EP3178952B1 - High plasticity moderate strength aluminium alloy for manufacturing semi-finished products or components of motor vehicles - Google Patents

Description

The invention relates to an aluminum alloy for the production of semi-finished products or components of motor vehicles and a structural part of a motor vehicle consisting of an aluminum alloy sheet.

Semi-finished products and components for motor vehicles must meet different requirements depending on their location and purpose in the motor vehicle. During the manufacture of semi-finished products and components for motor vehicles, the forming properties of the aluminum alloy or the strips and sheets made from it are crucial. When used later in a motor vehicle, the strength values also play a significant role, particularly the corrosion properties.

For example, in the case of structural parts of a motor vehicle, such as interior door parts, the mechanical properties are primarily determined by the rigidity, which primarily depends on the shape of the interior door parts. In contrast, tensile strength, for example, has a rather minor influence. However, the materials used for an inner door part must not be too soft. Good formability, on the other hand, is particularly important for the introduction of aluminum alloy materials into the automotive sector, since the components and semi-finished products go through particularly complex forming processes during their manufacture. This applies in particular to components that are manufactured in a one-piece sheet metal shell construction, such as, for. B. Sheet metal interior door parts with integrated window frame area. By saving on joining operations, such components have considerable cost advantages compared to an aluminum profile solution for the window frame, which is joined, for example. The aim, for example, is to be able to manufacture semi-finished products or components in one piece from an aluminum alloy while using as few forming operations as possible. This requires maximization the forming behavior of the aluminum alloy to be used. The aluminum alloy of type AA5005 (AlMg1), which is occasionally used for similar applications, does not meet these requirements because it does not have sufficient formability due to hardening during forming.

Corrosion resistance also plays an important role, since components of motor vehicles are often exposed to condensation, water spray and condensation. The aluminum alloy to be used should therefore be as corrosion-resistant as possible, especially in the painted state against intergranular corrosion and against filiform corrosion. Filiform corrosion is understood to mean a type of corrosion that occurs in coated components and shows a thread-like course. Filiform corrosion occurs in high humidity in the presence of chloride ions. The aluminum alloy of type AA8006 (AlFe1.5Mn 0.5) has sufficient strength and very high formability, but is susceptible to filiform corrosion. The AA8006 alloy is therefore less suitable for coated, in particular painted, components such as interior door parts.

• Fe ≤ 0,8 %,
• Si ≤ 0,5 %,
• 0,9 % ≤ Mn ≤ 1,5 %,
• Mg ≤ 0,25 %,
• Cu ≤ 0,20 %,
• Cr ≤ 0,05 %,
• Ti ≤ 0,05 %,
• V ≤ 0,05 %,
• Zr ≤ 0,05 %,

From the applicant's previously unpublished international patent application PCT / EP2014 / 053323 an aluminum alloy is known as an alternative to the aluminum alloy of type AA8006, which has the following alloy components in% by weight:

• Fe ≤ 0.8%,
• Si ≤ 0.5%,
• 0.9% ≤ Mn ≤ 1.5%,
• Mg ≤ 0.25%,
• Cu ≤ 0.20%,
• Cr ≤ 0.05%,
• Ti ≤ 0.05%,
• V ≤ 0.05%,
• Zr ≤ 0.05%,

Rest of aluminum, unavoidable accompanying elements individually <0.05%, in total <0.15%, whereby the sum of the Mg and Cu contents fulfills the following relation:
0.15% ≤ Mg + Cu ≤ 0.25%.

It has been shown that this aluminum alloy is also in need of improvement, particularly with regard to its forming behavior. In addition, the high Mn content can lead to problems when recycling this aluminum alloy if it is mixed in the scrap cycle with the Al-Mg-Si alloys of the alloy type AA6XXX commonly used in automotive applications.

From the JP 2006-152358 A an aluminum alloy for the manufacture of beverage cans is known, which shows good formability and strength for beverage cans.

Starting from this prior art, the present invention is therefore based on the object of providing an aluminum alloy for the production of semi-finished products or components for motor vehicles which is highly malleable, medium-strength and very corrosion-resistant. In addition, a structural part of a motor vehicle is to be proposed.

• 0,6 % ≤ Si ≤ 0,9 %,
• 0,6 % ≤ Fe ≤ 1,0 %,
  Cu ≤ 0,1 %,
• 0,6 % ≤ Mn ≤ 0,9 %,
• 0,5 % ≤ Mg ≤ 0,8 %,
  Cr ≤ 0,05 %,

According to a first teaching of the present invention, the object shown above is achieved by an aluminum alloy for the production of semi-finished products or components of motor vehicles, which has the following alloy components in% by weight:

• 0.6% ≤ Si ≤ 0.9%,
• 0.6% ≤ Fe ≤ 1.0%,
  Cu ≤ 0.1%,
• 0.6% ≤ Mn ≤ 0.9%,
• 0.5% ≤ Mg ≤ 0.8%,
  Cr ≤ 0.05%,

Remainder Al and impurities, individually a maximum of 0.05% by weight, in total a maximum of 0.15% by weight.

In contrast to previous approaches, the present aluminum alloy is based on the knowledge that Al-Mg-Si alloys of the alloy type AA6XXX have a very good formability in a soft-annealed condition. However, they were too soft for the previous applications. The lower limits of the compulsory alloy elements of 0.6% by weight for Si, 0.6% by weight for Fe, 0.6% by weight for Mn and 0.5% by weight for Mg ensure that the Aluminum alloy in soft annealed condition can provide sufficient strength. The upper limits of 0.9% by weight for Si, 1.0% by weight for Fe, 0.9% by weight for Mn and 0.8% by weight for Mg prevent the elongation at break from decreasing and thus the forming behavior is deteriorated. For the same reason, the alloying elements Cu are limited to a maximum of 0.1% by weight and Cr to a maximum of 0.05% by weight. The combination of the proposed alloy constituents of Si, Fe, Mg and Mn ensures that on the one hand the very good forming behavior of the Al-Mg-Si alloys is combined with increased strength without having too great a loss in ductility. The investigations showed that the aluminum alloy specified in the soft-annealed condition meets the requirements for formability and in particular corrosion resistance and is therefore suitable for the production of semi-finished products or components in motor vehicles. With the mentioned ranges of the compulsory alloy elements Si, Fe, Mn and Mg, the aluminum alloy according to the invention falls into the class of Al-Mg-Si alloys of the alloy type AA6XXX. This enables an improved recyclability of this aluminum alloy if it is mixed in the scrap cycle with the Al-Mg-Si alloys of the alloy type AA6XXX commonly used in automotive applications.

• 0,7 % ≤ Si ≤ 0,9 %,
• 0,7 % ≤ Fe ≤ 1,0 %,
• 0,7 % ≤ Mn ≤ 0,9 % und
• 0,6 % ≤ Mg ≤ 0,8 %.

According to a first embodiment of the aluminum alloy according to the invention, the alloy components Si, Fe, Mn and Mg have the following proportions in% by weight:

• 0.7% ≤ Si ≤ 0.9%,
• 0.7% ≤ Fe ≤ 1.0%,
• 0.7% ≤ Mn ≤ 0.9% and
• 0.6% ≤ Mg ≤ 0.8%.

By raising the lower limits for Si, Fe, Mn and Mg it is achieved that the strength of the aluminum alloy increases even further without deteriorating the forming behavior or the elongation at break of the soft sheets or strips made of aluminum alloy.

• 0,7 % ≤ Si ≤ 0,8 %,
• 0,7 % ≤ Fe ≤ 0,8 %,
• 0,7 % ≤ Mn ≤ 0,8 % und
• 0,6 % ≤ Mg ≤ 0,7 %.

A further improvement of the aluminum alloy according to the invention with regard to a maximum elongation at break is achieved in that the alloy components Si, Fe, Mn and Mg have the following proportions in% by weight:

• 0.7% ≤ Si ≤ 0.8%,
• 0.7% ≤ Fe ≤ 0.8%,
• 0.7% ≤ Mn ≤ 0.8% and
• 0.6% ≤ Mg ≤ 0.7%.

It has been found that this narrow corridor of constrained contents with regard to the alloy components Si, Fe, Mn and Mg is a very good compromise between the strength achieved and the elongation at break properties, i. H. Forming properties of the aluminum alloy is achieved.

Although the aluminum alloy according to the invention has good corrosion properties, the resistance to intergranular corrosion can be further improved in accordance with a further embodiment of the aluminum alloy in that the Si content of the alloy exceeds the Mg content by a maximum of 0.2% by weight, preferably a maximum of 0.1% by weight.

According to a further embodiment of the aluminum alloy according to the invention, the elongation at break of the aluminum alloy can be further improved by further reducing the Cr content to a value of at most 0.01% by weight, preferably to a maximum of 0.001% by weight. It has been shown that chromium has a negative effect on the elongation at break properties even in very low concentrations.

The reduction of the Cu contents to a maximum of 0.05% by weight, preferably a maximum of 0.01% by weight, also has a similar effect, with the tendency towards filiform corrosion or intergranular corrosion due to the reduction of the Cu contents generally declines.

• Gießen eines Walzbarrens,
• Homogenisieren bei einer Temperatur zwischen 500°C und 600°C für mindestens 0,5 h
• Warmwalzen des Walzbarrens bei Temperaturen von 280°C bis 500° C, vorzugsweise bei Temperaturen von 300°C bis 400°C auf eine Dicke von 3 mm bis 12 mm,
• Kaltwalzen mit oder ohne Zwischenglühung mit einem Abwalzgrad von mindestens 50%, bevorzugt mindestens 70% auf eine Enddicke von 0,2 mm bis 5 mm und
• Schlussweichglühung bei 300°C bis 400°C, bevorzugt 330°C bis 370°C für mindestens 0,5 h, vorzugsweise mindestens 2 h in einem Kammerofen.

A method for producing a strip from an aluminum alloy according to the invention has the following method steps:

• Casting a billet,
• Homogenize at a temperature between 500 ° C and 600 ° C for at least 0.5 h
• Hot rolling the billet at temperatures from 280 ° C to 500 ° C, preferably at temperatures from 300 ° C to 400 ° C to a thickness of 3 mm to 12 mm,
• Cold rolling with or without intermediate annealing with a rolling degree of at least 50%, preferably at least 70% to a final thickness of 0.2 mm to 5 mm and
• Final soft annealing at 300 ° C to 400 ° C, preferably 330 ° C to 370 ° C for at least 0.5 h, preferably at least 2 h in a chamber furnace.

After casting, the homogenization at a temperature of 500 ° C. to 600 ° C. for at least 0.5 h, preferably at least 2 h, ensures that a homogeneous structure the further processing of the billet is provided. The hot rolling temperatures enable good recrystallization during hot rolling, so that the structure after the hot rolling is as fine-grained as possible. This fine-grain structure is only stretched by cold rolling and recrystallized again in the final soft annealing. In the case of production without intermediate annealing, a particularly high number of dislocations are created in the structure by cold rolling, which produces a very fine-grained, fully recrystallized structure in the final soft annealing. For this purpose, the degree of rolling of the final thickness before the final soft annealing must have at least 50%, preferably at least 70%, of the desired final thickness.

A further positive influence on the fine grain of the structure can be achieved in that, according to a further embodiment of the method, the homogenization is carried out in two stages, the rolled ingot first being heated to 550 ° C to 600 ° C for at least 0.5 h and then the rolled ingot at 450 ° C to 550 ° for at least 0.5 h, preferably at least 2 h. The ingot is then hot rolled.

The corrosion properties can be improved by milling the ingot after casting or after homogenizing on the top and bottom in order to exclude contaminants from the top and bottom of the ingot, which can negatively influence the corrosion resistance.

According to a further embodiment of the method, at least one intermediate annealing is carried out after a first cold rolling at a temperature of 300 ° C. to 400 ° C., preferably at a temperature of 330 ° C. to 370 ° C., for at least 0.5 h, before and after the intermediate annealing the rolling degree is at least 50%, preferably at least 70%. The degree of rolling selected before the intermediate annealing or after the intermediate annealing ensures that the structure recrystallizes sufficiently during the intermediate annealing. The intermediate annealing time is at least 0.5 h, preferably at least 2 h.

If the intermediate annealing takes place at a temperature of 330 ° C to 370 ° C, it is ensured that due to the raised lower temperature of 330 ° C there is sufficient recrystallization and at the same time an efficient intermediate annealing is carried out by reducing the upper limit, which uses as little thermal energy as possible needed.

An aluminum alloy strip or sheet can be produced from an aluminum alloy according to the invention, the strip having a thickness of 0.2 mm to 5 mm and, in the soft-annealed state, a yield strength R _p0.2 of at least 45 MPa and a uniform elongation A _g of at least 23% and has an elongation at break A _80mm of at least 35%. In particular, given the thickness of the strip in conjunction with the alloy composition and the resulting mechanical properties in the soft-annealed condition, the prerequisites exist that the aluminum alloy strip or sheet can be used for components in the motor vehicle, which, in addition to very good forming properties, also has a very good one Resistance to intergranular corrosion or filiform corrosion. This also applies in particular to painted or coated components.

In this respect, the use of the aluminum alloy strip for producing semi-finished products or components of a motor vehicle, in particular structural parts of a motor vehicle, also achieves the above-mentioned object. Structural parts in particular can be produced with very large degrees of forming and can take on very complex shapes without requiring particularly complicated forming operations. In particular, they are also particularly corrosion-resistant in lacquered form, in particular against intergranular corrosion and filiform corrosion.

According to a further teaching of the present invention, the stated object is achieved by a structural part of a motor vehicle, in particular a door inner part of a motor vehicle, having at least one formed sheet from one solved aluminum alloy according to the invention. As already stated above, the investigations have shown that the aluminum alloy according to the invention not only provides the necessary forming properties in a soft-annealed state, but also simultaneously guarantees the necessary corrosion resistance and strength of the structural parts.

In order to achieve the optimum degrees of deformation, the structural part according to the invention is produced from a strip which has been produced using the method described. It has been shown that the process enables the forming properties and also the strength properties of the structural part to be achieved in a process-reliable manner, so that economical production of the structural parts which meet the stated requirements is possible.

• Fig. 1 ein Ablaufdiagramm eines ersten Ausführungsbeispiels des Verfahrens zur Herstellung eines Aluminiumlegierungsbandes,
• Fig. 2 ein Ablaufdiagramm für ein weiteres Ausführungsbeispiel des Verfahrens und
• Fig. 3 ein schematisch dargestelltes Ausführungsbeispiel eines Strukturteils eines Kraftfahrzeugs.

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

• Fig. 1 1 shows a flowchart of a first exemplary embodiment of the method for producing an aluminum alloy strip,
• Fig. 2 a flowchart for a further embodiment of the method and
• Fig. 3 a schematically illustrated embodiment of a structural part of a motor vehicle.

A first exemplary embodiment in a schematic flow chart now shows Fig. 1 . In a first step 2, the billet is cast, for example in the DC continuous casting process or in the strip casting process. In process step 4, the ingot is then heated to a temperature of 500 ° C. to 600 ° C. and kept at this temperature for homogenization for at least 0.5 h, preferably at least 2 h. The rolled bar is then homogenized at a temperature of 280 ° C to 500 ° C, preferably 300 ° C to 400 ° G hot rolled to a final thickness of 3 to 12 mm. This is followed in step 8 by cold rolling to final thickness, which is followed by a recrystallizing final soft annealing in accordance with step 10. When cold rolling to the final thickness in one or more passes, the degree of rolling must be at least 50%, preferably at least 70%, in order to produce a sufficiently fine-grained structure in the final soft annealing. The final soft annealing, in which the strip recrystallizes again, takes place in the chamber furnace at 300 ° C. to 400 ° C., preferably at 330 ° C. to 370 ° C. in step 10. Despite the alloy components of Mg, Si, Fe and Mn according to the invention, the use is a continuous furnace for the production of the aluminum alloy strip is not possible because different structures would be provided due to the different heating and cooling speeds.

As an alternative to manufacturing the aluminum alloy strip without intermediate annealing, intermediate annealing can also be carried out in a chamber furnace at 300 ° C to 400 ° C, preferably at 330 ° C to 370 ° C according to step 14, with a rolling degree of both before the intermediate annealing and after the intermediate annealing at least 50%, preferably at least 70%, should be ensured in order to positively influence the fine grain structure of the structure after the recrystallizing final soft annealing. Optionally, after the casting of the billet in step 2, milling according to step 12 of the top and bottom of the billet can be carried out in order to minimize the influence of impurities on the edges of the billets during the manufacture of the billets on the finished product. In particular, this has a positive influence on the corrosion resistance of the components.

Fig. 2 now shows a further flow chart, which shows step 16 of the homogenization as an alternative to step 4. The homogenization has an influence on the fine grain of the desired final structure of the strip or finished component. In order to further improve the fine grain of the structure, the homogenization is carried out in several stages. So instead of step 4 in Fig. 1 in Fig. 2 a homogenization step 16 is carried out. The homogenization step 16 initially has a first homogenization phase, step 18, in which the milled one or unmilled rolled ingot is heated to a temperature of 550 ° C to 600 ° C for at least 0.5 h, preferably at least 2 h. In a next step 20, the roll bar heated in this way is cooled to a temperature of 450 ° C. to 550 ° C. and kept at this temperature for at least 0.5 h, preferably at least 2 h Fig. 2 is shown in step 22.

Alternatively, after the first homogenization step 18, the rolled ingot can also be cooled to room temperature in a step 24 and heated to the temperature for the second homogenization in a subsequent step 26. This is necessary, for example, if the rolled bar has to be stored between the homogenization step. Optionally, this phase can be used at room temperature to mill the billet on the top and bottom, step 28. After the second homogenization step 22, the hot rolling is carried out as in FIG Fig. 1 shown with the parameters specified there. It has been shown that the multi-stage homogenization, in particular the two-stage homogenization, leads to a finer structure in the end product.

The effect according to the invention of providing a medium-strength and very highly formable aluminum alloy or an aluminum alloy strip was demonstrated on the basis of 10 exemplary embodiments.

First, 10 different rolled bars consisting of different alloys were cast in DC continuous casting. The upper and lower sides of the billets were milled according to step 12 after casting. This was followed by a two-stage homogenization, in which the rolling bars were first kept at 600 ° C. for 3.5 h and then at 500 ° C. for 2 h. Immediately after homogenization, the rolled bars were hot-rolled directly at about 500 ° C. to form an aluminum alloy hot strip with a thickness of 8 mm. The 8 mm thick hot strip was finally cold rolled to a final thickness of 1.5 mm without intermediate annealing, ie with a rolling degree of more than 70%. The recrystallizing final soft annealing of the cold-rolled aluminum alloy strips with a thickness of 1.5 mm was carried out for 1 h at 350 ° C. in a chamber furnace. The various aluminum alloys tested are shown in Table 1. Table 1 (V): Comparison (E): Invention Aluminum alloy components in% by weight, variant Si Fe Cu Mn Mg Cr 1 V 0.66 0.66 0.26 0.7 0.62 0.14 2nd V 0.53 0.46 0.19 0.52 0.44 0.13 3rd V 0.67 0.66 0.27 0.69 0.61 0.0005 4th V 0.73 0.68 0.0016 1.0 0.67 0.0002 5 E 0.72 0.69 0.0016 0.74 0.66 0.0006 6 E 0.67 0.65 0.07 0.69 0.61 0.0005 7 E 0.72 1.0 0.0017 0.72 0.66 0.0004 8th E 0.8 0.68 0.0015 0.72 0.63 0.0003 9 V 0.4 0.41 0.004 0.47 0.41 0.001 10th V 0.5 0.27 0.0013 0.66 0.42 0.0008

Variants 1 to 4 and 9 and 10 are comparative examples which do not correspond to the aluminum alloy according to the invention. The exemplary embodiments 5 to 8, on the other hand, correspond to the aluminum alloy compositions claimed according to the invention.

The yield strength R _p0.2 , the tensile strength R _m , the uniform elongation A _g , the elongation at break A _{80 mm} and the depression SZ 32 achieved during stretch drawing were measured in millimeters on the cold-rolled aluminum alloy strips produced in this way. The values for the yield strength R _p0.2 and the tensile strength R _m were measured in the tensile test perpendicular to the rolling direction of the sheet according to DIN EN ISO 6892-1: 2009. According to the same standard, the uniform elongation A _g and the elongation at break A _80mm in percent were measured perpendicular to the rolling direction of the sheet with a flat tensile test according to DIN EN ISO 6892-1: 2009, Appendix B, Form 2. The forming _behavior can also be measured, for example, in a stretch drawing test SZ 32 can be measured by a deepening test according to Erikson (DIN EN ISO 20482) which a test specimen is pressed against the sheet so that cold deformation occurs. During the cold deformation, the force and the ram path of the test specimen are measured until there is a load drop, which is caused by the formation of a crack. In the present exemplary embodiments, the cupping test was carried out with a punch head diameter of 32 mm and die diameter of 35.4 mm, matched to the sheet metal ceiling, with the aid of a Teflon drawing film to reduce the friction. The overview of the results is shown in Table 2. Table 2 variant M: Comparison (E): Invention R _p0.2 N / mm ² R _m N / mm ² A _g % A _80mm % SZ 32 mm 1 V 65 145 19.6 26.5 15.8 2nd V 52 131 21.9 30.3 16.2 3rd V 60 135 22.7 30.3 16.4 4th V 51 122 22.3 33.5 15.6 5 E 48 112 23.1 35.3 16.0 6 E 47 118 23.5 35.0 16.5 7 E 50 120 23.4 36.2 16.1 8th E 47 112 23.8 36.6 15.0 9 V 41 98 23.6 37.9 16.5 10th V 41 102 24.2 38.0 16.3

By comparing, for example, variant 2 with variants 5 to 8 according to the invention, the exemplary embodiments show that an excessive reduction in the contents Si, Fe, Mn, Mg with an increase in the contents for Cu and Cr leads to the fact that the yield strength values are above 45 MPa remains, but the elongation at break drops significantly to around 30%. This effect can also be demonstrated if the Mn content alone is, for example, 1.0%, which already pushes the elongation A _80mm to less than 35%, variant 4. Variants 9 and 10 show the effect of reduced Si, Fe, Mn and Mg. Comparative _examples 9 and 10 show a very good elongation at break A _{80 mm} with more than 35%, but the yield strength of 41 MPa is below that of the exemplary embodiments 5 to 8 _according to the invention.

The exemplary embodiments according to the invention showed, in particular in the case of strong deformations, very good forming behavior, which can be seen from the very good stretch drawing results SZ 32 and the high elongation _{values for} both the uniform elongation A _g and the elongation at break A _{80 mm} . From this it can be seen that the interplay of the alloy contents Si, Fe, Mn, Mg is important, the components Cr and Cu having to be kept particularly low, the Cu content ≤ 0.05% by weight being preferred ≤ 0.01% by weight and the chromium content ≤ 0.01% by weight, preferably ≤ 0.001% by weight. Coupled with the very good corrosion resistance of the exemplary embodiments, semifinished products and components, in particular structural components such as interior door parts, can be provided for vehicles, which not only guarantee the specifications of the area of application with regard to mechanical and chemical properties, but can also be economically produced by a few forming operations.

The aluminum alloy strips are therefore ideally suited, for example structural parts of a motor vehicle, such as that in Fig. 3 to provide shown door inner parts 30 or to be used for their manufacture. The inner door part is made from a sheet of aluminum alloy according to the invention with a thickness of 1.5 mm, which provides a window frame only by forming operations, but without joining operations.

Claims (7)

1. Aluminium alloy for the manufacture of semi-finished products or components for motor vehicles, which comprises the following alloy components in % by weight:

   0.6% ≤ Si ≤ 0.9%,

   0.6% ≤ Fe ≤ 1.0%,

   Cu ≤ 0.1%,

   0.6% ≤ Mn ≤ 0.9%,

   0.5% ≤ Mg ≤ 0.8%,

   Cr ≤ 0.05%,

   the remainder A1 and impurities, individually up to a maximum of 0.05% by weight, in total up to a maximum of 0.15% by weight.
2. Aluminium alloy according to claim 1, characterised in that the alloy components Si, Fe, Mn and Mg have the following contents in % by weight: 0.7% ≤ Si ≤ 0.9%,

   0.7% ≤ Fe ≤ 1.0%,

   0.7% ≤ Mn ≤ 0.9% and

   0.6% ≤ Mg ≤ 0.8%.
3. Aluminium alloy according to claim 2, characterised in that the alloy components Si, Fe, Mn and Mg have the following contents in % by weight: 0.7% ≤ Si ≤ 0.8%,

   0.7% ≤ Fe ≤ 0.8%,

   0.7% ≤ Mn ≤ 0.8% and

   0.6% ≤ Mg ≤ 0.7%.
4. Aluminium alloy according to one of the claims 1 to 3, characterised in that the aluminium alloy has the following Cr content in % by weight:
   Cr ≤ 0.01%.
5. Aluminium alloy according to one of the claims 1 to 4, characterised in that the aluminium alloy has the following Cu content in % by weight:
   Cu ≤ 0.05%.
6. Structural component, in particular interior door part (30), of a motor vehicle comprising at least one formed sheet manufactured from an aluminium alloy according to one of the claims 1 to 5.
7. Structural component according to claim 6, characterised in that the sheet is cut from a strip produced using a method for manufacturing a strip from an aluminium alloy according to one of the claims 1 to 5 with following method steps:

   - casting (2) of a rolling ingot,

   - homogenisation (4,16) at a temperature of between 500°C and 600°C for at least 0.5 h,

   - hot rolling (6) of the rolling ingot at temperatures of 280°C to 500°C to a thickness of 3 mm to 12 mm,

   - cold rolling (8) with or without intermediate annealing with a degree of reduction of at least 50%, preferably at least 70% to a final thickness of 0.2 mm to 5 mm and

   - final soft annealing (10) at 300°C to 400°C for at least 0.5h in a chamber furnace.

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