Aluminium-magnesium alloy product

Abstract

Method for making an aluminium-magnesium alloy in the form of a rolled product, having the composition in weight percent of: Mg 4.8-5.6, Mn 0.05-0.4, Zn 0.40-0.6, Cu 0.06-0.35, Cr 0.25 max., Fe 0.35 max., Si 0.25 max., Zr 0.12 max., Ti 0.3 max., others (each) max. 0.05, (total) max. 0.15, and balance aluminium.

1 . Method of producing a wrought aluminium alloy rolled product comprising the steps of:
 (i) providing an intermediate alloy product having a composition in weight percent consisting of:   
     
       
         
               
               
               
             
                   
                   
               
                   
                 Mg 
                  4.8-5.6 
               
                   
                 Mn 
                 0.05-0.4 
               
                   
                 Zn 
                 0.40-0.6 
               
                   
                 Cu 
                 0.06-0.35 
               
                   
                 Cr 
                 0.25 max. 
               
                   
                 Fe 
                 0.35 max. 
               
                   
                 Si 
                 0.25 max. 
               
                   
                 Zr 
                 0.12 max. 
               
                   
                 Ti 
                  0.3 max. 
               
                   
                   
               
           
              
             
             
              
              
              
              
              
              
              
              
              
              
             
          
         
       
       impurities (each) max. 0.05, (total) max. 0.15 balance aluminium, 
       (ii) cold working the intermediate alloy product to a final gauge to obtain an intermediate wrought product, 
       (iii) annealing the intermediate wrought product by heating the product at a heating rate in the range of 2 to 200° C./sec, holding the product at a soaking temperature in the range of 480 to 570° C. for a duration of up to 100 sec, followed by a cooling rate in the range of 10 to 500° C./sec to below a temperature of 150° C. 
     
   
   
       2 . The method according to  claim 1 , wherein the amount of Zr does not exceed 0.05 wt. %. 
   
   
       3 . The method according to  claim 1 , wherein the amount of Zr does not exceed 0.02 wt. %. 
   
   
       4 . The method according to  claim 1 , wherein the amount of Cu is more than 0.075 wt. %. 
   
   
       5 . The method according to  claim 1 , wherein the amount of Cu is more than 0.10 wt. %. 
   
   
       6 . The method according to  claim 1 , wherein the amount of Cu does not exceed 0.24 wt. %. 
   
   
       7 . The method according to  claim 1 , wherein the amount of Cu does not exceed 0.15 wt. %. 
   
   
       8 . Method according to  claim 1 , wherein the soaking temperature during step (iii) is in the range of 520 to 550° C. 
   
   
       9 . Method according to  claim 1 , wherein the heating rate during step (iii) is at least 50° C./sec. 
   
   
       10 . Method according to  claim 9 , wherein the heating rate during step (iii) is at least 80° C./sec. 
   
   
       11 . Method according to  claim 1 , wherein the annealing of step (iii) is carried out in a continuous annealing facility. 
   
   
       12 . wherein the final gauge of the aluminium product is at most 5 mm. 
   
   
       13 . Method according to  claim 1 , wherein the final gauge of the aluminium product is in a range of 0.5 to 5 mm. 
   
   
       14 . Method according to  claim 1 , wherein the product after annealing has a weight loss after sensitizing for 100 hours at 100° C. of less than 25 mg/cm 2  when tested against intergranular corrosion in accordance with ASTM G67. 
   
   
       15 . Method according to  claim 1 , wherein the product after annealing has a weight loss after sensitizing for 100 hours at 85° C. of less than 15 mg/cm 2  when tested against intergranular corrosion in accordance with ASTM G67. 
   
   
       16 . Method according to  claim 1 , wherein the amount of Zn in the alloy product does not exceed 0.6 wt. %. 
   
   
       17 . Product according to  claim 1 , wherein the amount of Cr in the alloy product is in a range of 0.11 to 0.35 wt. %. 
   
   
       18 . Product according to  claim 1 , wherein the amount of Cr in the alloy product is in a range of 0.11 to 0.2 wt. %. 
   
   
       19 . Product according to  claim 1 , wherein the amount of Fe in the alloy product is less than 0.2 wt. %. 
   
   
       20 . Product according to  claim 1 , wherein the amount of Si in the alloy product is maximum 0.12 wt %. 
   
   
       21 . Product according to  claim 1 , wherein the amount of Si in the alloy product is maximum 0.1 wt. %. 
   
   
       22 . Method according to  claim 1 , wherein the amount of Mg in the alloy product is at least 5%. 
   
   
       23 . Method according to  claim 1 , wherein the amount of Ti in the alloy product is less than 0.15 wt. %. 
   
   
       24 . Method according to  claim 1 , wherein the amount of Mn in the alloy product is in the range of 0.05 to 0.2 wt %. 
   
   
       25 . Method according to  claim 1 , wherein the amount of Mn in the alloy product is in the range of 0.1 to 0.2 wt. %.