DK2665842T3 - Exterior facade metal plate made of aluminum with a high surface roughness - Google Patents

Description

The invention relates to a facade plate or strip consisting of aluminium or an aluminium alloy of the type AA 5005 with a thickness of from more than 2 mm to 4 mm, and to a method for its production.

Exterior facades of buildings are often clad with brushed steel plates, which have a particular visual appearance because of their rough surface. A problem with using steel plates, however, is that they are heavy and therefore require higher effort for the fastening structure and higher strength requirements overall for the facade on which they are fastened. Steel plates furthermore corrode, so that expensive stainless steels need to be used. In the field of furniture manufacture, for interior room ceiling panels or in the kitchen sector, the use of anodised aluminium sheets is known, which have a so-called "Butler finish" because of the ground structure of the rolls. The plates used for furniture, ceiling panels, in the kitchen sector, for stand and exhibition structures and for doors and window fittings conventionally have a thickness of up to 1.5 mm, or much less, and are delivered with an at most 10 ym thick anodised layer on the visible side. Use of these aluminium alloy plates for facades has not previously been possible because of the small thicknesses. Furthermore, the use of aluminium or aluminium alloys in the field of exterior facades has been problematic since, in particular, problems with a consistent visual surface appearance under the effects of weathering have been found in this case.

From US 4, 715,901, architectural sheets for covering buildings are known, which consist of aluminium or aluminium alloy of the type 5xxx, in particular of the type 5005, and have a thickness of 0.02 to 0.25 inches (0.5 to 6 mm).

Finally, from JP 4-041003 aluminium sheets for covering buildings are known, which are treated at the end of their production by rolls in such a way that a surface roughness of 0.3 to 1.6 ym is created.

It is therefore an object of the present invention to provide an alternative to the previously used steel plates in the field of exterior facades of buildings.

This object is achieved according to the teaching of the present invention by a facade plate or strip consisting of aluminium or an aluminium alloy of the type AA 5005, in that the facade plate has an average roughness Ra of from 1.2 ym to 1.7 ym, wherein the average roughness depth Rz being from 7 ym to 12 ym measured according to DIN EN ISO 4287.

The said roughness values ensure an attractive visual appearance, which corresponds approximately to that of steel plates. Plate or strip thicknesses of more than 2 mm and at most 4 mm furthermore ensure sufficient strength of the facade plate or strip, for example against the effects of wind, wherein plate or strip thicknesses of from 2.5 mm to 4 mm are preferably used. On the other hand, a facade plate or strip with a maximum thickness of 4 mm also ensures a significant weight advantage over steel plates with similar strength, so that elaborate fastening structures on the facade can be obviated.

According to a first configuration of the facade plate or strip, the line length, i.e. the length of the rolled structures impressed on the plate or strip, is preferably from 6 mm to 15 mm, preferably from 8 to 12 mm, particularly preferably 10 mm. Owing to the selected parameters, the surface of the aluminium alloy strip or plate is provided with a visual surface appearance almost identical to brushed steel.

According to another embodiment of the facade plate, the facade plate comprises an anodised layer having a thickness of from 15 ym to 30 ym, preferably from 18 ym to 22 ym or from 20 ym to 25 ym. It has been found that the 10 ym thick anodised layers previously used are not sufficient to ensure satisfactory corrosion protection and a permanently attractive visual appearance in the application field of exterior facades. If facade plates with an anodised layer having a thickness of from 18 to 22 ym are used, a facade plate or strip optimised in relation to production costs can be provided, while the visual surface appearance on exterior facades is constant. An anodised layer thickness of from more than 20 ym to 25 ym is also advantageous, since with little extra outlay in production this ensures further improved corrosion protection and therefore improved longevity of the facade plates, in particular with heavy air pollution. Anodised layers having a thickness of more than 30 ym, however, again demonstrate less protection. The facade plates or strips are then ideally suitable for an exterior facade.

Lastly, the facade plate may be additionally coloured during the anodising, so that coloured visual appearances can also be provided.

The facade plate or strip preferably consists of an aluminium alloy of the type AA 5005 having at most 0.30 wt. % Si, at most 0.7 wt. % Fe, at most 0.20 wt. % Cu, at most 0.20 wt. % Mn, from 0.50 wt. % to 1.1 wt. % Mg, at most 0.10 wt. % Cr, at most 0.25 wt. % Zn and inevitable impurities of at most 0.05 wt. % individually and in total at most 0.15 wt. %. This aluminium alloy provides sufficient strength with good corrosion resistance and can be processed easily to form a facade plate or strip.

According to a second teaching of the present invention, the object is achieved by a method which comprises the following method steps: a rolling ingot of aluminium or of an aluminium alloy of the type AA 5005 is cast, the rolling ingot is scalped, hot-rolled and subsequently cold-rolled, the degree of rolling reduction in the last cold-rolling pass being from 15% to 30% and the working rolls of the last cold-rolling pass having a surface structure which generates an average roughness Ra of from 1.2 ym to 1.7 ym with a roughness depth Rz of from 7 ym to 12 ym on the strip surface .

It has been found that, in particular, the production of a strip or plate by casting a rolling ingot, hot-rolling the rolling ingot and subsequently cold-rolling the rolling ingot can achieve a homogeneous surface roughness on the finished facade plate or facade strip. As already mentioned above, the facade plate produced from a corresponding strip has not only sufficient strength and a lighter weight than a steel plate, but also a very similar visual surface appearance. Furthermore, a degree of rolling reduction of preferably 20% in the last cold-rolling pass ensures a very good transfer of the surface structure of the working rolls onto the aluminium alloy strip in the last cold-rolling pass.

If the surface structure generated on the strip has a line length of from 6 to 15 mm, preferably from 8 to 12 mm and particularly preferably 10 mm, a surface very similar to brushed steel can be produced in the strip.

According to a further variant of the method, in the last cold-rolling pass only one working roll which has a surface structure that generates an average roughness Ra of from 1.2 ym to 1.7 ym with an average roughness depth Rz of from 7 ym to 12 ym on the strip surface is used. In this case, distinction can clearly be made between the inner side and the outwardly facing side, which forms the facade, of the facade plate.

The aluminium strip produced in this way is preferably shaped and only then anodised, i.e. in the shaped state, in order to avoid damaging the anodised layer during the shaping.

As already mentioned above, the shaped facade plate with an anodised layer thickness of from 15 to 30 ym, preferably from 18 to 22 ym or 20 ym to 25 ym, is anodised in order to satisfy the specific requirements of the environment of the facade plates.

The invention will be explained in more detail below based on exemplary embodiments in conjunction with the drawing. In the drawing:

Fig. 1 shows a schematic view of an exterior facade of the building,

Fig. 2 shows a sectional view of an exemplary embodiment of a facade plate and

Fig. 3a), b) show a schematic perspective view of the working rolls of two different cold-rolling stands for generating the surface structure of the facade plate.

Fig. 1 shows, in a highly schematic perspective view, an exterior facade 1 of a building which is clad with facade plates 2 according to the invention. The facade plates consist of an aluminium alloy of the type AA 5005 and have a thickness of from more than 2 mm to at most 4 mm, preferably from 2.5 to 4 mm.

Because of the plate thickness and the low weight resulting therefrom, the aluminium plates according to the invention can be fastened easily on a facade and furthermore offer sufficient strength, for example against forces caused by wind load.

The surface of the facade plates 2 was produced by the method according to the invention and has a visual surface appearance very similar to a brushed steel surface. The surface of the facade plate has an average roughness Ra of from 1.2 ym to 1.7 ym with a roughness depth Rz of from 7 ym to 12 ym measured according to DIN EN ISO 4287. Furthermore, the line length of the roughness structure is from 8 mm to 12 mm, preferably 10 mm. Nevertheless, the facade plate 2 is much lighter than a brushed steel plate. The facade plate 2 represented in a sectional view in Figure 2 has an anodised layer of from 15 to 30 ym, preferably from 18 to 22 ym.

This anodised layer ensures that the aluminium alloy plate is corrosion-resistant and at the same time can have an individual colour. Improved corrosion protection can be achieved by a preferably 20 ym to 25 ym thick anodised layer.

It is not necessary to coat this facade plate, since it is extremely corrosion-resistant. It can furthermore be coloured during the anodising, wherein the colorant penetrates into the pores remaining in the anodised layer and stays there.

The facade plate 2 according to the invention is furthermore much lighter than a brushed facade plate made of steel.

Since a shaping process may possibly damage the anodised layer, the anodised layer is preferably applied after having shaped the plate or strip.

Figures 3a) to 3b) show, in a schematic perspective representation, the working rolls 3, 3', 4, 4' of the coldrolling stand of the last cold-rolling pass, which impart the surface structure to the aluminium alloy strip 5, 5' and cold-roll it to a final thickness of from more than 2 mm to 4 mm, preferably 2.5 mm to 4 mm. In contrast to the working rolls 3, 4 in Fig. 3a), only one working roll 3' in Fig. 3b) has the surface structure required for the facade plate. The plate produced in this way therefore has a clearly visible preferred side for the facade, which is provided with the surface structure. Process-reliable impression of the surface structure into the strip is achieved by a degree of rolling reduction of from 15% to 30%, preferably 20% in the last cold-rolling pass.

Claims (8)

1. Facade metal plate or strip consisting of aluminum or an aluminum alloy of type AA 5005, wherein the facade metal plate has a thickness of more than 2 mm to a maximum of 4 mm and the surface of the facade metal plate has an average roughness Ra of 1.2 pm to 1.7 pm and the roughness depth Rz is from 7 pm to 12 pm measured in accordance with DIN EN ISO 4287. Facade metal plate or strip according to claim 1, characterized in that the line length of the roughness structure is 6 mm to 15 mm. Facade metal plate or strip according to claim 1 or 2, characterized in that the aluminum strip or plate comprises an anodized layer having a thickness of 15 µm to 30 µm, preferably a thickness of 18 µm to 22 µm or 20 µm to 25 µm. Process for producing a facade metal plate or strip according to any one of claims 1 to 3, characterized in that an aluminum roll bar or an aluminum alloy of type AA 5005 is cast, the scalloped roll bar hot roll and subsequently cold roll to a final thickness of more than the 2 mm to 4 mm, the rolling reduction in the last cold rolling stage being 15 to 30%, preferably 20%, and the working rolls of the last cold rolling step having a surface structure which provides an average roughness Ra of 1.2 µm to 1.7 pm with an average roughness depth Rz of 7 pm to 12 pm on the tape surface. Method according to claim 4, characterized in that the line length of the roughness structure produced on the cold rolled strip is 6 mm to 15 mm. Method according to claim 4 or 5, characterized in that only one working roller has a surface structure which provides an average roughness Ra of 1.2 µm to 1.7 µm with an average roughness depth Rz of 7 µm to 12 µm on the belt surface. Process according to any one of claims 4 to 6, characterized in that metal sheets are cut from the cold rolled aluminum alloy band which are converted to facade metal plates and anodized after the transformation. Process according to any one of claims 4 to 7, characterized in that the reshaped facade metal plate is anodized with an anodizing thickness of 15 µm to 30 µm, preferably 18 µm to 22 µm or 20 µm to 25 µm.