzeug gemäß einem weiteren Ausführungsbeispiel.

The invention will now be explained in more detail using embodiments in conjunction with the drawing. The drawing shows in

Fig. 1

a schematic flow chart for an embodiment of a manufacturing process,

Fig. 2

in a diagram the grain size depending on the magnesium content of the embodiments and

Fig. 3

a component for a motor vehicle according to a further embodiment.

Extensive tests were carried out to investigate whether there is a relationship between the grain size of an aluminum alloy strip made from an aluminum alloy of type AA 5xxx and the Mg content in relation to resistance to intergranular corrosion. For this purpose, various aluminum alloys were used and different process parameters applied. Table 1 shows the various alloy compositions used to investigate the relationship between grain size, resistance to intergranular corrosion and yield strength. In addition to the contents of the alloying elements Si, Fe, Cu, Mn, Mg, Cr, Zn and Ti in wt.%, the aluminum alloys listed in Table 1 contain aluminum as the remainder and impurities individually up to a maximum of 0.05 wt.% and in total up to a maximum of 0.15 wt.%.

Since the final annealing and the final rolling degree in particular have an influence on the grain size, these were varied or measured in the respective tests. The grain size varied, for example, from 16 µm to 61 µm, the final rolling degree from 17% to 57%. The final annealing was carried out either in a chamber furnace (KO) or in a continuous strip furnace (BDLO).

Fig. 1 shows the sequence of examples for the production of aluminum strips. The flow chart of Fig.1 shows schematically the various process steps of the manufacturing process of the aluminum alloy strip according to the invention.

In step 1, a rolling ingot made of an aluminum alloy of type AA 5xxx with a Mg content of at least 4 wt.% is cast, for example in DC continuous casting. The rolling ingot is then subjected to homogenization in process step 2, which can be carried out in one or more stages. During homogenization, temperatures of the rolling ingot of 480 to 550 °C are reached for at least 0.5 h. In process step 3, the rolling ingot is then hot rolled, with typical temperatures of 280 °C to 500 °C being reached. The final thicknesses of the hot strip are, for example, 2 to 12 mm. The final hot strip thickness can be selected so that after hot rolling only a single cold rolling step 4 takes place, in which the hot strip is reduced in thickness with a rolling degree of less than 40%, preferably a maximum of 30%, particularly preferably a maximum of 25%.

The aluminium alloy strip, cold rolled to final thickness, is then subjected to soft annealing. The soft annealing was carried out in a continuous furnace or in a chamber furnace in order to determine the dependence of the To test corrosion properties of the chamber or continuous furnace. In the embodiments shown in Table 1, the second method with an intermediate annealing was used. For this, after hot rolling according to process step 3, the hot strip is fed to a cold roller 4a, which has a rolling degree of more than 30% or more than 50%, so that the aluminum alloy strip preferably recrystallizes throughout during a subsequent intermediate annealing. In the embodiments, the intermediate annealing was carried out either in a continuous furnace at 400 °C to 450 °C or in a chamber furnace at 330 °C to 380 °C.

The intermediate annealing is in Fig. 1 with the process step 4b. In process step 4c according to Fig. 1 the intermediately annealed aluminum alloy strip is finally fed to a cold rolling process to the final thickness, with the degree of rolling in process step 4c being less than 40%, preferably a maximum of 30%, particularly preferably a maximum of 25%. The aluminum alloy strip is then returned to the soft state by soft annealing, with the soft annealing being carried out either in a continuous furnace at 400 °C to 450 °C or in a chamber furnace at 330 °C to 380 °C. In the various tests, different aluminum alloys and different degrees of rolling after the intermediate annealing were set in addition to different ones. The values for the degree of rolling after the intermediate annealing are also shown in Table 1. In addition, the grain size of the annealed aluminum alloy strip was measured in each case.

Mechanical parameters, in particular the yield strength R _p0.2 , tensile strength R _m , the uniform elongation A _g and the elongation A _80mm , were determined on the aluminum alloy strips produced in this way. In addition, the corrosion resistance to intergranular corrosion was measured in accordance with ASTM G67, without additional heat treatment in the initial state (output 0h). In addition to the mechanical parameters of the aluminum alloy strips measured in accordance with EN 10002-1 and ISO 6892, the calculated grain sizes are shown in Table 2 as column KG(IK) and column KG(Rp) according to the formulas (1) set out below for resistance to intergranular corrosion and formula (2) for achieving the necessary mechanical properties, in particular a sufficiently high yield strength. The grain sizes were determined in accordance with ASTM E1382 and are given in µm.

In order to simulate use in motor vehicles, the aluminum alloy strips were also subjected to various heat treatments before the corrosion test. A first heat treatment consisted of storing the aluminum strips for 20 minutes at 185 °C to simulate the KTL cycle. In a further series of measurements, the aluminum alloy strips were stored for an additional 200 hours or 500 hours at 80 °C and then subjected to the corrosion test. Since forming of aluminum alloy strips or sheets can also influence corrosion resistance, the aluminum alloy strips were stretched by around 15% in a further test, subjected to heat treatment or storage at an elevated temperature and then subjected to an intergranular corrosion test in accordance with ASTM G67, in which the mass loss was measured.

It was found that there is a close relationship between grain size, Mg content and resistance to intergranular corrosion. The examples 11 to 19 can all be classified as resistant to intergranular corrosion. This also applies to their use in motor vehicles with thermal stress and the presence of moisture or a corrosive medium. In addition, examples 12, 14, 16 and 17 showed the mechanical properties of an aluminum alloy strip of type AA 5182 required by DIN EN 485-2.

mit c_Mg als Mg-Gehalt in Gew.-%.In Fig. 2 The diagram shows the measured grain sizes as a function of the Mg content in wt.%. In addition to the measuring points, the diagram also contains two curves A and B. The straight line A shows the grain sizes above which the aluminum alloy strip can be described as resistant to intergranular corrosion at a specific Mg content. The corresponding grain size (KG) is calculated from the following equation: $$\mathrm{KG}=22+2*\mathrm{c\_Mg},$$

with c_Mg as Mg content in wt.%.

Curve B, on the other hand, shows the limit from which the aluminium alloy strips have a yield strength that is too low, less than 110 MPa, so that they cannot be considered alloy AA 5182 according to DIN EN485-2. Curve B is determined by the following equation: $$\mathit{KG}={\left(\frac{253}{265-50*c\_\mathit{<figure-callout\; id="2"\; label="Mg"\; filenames="imgf0001.png"\; state="\{\{state\}\}">Mg</figure-callout>}}\right)}^2$$

All examples to the right of curve B therefore meet the requirement of a yield strength of more than 110 MPa.

Finally, Fig. 3 a typical component of a motor vehicle, shown schematically in the form of an inner door part. Inner door parts 6 are usually made of steel. However, the aluminum alloy strips produced show that the provision of high strengths with resistance to intergranular corrosion can also be achieved, provided that the grain size ratio in relation to the Mg content is adjusted according to the invention. The component according to the invention according to Fig. 3 is significantly lighter than a comparable component made of steel and is nevertheless resistant to intergranular corrosion.

patent claims

Claims (10)

1. Aluminium alloy strip composed of an AA 5 xxx -type aluminium alloy, which apart from Al and inevitable impurities has an Mg content of at least 4 wt.%, characterised in that the aluminium alloy strip has a recrystallized microstructure, wherein the grain size (GS) of the microstructure satisfies the following dependency on the Mg content (c_Mg) in wt.%: $$\mathrm{GS}>22+2*\mathrm{c\_Mg}.$$

   

   and in that the aluminium alloy of the aluminium alloy strip has the following composition in wt.%: Si ≤ 0.2%, Fe ≤ 0.35%, 0.04% ≤ Cu ≤ 0.08%, 0.2% ≤ Mn ≤ 0.5%. 4.35% ≤ Mg ≤ 4.8%, Cr ≤ 0.1%, Zn ≤ 0.25%, Ti ≤ 0.1%,

   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, whereas the aluminium alloy strip is cold rolled and soft annealed and the aluminium alloy strip has a yield point R_p0.2 of greater than 120 MPa and a tensile strength R_m of greater than 260 MPa.
2. Aluminium alloy strip according to Claim 1, characterised in that the grain size (GS) of the microstructure of the aluminium alloy strip also satisfies the following dependency on the Mg content (c_Mg) in wt.%: $$\mathit{GS}<{\left(\frac{253}{265-50*c\_\mathit{Mg}}\right)}^2$$

   
3. Aluminium alloy strip according to any one of Claims 1 or 2, characterised in that the aluminium alloy of the aluminium alloy strip has 4.45% ≤ Mg ≤ 4.8%.
4. Aluminium alloy strip according to any one of Claims 1 to 3, characterised in that the grain size is a maximum of 50 µm, preferably a maximum of 40 µm.
5. Aluminium alloy strip according to any one of Claims 1 to 4, characterised in that the aluminium alloy strip has a thickness of 0.5 mm to 5 mm.
6. Method for producing an aluminium alloy strip according to any one of Claims 1 to 5 comprising the following process steps:

   - casting a rolling ingot;

   - 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

   - cold rolling of the aluminium alloy strip to the final thickness with a degree of rolling of less than 40%, preferably a maximum of 30%, particularly preferably a maximum of 25%;

   - soft-annealing of the finished-rolled aluminium alloy strip at 300°C to 500°C..
7. Method according to Claim 6, wherein after the hot rolling alternatively the following process steps are carried out:

   - cold rolling of the hot-rolled aluminium alloy strip with a degree of rolling of at least 30%, preferably at least 50%;

   - intermediate annealing of the aluminium alloy strip at between 300°C and 500°C;

   - subsequent cold rolling to the final thickness with a degree of rolling of less than 40%, preferably a maximum of 30%, particularly preferably a maximum of 25%;

   - soft annealing of the finish-rolled aluminium alloy strip at between 300°C and 500°C.
8. Method according to Claim 6 or 7, characterised in that the intermediate annealing and/or the soft annealing is/are carried out in a batch furnace or a continuous furnace.
9. Component for a motor vehicle at least partially composed of an aluminium alloy strip according to any one of Claims 1 to 5.
10. Component according to Claim 9, characterised in that the component is a body part or a body accessory of a motor vehicle.

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