Low internal stress Al-Zn-Cu-Mg plates

Abstract

The present invention relates to a method for producing Al—Zn—Cu—Mg type alloy plates comprising between 4 and 12% zinc, less than 4% magnesium and less than 4% copper, other elements≦0.5% each, and the remainder aluminum. The method comprising hot rolling, solution heat-treatment, quenching, controlled stretching with permanent elongation greater than 0.5% and aging, wherein the elapsed time D between the end of quenching and the start of controlled stretching is less than 2 hours. The invention further relates to plates and products produced or capable of being produced using such methods.

1 . A method for producing an Al—Zn—Cu—Mg alloy plate comprising between 4 and 12% zinc, less than 4% magnesium and less than 4% copper, other elements≦0.5% each, and the remainder aluminum, said method comprising hot rolling, solution heat-treatment, quenching, controlled stretching with permanent elongation greater than 0.5% and aging, wherein 
 the elapsed time D between the end of quenching and the start of controlled stretching is less than 2 hours.    
   
   
       2 . Method according to  claim 1 , wherein the elapsed time D is less than or equal to 1 hour and preferentially less than 30 minutes.  
   
   
       3 . Method according to  claim 1 , wherein said alloy is selected from the group consisting of the alloys AA7010, 7050, 7056, 7449, 7075, 7475, 7150, and 7175.  
   
   
       4 . Method according to  claim 1 , wherein the thickness of said plate is greater than 40 mm.  
   
   
       5 . Method according to  claim 1 , wherein the thickness of said plate is between 40 and 80 mm.  
   
   
       6 . Method according to  claim 1 , wherein the thickness of said plate is between 40 and 150 mm.  
   
   
       7 . Method according to  claim 1 , wherein said plate has a total elastic energy less than or equal to  
         W  [kJ/m 3 ]=0.54+0.013( R   p0.2(L)  [MPa]−400).  
   
   
       8 . Al—Zn—Cu—Mg alloy thick plate comprising between 4 and 12% zinc, less than 4% magnesium and less than 4% copper, other elements≦0.5% each, and the remainder aluminum, which is hot rolled, solution treated, quenched, stretched with a permanent elongation greater than 0.5%, aged, 
 wherein the total elastic energy of said plate is less than or equal to        W  [kJ/m 3 ]=0.54+0.013( R   p0.2(L)  [MPa]−400).    
   
   
       9 . Plate according to  claim 8 , having a thickness between 60 and 100 mm and a total elastic energy less than 2 kJ/m 3 .  
   
   
       10 . Plate according to  claim 9 , wherein said total elastic energy is less than 1.5 kJ/m 3 .  
   
   
       11 . Plate according to  claim 8 , having a thickness greater than 100 mm and a total elastic energy less than 1.5 kJ/m 3 .  
   
   
       12 . Thick plate obtainable by the method according to  claim 7 .  
   
   
       13 . Inspection lot or heat treatment batch of Al—Zn—Cu—Mg alloy plates comprising between 4 and 12% zinc, less than 4% magnesium and less than 4% copper, other elements≦0.5% each, the remainder aluminum, in a solution-treated, quenched, stretched and aged temper, wherein the total elastic energy W in kJ/m of the plates displays a standard deviation less than or equal to  
       0.20+0.0030( R   p0.2(L)  [MPa]−400) around an average value of said total elastic energy.  
   
   
       14 . Inspection lot or heat treatment batch of thick plates according to  claim 13 , wherein said average total elastic energy value is less than W [kJ/m 3 ]=0.54+0.013(R p0.2(L)  [MPa]−400).  
   
   
       15 . Inspection lot or heat treatment batch of thick plates according to  claim 13 , characterised in that said average total elastic energy value is less than 3 kJ/m 3 .  
   
   
       16 . Inspection lot or heat treatment batch according to  claim 13  wherein said average total elastic energy value is less than 2 kJ/m 3 .  
   
   
       17 . Inspection lot or heat treatment batch according to  claim 13  wherein a nominal thickness of the plates is between 40 and 100 mm.  
   
   
       18 . Inspection lot or heat treatment batch according to  claim 13  wherein the plates comprise an alloy selected from the group consisting of AA7010, 7050, 7056, 7449, 7075, 7475, 7150, and 7175.  
   
   
       19 . Inspection lot or heat treatment batch according to  claim 13  comprising at least 3 plates.  
   
   
       20 . Inspection lot or heat treatment batch according to  claim 13  wherein said plates are obtained by a method comprising hot rolling, solution heat-treatment, quenching, controlled stretching with permanent elongation greater than 0.5% within a time after quenching of less than 2 hours.  
   
   
       21 . A method for the production of machine components comprising obtaining a plate according to  claim 8  and using said plate for the production of machine components.  
   
   
       22 . A method for reducing the dispersion of the stress level between different nominally identical plates comprising subjecting said plates to hot rolling, solution heat-treatment, quenching, and after quenching, controlling the time period for a predetermined time before subjecting said plates to controlled stretching with permanent elongation greater than 0.5%.  
   
   
       23 . A method of  claim 22  wherein said predetermined time is less than 2 hours.  
   
   
       24 . A method of  claim 22 , wherein said plates are in the same production or heat treatment batch.  
   
   
       25 . A method of  claim 22  wherein said plates comprise an Al—Zn—Cu—Mg alloy plate comprising between 4 and 12% zinc, less than 4% magnesium and less than 4% copper, other elements≦0.5% each, and the remainder aluminum  
   
   
       26 . A plate prepared by a method of  claim 1 .  
   
   
       27 . An inspection lot or heat treatment batch of  claim 13 , wherein said standard deviation is calculated based on at least 3 samples.  
   
   
       28 . An inspection lot or heat treatment batch of  claim 13 , wherein said standard deviation is calculated based on at least 5 samples.  
   
   
       29 . Method according to  claim 4 , wherein said plate has a total elastic energy less than or equal to  
         W  [kJ/m 3 ]=0.54+0.013( R   p0.2(L)  [MPa]−400).