EP2888383B1 - Aluminium alloy strip which is resistant to intercrystalline corrosion and method for producing same - Google Patents

Description

The invention relates to a cold-rolled aluminum alloy strip consisting of an AlMg-aluminum alloy and a process for its preparation. Furthermore, it is also intended to propose corresponding components made of the aluminum alloy strips.

Aluminum magnesium (AIMg) alloys of the type AA 5xxx are used in the form of sheets or plates or strips for the construction of welded or joined structures in shipbuilding, automobile and aircraft construction. They are characterized in particular by a high strength, which increases with increasing magnesium content. AlMg alloys of the type AA 5xxx with Mg contents of more than 3%, in particular more than 4%, are increasingly prone to intercrystalline corrosion when exposed to elevated temperatures. At temperatures of 70 - 200 ° C, β-Al5Mg3 phases separate out along the grain boundaries, which are called β-particles and can be selectively dissolved in the presence of a corrosive medium. This has the consequence that in particular the very good strength properties and a very good formability aluminum alloy of the type AA 5182 (Al 4.5% Mg 0.4% Mn) is not used in heat-stressed areas, provided that with the presence of a corrosive medium, For example, water in the form of moisture, must be expected. This relates in particular to the components of a motor vehicle, which are usually subjected to a cathodic dip coating (KTL) and then dried in a baking process, since sensitization with respect to intercrystalline corrosion can already be caused by this baking process in conventional aluminum alloy tapes. In addition, for use in the automotive sector, the forming during the production of a component and the subsequent operating load of the component must be taken into account.

The susceptibility to intergranular corrosion is usually tested in a standard test (NAMLT test) according to ASTM G67, in which the samples are exposed to nitric acid and the mass loss due to intergranular corrosion is measured. According to ASTM G67, the mass loss for materials which are not resistant to intergranular corrosion is more than 15 mg / cm ² .

Automotive sheets require very good formability, as in the case of interior door parts, for example. The requirements are essentially determined by the rigidity of the respective component, where the strength of the material plays only a minor role. The components often go through multi-stage forming processes, such as door interiors with integrated window frame areas.

In addition to the corrosion properties, the formability of the AlMg aluminum alloy has a major influence on the possibilities for using these materials. For example, the previously known materials meant that the side walls of a motor vehicle could not be pulled deep from a single sheet, which not only made a redesign of the side wall, but also additional process steps to provide the side wall portion of a motor vehicle required.

The forming behavior can be measured, for example, in a stretch-drawing test by a cupping test according to Erichsen (DIN EN ISO 20482), in which a test piece is pressed against the sheet, so that cold deformation occurs. During cold working, the force as well as the punch travel of the test specimen is measured until there is a load drop, which causes the formation of a crack. The SZ32 stretch drawing measurements mentioned in the application were carried out with a punch head diameter of 32 mm and a die diameter of 35.4 mm with the aid of a Teflon drawing film to reduce the friction. Further measurements of the thermoformability were made by the so-called Plane-Strain-Tiefungsversuch with a Nakajima geometry according to DIN EN ISO 12004 with a punch diameter of 100 mm. For this purpose, specimens with a specified geometry are subjected to deepening tests until the formation of cracks, the subsidence during the crack is then used as a measure of the formability of the material.

From the JP 2011-052290 A an aluminum alloy strip for can lids is known, which should be as strong as possible despite its small thickness. In this case, the band has a recrystallized structure.

Furthermore, from the EP 2 302 087 A1 For example, an aluminum composite chassis member having aluminum alloy layers as outer layers is known. Due to the alloying components used therein, the AL composite material is excellent in strength with high corrosion resistance and low weight.

However, composite solutions consisting of high Mg-containing AA5xxx aluminum alloys with corrosion-protective outer aluminum alloy layers have the disadvantage that the production is complex and also at joints where the aluminum composite is connected to other parts, such as cut edges, holes and breakthroughs continue to increase Risk of corrosion is given.

The present invention is therefore concerned with single-layer aluminum materials. Proceeding from this, the object of the present invention is to provide a single-layered aluminum alloy strip which has sufficient resistance to intergranular corrosion and is nevertheless very easy to form, so that large-area deep-drawn parts, for example door parts of motor vehicles, can be provided with sufficient strength , In addition, a method is to be specified with which single-layer aluminum alloy strips can be produced.

Finally, components produced from the aluminum alloy strips according to the invention are to be specified.

According to a first teaching of the present invention, the object indicated is achieved by a cold-rolled aluminum alloy strip consisting of an AlMg aluminum alloy, the aluminum alloy having the following alloy constituents: Si ≤ 0.2% by weight, Fe ≤ 0.35% by weight, Cu ≤ 0.15% by weight, 0.2% by weight ≤ Mn ≤ 0.35% by weight, 4.1% by weight ≤ mg ≤ 4.5% by weight, Cr ≤ 0.1% by weight, Zn ≤ 0.25% by weight, Ti ≤ 0.1% by weight,

Rest Al and unavoidable impurities individually max. 0.05% by weight, in total max. 0.15 wt .-%, wherein the aluminum alloy strip has a recrystallized structure, the average grain size of the structure between 15 .mu.m and 30 .mu.m, preferably between 15 .mu.m and 25 .mu.m and the final soft annealing of the aluminum alloy strip has been carried out in a continuous furnace.

Within the specification of the AA5182 aluminum alloy, it has been found that there is a specified, narrowly limited alloying range which, on the one hand, has sufficient resistance to intergranular corrosion and, at the same time, taking into account certain secondary conditions, such as mean grain size and the type of final soft annealing, also has an excellent forming behavior. In particular, the combination of the mean grain size with the claimed alloy constituents of the aluminum alloy of the aluminum alloy strip make it possible to achieve degrees of deformation which, with sufficient strength, allow the production of deep-drawn sheet-aluminum parts of large area. In particular, it has been shown that the use of a continuous furnace instead of a conventionally carried out Coilglühung in a chamber furnace significantly increases the formability again.

According to a first aspect of the aluminum alloy strip, the aluminum alloy additionally has one or more of the following restrictions on the contents of alloy components: 0.03% by weight Si ≤ 0.10% by weight, Cu ≤ 0.1%, preferably 0.04% ≤ Cu ≤ 0.08%, Cr ≤ 0.05% by weight, Zn ≤ 0.05% by weight, 0.01% by weight ≤ Ti ≤ 0.05% by weight

The limited alloying content of copper to at most 0.1% by weight leads to an improvement in the corrosion resistance of the aluminum alloy strip. With a Cu content of 0.04 wt .-% to 0.08 wt .-% is achieved that copper participates in an increase in strength, but still does not reduce the corrosion resistance too strong. Higher contents of silicon, chromium, zinc and titanium than the stated values lead to a deteriorated formability of the aluminum alloy. The amount of silicon present in the alloy of 0.03 to 0.1 wt .-% leads in combination with the iron and manganese 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 without adversely affecting other properties such as formability or corrosion behavior.

Titanium is commonly added in continuous casting of the aluminum alloy as a grain refining agent, for example in the form of Ti-boride wire or rods. Therefore, in another embodiment, the aluminum alloy has a Ti content of at least 0.01% by weight.

A further improvement of the corrosion behavior and the formability of the aluminum alloy strip can be achieved in that the aluminum alloy additionally has one or more of the following restrictions on the contents of alloy constituents: Cr ≤ 0.02 wt.%, Zn ≤ 0.02% by weight

It has been found that chromium significantly influences the formability of the aluminum alloy strip in contents below the contamination threshold of 0.05% by weight and thus in the smallest possible amounts in the aluminum alloy of the aluminum alloy strip according to the invention may be included. The zinc content is set below the impurity threshold of 0.05% by weight so as not to deteriorate the general corrosion behavior of the aluminum alloy ribbon.

In addition, it has been found that iron within the values allowed according to the AA5182 aluminum alloy, in combination with the silicon and manganese contents as described above, has an effect on formability. Iron contributes to the temperature resistance of the aluminum alloy ribbon in combination with silicon and manganese, so that the Fe content of the aluminum alloy ribbon according to a next aspect is preferably 0.1 wt% to 0.25 wt% or 0.10 wt%. to 0.20 wt .-% is.

The same applies to the Mn content according to another embodiment of the aluminum alloy strip, which should preferably be limited to 0.20 wt .-% to 0.30 wt .-%, in order to achieve optimum formability of the aluminum alloy strip.

A particularly good compromise between the provision of high strength, good corrosion resistance against intergranular corrosion and improved forming properties can be achieved according to a further embodiment of the aluminum alloy strip having a Mg content of 4.2 wt .-% to 4.4 wt .-%.

In order to provide the necessary strength for the applications, the aluminum alloy strip according to a next embodiment has a thickness of 0.5 mm to 4 mm. Preferably, the thickness is 1 mm to 2.5 mm, as in this area are the most applications of the aluminum alloy strip.

Finally, in particular areas of application in the automotive sector for the aluminum alloy _{strip according} to the invention are made possible by the fact that the aluminum alloy _strip in the soft state has a yield strength R _p0.2 of min. 110 MPa and a tensile strength R _m of min. 255 MPa. It has been found that especially aluminum alloy tapes with corresponding yield strengths and tensile strengths are particularly well suited for use in the automotive sector.

• Gießen eines Walzbarrens, vorzugsweise im DC-Strangguss,
• Homogenisieren des Walzbarrens bei 480 °C - 550 °C für min. 0,5 Std.,
• Warmwalzen des Walzbarrens bei einer Temperatur von 280 °C bis 500 °C,
• Kaltwalzen des Aluminiumlegierungsbandes an Enddicke mit einem Abwalzgrad von 40 % bis 70 % oder 50 % bis 60 % und
• Weichglühen des fertig gewalzten Aluminiumlegierungsbandes bei 300 °C - 500 °C in einem Durchlaufofen

According to a second teaching of the present invention, the above-described object is achieved by a method for producing an aluminum alloy strip according to the above-described embodiments in that the method comprises the following method steps:

• Casting a rolling bar, preferably in DC continuous casting,
• Homogenizing the rolling ingot at 480 ° C - 550 ° C for min. 0.5 hours,
• Hot rolling of the rolling ingot at a temperature of 280 ° C to 500 ° C,
• Cold rolling of the aluminum alloy strip to final thickness with a rolling degree of 40% to 70% or 50% to 60% and
• Annealing of the finished rolled aluminum alloy strip at 300 ° C - 500 ° C in a continuous furnace

It has been found that with the specified parameters in conjunction with the aluminum alloy constituents mentioned, an aluminum alloy strip with mean particle sizes of 15 .mu.m-30 .mu.m can be produced, which has sufficient resistance to intercrystalline corrosion, provides sufficient strength and, in addition, has very good forming properties , deep-drawn sheet metal parts can be produced. The homogenization of the rolling ingot ensures a homogenous structure and a homogeneous distribution of the alloy components in the hot rolling bar to be rolled. Hot rolling at temperatures of 280 ° C - 500 ° C allows for continuous recrystallization during hot rolling with hot rolling typically to a thickness of 2.8mm - 8mm. The final cold rolling step is limited to a degree of rolling of 40% to 70% or 50% to 60%, to provide in both cases in the soft annealing for a continuous recrystallization of the aluminum alloy strip. The bigger the Abwalzgrad the aluminum alloy strip, the lower the average grain sizes, it has been found that above 70% degree of reduction in the final annealing can result in a too small average grain size. Below 40% degree of reduction in the soft annealing, the average grain sizes are again too large, so that although the resistance to intergranular corrosion increases, but the formability is reduced. The soft annealing of the finished rolled aluminum alloy strip takes place in the continuous furnace, which usually heating rates of 1-10 ° C / sec. and thus, in contrast to chamber furnaces, in which an entire coil is heated, due to the rapid heating have a significant influence on the subsequent properties of the structure of the aluminum alloy strip. In particular, it has been found that in soft annealing in a continuous furnace improved formability of the strip is achieved in comparison to variants annealed in the chamber furnace.

• Kaltwalzen des warmgewalzten Aluminiumlegierungsbandes auf eine Zwischendicke, welche derart bestimmt ist, dass der abschließende Kaltwalzgrad an Enddicke 40 % bis 70 % oder 50 % bis 60 % beträgt
• Zwischenglühen des Aluminiumlegierungsbandes bei 300 °C bis 500 °C,
• Kaltwalzen des Aluminiumlegierungsbandes an Enddicke mit einem Abwalzgrad von 40 % bis 70 % oder 50 % bis 60 %,
• Weichglühen des fertig gewalzten Aluminiumlegierungsbandes bei 300 °C bis 500 °C in einem Durchlaufofen

Alternatively, according to a further embodiment of the method, the aluminum alloy strip can also be produced with an intermediate annealing. According to this alternative variant, the following method steps are alternatively carried out after hot rolling:

• Cold rolling the hot rolled aluminum alloy strip to an intermediate thickness determined such that the final cold rolling degree at final thickness is 40% to 70% or 50% to 60%
• Intermediate annealing of the aluminum alloy strip at 300 ° C to 500 ° C,
• Cold rolling of the aluminum alloy strip to final thickness with a rolling degree of 40% to 70% or 50% to 60%,
• Annealing of the finished rolled aluminum alloy strip at 300 ° C to 500 ° C in a continuous furnace

The intermediate annealing of the aluminum alloy strip can take place both in the chamber furnace and in the continuous furnace. An influence on the formability could not be determined. The decisive factor is which degree of rolling is achieved during cold rolling to final thickness and whether the soft annealing of the strip takes place in the continuous furnace.

As a result, regardless of the type of intermediate annealing, the formability and the corrosion resistance are determined in connection with the alloy composition.

In order to prevent a further change in the structural state in the wound state after the soft annealing, the aluminum alloy strip according to a further embodiment of the method after annealing to a temperature of max. 100 ° C, preferably to max. Cooled to 70 ° C and then wound up.

As already stated above, according to another embodiment of the method, the intermediate annealing can be carried out in a batch furnace or in a continuous furnace.

If the aluminum alloy strip cold rolled to a final thickness of 0.5 mm - 4 mm, preferably to a final thickness of 1 mm - 2.5 mm, the typical application areas, especially in automotive very well convertible sheets are available, which can be deep-drawn extensively and simultaneously provide high strength combined with adequate corrosion resistance to intergranular corrosion.

Preferably, the soft annealing is carried out in a continuous furnace at a metal temperature of 350 ° C - 550 ° C, preferably at 400 ° C - 450 ° C for 10 sec. - 5 min., Preferably 20 sec. - 1 min. This ensures that the cold strip sufficiently recrystallized and the corresponding properties in terms of the very good formability and the average grain size with high process reliability and efficiency can be achieved.

Finally, the object shown above is achieved by a component for a motor vehicle, which consists of the aluminum alloy strip according to the invention. The components are characterized by the fact that they, as already stated, can be deep-drawn over a large area and thus, for example, large-area components can be made available for the automotive industry. In addition, these have due to the provided strength also the necessary rigidity and corrosion resistance, which are required for use in motor vehicle construction on.

It is conceivable, for example, that the component is according to a further embodiment, a body part or a body part of a motor vehicle, which is loaded in addition to high strength requirements and temperature. The "body-in-white parts", for example a door inner part or a tailgate inner part, are preferably produced from the aluminum alloy strip according to the invention.

Fig. 1

Ein schematisches Ablaufdiagramm eines Ausführungsbeispiels des Herstellungsverfahrens des Aluminiumlegierungsbandes,

Fig. 2a

in einer Draufsicht die Probengeometrie für die Plane-Strain-Tiefungsmessung gemäß DIN EN ISO 12004,

Fig. 2b

in einer Schnittansicht den schematischen Versuchsaufbau der Plane-Strain-Tiefungsmessung gemäß DIN EN ISO 12004,

Fig. 3

in einer Schnittansicht die Versuchsanordnung zur Tiefungsmessung SZ32 im Erichsen Tiefungsversuch nach DIN EN ISO 20482 und

Fig. 4

ein typisches Ausführungsbeispiel für ein großflächiges, tiefbezogenes Blechteil gemäß der vorliegenden Erfindung.

In addition, the invention will be explained in more detail with reference to embodiments in conjunction with the drawings. The drawing shows in

Fig. 1

A schematic flow diagram of an embodiment of the manufacturing process of the aluminum alloy strip,

Fig. 2a

in a plan view, the sample geometry for the Plane-Strain-Tiefungsmessung according to DIN EN ISO 12004,

Fig. 2b

in a sectional view of the schematic experimental setup of the Plane-Strain-Tiefungsmessung according to DIN EN ISO 12004,

Fig. 3

in a sectional view of the test arrangement for Tiefungsmessung SZ32 in Erichsen roughness test according to DIN EN ISO 20482 and

Fig. 4

a typical embodiment of a large-scale, deep-drawn sheet metal part according to the present invention.

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

In step 1, a rolling ingot of an AlMg aluminum alloy is cast with the following alloying constituents, for example in DC continuous casting: Si ≤ 0.2% by weight, Fe ≤ 0.35% by weight, Cu ≤ 0.15% by weight, 0.2% by weight ≤ Mn ≤ 0.35% by weight, 4.1% by weight ≤ mg ≤ 4.5% by weight, Cr ≤ 0.1% by weight, Zn ≤ 0.25% by weight, Ti ≤ 0.1% by weight,

Residual Al and unavoidable impurities individually a maximum of 0.05 wt .-%, in total not more than 0.15 wt .-%.

Subsequently, the rolling ingot in process step 2 is subjected to homogenization, which can be carried out in one or more stages. In a homogenization temperatures of the rolling ingot are reached from 480 to 550 ° C for at least 0.5 h. In process step 3, the rolling ingot is then hot rolled, with typical temperatures of 280 ° C to 500 ° C can be achieved. The final thicknesses of the hot strip are, for example, 2.8 to 8 mm. The hot strip thickness can be selected so that after hot rolling only a cold rolling step 4 takes place, in which the hot strip with a rolling degree of 40% to 70%, preferably 50% to 60% in its thickness is reduced to the final thickness.

Subsequently, the aluminum alloy strip cold rolled to final thickness is subjected to soft annealing. The soft annealing is carried out according to the invention in a continuous furnace. In the embodiments shown in Table 1 the second way was used with an intermediate glow. For this purpose, the hot strip after hot rolling according to process step 3 is fed to a cold rolling 4a, which cold rolls the aluminum alloy strip to an intermediate thickness, which is determined such that the final cold rolling degree of final thickness 40% to 70% or 50% to 60%. In a subsequent intermediate annealing, the aluminum alloy ribbon is preferably recrystallized throughout. The intermediate annealing was carried out in the embodiments either in a continuous furnace at 400 ° C to 450 ° C or in the chamber furnace at 330 ° C to 380 ° C.

The intermediate annealing is in Fig. 1 represented by the method step 4b. In method step 4c according to Fig. 1 Finally, the intermediate annealed aluminum alloy strip is fed to cold rolling to final thickness, wherein the degree of rolling in step 4c is between 40% and 70%, preferably between 50% and 60%. Subsequently, the aluminum alloy strip is again transferred to the soft state by a soft annealing, wherein the soft annealing is carried out according to the invention in a continuous furnace at 400 ° C to 450 ° C. The anneals of Comparative Examples in Table 4 were carried out in the chamber furnace (KO) at 330 ° C to 380 ° C. In the various tests, different degrees of rolling were set after intermediate annealing in addition to different aluminum alloys. The values for the degree of rolling after the intermediate annealing are also given in Tables 1 and 4. In addition, the mean grain diameter of the soft-annealed aluminum alloy strip was determined. For this purpose, longitudinal slices were anodized according to the Barker method and then measured under the microscope in accordance with ASTM E1382 and the mean grain size determined by the mean grain diameter.

Mechanical properties, in particular the yield strength R _p0.2 , tensile strength R _m , the uniform elongation Ag and the elongation A _{80 mm were} determined on the correspondingly produced aluminum alloy _strips , Table 2, 5. In addition to the mechanical parameters measured according to EN 10002-1 or ISO 6892 The aluminum alloy strips are also given the mean particle sizes according to ASTM E1382 in μm. In addition, the corrosion resistance was against Intercrystalline corrosion measured according to ASTM G67, without additional heat treatment in the initial state (output 0h). In order to simulate use in motor vehicles, the aluminum alloy strips were subjected to different heat treatments before the corrosion test. A first heat treatment consisted of storing the aluminum strips for 20 minutes at 185 ° C to image the KTL cycle.

In a further series of measurements, the aluminum alloy strips were additionally stored for 200 hours or 500 hours at 80 ° C. and then subjected to the corrosion test. In addition, since transformations of aluminum alloy tapes or sheets may affect the corrosion resistance, the aluminum alloy tapes were further stretched by about 15%, subjected to heat treatment at elevated temperature, and then subjected to intergranular corrosion test according to ASTM G67, in which the mass loss was measured.

In Table 1, the alloy contents of a total of four different aluminum alloys which are within the specification of the AA5182 aluminum alloy are indicated. The reference alloy represents the material used hitherto and is given in comparison to variants 1, 2 and 3. In addition, Table 1 gives an indication of the type of final annealing, the degree of final rolling and the measured mean grain size (grain diameter) in μm. The variants 1 and 2 differed only in the final rolling, which leads to the formation of a different grain size. Thus variant 2 differs from variant 1, apart from almost identical alloy components, essentially by a final rolling degree of 57% at identical belt continuous furnace conditions. The result was that variant 2 had a mean particle size of 18 μm compared to 33 μm of variant 1. The tapes in Table 1 were brought to a temperature of 400 ° C - 450 ° C in a continuous band oven for 20 sec. -1 min., Then cooled and wound up at less than 100 ° C. The samples taken were then measured according to the corresponding DIN EN ISO standards as indicated in Table 2.

It is clear from Table 2 that variant 1 does not reach the value of 110 MPa with respect to the yield strength and that it has a value of less than 110 MPa in the diagonal measurement, marked with the symbol D. The measurement in the rolling direction L and transverse to the rolling direction Q, however, showed that variant 1 just reached a yield strength R _p0.2 of 110 MPa. The reference as well as the variants 2 and 3 were clearly above this lower limit for the yield strength. The embodiment variant 2 according to the invention certainly reached the yield strength values of at least 110 MPa in all tensile directions. It can be clearly seen that variant 3 with the highest Mg content of 4.95% by weight achieves the highest yield strength and tensile strength values. In addition, it can be seen that the varying degree of rolling between variants 1 and 2 not only significantly affects the grain size, but in particular raises the yield strength to a value of significantly more than 110 MPa.

In particular, the alloy variant 2 according to the invention has a lower anisotropy compared to the reference, which is reflected in low values of the planar anisotropy Δ r . In this case, the planar anisotropy Δ r is defined as ½ · (r _L + rQ-2r _D ), where r _L , r _Q and r _D correspond to the r values in the longitudinal, transverse or diagonal direction. The mean r-value is different r calculated from 1/4 x (rL + rQ + 2r _D ), not significantly different from that of the reference material.

Table 3 now shows the measured values taken with respect to intergranular corrosion resistance. It has been found that variant 2 according to the invention has comparable values with respect to the measured values of the reference, in particular with regard to the long-term loading, both in the stretched state and in the unstretched state. Here the variant 2 and the reference are nearly identical. Variant 3, which has the highest yield strength and tensile strength values, showed in the corrosion test, however, that the excessive Mg content would lead to excessive mass loss, especially in the long-term tests, which in addition to a short temperature cycle of 20 min of 200 hrs. at 80 ° C have resulted in.

With regard to the measurements in Table 3 with respect to the formability, it was found that, in particular, variant 2 was superior to the reference alloy in the stretch-drawing properties in the SZ32 deepening test as well as in the plane-strain creep test. The significantly improved forming behavior of the aluminum alloy strip according to Variant 2 over the reference aluminum alloy strip shows that even with a reduced Mg content, equivalent yield strengths and tensile strengths can be achieved with the reference alloy without sacrificing resistance to intergranular corrosion. This was demonstrated in particular by the mass loss measurement according to ASTM G67 in the NAML test. Significantly, variant 2 was used to determine an improvement of the thermoforming behavior in the Erichsen crimping test by 7% and in the plane strain crimping test by about 10%, which shows the additional forming potential of the aluminum alloy strips according to the invention. This additional forming potential can be used to produce deep-drawn, large-area sheet-metal shaped parts, for example, door inner parts of a car.

In addition, the experimental setup for the "SZ32 Sump" test according to DIN EN ISO 20482 as well as the Plane-Strain Seaming Test in accordance with Nakajima geometry according to DIN EN ISO 12004 will be briefly explained.

In the Fig. 2a the geometry of the sample body 1 is shown. From a circular sheet metal blank of the waisted specimen 1 is cut so that the web 4 has a width of 100 mm and the radii 2 at the waistings 20 mm. With the measure 3, which is 100 mm, the punch diameter is shown. Fig. 2b now shows the specimen 1 clamped between two hold-downs 5, 6. The specimen 1, which was placed on a receptacle 8 and was pressed over the holders 5, 6 against the support, with a punch 7, which is a hemispherical tip with a radius of 100 mm, pulled in the direction of the arrow. The hold-downs additionally have inlet radii of 5 or 10 mm on their side facing the support 8. The force with which the tilling test is performed becomes during deformation measured and a sudden load drop, which signals the formation of a crack, leading to the measurement of the corresponding Ziehstempeltiefe.

A similar structure shows the deepening trial "Suzin SZ32" according to Erichsen, although no waisted samples are used. Here, only a test piece 9 is held between a hold-down 10 and a receptacle 11 and pulled with a punch 12 until a load drop in the pulling force can also be measured. Subsequently, in turn, the corresponding position of the punch is measured. The opening of the die in Fig. 3 was 35.4 mm, the punch head diameter 32 mm, ie the punch radius was 16 mm. In addition, a Teflon drawing film was used to reduce friction in SZ32.

In Tables 4 and 5, further embodiments and comparative examples have now been prepared and measured in terms of their mechanical properties and resistance to intergranular corrosion. It was found that the combination of the use of the continuous furnace in conjunction with a specifically selected particle size of 15 μm-30 μm, preferably 15 μm-25 μm, leads to a good compromise between corrosion resistance and mechanical measured values. For example, the embodiments of the invention no. 3, 4, 7 and 11 are equipped with sufficient resistance to intergranular corrosion and also have the necessary for use in the automotive sector mechanical measurements R _p0,2 and R _m , so that this ideal for Provision of large, deep-drawn components are suitable.

In Fig. 4 For example, a corresponding body-in-white part, in the form of a door inner part, can be produced using the aluminum alloy strip of the present invention from a single, deep-drawn sheet metal, the sheet thickness being preferably 1.0-2.5 mm In addition, further parts of a motor vehicle in a sheet metal shell design are conceivable, such as the inner parts of the boot lid, bonnet, as well as components in the vehicle structure, which have high demands on formability and intergranular corrosion. Table 1 Material [wt .-%] Si Fe Cu Mn mg Cr Zn Ti impurities final annealing Final rolling degree (cold rolling)% Grain size [μm ] minute 0.20 4.0 Individually max. 0.05 AA 5182 Max. 0.20 0.35 0.15 0.50 5.0 0.10 0.25 0.10 in total max. 0.15 reference 0.07 0.24 0,036 0.3 4.57 0.005 0007 0.016 0.05 BDLO 46 15 0.15 Var. 1 0.06 0.16 0,004 0.27 4.37 0,008 0,002 0,013 0.05 BDLO 21 33 0.15 Var. 2 0.06 0.16 0,004 0.27 4.38 0,008 0,003 0,013 0.05 BDLO 57 18 0.15 Var. 3 0.05 0.17 0.023 0.26 4.95 0,008 0,003 0.026 0.05 BDLO 57 17 0.15 sample Pos. _Rp0.2 R _m A _g A _{g (corrected)} A _80mm A _80mm (hand) Z value n value r value Δ r r N / mm ² N / mm ² % % % % % reference L 137 284 21.3 20.7 24.5 25.2 69 0.316 0.827 0.197 0.754 D 133 276 22.2 21.4 25.2 25.8 72 0306 0.704 Q 133 277 21.9 21.6 25.5 26.3 71 0,305 0.779 Var.1 L 110 262 21.2 21.9 25.9 26.4 71 0.335 0.668 -0.363 0.779 D 107 256 24.7 23.0 27.7 28.7 72 0.338 0.870 Q 111 259 22.0 21.2 24.6 25.7 65 0.332 0.708 Var.2 L 128 266 23.2 22.7 26.8 27.7 67 0.332 0.724 0,035 0.693 D 127 261 23.1 22.2 26.2 27.0 67 0.332 0.685 Q 128 262 23.9 22.5 26.5 27.6 66 0.333 0.681 Var.3 L 141 290 24.1 23.5 28.4 29.1 70 0.335 0.697 -0.12 0,710 D 140 286 22.6 23.4 27.0 27.8 68 0,336 0,740 Q 141 286 22.6 23.3 27.1 27.7 65 0.335 0.663 DIN EN ISO 6892-1: 2009 DIN EN ISO 10275: 2009 DIN EN ISO 10113: 2009 IK-mass losses formability variant not thermally treated 20 min. 185 ° C 20 min 185 ° C plus 200 h 80 ° C 17h 130 ° C 15% stretched 20 min. 185 ° C 15% stretched 20 min.185 ° C plus 200 h 80 ° C Deepening SZ32 [mm] Tarpaulin Straining [mm] limit 2.0 4.0 35.0 50.0 15.0 45.0 reference 1.2 2.1 29.8 48.8 10.4 42.1 14.2 27.9 Var. 1 (compare) 1.2 1.7 10.4 21.3 4.4 12.9 14.5 30.3 Var. 2 (Erf.) 1.2 2.4 33.7 42.2 13.5 40.1 14.6 30.7 Var. 3 (compare) 1.3 5.3 41.7 55.0 30.4 53.5 14.6 31.6 No alloy Final rolling degree [%] final annealing Grain size [μm] Si Fe Cu Mn mg Cr Zn Ti 1 III 46 KO 16 0.07 0.24 0,040 0.30 4.50 0.005 0,007 0.016 3 II 57 BDLO 18 0.06 0.16 0,004 0.27 4.35 0,008 0,002 0,013 4 I 45 BDLO 18 0.03 0.13 0,002 0.25 4.15 0.001 0,004 0,021 6 I 45 KO 21 0.03 0.13 0,002 0.25 4.15 0.001 0,004 0,021 7 III 30 BDLO 22 0.07 0.24 0,040 0.30 4.50 0.005 0,007 0.016 11 III 25 BDLO 27 0.07 0.24 0,040 0.30 4.50 0.005 0,007 0.016 13 I 32 BDLO 29 0.03 0.13 0,002 0.25 4.15 0.001 0,004 0,021 15 III 30 KO 30 0.07 0.24 0,040 0.30 4.50 0.005 0,007 0.016 16 I 25 BDLO 31 0.03 0.13 0,002 0.25 4.15 0.001 0,004 0,021 18 II 21 BDLO 33 0.06 0.16 0,004 0.27 4.35 0,008 0,002 0,013 20 I 20 BDLO 34 0.03 0.13 0,002 0.25 4.15 0.001 0,004 0,021 IK mass losses, unstretched ** IK-mass losses, 15% stretched ** mechanical characteristics, state soft No Output [0h) 20 min. 185 ° C 20 min. 185 ° C + 200 h 80 ° C 20 min. 185 ° C + 500 h / 80 ° C 20 min, 185 ° C 20 min. 185 ° C + 200 h 80 ° C R _{p 0 , 2} R _m A _g A _80mm Result 1 III 15.4 16.6 25.7 26.9 18.8 33.6 135 279 20.7 25.2 comparison 3 II 1.2 2.4 33.7 36.7 13.5 40.1 128 262 23.9 26.5 invention 4 I 1.3 1.9 17.8 22.2 1.6 20.1 117 258 22.8 25.3 invention 6 I 8.2 10.8 18.6 22.1 9.6 20.7 106 250 23.8 26.7 comparison 7 III 1.1 1.7 18.0 24.5 3.3 25.1 119 276 20.3 24.9 invention 11 III 1.1 1.6 14.3 17.7 2.8 19.8 116 275 20.2 24.4 invention 13 I 1.1 1.2 13.3 16.7 2.1 17.4 104 251 22.2 24.8 comparison 15 III 2.8 3.0 7.9 10.9 6.4 18.0 125 281 19.5 23.6 comparison 16 I 1.1 1.3 10.8 13.1 1.9 14.2 103 252 21.6 26.1 comparison 18 II 1.2 1.7 10.4 12.5 4.4 12.9 109 259 22.0 24.6 comparison 20 1 1.1 1.2 8.3 11.1 1.7 12.4 101 251 20.8 25.1 comparison

Claims (16)

1. Cold-rolled aluminium alloy strip composed of an AlMg aluminium alloy, characterised in that the aluminium alloy has the following alloying elements: Si ≤ 0.2 wt.%, Fe ≤ 0.35 wt.%, Cu ≤ 0.15 wt.%, 0.2 wt.% ≤ Mn ≤ 0.35 wt.%, 4.1 wt.% ≤ Mg ≤ 4.5 wt.%, Cr ≤ 0.1 wt.%, Zn ≤ 0.25 wt.%, Ti ≤ 0.1 wt.%, the remainder being Al and inevitable impurities, amounting to a maximum of 0.05 wt.% individually and to a maximum of 0.15 wt.% in total, wherein the aluminium alloy strip has a recrystallized microstructure, the grain size of the microstructure ranges from 15 µm to 25 µm and the final soft annealing of the aluminium alloy strip is performed in a continuous furnace.
2. Aluminium alloy strip according to Claim 1, characterised in that aluminium alloy the aluminium alloy also has one or more of the following restrictions to the contents of alloying elements: 0.03 wt.% Si ≤ 0.10 wt.%, Cu ≤ 0.1, Cr ≤ 0.05 wt.%, Zn ≤ 0.05 wt.%, 0.01 wt.% ≤ Ti ≤ 0.05 wt.%.
3. Aluminium alloy strip according to Claim 1 or 2, characterised in that the aluminium alloy also has one or more of the following restrictions to the contents of alloying elements:

   Cr ≤ 0.02 wt.%,

   Zn ≤ 0.02 wt.%.
4. Aluminium alloy strip according to any one of Claims 1 to 3, characterised in that the Fe content is 0.10 wt.% to 0.25 wt.% or 0.10 wt.% to 0.2 wt.%.
5. Aluminium alloy strip according to any one of Claims 1 to 4, characterised in that the Mn content is 0.20 wt.% to 0.30 wt.%.
6. Aluminium alloy strip according to any one of Claims 1 to 5, characterised in that the Mg content is 4.2 wt.% to 4,4 wt.%.
7. Aluminium alloy strip according to any one of Claims 1 to 6, characterised in that the aluminium alloy strip has a thickness of 0.5 mm to 4 mm.
8. Aluminium alloy strip according to any one of Claims 1 to 7, characterised in that the aluminium alloy strip in the soft state has a yield point R_p0.2 of at least 110 MPa and a tensile strength R_m of at least 255 MPa.
9. Method for producing an aluminium alloy strip according to any one of Claims 1 to 8 comprising the following process steps:

   - casting a rolling ingot;

   - homogenisation of the rolling ingot at 480°C to 550°C for at least 0.5 hours;

   - hot rolling of the rolling ingot at a temperature of 280°C to 500°C;

   - cold rolling of the aluminium alloy strip to the final thickness with a degree of rolling of 40% to 70% or 50% to 60%; and

   - soft annealing of the finished-rolled aluminium alloy strip at 300°C to 500°C in a continuous furnace.
10. Method according to Claim 9, wherein after hot rolling alternatively the following process steps are performed:

    - cold rolling of the hot-rolled aluminium alloy strip to an intermediate thickness which is determined in such a way that the final degree of cold rolling to the final thickness is 40% to 70% or 50% to 60%;

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

    - cold rolling of the aluminium alloy strip to the final thickness with a degree of rolling of 40% to 70% or 50% to 60%;

    - soft annealing of the finish-rolled aluminium alloy strip at 300°C - 500°C in a continuous furnace.
11. Method according to Claim 9 or 10, characterised in that aluminium alloy strip after soft annealing is cooled to a maximum temperature of 100°C and then coiled.
12. Method according to any one of Claims 10 or 11, characterised in that the intermediate annealing is performed in a batch furnace or in a continuous furnace.
13. Method according to any one of Claims 9 to 12, characterised in that the aluminium alloy strip is cold rolled to a final thickness of 0.5 mm to 4 mm.
14. Method according to any one of Claims 9 to 13, characterised in that the soft annealing is performed in the continuous furnace at a metal temperature of 350°C to 550°C for 10 seconds to 5 minutes.
15. Component for a motor vehicle, composed of an aluminium alloy strip according to any one of Claims 1 to 8.
16. Component according to Claim 15, characterised in that the component is a body part or a body accessory of a motor vehicle.

Images