High Strength Precipitation Hardenable Stainless Steel

Abstract

A precipitation hardenable, martensitic stainless steel alloy is disclosed. The alloy has the following composition in weight percent, about C 0.03 max Mn 1.0 max Si 0.75 max P 0.040 max S 0.020 max Cr 10-13 Ni 10.5-11.6 Mo 0.25-1.5  Co 0.5-1.5 Cu 0.75 max Ti 1.5-1.8 Al 0.3-0.8 Nb 0.3-0.8 B 0.010 max N 0.030 max The balance is iron and usual impurities. The disclosed alloy provides a unique combination of corrosion resistance, strength, and toughness.

1 . A precipitation hardenable, martensitic stainless steel alloy consisting essentially of, in weight percent, 
       
         
           
                 
                 
                 
               
                     
                     
                 
                     
                   Mn 
                   up to about 0.10 
                 
                     
                   Si 
                   up to about 0.10 
                 
                     
                   Cr 
                   about 11.0 to about 12.0 
                 
                     
                   Ni 
                   about 10.75 to about 11.25 
                 
                     
                   Mo 
                   about 0.75 to about 1.1 
                 
                     
                   Co 
                   about 0.9 to about 1.1 
                 
                     
                   Cu 
                   not more than about 0.25 
                 
                     
                   Ti 
                   about 1.5 to about 1.8 
                 
                     
                   Al 
                   about 0.4 to about 0.8 
                 
                     
                   Cb 
                   about 0.3 to about 0.7 
                 
                     
                   B 
                   about 0.010 max.; and 
                 
                     
                   Ca 
                   from an amount effective to combine with available 
                 
                     
                     
                   phosphorus and sulfur to remove those elements 
                 
                     
                     
                   from the alloy up to about 0.005; or 
                 
                     
                   REM 
                   about 0.001 to about 0.025 
                 
                     
                     
                 
             
                
               
               
                
                
                
                
                
                
                
                
                
                
                
                
                
                
                
                
               
            
           
         
       
       wherein the balance of the alloy composition is iron and usual impurities, and said impurities include about 0.010% max. phosphorus, about 0.005% max. sulfur, about 0.02% max. carbon, and about 0.015% max. nitrogen. 
     
     
         2 . The alloy as claimed in  claim 1  which contains not more than about 0.015% carbon. 
     
     
         3 . The alloy as claimed in  claim 1  which contains at least about 10.85% nickel. 
     
     
         4 . The alloy as claimed in  claim 1  which contains at least about 0.9% cobalt. 
     
     
         5 . The alloy as claimed in  claim 1  which contains not more than about 1.7% titanium. 
     
     
         6 . The alloy as claimed in  claim 1  which contains not more than about 0.7% aluminum. 
     
     
         7 . The alloy as claimed in  claim 1  which contains not more than about 0.6% columbium. 
     
     
         8 . The alloy as claimed in  claim 1  which contains at least about 0.001% boron. 
     
     
         9 . The alloy as claimed in  claim 1  which contains not more than about 0.010% nitrogen. 
     
     
         10 . A precipitation hardenable, martensitic stainless steel alloy consisting essentially of, in weight percent, 
       
         
           
                 
                 
                 
               
                     
                     
                 
                     
                   Mn 
                   up to about 0.10 
                 
                     
                   Si 
                   up to about 0.10 
                 
                     
                   Cr 
                   about 11.0 to about 12.0 
                 
                     
                   Ni 
                   about 10.85 to about 11.25 
                 
                     
                   Mo 
                   about 0.9 to about 1.1 
                 
                     
                   Co 
                   about 0.9 to about 1.1 
                 
                     
                   Cu 
                   not more than about 0.25 
                 
                     
                   Ti 
                   about 1.5 to about 1.7 
                 
                     
                   Al 
                   about 0.45 to about 0.65 
                 
                     
                   Cb 
                   about 0.4 to about 0.6 
                 
                     
                   B 
                   about 0.0015 to about 0.0035; and 
                 
                     
                   Ca 
                   from an amount effective to combine with available 
                 
                     
                     
                   phosphorus and sulfur to remove those elements 
                 
                     
                     
                   from the alloy up to about 0.005; or 
                 
                     
                   REM 
                   about 0.001 to about 0.025; 
                 
                     
                     
                 
             
                
               
               
                
                
                
                
                
                
                
                
                
                
                
                
                
                
                
                
               
            
           
         
       
       wherein the balance of the alloy composition is iron and usual impurities, and said impurities include about 0.010% max. phosphorus, about 0.005% max. sulfur, about 0.015% max. carbon, and about 0.010% max. nitrogen.