EP2770071B2 - Aluminium alloy for the production of semi-finished products or components for motor vehicles, method for producing an aluminium alloy strip from this aluminium alloy and aluminium alloy strip and uses thereof - Google Patents

Description

The invention relates to an aluminum alloy strip and uses therefor.

Semi-finished products and components for motor vehicles have to meet different requirements depending on their location and intended use in the motor vehicle, in particular with regard to their mechanical properties and their corrosion properties.

In the case of interior door parts, the mechanical properties are predominantly determined, for example, by the rigidity, which depends in particular on the shape of these parts. In contrast, the strength has a minor influence, although the materials used must not be too soft. Good formability, on the other hand, is very important, since the components and semi-finished products generally go through complex forming processes, for example in the manufacture of door interior parts. This applies in particular to components that are manufactured in a one-piece sheet metal shell construction, e.g. a sheet metal inner door with integrated window frame area. By saving joining operations, such components have cost advantages compared to an attached profile solution for the window frame.

It would be particularly advantageous if a corresponding semifinished product or component made of an aluminum alloy could be formed on a tool for steel components, since in this case aluminum or steel components can be produced on the same tool as required, thus reducing investment and operating costs for an additional tool or can be avoided.

For the reasons mentioned above, there is great interest in the automotive industry in highly formable, medium strength aluminum alloys, which in particular have better formability than, for example, the standard alloy AA (Aluminum Association) 5005 (AlMgl).

In addition to the mechanical properties, corrosion resistance also plays a major role in motor vehicles, since motor vehicle components such as door interior parts are exposed to splash water, condensation water or condensation water. It is therefore desirable that the motor vehicle components have good resistance to various corrosion attacks, in particular to intergranular corrosion and to filiform corrosion.

Filiform corrosion means 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.

In the past, attempts have been made to manufacture semi-finished products or components for motor vehicles from the alloy AA 8006 (AlFe1.5Mn0.5). With this alloy, semi-finished products with sufficient strength and high formability can be produced, but the corresponding components showed a high susceptibility to filiform corrosion after painting, so that the alloy AA 8006 is not suitable for coated, especially painted components such as door parts is.

Hardenable AA 6xxx alloys have high strengths as well as good resistance to intergranular corrosion and filiform corrosion, but are much more difficult to form than AA 8006 and are therefore not particularly suitable for the production of complex components such as door parts. In addition, the production of semi-finished products and components from an AA 6xxx alloy is quite complex and expensive, since it requires continuous annealing as a special process step.

AA 5xxx alloys with a high magnesium content combine high strength with quite good formability. However, the formability is not as good as that of steel solutions, which leads to restrictions in the design of the components. In addition, these alloys tend to intergranular corrosion. Steel materials are very easy to form, but have the same rigidity and a weight disadvantage and are also prone to corrosion. Starting from this prior art, the present invention is based on the object of providing an aluminum alloy strip which is highly malleable, medium-strength and corrosion-resistant. Should continue advantageous uses for the tape are provided. This object is achieved with an aluminum alloy strip and a use of the strip with the features of claims 1 or 8 and 9.

With regard to the aluminum alloy of the aluminum alloy strip, the aforementioned object is achieved according to the invention in that the alloy components of the aluminum alloy have the following proportions in percent by weight: Fe ≤ 0.80%, Si ≤ 0.50%, 0.90% ≤ Mn ≤ 1.50%, 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%, and the combined proportion of Mg and Cu fulfills the following relation in% by weight: $$0.17\%\le \mathrm{Mg}+\mathrm{Cu}\le 0.25\%.$$

The aluminum alloy of the aluminum alloy strip according to the invention is based on the alloy type AA 3xxx, in particular AA 3103 (AlMn1). Such alloys have a very good formability, but are usually too soft for many applications such as components of motor vehicles. The addition of certain alloying elements, in particular Mg and Cu, can increase the strength of the aluminum alloy, but this also leads to a significant reduction in ductility and thus in turn to poorer formability.

In the context of the invention, it was recognized, among other things, that the combined proportion of copper and magnesium in the aluminum alloy of the aluminum alloy _{strip according to} the invention must be precisely controlled in order to achieve the desired mechanical properties, namely an _elastic limit R _p0.2 of at least 45 MPa with a uniform expansion A _g of at least 23% and an elongation at break A _80mm of at least 30%, with good corrosion resistance. Experiments have shown that a combination of Mg and Cu between 0.15 and 0.25% by weight achieves a combination of strength and formability of the aluminum alloy that is advantageous for the applications mentioned.

The combined proportion of magnesium and copper must be at least 0.17% by weight so that the aluminum alloy of the aluminum alloy _{strip according to the invention achieves} sufficient strength, in particular with an _elastic limit R _p0.2 of at least 45 MPa. On the other hand, the combined proportion of Mg and Cu must be limited to at most 0.25% by weight, preferably at most 0.23% by weight, in particular at most 0.20% by weight, since otherwise uniform _expansion A _g and elongation at break A _{80 mm} fall too much, namely below 23% for A _g or below 30% for A _80mm . The combined proportion of magnesium and copper is generally understood to mean the sum of the two individual proportions for Mg and Cu in% by weight.

With regard to the individual proportions, the aluminum alloy of the aluminum alloy strip according to the invention has a Cu content of at most 0.20% by weight, preferably at most 0.10% by weight, in particular at most 0.05% by weight, and a magnesium Proportion of at most 0.25% by weight, preferably at most 0.2% by weight. Furthermore, the aluminum alloy preferably has a Mg content of at least 0.06% by weight, more preferably of at least 0.10% by weight, in particular of at least 0.15% by weight.

The previously described aluminum alloy of the aluminum alloy strip according to the invention has proven to be highly malleable and medium-strength in tests. As a result, the aluminum alloy can be used particularly well for semi-finished products and components of motor vehicles, the production of which comprises complex forming processes. With the aluminum alloy, it is sometimes even possible to achieve such a good formability that semi-finished products and components made from the alloy can be formed on forming tools for steel components.

Tests have also shown that the aluminum alloy of the aluminum alloy strip according to the invention has good corrosion resistance. In particular, no intercrystalline corrosion occurs with AA 3xxx alloys, to which the above-mentioned alloy belongs. Furthermore, the aluminum alloy of the aluminum alloy strip according to the invention showed in laboratory tests a considerably better resistance to filiform corrosion than, for example, AA 8006 alloys.

• Der Mn-Anteil der Legierung von 0,9 bis 1,5 Gew.-%, vorzugsweise von 1,0 bis 1,4 Gew.-%, insbesondere von 1,0 bis 1,2 Gew.-%, führt in Kombination mit den Fe- und Si-Anteilen in den angegebenen Mengen insbesondere zu relativ gleichförmig verteilten, kompakten Partikeln der quaternären α-Al(Fe,Mn)Si-Phase, die die Festigkeit der Aluminiumlegierung des erfindungsgemäßen Aluminiumlegierungsbandes steigern, ohne andere Eigenschaften wie die Umformbarkeit oder das Korrosionsverhalten negativ zu beeinflussen.

The effect of the individual alloy components is now explained below:

• The Mn content of the alloy from 0.9 to 1.5% by weight, preferably from 1.0 to 1.4% by weight, in particular from 1.0 to 1.2% by weight, results in combination with the Fe and Si fractions in the specified amounts, in particular to relatively uniformly distributed, compact particles of the quaternary α-Al (Fe, Mn) Si phase, which increase the strength of the aluminum alloy of the aluminum alloy strip according to the invention, without other properties such as formability or negatively influence the corrosion behavior.

The elements titanium, chromium, vanadium and in particular zircon can hinder the recrystallization during the final annealing and thus impair the formability of the aluminum alloy of the aluminum alloy strip according to the invention. In order to achieve better formability, the aluminum alloy of the aluminum alloy strip according to the invention therefore has Ti, Cr, V and Zr portions of at most 0.05% by weight and preferably in particular a Zr portion of at most 0.02% by weight. -% on.

The proportions of all other inevitable accompanying elements are individually less than 0.05% by weight and together less than 0.15% by weight, so that they do not cause any undesirable phase formation and / or negative influences on the material properties.

In a first preferred embodiment, the Mg content of the aluminum alloy of the aluminum alloy strip according to the invention is greater than the Cu content of the aluminum alloy. In this way, the corrosion behavior of the aluminum alloy of the aluminum alloy strip according to the invention, in particular with regard to filiform corrosion, can be further improved.

The formability of the aluminum alloy of the aluminum alloy strip according to the invention is further improved in a further embodiment in that the aluminum alloy has a Cr content ≤ 0.02% by weight, preferably ≤ 0.01% by weight, and / or a V content ≤ 0.02 wt .-%, preferably ≤ 0.01 wt .-%, and / or a Zr content ≤ 0.01 wt .-%.

Titanium can be added during the continuous casting of the aluminum alloy of the aluminum alloy strip according to the invention as a grain refining agent, for example in the form of Ti boride wire or rods. In a further embodiment, the aluminum alloy therefore has a Ti content of at least 0.01% by weight, preferably of at least 0.015% by weight, in particular of at least 0.02% by weight.

In a further embodiment, the material properties of the aluminum alloy of the aluminum alloy strip according to the invention can be improved in that the aluminum alloy has an Fe content of ≤ 0.7% by weight, preferably ≤ 0.6% by weight, in particular ≤ 0.5% by weight. %, having. The further limitation of the Fe content prevents the susceptibility of the aluminum alloy of the aluminum alloy strip according to the invention to filiform corrosion.

Furthermore, the aluminum alloy of the aluminum alloy strip according to the invention preferably has a Si content of 0,4 0.4% by weight, preferably ≤ 0.3% by weight, in particular ≤ 0.25% by weight. The further restriction of the Si content can prevent the formability from being reduced too much.

To increase the strength, the aluminum alloy of the aluminum alloy strip according to the invention further preferably has an Fe content of at least 0.10% by weight, preferably at least 0.25% by weight, in particular at least 0.40% by weight, and / or Si content of at least 0.06% by weight, preferably at least 0.10% by weight, in particular at least 0.15% by weight.

Good strength and formability are achieved in a preferred embodiment of the aluminum alloy of the aluminum alloy strip according to the invention in that the alloy components of the aluminum alloy have the following proportions in percent by weight: 0.40% ≤ Fe ≤ 0.70%, 0.10% ≤ Si ≤ 0.25%, 1.00% ≤ Mn ≤ 1.20%, Mg ≤ 0.25%, Cu ≤ 0.10%, Cr ≤ 0.02%, Ti ≤ 0.05%, V ≤ 0.05%, Zr ≤ 0.05%,

Rest of aluminum, unavoidable accompanying elements individually <0.05%, in total <0.15%, whereby the combined proportion of Mg and Cu fulfills the following relation in% by weight: $$0.17\%\le \mathrm{Mg}+\mathrm{Cu}\le 0.25\%.$$

The formability of this alloy can be improved in that the alloy has a V content 0,0 0.02% by weight and / or a Zr content ≤ 0.01% by weight. Grain refinement can also be improved by a Ti content of at least 0.01% by weight.

In a preferred embodiment of the aluminum alloy of the aluminum alloy strip according to the invention, very good formability with sufficient strength is achieved in that the alloy components of the aluminum alloy have the following proportions in percent by weight: 0.40% ≤ Fe ≤ 0.70%, 0.10% ≤ Si ≤ 0.25%, 1.00% ≤ Mn ≤ 1.20%, Mg ≤ 0.20%, Cu ≤ 0.05%, Cr ≤ 0.02%, Ti ≤ 0.05%, V ≤ 0.05%, Zr ≤ 0.05%,

Rest of aluminum, unavoidable accompanying elements individually <0.05%, in total <0.15%, whereby the combined proportion of Mg and Cu fulfills the following relation in% by weight: $$0.17\%\le \mathrm{Mg}+\mathrm{Cu}\le 0.20\%.$$

The formability of this alloy can be improved in that the alloy has a V content 0,0 0.02% by weight and / or a Zr content ≤ 0.01% by weight. Grain refinement can also be improved by a Ti content of at least 0.01% by weight.

• Gießen eines Walzbarrens aus einer Aluminiumlegierung des erfindungsgemäßen Aluminiumlegierungsbandes,
• Homogenisieren des Walzbarrens bei 480 °C bis 600 °C für mindestens 0,5 h,
• Warmwalzen des Walzbarrens bei 280 °C bis 500 °C zu einem Aluminiumlegierungsband,
• Kaltwalzen des Aluminiumlegierungsbands auf Enddicke und
• rekristallisierendes Schlussglühen des Aluminiumlegierungsbands.

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

• Casting of a billet from an aluminum alloy of the aluminum alloy strip according to the invention,
• Homogenize the billet at 480 ° C to 600 ° C for at least 0.5 h,
• Hot rolling the billet at 280 ° C to 500 ° C to an aluminum alloy strip,
• Cold rolling the aluminum alloy strip to final thickness and
• recrystallizing final annealing of the aluminum alloy strip.

The process steps of the previously described process are carried out in particular in the order specified.

Experiments have shown that this process can be used to produce an aluminum alloy strip that is highly malleable, medium-strength and corrosion-resistant, especially against intergranular corrosion and filiform corrosion. Furthermore, this process allows the aluminum alloy strip to be produced economically, since the process comprises standard process steps (i.e. continuous casting, homogenizing, hot rolling, cold rolling, soft annealing) and does not necessarily require special, complex process steps such as continuous strip annealing.

The rolling ingot is preferably cast in DC continuous casting. Alternatively, however, a strip casting process can also be used, for example.

By homogenizing the billet at 480 ° C to 600 ° C, preferably at 500 ° C to 600 ° C, in particular at 530 ° C to 580 ° C, for at least 0.5 h, it is achieved that the aluminum alloy strip after the final annealing has fine-grained structure with good strength and formability. These properties can be further improved by homogenizing the billet for at least 2 hours.

The hot rolling of the rolled ingot takes place at a temperature between 280 ° C. and 500 ° C., preferably between 300 ° C. and 400 ° C., in particular between 320 ° C. and 380 ° C. In hot rolling, the billet is preferably rolled down to a thickness between 3 and 12 mm. This ensures that a sufficiently high degree of rolling, preferably at least 70%, in particular at least 80%, is achieved in the subsequent cold rolling, by means of which the strength, formability and elongation values of the aluminum alloy strip are also determined.

The cold rolling of the aluminum alloy strip can be done in one or more passes. The aluminum alloy strip is preferably rolled to a final thickness in the range from 0.2 to 5 mm, preferably from 0.25 to 4 mm, in particular from 0.5 to 3.6 mm. The desired material properties of the aluminum alloy strip can be achieved particularly well in these thickness ranges.

The final annealing of the aluminum strip enables a fine-grained, crystallized structure with good strength and formability to be achieved. The final annealing is therefore a recrystallizing soft annealing. The final annealing can take place in particular in a chamber furnace at 300 ° C. to 400 ° C., preferably at 320 ° C. to 360 ° C. or in a continuous furnace at 450 ° C. to 550 ° C., preferably at 470 ° C. to 530 ° C. The chamber furnace is less expensive to operate and purchase than the continuous furnace. The final annealing time in the chamber furnace is typically 1 hour or more.

• Fräsen der Ober- und/oder Unterseite des Walzbarrens.

In a first embodiment of the method, the method additionally comprises the following method step:

• Milling the top and / or bottom of the billet.

This process step can improve the corrosion properties of the aluminum alloy strip produced or of an end product produced from this aluminum alloy strip. The milling of the top and / or bottom of the roll ingot can be carried out, for example, after casting and before homogenizing the roll ingot.

• erstes Homogenisieren bei 500 °C bis 600 °C, bevorzugt bei 550 °C bis 600 °C, für mindestens 0,5 h, bevorzugt für mindestens 2 h, und
• zweites Homogenisieren bei 450 °C bis 550 °C für mindestens 0,5 h, bevorzugt für mindestens 2 h.

In a further embodiment of the method, the homogenization is carried out at least in two stages with the following steps:

• first homogenization at 500 ° C to 600 ° C, preferably at 550 ° C to 600 ° C, for at least 0.5 h, preferably for at least 2 h, and
• second homogenization at 450 ° C to 550 ° C for at least 0.5 h, preferably for at least 2 h.

The at least two-stage homogenization enables a fine-grained structure with good strength and formability to be achieved after the final annealing. It has been shown that in this way, after the final annealing, in particular grain sizes, determined according to ASTM E1382, of less than 45 μm, in particular even less than 35 μm, can be achieved. The second homogenization is preferably carried out at the hot rolling temperature which the rolling bar has at the beginning of the subsequent hot rolling step.

• erstes Homogenisieren bei 500 °C bis 600 °C, bevorzugt bei 550 °C bis 600 °C, für mindestens 0,5 h, bevorzugt für mindestens 2 h,
• Abkühlen des Walzbarrens nach dem ersten Homogenisieren auf die Temperatur für das zweite Homogenisieren und
• zweites Homogenisieren bei 450 °C bis 550 °C für mindestens 0,5 h, bevorzugt für mindestens 2 h.

In a further embodiment, the at least two-stage homogenization preferably comprises the following steps:

• first homogenization at 500 ° C to 600 ° C, preferably at 550 ° C to 600 ° C, for at least 0.5 h, preferably for at least 2 h,
• Cooling the billet after the first homogenization to the temperature for the second homogenization and
• second homogenization at 450 ° C to 550 ° C for at least 0.5 h, preferably for at least 2 h.

• erstes Homogenisieren bei 500 °C bis 600 °C, bevorzugt bei 550 °C bis 600 °C, für mindestens 0,5 h, bevorzugt für mindestens 2 h,
• Abkühlen des Walzbarrens nach dem ersten Homogenisieren auf Raumtemperatur,
• Anwärmen des Walzbarrens auf die Temperatur für das zweite Homogenisieren und
• zweites Homogenisieren bei 450 °C bis 550 °C für mindestens 0,5 h, bevorzugt für mindestens 2 h.

In an alternative embodiment, the at least two-stage homogenization preferably comprises the following steps:

• first homogenization at 500 ° C to 600 ° C, preferably at 550 ° C to 600 ° C, for at least 0.5 h, preferably for at least 2 h,
• Cooling the billet after the first homogenization to room temperature,
• Warming the billet to the temperature for the second homogenization and
• second homogenization at 450 ° C to 550 ° C for at least 0.5 h, preferably for at least 2 h.

In a further embodiment, the upper and / or lower side of the roll ingot can be milled between the first homogenization and the second homogenization, particularly preferably after the roll ingot has cooled to room temperature.

In a further embodiment of the method, the degree of rolling during cold rolling is at least 70%, preferably at least 80%. Due to this minimum degree of rolling, a fine-grained structure with good strength and formability can be achieved with the aluminum alloy strip after the final annealing.

In a further embodiment of the method, the degree of rolling during cold rolling is a maximum of 90%, preferably a maximum of 85%. This maximum degree of rolling can prevent an excessive decrease in the elongation values of the aluminum alloy strip.

In a further embodiment, the method can be carried out particularly economically in that the cold rolling is carried out without intermediate annealing. It has been found that the desired properties of the aluminum alloy strip can also be achieved without intermediate annealing. In the production of the aluminum alloy strip, there is preferably also no complex and expensive continuous strip annealing.

In an alternative embodiment of the method, the aluminum alloy strip is annealed between two cold rolling passes, in particular between the penultimate and the last cold rolling pass, in particular at one temperature from 300 ° C to 400 ° C, preferably at a temperature of 330 ° C to 370 ° C. The intermediate annealing can take place, for example, in a chamber furnace. The intermediate annealing is in particular an intermediate soft annealing of the strip.

Although the production process becomes more complex due to the intermediate annealing, the structure can be positively influenced in the case of a relatively thick hot strip, so that the aluminum alloy strip produced has better material properties as a result. The intermediate annealing is preferably carried out when the degree of rolling during cold rolling is more than 85%, in particular more than 90%. The cold rolling and the intermediate annealing are then preferably carried out such that the degree of rolling after the intermediate annealing is less than 90%, in particular less than 85%. The degree of rolling after the intermediate annealing is particularly preferably between 70% and 90%, in particular between 80% and 85%.

The object described _{above is achieved according to the} invention in the case of an aluminum alloy strip, which is preferably produced using one of the methods described _above , in that the aluminum alloy _strip consists of the alloy described _above and an _elastic limit R _p0.2 of at least 45 MPa, a uniform expansion A _g of has at least 23% and an elongation at break A _80mm of at least 30%.

Tests have shown that an aluminum alloy strip according to the invention can be produced with the alloy described and in particular also by the method described above, which has the material properties mentioned above and also has good corrosion resistance to intergranular corrosion and filiform corrosion. The aluminum alloy strip according to the invention is therefore particularly well suited for components and semi-finished products for motor vehicles, in particular for coated components such as interior door components.

The _{proof stress} R _p0.2 is determined according to DIN EN ISO 6892-1: 2009. The uniform elongation A _g and the elongation A _80mm are also determined according to DIN EN ISO 6892-1: 2009 with a flat tensile test according to DIN EN ISO 6892-1: 2009, Appendix B, Form 2.

In one embodiment, the aluminum alloy strip has a thickness in the range from 0.2 to 5 mm, preferably from 0.25 to 4 mm, in particular from 0.5 to 3.6 mm. The desired material properties of the aluminum alloy strip can be achieved particularly well in these thickness ranges.

The object described above is further achieved by the use of the aluminum alloy strip according to the invention described above for semi-finished products or components for motor vehicles, in particular for coated components for motor vehicles. It has been found that material properties which are particularly advantageous for these uses can be achieved with the aluminum alloy strip according to the invention. According to one embodiment, the aluminum alloy strip can be used particularly advantageously for interior door components of a motor vehicle.

The object described above is further achieved by the use of a sheet made from an aluminum alloy strip according to the invention as a component in the motor vehicle. As described above, the material properties of the aluminum alloy strip and thus also the material properties of a sheet made from it are particularly suitable for use in a motor vehicle, especially as an inner door sheet.

Because of the good resistance to filiform corrosion, the sheet metal produced from the aluminum alloy strip according to the invention is particularly preferably used for coated, in particular painted, components of a motor vehicle.

Further features and advantages of the invention can be found in the following description of several exemplary embodiments, reference also being made to the attached drawing.

Fig. 1

ein Ablaufdiagramm für mehrere Ausführungsbeispiele zur Herstellung eines erfindungsgemäßen Aluminiumlegierungsbands,

Fig. 2

ein Ablaufdiagramm für weitere Ausführungsbeispiele zur Herstellung eines erfindungsgemäßen Aluminiumlegierungsbands,

Fig. 3

ein Diagramm mit Messergebnissen von Ausführungsbeispielen der erfindungsgemäßen Aluminiumlegierungsbänder und

Fig. 4

ein Bauteil für ein Kraftfahrzeug gemäß einem weiteren Ausführungsbeispiel.

Show in the drawing

Fig. 1

1 shows a flowchart for several exemplary embodiments for producing an aluminum alloy strip according to the invention,

Fig. 2

1 shows a flowchart for further exemplary embodiments for producing an aluminum alloy strip according to the invention,

Fig. 3

a diagram with measurement results of embodiments of the aluminum alloy strips according to the invention and

Fig. 4

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

Fig. 1 shows a flow chart for a first embodiment of the method for producing an aluminum alloy strip according to the invention.

In a first step 2, a billet is first cast from an aluminum alloy. The casting can take place, for example, in DC continuous casting or in strip casting. After casting, the billet is homogenized in step 4 at a temperature in the range from 480 ° C to 600 ° C for at least 0.5 h. In step 6, the billet is then hot-rolled to a final thickness between 3 and 12 mm at a temperature in the range from 280 ° C to 500 ° C. The hot strip hot-rolled from the rolled bar is then cold-rolled in step 8 to a final thickness of preferably 0.2 mm to 5 mm. Finally, in step 10, after the cold rolling, the aluminum alloy strip is finally annealed, for example in a chamber furnace at a temperature between 300 ° C and 400 ° C or in a continuous furnace between 450 ° C and 550 ° C.

Between the casting of the billet in step 2 and the homogenization in step 4, the top and / or bottom of the billet can optionally be milled in a step 12.

Furthermore, during the cold rolling in step 8, the aluminum alloy strip can optionally be annealed in a step 14, preferably in a chamber furnace at a temperature between 300 ° C. and 400 ° C. The intermediate annealing is particularly suitable for improving the material properties of the aluminum alloy strip if the hot strip is relatively thick and therefore the degree of rolling in cold rolling is more than 85% overall, in particular more than 90%. The intermediate annealing is preferably carried out before the last cold rolling pass.

With a hot strip thickness of 12 mm and a final thickness of 0.4 mm, the degree of rolling during cold rolling is, for example, a total of approximately 96.7%. In this case, for example, the hot strip can first be rolled to 2 mm in a first cold rolling pass, then annealed and finally rolled to 0.4 mm in a second cold rolling pass. The degree of rolling after the intermediate annealing is then only 80% and is therefore in a preferred range.

Figure 2 shows a part of a flow chart for further exemplary embodiments of the method. The process sequence of these exemplary embodiments essentially agrees with the process sequence with reference to Figure 1 described method. The homogenization of the billet takes place in the exemplary embodiments Figure 2 however, not in step 4, but in a step 16, which is divided into several individual steps. Figure 2 shows possible sequences of the individual steps of step 16.

Accordingly, after the casting of the billet in step 2 or after the milling of the billet in step 12 in the first sub-step 18 of step 16, there is first a first homogenization at a temperature between 550 and 600 ° C. for at least 0.5 h, preferably for at least 2 h. In a subsequent step 20, the billet is cooled to the temperature of the second homogenization in the range from 450 ° C. and 550 ° C., before the second homogenization at this temperature in turn in the subsequent step 22 for at least 0.5 h, preferably for at least 2 h, is done.

Alternatively, after the first homogenization in step 18, the billet can also be cooled to room temperature in a step 24 and warmed to the temperature for the second homogenization in a subsequent step 26. Between step 24 and step 26, the top and / or bottom of the roll bar can optionally be milled.

Within the scope of the invention, aluminum alloys of the AA 3xxx type, in particular based on AA 3103, with different Mg and Cu contents were produced. The alloy compositions of these aluminum alloys are compiled in Table 1 below, the individual alloy proportions each being given in% by weight. Table 1 No. Si Fe Cu Mn Mg Cr Zn Ti V Zr Cu + Mg 1 V 0.063 0.54 0.0029 1.07 0.0102 0.0005 0.0051 0.0053 0.0038 0.0005 0.013 2nd V 0.23 0.55 0.055 0.93 0.059 0.0096 0.0131 0.0151 0.0099 0.0008 0.114 3rd V 0.208 0.546 0.064 1,026 0.071 0.004 0.005 0.018 0.0081 0.0006 0.135 4th V 0.154 0.51 0.152 1.02 0.0019 0.0005 0.0034 0.0602 0.0073 0.0005 0.154 5 E 0.23 0.5 0.18 1.06 0.0109 0.0101 0.0055 0.0093 0.0112 0.0008 0.191 6 E 0.142 0.62 0.0019 1.1 0.19 0.0004 0.0011 0.0066 0.0091 0.0005 0.192 7 E 0.17 0.54 0.19 1.03 0.053 0.0005 0.0032 0.0217 0.0064 0.0005 0.243 8th V 0.42 0.45 0.086 1.01 0.19 0.0331 0.0058 0.028 0.0066 0.0006 0.276 9 V 0.052 0.21 0.28 0.87 0.22 0.0006 0.0028 0.018 0.0061 0.0005 0.5 10th V 0.162 0.59 0.0016 1.1 0.52 0.0002 0.001 0.0055 0.0072 0.0005 0.522 11 V 0.179 0.38 0.116 1.05 0.51 0.003 0.006 0.014 0.0068 0.0006 0.626

The last column in Table 1 shows the combined proportion of copper and magnesium, which has proven to be particularly important for the desired material properties. Alloys Nos. 5-7 are exemplary embodiments of the strips according to the invention made of alloy (E), while alloys Nos. 1-4 and 8-11 are comparative examples (V).

Aluminum alloy strips were then made from these aluminum alloys Nos. 1-11 using the previously described process. Specifically, each of these alloys 1 to 11 was cast in a DC ingot with a thickness of 600 mm, which was then homogenized in two stages, first for several hours at approx. 580 ° C and then for several hours approx. 500 ° C. After homogenization, the rolled bars were hot-rolled at about 500 ° C. to form aluminum alloy hot strips with a thickness of 4 to 8 mm. These aluminum alloy hot strips were then cold rolled to a final thickness of 1.2 mm and finally subjected to a recrystallizing final annealing at 350 ° C. for 1 h.

The aluminum alloy strips were then examined for their mechanical properties, in particular for their strength and formability.

The results of these tests are summarized in Table 2 below. Table 2 also shows in the last line the corresponding material properties of an alloy of the type AA 8006, as is known from the prior art. Table 2 No. R _p0.2 [MPa] R _m [MPa] A _g [%] A _80mm [%] n value r value SZ 32 [mm] 1 V 42 101 25.1 41.3 0.214 0.472 16.7 2nd V 42 103 24.6 35.7 0.216 0.579 16.3 3rd V 43 111 24.5 36.1 0.218 0.484 16.4 4th V 48 111 25.3 35.9 0.214 0.417 16.6 5 E 49 115 25.1 34.2 0.218 0.420 16.2 6 E 50 113 24.2 35.0 0.210 0.598 16.4 7 E 53 118 23.8 32.5 0.216 0.344 15.9 8th V 51 119 21.8 29.5 0.207 0.635 15.9 9 V 58 134 21.2 26.9 0.220 0.556 15.4 10th V 57 135 20.8 28.0 0.221 0.652 15.5 11 V 66 152 19.7 21.0 0.225 0.582 14.9 AA 8006 V 49 104 27.5 42.0 0.223 0.431 17.3

• die Dehngrenze R_p0,2 in MPa sowie die Zugfestigkeit R_m in MPa, gemessen im Zugversuch senkrecht zur Walzrichtung des Blechs nach DIN EN ISO 6892-1:2009,
• die Gleichmaßdehnung A_g in Prozent sowie die Bruchdehnung A_80mm in Prozent, gemessen im Zugversuch senkrecht zur Walzrichtung des Blechs mit einer Flachzug-Probe nach DIN EN ISO 6892-1:2009, Anhang B, Form 2,
• den Verfestigungsexponenten n (n-Wert), gemessen im Zugversuch senkrecht zur Walzrichtung des Blechs nach DIN ISO 10275:2009,
• die senkrechten Anisotropie r (r-Wert), gemessen im Zugversuch senkrecht zur Walzrichtung des Blechs nach DIN ISO 10113:2009, und
• die beim Streckziehen erreichte Tiefung SZ 32 in Millimeter als weiteres Maß für die Umformbarkeit der Legierung. Die Tiefung SZ 32 wurde im Erichsen-Tiefungsversuch nach DIN EN ISO 20482 ermittelt, aber mit einem auf die Blechdicke abgestimmten Stempelkopfdurchmesser von 32 mm und Matrizendurchmesser von 35,4 mm und unter Zuhilfenahme einer Teflon-Ziehfolie zur Reduzierung der Reibung.

Table 2 shows the following measurements:

• the yield strength R _p0.2 in MPa and the tensile strength R _m in MPa, measured in the tensile test perpendicular to the rolling direction of the sheet according to DIN EN ISO 6892-1: 2009,
• the uniform elongation A _g in percent and the elongation at break A _{80 mm} in percent, measured in a tensile test 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 hardening exponent n (n-value), measured in the tensile test perpendicular to the rolling direction of the sheet according to DIN ISO 10275: 2009,
• the vertical anisotropy r (r value), measured in the tensile test perpendicular to the rolling direction of the sheet according to DIN ISO 10113: 2009, and
• the SZ 32 indentation achieved in stretch drawing as a further measure of the formability of the alloy. The SZ 32 cupping was determined in the Erichsen cupping test in accordance with DIN EN ISO 20482, but with a punch head diameter of 32 mm and die diameter of 35.4 mm, which was matched to the sheet thickness, and with the help of a Teflon drawing film to reduce friction.

In Figure 3 The yield strengths R _p0.2 (empty squares), the elongation at break A _80mm (filled diamonds) and the cupping values SZ 32 (filled triangles) of the aluminum alloy strips No. 1 to 11 are plotted depending on the combined Cu and Mg content of the respective aluminum alloy . The R _p0.2 values are plotted in MPa on the left ordinate axis scale. The A _80mm values are given in percent and the SZ 32 values in mm according to the scale on the right ordinate axis. The combined Cu and Mg content is given on the abscissa in% by weight.

Furthermore, in Figure 3 In order to provide a better overview, the _{best-fit lines} for the measured values of R _p0.2 , A _80mm and SZ 32 are shown. Two vertical dashed lines indicate the values 0.15% by weight and 0.25% by weight for the combined Cu and Mg content.

As the measured values for the aluminum alloy strips made of the aluminum alloys No. 5-7 show, the setting of the combined Cu and Mg content in a range from 0.15% by weight to 0.25% by weight brings about the desired Combination of strength (R _p0.2 ≥ 45MPa) and formability (A _g ≥ 23% and A _80mm ≥ 30%) is achieved.

With combined Mg and Cu fractions of less than 0.15% by weight (No. 1-3), the strength proves to be too low (R _p0.2 <45 MPa) and with combined Mg and Cu fractions the elongation values and thus the formability decrease too much by more than 0.25% by weight (A _g <23% and / or A _80mm <30%).

The good formability is particularly evident from the measured cupping value, which in the aluminum alloy strips according to the invention preferably has a value SZ 32 15 15.8 mm, in particular ändern 15.9 mm.

As a result, the aluminum alloy tapes No. 5 - 7 have the same strength only a slightly poorer formability than the comparison alloy AA 8006. However, the aluminum alloy tapes No. 5 - 7 have the advantage over the alloy AA 8006 that they are considerably better Have corrosion resistance. In principle, intergranular corrosion does not occur with AA 3xxx alloys.

In addition, additional laboratory tests on corrosion resistance were carried out on the aluminum alloy strips made of aluminum alloys No. 5 - 7. These laboratory tests have shown that aluminum alloys No. 5 - 7 show a much better resistance to filiform corrosion than alloy type AA 8006. Aluminum alloys such as aluminum alloys No. 5 - 7 or aluminum alloy strips made from these aluminum alloys are therefore particularly suitable for coated coatings Components suitable.

Finally, the measured values in Table 2 show that the exemplary embodiments for the aluminum alloy strips according to the invention also achieve good values for the tensile strength R _m and for the n and r values, which are in particular within the scope of conventional AA 3xxx alloys or are even better.

Figure 4 shows a schematic representation of a typical component of a motor vehicle in the form of an inner door part. Such inner door parts 40 are usually made of steel. However, steel components are heavy and prone to corrosion with the same rigidity.

It has been shown that the aluminum alloys described above, such as aluminum alloys No. 5-7, can be used to produce aluminum alloy strips which are highly formable, medium-strength and very corrosion-resistant, in particular against intergranular corrosion and also against filiform corrosion.

The material properties of these aluminum alloy strips or the sheets produced from them are therefore particularly favorable for the production of motor vehicle components, such as the door inner part 40. The good resistance to filiform corrosion is particularly evident when using the aluminum alloys for coated, in particular painted, components such as the inner door part 40, advantageous.

In particular, the components made from these aluminum alloy strips have better corrosion resistance than corresponding components made from steel or from an alloy of type AA 8006. At the same time, they have a significantly lower weight than components made from steel.

Claims (9)

1. Aluminium alloy strip
   characterized in that
   the aluminium alloy strip consists of an aluminium alloy, wherein the alloying components of the aluminium alloy have the following contents in percent by weight: Fe ≤ 0.80%, Si ≤ 0.50%, 0.90% ≤ Mn ≤ 1.50%, Mg ≤ 0.25%, Cu ≤ 0.20%, Cr ≤ 0.05%, Ti ≤ 0.05%, V ≤ 0.05%, Zr ≤ 0.05%, the remainder being aluminium, unavoidable impurity elements individually <0.05%, in total <0.15%,
   and the combined content of Mg and Cu satisfies the following relation in percent by weight
   0.17% ≤ Mg + Cu ≤ 0.25% and wherein the aluminium alloy strip has an offset yield strength R_p0.2 of at least 45 MPa, a uniform elongation A_g of at least 23%, and an elongation at break A_80mm of at least 30%.
2. Aluminium alloy strip according to claim 1,
   characterized in that
   the aluminium alloy strip has a thickness in the range from 0.2 mm to 5 mm.
3. Aluminium alloy strip according to claim 1 or 2,
   characterized in that the aluminium alloy has a Cu content of at most 0.10% by weight and/or a Mg content in the range of 0.06% by weight to 0.20% by weight.
4. Aluminium alloy strip according to any one of claims 1 to 3,
   characterized in that
   the Mg content of the aluminium alloy is greater than the Cu content of the aluminium alloy.
5. Aluminium alloy strip according to any one of claims 1 to 4,
   characterized in that
   the aluminium alloy has a Cr content ≤ 0.02% by weight, and/or a V content ≤ 0.02% by weight, and/or a Zr content ≤ 0.02% by weight, particularly ≤ 0.01% by weight.
6. Aluminium alloy strip according to any one of claims 1 to 5,
   characterized in that
   the aluminium alloy has an Fe content from 0.4 to 0.7% by weight, and/or a Si content from 0.1 to 0.25% by weight, and/or a Mn content from 1.0 to 1.2% by weight.
7. Aluminium alloy strip according to any one of claims 1 to 6,
   characterized in that
   the aluminium alloy has a Ti content of at least 0.01% by weight.
8. Use of an aluminium alloy strip according to any one of claims 1 to 7 for semi-finished products or components for motor vehicles, particularly for interior door panels.
9. Use of a metal sheet made from an aluminium alloy strip according to any one of claims 1 to 7 as a component in the motor vehicle, particularly as an interior door panel.

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