Method for the manufacturing of extruded profiles that can be anodized with high gloss surfaces, the profiles being extruded of an age hardenable aluminium alloy that can be recrystallized after cold deformation, for example a 6xxx or a 7xxx alloy

Abstract

Method for the manufacturing of extruded profiles that can be anodized with high gloss surfaces, the profiles being extruded of an age hardenable aluminium alloy that can be recrystallized after cold deformation, for example a 6xxx or 7xxx alloy, where the alloy initially is cast to extrusion billet(s), where the billets are homogenized at a holding temperature between 480° C. and 620° C. and soaked at this temperature for 0-12 hours, where after the billets are subjected to cooling from the homogenization temperature at a rate of 150° C./h or faster, a) the billets are preheated to a temperature between 400 and 540° C. and extruded preferably to a solid shape profile and cooled rapidly down to room temperature, b) deforming the profile more than 10% by a cold rolling operation, where after c) the profile is flash annealed with a heating time of maximum two minutes to a temperature of between 400-530° C. and held at this temperature for not more than 5 minutes to obtain an average grain size of about 100 μm or less, and subsequently quenched, d) and the profile is finally aged.

1 . Method for the manufacturing of extruded profiles that can be anodized with high gloss surfaces, the profiles being extruded of an age hardenable aluminium alloy that can be recrystallized after cold deformation, for example a 6xxx or a 7xxx alloy, where the alloy initially is cast to extrusion billet(s), where the billets are homogenized at a holding temperature between 480° C. and 620° C. and soaked at this temperature for 0-12 hours, where after the billets are subjected to cooling from the homogenization temperature at a rate of 150° C./h or faster,
 a) the billets are preheated to a temperature between 400 and 540° C. and extruded preferably to a solid shape profile and cooled rapidly down to room temperature, 
 b) deforming the profile more than 10% by a cold rolling operation, where after 
 c) the profile is flash annealed with a heating time of maximum two minutes to a temperature of between 400-530° C. and held at this temperature for not more than 5 minutes to obtain an average grain size of about 100 μm or less, and subsequently quenched, and 
 d) the profile is finally aged. 
 
     
     
         2 . Method according to  claim 1   characterised in that   the profile between step c) and d) is further subjected to a cold deforming operation, preferably by stretching to remove residual stresses from cooling.   
     
     
         3 . Method according to  claim 1   characterised in that   the profile between step c) and d) is cut into blanks that is cold formed to a shape that saves material and machining time to produce the final product.   
     
     
         4 . Method according to  claim 1   characterised in that   the alloy is containing in wt. %:   Si: 0.00-1.00   Mg: 0.25-2.00   Fe: 0.00-0.25   Cu: 0.00-0.50   Mn: 0.00-0.20   Cr: 0.00-0.10   Zr: 0.00-0.20   Sc: 0.00-0.10   Zn: 0.00-7.00   Ti: 0.00-0.05, and   including incidental impurities and balance Al.   
     
     
         5 . Method according to  claim 1   characterised in that   the alloy is a 7xxx alloy containing in wt. %:   Si: 0.00-0.30   Mg: 0.50-2.00   Fe: 0.00-0.15   Cu: 0.00-0.30   Mn: 0.00-0.20   Cr: 0.00-0.10   Zr: 0.00-0.20   Sc: 0.00-0.10   Zn: 3.00-7.00   Ti: 0.00-0.05, and   including incidental impurities and balance Al.   
     
     
         6 . Method according to  claim 1   characterised in that   the alloy is a 6xxx alloy containing in wt. %:   Si: 0.30-1.00   Mg: 0.25-1.00   Fe: 0.00-0.25   Cu: 0.00-0.50   Mn: 0.00-0.20   Cr: 0.00-0.10   Zr: 0.00-0.20   Sc: 0.00-0.10   Zn: 0.00-0.50   Ti: 0.00-0.05, and   including incidental impurities and balance Al.   
     
     
         7 . Method according to  claim 1 ,
 characterised in that,   the profile according to step b) is deformed more than 20%.   
     
     
         8 . Method according to  claim 1 ,
 characterised in that   the profile according to step b) preferably is deformed between 30 and 50%.   
     
     
         9 . Method according to  claim 1 ,
 characterised in that   the profile is flash annealed according to step c) with a heating time of maximum 20 seconds to a temperature between 400-530° C. and held at this temperature for not more than 1 minute.   
     
     
         10 . Method according to  claim 1 ,
 characterised in that   the flash anneal heating according to step c) is obtained by induction heating of the profile.   
     
     
         11 . Method according to  claim 1 ,
 characterised in that   the flash anneal heating according to step c) is obtained by subjecting the profile to a salt bath or other convection or radiation heating means providing high heating rates.   
     
     
         12 . Method according to  claim 1 ,
 characterised in that   the alloy is cast without the use of grain refiner, except in the start-up of the casting operation.   
     
     
         13 . Method according to  claim 1 ,
 characterised in that   the ageing, step d) is a one step, two step or a dual rate ageing operation to a final hold temperature between 100° C. and 220° C. and where the total ageing cycle is performed in a time span of between 3 and 24 hours.   
     
     
         14 . Method according to  claim 1 ,
 characterised in that   the average grain size according to process step c) is 70 μm or less.