Patent Publication Number: US-2005139296-A1

Title: Aluminum alloy for producing roll-shaped products

Description:
This invention relates to an aluminium alloy for manufacturing rollform products, as well as a strip for rollform products.  
      Strips produced from the aluminium alloy according to the present invention are profiled in so-called rollformers into finished products, such as for example roller blind rods, skylights, panel and cladding strips. From the prior art it is known to manufacture corresponding strips for rollform products from the aluminium alloy AA 3005. The requirements for a strip for rollform products are essentially bending and buckling resistance, and therefore stability of the finished profiled product, in very good deformation properties even at critical curvature radii (with roller blind strips curvature radius t=0), very good rollformability with very good lacque adhesion at the same time.  
      For weight and cost reasons strips with less thickness, =0.3 mm, are used increasingly to manufacture rollform products. With these thicknesses the strips for rollform products, manufactured from the alloys known from the prior art, exhibit stability problems with respect to bending and buckling resistance.  
      Based on the aforementioned it is an object of the present invention according to a first teaching to provide an aluminium alloy for manufacturing rollform products, which guarantees high stability of the finished profiled product.  
      According to the first teaching of the invention the above mentioned object is solved in that an aluminium alloy for manufacturing rollform products comprises the following alloy constituent in weight percentages:  
                                                   0.1 ≦ Si ≦ 0.5           0.15 ≦ Fe ≦ 0.5           0.05 ≦ Cu ≦ 0.25            0.8 ≦ Mn ≦ 1.4            0.4 ≦ Mg ≦ 1.3                      
          others in sum maximum 0.15, individually maximum 0.05, rest Al.        

      This aluminium alloy according to the first teaching of the invention also ensures high stability of the finished product even when thin metal thicknesses are employed. In addition, the alloy has excellent deformation properties even at critical bending radii, very good rollformability as well as very good lacque adhesion after forming operation, due to a well and smooth metal surface.  
      According to a second teaching of the invention relates to a strip for rollform products, which is improved compared to the prior art in that the strip essentially comprises an aluminium alloy according to the first teaching of the invention. Regarding the advantages of the inventive strip for rollform products reference is made to the statements relating the first teaching of the invention.  
      In that the grain of the strip comprises 2 to 10 casting phases per 1000 μm 2  with a maximum size of 40 μm and an average length of 2 to 6 μm, 500 to 1200 fine precipitations per 1000 μm 2  as well as residual resistances within the range of 1.2 to 2.5 μohm, it is ensured that according to a second teaching of the invention the strip has very good flexibility and permits bending radii of t=0 without problems and moreover features a very good subsequent processing (=rollformability).  
      The second teaching of the invention grains a particularly advantageous development in that the strip comprises a coat of lacquer applied by coil coating method. Such a coat of lacquer applied by coil coating method has outstanding lacque adhesion, which ensures that the lacque does not detach respectively is not damaged during rollforming.  
      Furthermore, according to a third teaching of the invention the invention relates to a method for producing a strip for rollform products, which is improved compared to the prior art, in that the strip is essentially made from an aluminium alloy according to claim  1 . Regarding the advantages of the inventive method for manufacturing strips for rollform products reference is made to the statements relating the first teaching of the invention.  
      According to a first development of the third teaching of the invention an advantageous grain of the strip for rollform products is made in that the ingot is annealed during preheating of the warm rolling process within the temperature range of 480 to 610° C. for at least 3 hours.  
      This grain is further improved in that the strip is manufactured by warm rolling within the temperature range of 270 to 550° C.  
      There is now a large number of possibilities to further design and develop the inventive aluminium alloy for manufacturing rollform products, the inventive strip for rollform products or the inventive method for manufacturing a strip for rollform products. In this context for example reference is made on the one hand to the claims and on the other hand to the description of an embodiment for a rollform product in conjunction with the drawing. 
    
    
      In the drawing the sole FIGURE shows a partial perspective section through an embodiment of a rollform product manufactured from the aluminium alloy according to the present invention. 
    
    
      The rollform product illustrated in the sole FIGURE is a roller blind rod.  
      As is known from the prior art this roller blind rod is manufactured by rollforming from a strip for rollform products  1 . This strip for rollform products  1  comprises an aluminium alloy according to the present invention having the following alloy constituents in weight percentages:  
                                                   0.1 ≦ Si ≦ 0.5           0.15 ≦ Fe ≦ 0.5           0.05 ≦ Cu ≦ 0.25            0.8 ≦ Mn ≦ 1.4            0.4 ≦ Mg ≦ 1.3                      
          others in sum maximum 0.15, individually maximum 0.05, rest Al.        

      The cavity of the roller blind rod illustrated in the sole FIGURE is filled by a synthetic foam  2  in the illustrated embodiment.  
      The critical deformation with a curvature radius of t=0 is to be seen particularly clearly at position  3 . The aluminium alloy according to the present invention ensures such critical deformation on the finished lacquered product.  
      In addition, use of the aluminium alloy according to the present invention also ensures good stability of the roller blind rod in metal thicknesses under 0.3 mm.  
      The manufacture of the strip for rollform products  1  takes place starting with the ingot made of the aluminium alloy according to the present invention by preheating within the temperature range of 480 to 610° C. at a dwell time of at least 3 hours, warm rolling within the temperature range of 270 to 550° C., cold rolling and heat treatment.  
      The strip for rollform products comprises the following mechanical properties after lacquering: 
          Tensile strength: Rm 240-280 N/mm 2       Yield point: Rp&gt;215 N/mm 2       Elongation at break: ASO&gt;6%.        

      The desired grain is created by manufacturing the strip by continuous casting of a rolling ingot, ingot preheating within the temperature range of 480 to 610° C. and warm rolling within the temperature range of 550° C. to 270° C. The grain of the strip is characterised by a number of casting phases, also known as coarse precipitations, within the range of 2 to 10 per 1000 μm 2  with a maximum size of 40 μm and an average length of 2 to 6 μm. The strip also has fine precipitations of less than approximately 1 μm, which number is within the range of 500 to 1200 per 1000 μm 2 .  
      Finally the dissolution state of the strips is characterised by residual resistances within the range of 1.2 to 2.5 μohm cm. The residual resistance is measured at a helium temperature of 4.2 K.