EP3178952B9 - 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 decisive. When used later in a motor vehicle, the strength values, but also in particular the corrosion properties, play a significant role.

For example, in the case of structural parts of a motor vehicle, such as door interior parts, the mechanical properties are predominantly determined by the rigidity, which primarily depends on the shape of the door interior parts. In contrast, tensile strength, for example, has a rather subordinate influence. However, the materials used for a door inner part must not be too soft either. 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. B. Sheet metal interior door parts with integrated window frame area. By saving joining operations, such components have considerable cost advantages compared to a joined aluminum profile solution for the window frame, for example. The aim is, for example, 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 deformation behavior of the aluminum alloy to be used. The aluminum alloy of the type AA5005 (AlMg1), which is occasionally used for similar applications, does not meet these requirements, as it does not have sufficient formability due to hardening during forming.

Corrosion resistance plays a further important role, since components of motor vehicles are often exposed to condensation, splash water and condensation water. The aluminum alloy to be used should therefore be as resistant to corrosion as possible, especially in the lacquered state against intergranular corrosion and against filiform corrosion. Filiform corrosion is understood to be a type of corrosion that occurs in coated components and shows a thread-like course. Filiform corrosion occurs at high humidity in the presence of chloride ions. The aluminum alloy of the type AA8006 (AlFe1.5Mn 0.5) has sufficient strength and very high formability, but it is susceptible to filiform corrosion. The alloy AA8006 is therefore less suitable for coated, especially painted components such as door interior 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 not yet published international patent application of the applicant PCT / EP2014 / 053323 an aluminum alloy is known as an alternative to the aluminum alloy of the 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%,

Remainder 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, too, is still in need of improvement, particularly with regard to its deformation behavior. In addition, the high Mn content can lead to problems in the recycling 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.

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

Proceeding 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 that is highly deformable, 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 above-mentioned object is achieved by an aluminum alloy for the production of semi-finished products or components for 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%,

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

In contrast to the previous approaches, the present aluminum alloy is based on the knowledge that Al-Mg-Si alloys of the alloy type AA6XXX have very good formability in the soft-annealed state. However, they were too soft for previous applications. The lower limits of the mandatory alloying 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 can provide sufficient strengths in the soft annealed state. 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 hence the deformation behavior is worsened. For the same reason, the alloying elements Cu are also 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 deformation 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 specified aluminum alloy in the soft-annealed state meets the requirements for formability and in particular for corrosion resistance and is therefore suitable for the production of semi-finished products or components in motor vehicles. With the aforementioned ranges of the mandatory 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 that are 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%.

Raising the lower limits for Si, Fe, Mn and Mg ensures that the strength of the aluminum alloy increases even further without impairing the deformation 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 in relation to the alloy components Si, Fe, Mn and Mg provides a very good compromise between the strength achieved and the elongation at break. H. Forming properties of the aluminum alloy is achieved.

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

The reduction of the Cu content to a maximum of 0.05% by weight, preferably a maximum of 0.01% by weight, has a similar effect, while at the same time the tendency to filiform corrosion or intergranular corrosion due to the reduction in the Cu content generally declining.

• 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:

• Pouring a rolling ingot,
• Homogenize at a temperature between 500 ° C and 600 ° C for at least 0.5 h
• Hot rolling of the billet at temperatures of 280 ° C to 500 ° C, preferably at temperatures of 300 ° C to 400 ° C, to a thickness of 3 mm to 12 mm,
• Cold rolling with or without intermediate annealing with a degree of rolling 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 is achieved the further processing of the billet is provided. The hot rolling temperatures enable good recrystallization during hot rolling so that the structure is as fine-grained as possible after hot rolling. 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, the cold rolling produces a particularly high number of dislocations in the structure, which in the final soft annealing produces a very fine-grain, fully recrystallized structure. For this purpose, the degree of rolling of the final thickness before the final soft annealing must be at least 50%, preferably at least 70% of the desired final thickness.

Another positive influence on the fine-grained structure of the structure can be achieved in that, according to a further embodiment of the method, the homogenization takes place in two stages, whereby the rolling billet is first heated to 550 ° C to 600 ° C for at least 0.5 h and then the rolling billet at 450 ° C to 550 ° for at least 0.5 h, preferably at least 2 h. The billet is then hot rolled.

The corrosion properties can be improved by milling the rolling bar on the top and bottom after casting or after homogenization in order to exclude impurities from the top and bottom of the rolling bar, which can negatively affect 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, with before and after the intermediate annealing, the degree of rolling 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 hours, preferably at least 2 hours.

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, sufficient recrystallization takes place and, at the same time, by reducing the upper limit, efficient intermediate annealing is carried out, which requires 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 point R _p0.2 of at least 45 MPa and a uniform elongation A _g of at least 23% and an elongation at break A _80mm of at least 35%. In particular with the specified thickness of the strip in connection with the alloy composition and the resulting mechanical properties in the annealed state, the prerequisites are given that the aluminum alloy strip or sheet can be used for components in motor vehicles which, in addition to very good forming properties, also have very good Have 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 the production of semi-finished products or components of a motor vehicle, in particular structural parts of a motor vehicle, also solves the above-mentioned problem. Structural parts in particular can be produced with very high degrees of deformation and take on very complex shapes without the need for particularly complicated deformation operations. In particular, they are particularly corrosion-resistant even in a painted 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 an inner door part of a motor vehicle, comprising at least one formed sheet metal from a Aluminum alloy according to the invention solved. As already stated above, the investigations have shown that the aluminum alloy according to the invention not only provides the required forming properties in the soft-annealed state, but also ensures the necessary corrosion resistance and strength of the structural parts at the same time.

In order to achieve the optimum degree 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 forming properties as well as the strength properties of the structural part can be achieved in a process-reliable manner with the method, so that an economical production of the structural parts that 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 is to be explained in more detail using exemplary embodiments in conjunction with the drawing. The drawing shows in

• Fig. 1 a flow chart of a first 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 diagram is now shown Fig. 1 . In a first step 2, the rolling ingot is cast, for example in the DC continuous casting process or in the strip casting process. In process step 4, the bar is then heated to a temperature of 500 ° C. to 600 ° C. and kept at this temperature for at least 0.5 h, preferably at least 2 h, for homogenization. The thus homogenized rolling ingot is then 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 by cold rolling to the final thickness in step 8, which is followed by 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-grain structure during 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 inventive alloy components of Mg, Si, Fe and Mn, it is used a continuous furnace for the production of the aluminum alloy strip is not possible, since other structures would be provided due to the different heating and cooling speeds.

As an alternative to producing the aluminum alloy strip without intermediate annealing, intermediate annealing in a chamber furnace at 300 ° C to 400 ° C, preferably at 330 ° C to 370 ° C, can also be carried out in accordance with step 14, with a degree of rolling of at least 50%, preferably at least 70%, should be guaranteed in order to have a positive influence on the fine grain of the structure after the final recrystallizing annealing. Optionally, after the billet has been cast in step 2, the top and bottom sides of the billet can also be milled in accordance with step 12 in order to minimize the influence of impurities on the finished product at the edges of the billet during the production of the billet. In particular, this has a positive influence on the corrosion resistance of the components.

Fig. 2 now shows a further flowchart which, as an alternative to step 4, shows step 16 of the homogenization. The homogenization has an influence on the fine grain of the desired final structure of the strip or the 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 or unmilled rolling ingots 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 rolling ingot 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, which is shown in FIG Fig. 2 is shown in step 22.

Alternatively, after the first homogenization step 18, the rolling 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 rolling billet has to be stored between the homogenization step. Optionally, this phase can be used at room temperature to mill the rolling billet on the top and bottom, step 28. After the second homogenization step 22, hot rolling takes place 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 inventive effect of providing a medium-strength and very highly deformable aluminum alloy or an aluminum alloy strip was demonstrated on the basis of 10 exemplary embodiments.

First, 10 different rolling bars consisting of different alloys were cast using continuous DC casting. The top and bottom sides of the billets were milled according to step 12 after casting. This was followed by a two-stage homogenization, in which the rolling slabs were initially held at 600 ° C. for 3.5 hours and then at 500 ° C. for 2 hours. Immediately after homogenization, the billets were hot-rolled directly at approx. 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 degree of rolling of more than 70%. The final recrystallizing 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 2 V. 0.53 0.46 0.19 0.52 0.44 0.13 3 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 6th E. 0.67 0.65 0.07 0.69 0.61 0.0005 7th 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 10 V. 0.5 0.27 0.0013 0.66 0.42 0.0008

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

On the cold-rolled aluminum alloy strips produced in this way, the yield point R _p0.2 , the tensile strength R _m , the uniform elongation A _g , the elongation at break A _{80 mm} and the indentation SZ 32 achieved during stretch drawing were measured in millimeters. 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 in accordance with DIN EN ISO 6892-1: 2009. In accordance with the same standard, the uniform elongation A _g and the elongation at break A _{80mm were} measured in percent in each case 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 deformation behavior can also be, for example, in a stretching test SZ 32 are measured by a cupping test according to Erikson (DIN EN ISO 20482) which a test body is pressed against the sheet metal, so that it comes to a cold deformation. During the cold deformation, the force and the stamp travel 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 a die diameter of 35.4 mm, matched to the sheet metal ceiling, with the aid of a Teflon drawing film to reduce 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 2 V. 52 131 21.9 30.3 16.2 3 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 6th E. 47 118 23.5 35.0 16.5 7th 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 10 V. 41 102 24.2 38.0 16.3

By comparing variant 2 with variants 5 to 8 according to the invention, for example, the exemplary embodiments show that an excessive reduction in the contents of Si, Fe, Mn, Mg with an increase in the contents for Cu and Cr leads to the yield limit values being 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 at break A 80mm} to below 35%, variant 4. Variants 9 and 10 show the effect of reduced contents of Si, Fe, Mn and Mg. Although comparative examples 9 and 10 show a very good elongation at break A _{80 mm of} more than 35%, the yield point, at 41 MPa, is below that of exemplary embodiments 5 to 8 according to the invention.

The exemplary embodiments according to the invention showed very good deformation behavior, especially in the case of strong deformations, which can be read _{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. It can be seen from this that the overall interplay of the alloy contents Si, Fe, Mn, Mg is important, with the components Cr and Cu having to be kept particularly low; the Cu content is preferably 0.05% by weight, 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, semi-finished 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 application area with regard to mechanical and chemical properties, but can also be produced economically with 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 Fig. 3 To provide illustrated door inner parts 30 or to be used for their production. The inner door part is made from sheet metal made of an aluminum alloy according to the invention with a thickness of 1.5 mm, which provides a window frame only through 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 Al 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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