EP1749112B1 - Malleable, high mechanical strength aluminum alloy which can be anodized in a decorative manner, method for producing the same and aluminum product based on said alloy - Google Patents

Abstract

The invention relates to a malleable, high mechanical strength aluminum alloy of the AlMgSi type which can be anodized in a decorative manner, to a semifinished product produced from said alloy, in the shape of strips, sheets or extruded profiles, and to a structural component produced from the above semifinished products, especially a reshaped component that has been anodized in a decorative manner. The invention also relates to a method for producing an aluminum alloy component of the above type. Said aluminum alloy has good malleability, achieved by weight percentages of strontium in the alloy and defined weight ratios of silicon to magnesium and iron to strontium.

Description

The invention relates to a decorative anodizable, well deformable and mechanically highly resilient aluminum alloy of the type AlMgSi, a semi-finished product of this alloy, in the form of tapes, sheets or extruded profiles and a made of the aforementioned semi-finished, in particular deformed and decorative anodized component. Within the scope of the invention is also a process for producing such an aluminum alloy.

Non-alloyed aluminum (1xxx alloys), AlMg alloys (5xxx alloys or clad 8xxx alloy cladding, unalloyed aluminum cladding (lxxx alloy) are generally used to produce decorative anodized aluminum sheet components not hardenable, ie an increase of the strength takes place exclusively by a cold work hardening, a reduction in consequence then by defrosting annealing.All of these systems have in common that their formability and their strength state by the Semi-finished delivery state, which may be either solidified by rolling or softened by a subsequent annealing, for example, is set. It is therefore possible in the sense of good formability to use these systems in a state of maximum softening and then reshape. After the forming process, however, curing to improve the performance is no longer possible. In terms of good performance properties, the systems can be used in a high-strength condition, but the forming capacity for a forming step, due to the high initial strength of the delivery condition, is severely limited.

Thermosetting AlMgSi alloys (6xxx) with good formability are for example from EP 0 714 993 respectively. EP 0 811 700 known. The disclosed AlMgSi alloys are also used for the production of tapes and sheets. Due to the good thermoformability, they are suitable for the production of body panels for the automotive industry. The alloy composition disclosed there achieves an optimum between good strength and good forming behavior. However, these alloys are not decorative, especially not high gloss, anodisierbar, since on the one hand in the EP 0 811 700 The disclosed iron content of 0.25 to 0.55% by weight is too high and causes turbidity of the anodized layer. It is known that the FeSiMgMn intermetallic quaternary phases formed by the iron are incorporated in the anodized layer. These coarse particles lead to a scattering of light in the anodized layer, which appears to the observer as clouding. Also with the in EP 0 714 993 mentioned levels of vanadium in the order of 0.05 to 0.4% by weight is not sufficiently transparent anodized to achieve. Vanadium at higher levels is also difficult to dissolve in the melt. Replacement of the vanadium with other recrystallization inhibitors, such as zirconium or chromium, also does not provide the desired result. Chromium and zircon lead to an anodized coating, which has a yellowish effect when polished or gloss anodised.

A known A199.9MgSi alloy (6401 special) for extruded profiles used by the Applicant for decorative components therefore contains no zirconium, vanadium or chromium. Likewise, the contamination of the AlMgSi alloy with iron is limited to 0.04 wt% iron. This ensures that the aforementioned anodizing errors are avoided and a high gloss size of the polished and gloss anodised component is achieved. Due to the lack of recrystallization inhibitors (Fe, Zr, Cr, V), however, such an alloy does not show optimal forming capacity, since the relatively coarse grain causes constrictions and orange peel at an early stage.

The document EP-A-0 676 480 discloses an aluminum alloy having a composition of: 0.2 up to 2 Wt% silicon, 0.3 to 1.7 Wt% magnesium, 0 to 1.2 % By weight of copper, 0 to 1.1 Wt% manganese, 0.01 to 0.4 Chrome, at least one of the elements from the group 0.01 to 0.3 Wt% vanadium, 0.001 to 0.1 % By weight of beryllium, and 0.01 to 0.1 Wt% strontium,

Remaining aluminum and unavoidable impurities.

As a result, selection of an alloy composition for an extruded or rolled product is a trade-off in deformation flexibility, decorative appearance and mechanical strength expressed in ultimate strength, ductility and toughness.

The invention has for its object to provide an aluminum alloy available for components that have good formability, which have sufficient strength and ductility in the application state and decorative decorative anodization.

This object is achieved with an aluminum alloy with the composition mentioned in claim 1 and the features listed there. The optimum properties with regard to mechanical strength and deformation behavior are achieved, on the one hand, by the proportion of 0.3 to 0.9% by weight of silicon and 0.1 to 0.5% by weight of magnesium, the weight ratio of these two constituents being set such that Excess of silicon over magnesium is present, in particular a silicon-magnesium weight ratio of 1.8 to 3.3. The strength is further assisted by a proportion of 0.1 to 0.4% by weight of copper, which causes a Mischlcristallhärtung. The good forming capacity is determined by the proportion the recrystallization inhibitor (iron, zirconium, chromium, vanadium) guaranteed. Iron is often present in a starting alloy as an impurity. However, it can also be added up to a proportion of 0.2% by weight. Zirconium, chromium and vanadium may be contained individually or together up to a proportion of 0.22% by weight in the alloy. Despite the presence of the aforementioned recrystallization inhibitors, the alloy according to the invention is decorative anodizable and does not show a yellowish or cloudy anodized layer. This is effected by the proportion of 0.005 to 0.1% by weight of strontium. It is believed that the strontium alters the iron zirconium, chromium and / or vanadium-containing phases, in particular, to such an extent that, even when incorporated into the anodizing layer, they do not cause any visible haze. It has surprisingly been found that a weight ratio of iron to strontium
3: 1 to 5:
proves to be particularly advantageous.

Such an alloy is made of aluminum base material with more than 99.85 wt% aluminum. To the melt, the alloying ingredients are added as follows, namely 0.3 to 0.9% by weight silicon, 0.1 to 0.5% by weight magnesium, wherein the weight ratio of silicon to magnesium is 1.8: 1 to 3.3: 1 is. After determining the iron content of the aluminum base material, which may be present as an impurity in the base material, further iron is alloyed if necessary so that the alloy to be produced contains up to 0.2% by weight of iron. Further, 0.005 to 0.1% by weight of strontium is added, with the weight ratio of iron to strontium being adjusted from 3: 1 to 5: 1. Preference is given to an addition of 0.008 to 0.07% by weight of strontium. 0.1 to 0.4% by weight of copper, 0.03 to 0.2% by weight of manganese, 0.01% by weight of titanium and zirconium and / or chromium and / or vanadium in total of 0.08 to 0.22 are used as further alloy constituents % By weight added. The alloy should contain no more than 0.04% by weight of zinc, not more than 0.02% by weight. unavoidable impurity individually or not more than 0.15% by weight in total. Furthermore, a certain amount, namely 0.0005 to 0.005% by weight of silver can be added to identify the alloy.

The melt produced in this way is cast in a continuous casting process to form a rolling ingot or continuous casting bolt and then homogenized (annealing for at least 2 hours at at least 500 ° C.). The aluminum base material used is preferably pure aluminum with at least 99.85% by weight of aluminum in order to limit the proportion of impurities; overall, a content of not more than 0.15% by weight of unavoidable impurities should not be exceeded. The alloying ingredients may be added in the form of pure metals or master alloys. The strontium is preferably added in the form of an aluminum-strontium master alloy, in particular by means of an AlSr3.5 master alloy, an AlSr5 master alloy or an AlSr10 master alloy.

From the homogenized continuous casting bolt of the aluminum alloy according to the invention can be obtained by extrusion open or hollow profile sections, which are stretched in the rule and assembled by sawing. From the profile pieces brought to the desired length can be produced by subsequent forming, in particular cold forming, such as rolling, bending, deep drawing or active media based sheet and tube forming, three-dimensionally shaped shell components. Regardless of whether the forming is a bending process, an active-medium-based forming or deep-drawing, the resulting component shows good contour accuracy with very little orange peel formation, caused by low springback. Due to the hardenability of the alloy, the strength and ductility can be adjusted after forming. After curing, in addition to possible mechanical processing, in particular a chemical and electrolytic treatment of the component follows. Such chemical and electrolytic treatment includes polishing, glazing, anodizing, eventually a coloring and a final compaction of the components. The resulting anodized layer of the decorative anodized shaped aluminum component is very satisfactory, it is transparent, ie not cloudy and not yellowish.

From the ingot can be achieved by hot rolling sheet steel, which can be further processed by cold rolling and intermediate annealing. By further forming steps (possibly recrystallization and / or Entfestigungsglühung), such as deep drawing, active media-based sheet metal forming, including patterning and smoothing or roughening the surfaces and possibly re-annealing, optionally mechanical machining, a shell component is formed, which also subsequently by chemical or electrolytic treatment with a decorative Eloxalschicht can be provided. In this production process, too, it can be demonstrated that the aluminum alloy has a good to very good deformation behavior at room temperature with only slight orange peel formation, has a stable forming behavior and leads to a good contour accuracy of the component. The anodized coating shows no defects, on the contrary, even glossy surfaces can be realized if pure aluminum with at least 99.9% by weight aluminum is used as the base material.

Exemplary embodiments of aluminum alloys according to the invention are reproduced below in three tables. Table 1 shows high-strength AlMgSi alloys, Table 2 medium-strength AlMgSi alloys and Table 3 low-strength AlMgSi alloys. In Table 4 known comparative alloys are listed, including the applicant's AA6401-specialty alloy, a medium-strength AlMgSi alloy, which has been used for decorative applications, but does not show optimal forming behavior. The further comparative alloys provide optimum strength and deformation behavior, but are not decorative anodisable.

An overview of the various process variants for the production of a decorative anodized formed aluminum component are illustrated in the following scheme:

An aluminum component was produced according to one of these process variants from an alloy according to the invention by continuous casting, homogenization, extrusion, stretching, cutting to length, deep drawing, polishing, glazing, anodizing. For comparison, similarly shaped components made of a 6401 alloy and a 6016 alloy were produced by the same process. The properties of the components are shown in Table 5. For the surface properties, the image sharpness was measured in various surface areas of the finished components. High image intensities are an expression of a high gloss and a high accuracy of an image, ie whether lines are displayed straight or distorted. The formability was listed as a comparative degree of deformation. For this purpose, with the aid of a previously applied measuring grid on flat extruded profile pieces of the different alloys, the forming degrees from the changed line pattern were determined by a deep drawing-like process. It becomes clear that the component according to the invention is the only component that exhibits a high image sharpness (80%) with good formability (40%). <b><u> Table 1: Higher strength AlMgSi </ u></b> % by weight description Si / Mg Si Fe Cu Mn mg Cr Ti Adv. 1 Add. 2 Admissible admixtures individually Permitted admixtures total A 2 0.8 0.2 0.4 0.2 0.4 0.2 0,010 Zr 0.1 Sr 0.04 0.02 0.15 B 3 0.9 0.2 0.4 0.2 0.3 0.2 0,010 Zr 0.1 Sr 0.04 0.02 0.15 C 2 0.8 0,040 0.10-0.15 0.03 0.4 - 0,010 Zr 0.1 Sr 0.01 0.02 0.15 D 3 0.9 0,040 0.10-0.15 0.03 0.3 - 0,010 Zr 0.1 Sr 0.01 0.02 0.15 % by weight description Si / Mg Si Fe Cu Mn mg Cr Ti Add. 1 Add. 2 Admissible admixtures individually Permitted admixtures total e 2 0.5 0.2 0.4 0.2 0.25 0.2 0,010 Zr 0.1 Sr 0.04 0.02 0.15 F 3 0.6 0.2 0.4 0.2 0.2 0.2 0,010 Zr 0.1 Sr 0.04 0.02 0.15 G 2 0.5 0,040 0.10-0.15 0.03 0.25 - 0,010 Zr 0.1 Sr 0.01 0.02 0.15 H 3 0.6 0,040 0.10-0.15 0.03 0.2 - 0,010 Zr 0.1 Sr 0.01 0.02 0.15 % by weight description Si / Mg Si Fe Cu Mn mg Cr Ti Add. 1 Add. 2 Admissible admixtures individually Permitted admixtures total I 2 0.3 0.2 0.4 0.2 0.15 0.2 0,010 Zr 0.1 Sr 0.04 0.02 0.15 K 3 0.4 0.2 0.4 0.2 0.13 0.2 0,010 Zr 0.1 Sr 0.04 0.02 0.15 L 2 0.3 0,040 0.10-0.15 0.03 0.15 - 0,010 Zr 0.1 Sr 0.01 0.02 0.15 M 3 0.4 0,040 0.10-0.15 0.03 0.13 - 0,010 Zr 0.1 Sr 0.01 0.02 0.15 % by weight description Si / Mg Si Fe Cu Mn mg Cr Zn Ti Add. 1 Add. 2 Admissible admixtures individually Permitted admixtures total AA6401 Special 0.9 to 1.25 0.4-0.5 0.04 0.10-0.15 0.03 0.35-0.45 - 0.04 0.01 - - <0.01 <0.10 AA6016 6 to 1.7 1.0-1.5 0.50 0.20 0.20 0.25-0.6 0.10 0.20 0.15 - - <0.05 <0.15 AA6014V 1.5 to 0.4 0.3-0.6 0.35 0.25 0.05-0.20 0.40-0.80 0.20 0.1 0.10 V 0.05-0.20 - <0.05 <0.15 AA6082 2.2 to 0.6 0.7 1.3 <0.5 <0.1 0.4-1.0 0.6-1.2 <0.25 <0.20 0.10 - - <0.05 <0.15 AA6111 2.2 to 0.6 0.6-1.1 0.40 0.50 to 0.9 0.10-0.45 0.5-1.0 0.10 0.15 0.10 - - <0.05 <0.15 AA6022 7.5 to 1.1 0.8-1.5 0.05-0.20 0.02-0.1 0.02-0.10 0.2-0.7 0.1 0.25 0.15 - - <0.05 <0.15 Material of the aluminum component distinctness of image deformation 6401 80% maximum 20% 6016 30% maximum 45% Aluminum alloy according to the invention 80% maximum 40%

Claims (17)

1. Highly ductile aluminum alloy with high mechanical strength which can be decoratively anodized, with the following composition:

   0.3 to 0.9 wt.% silicon,

   0.1 to 0.5 wt.% magnesium,

   up to 0.2 wt.% iron,

   0.1 to 0.4 wt.% copper

   0.03 to 0.2 wt.% manganese

   0.01 wt.% titanium,

   0.08 to 0.22 wt.% zirconium and/or chromium and/or vanadium, total

   0.005 to 0.1 wt.% strontium,

   maximum 0.04 wt.% zinc,

   no or maximum 0.005 wt.% silver,

   maximum 0.02 wt.% unavoidable impurities, each,

   maximum 0.15 wt.% unavoidable impurities, total,

   the remainder consisting of aluminum,

   wherein the ratio by weight of silicon to magnesium is 1.8:1 to 3.3:1, wherein the ratio by weight of iron to strontium is 3:1 to 5:1.
2. Aluminum alloy in accordance with Claim 1, characterized by the fact that strontium is present in amounts of 0.008 to 0.07 wt.%.
3. Aluminum alloy in accordance with Claim 1 or Claim 2, characterized by the fact that silver is present in amounts of 0.0005 to 0.005 wt.% for alloy identification.
4. Method for producing a decoratively anodized, formed structural member from an aluminum alloy, characterized by the following process steps:

   - - melting an aluminum parent material with more than 99.7 wt.% aluminum and addition of alloying components to the aluminum melt up to a total composition of:

   0.3 to 0.9 wt.% silicon,

   0.1 to 0.5 wt.% magnesium,

   wherein the ratio by weight of silicon to magnesium is 1.8:1 to 3.3:1,

   up to 0.2 wt,% iron,

   0.005 to 0.1 wt.% strontium,

   wherein the ratio by weight of iron to strontium is 3:1 to 5:1,

   0.1 to 0.4 wt.% copper

   0.03 to 0.2 wt.% manganese

   0.01 wt.% titanium,

   0.08 to 0.22 wt.% zirconium and/or chromium and/or vanadium, total

   maximum 0.04 wt.% zinc,

   maximum 0.02 wt.% unavoidable impurities, each,

   maximum 0.15 wt.% unavoidable impurities, total,

   the remainder consisting of aluminum,

   - - casting the aluminum alloy melt into a rolling billet or continuously cast billet,

   - - homogenizing the rolling billet or continuously cast billet,

   - - hot forming and, if necessary, cold forming to a formed unfinished structural member, and

   - - chemical and/or electrolytic surface treatment of the formed unfinished structural member, comprising an anodic oxidation.
5. Method in accordance with Claim 4, characterized by the fact that the iron content of the aluminum parent material that is used is determined, and the desired ratio by weight of iron to strontium is adjusted by addition of strontium and additional iron.
6. Method in accordance with Claim 4 or Claim 5, characterized by the fact that the aluminum parent material is pure aluminum that contains at least 99.9 wt.% aluminum.
7. Method in accordance with any of Claims 4 to 6, characterized by the fact that the strontium is added in the form of an aluminum-strontium master alloy.
8. Method in accordance with Claim 7, characterized by the fact that the strontium is added in the form of an AlSr5 master alloy, an AlSr10 master alloy, or an AlSr3.5 master alloy.
9. Method in accordance with any of Claims 4 to 8, characterized by the fact that the homogenized rolling billet is hot formed into a sheet bar by hot rolling.
10. Method in accordance with Claim 9, characterized by the fact that the sheet bar is cold rolled to the desired final thickness with possible process annealing and, after a possible recrystallization annealing and/or removal of work hardening by heat treatment, the surface is patterned, smoothed, or roughened, and then the product is possibly subjected to another soft annealing and then cut to the desired lengths of sheet.
11. Method in accordance with any of Claims 4 to 8, characterized by the fact that the homogenized continuously cast billet is hot formed into an open or hollow chamber section by extrusion, stretched, and cut into section lengths.
12. Method in accordance with Claim 10 or Claim 11, characterized by the fact that the lengths of section or lengths of sheet are cold formed in one or more additional steps,
    especially by rolling, bending, deep drawing, or tube forming or sheet-metal forming based on active means.
13. Method in accordance with any of Claims 4 to 12, characterized by the fact that formed unfinished structural members are polished, finish-polished, anodically oxidized (anodized), and sealed.
14. Method in accordance with Claim 13, characterized by the fact that an electrolytic coloring step is additionally performed.
15. Aluminum product made of aluminum alloy with a composition in accordance with any of Claims 1 to 3.
16. Aluminum product in accordance with Claim 15, characterized by the fact that the aluminum product is a strip, a sheet, an extruded section, or a formed structural member produced from the aforementioned semifinished products.
17. Aluminum product in accordance with Claim 16, characterized by the fact that the aluminum product is a decoratively anodized, formed structural member.