MICROALLOYED MARTENSITIC STAINLESS STEEL GRADE 403Cb WITH IMPROVED TOUGHNESS AND STRENGTH

Abstract

The microalloyed martensitic stainless steel grade 403Cb disclosed herein specifies a composition range including a minimum level and a maximum level that improves material properties leading to increased toughness and strength. In addition, a chromium-nickel equivalent balance (CNB) is controlled within a proper level. With increased toughness and strength, the sensitivity to temper brittleness is decreased.

What is claimed is: 
     
         1 . A microalloyed martensitic stainless steel grade 403Cb consisting essentially of, by weight percent: 
       
         
           
                 
                 
                 
               
                     
                     
                 
                     
                   carbon 
                   0.13 to 0.18 
                 
                     
                   manganese 
                   0.40 to 0.60 
                 
                     
                   silicon 
                   up to 0.50 
                 
                     
                   phosphorous 
                   up to 0.025 
                 
                     
                   sulfur 
                   up to 0.010 
                 
                     
                   nickel 
                   0.30 to 0.60 
                 
                     
                   chromium 
                   11.5 to 13.0 
                 
                     
                   molybdenum 
                   0.05 to 0.20 
                 
                     
                   niobium 
                   0.15 to 0.25 
                 
                     
                   vanadium 
                   up to 0.10 
                 
                     
                   iron 
                   balance 
                 
                     
                   CNB (Cr—Ni equivalent balance) 
                   5.0 to 7.5. 
                 
                     
                     
                 
             
                
               
               
                
                
                
                
                
                
                
                
                
                
                
                
                
               
            
           
         
       
     
     
         2 . The microalloyed martensitic stainless steel grade 403Cb of  claim 1 , wherein the weight percent of nickel is about 0.53 and the weight percent of molybdenum is about 0.04. 
     
     
         3 . The microalloyed martensitic stainless steel grade 403Cb of  claim 1 , wherein a weight ratio of the nickel to the molybdenum is larger than 3 
     
     
         4 . The microalloyed martensitic stainless steel grade 403Cb of  claim 1 , wherein the microalloyed martensitic stainless steel grade 403Cb has a yield strength that ranges from 740 MPa to 800 MPa. 
     
     
         5 . The microalloyed martensitic stainless steel grade 403Cb of  claim 1 , wherein the microalloyed martensitic stainless steel grade 403Cb has a tensile strength that ranges from 880 MPa to 950 MPa. 
     
     
         6 . The microalloyed martensitic stainless steel grade 403Cb of  claim 1 , wherein the microalloyed martensitic stainless steel grade 403Cb has an impact toughness over 50 J. 
     
     
         7 . A microalloyed martensitic stainless steel grade 403Cb consisting essentially of, by weight percent: 
       
         
           
                 
                 
                 
               
                     
                     
                 
                     
                   carbon 
                   0.13 to 0.18 
                 
                     
                   manganese 
                   0.40 to 0.60 
                 
                     
                   silicon 
                   up to 0.50 
                 
                     
                   phosphorous 
                   up to 0.025 
                 
                     
                   sulfur 
                   up to 0.010 
                 
                     
                   nickel 
                   0.30 to 0.6 
                 
                     
                   chromium 
                   11.5 to 13.0 
                 
                     
                   molybdenum 
                   0.05 to 0.2 
                 
                     
                   niobium 
                   0.15 to 0.25 
                 
                     
                   vanadium 
                   up to 0.10 
                 
                     
                   iron 
                   balance 
                 
                     
                   CNB (Cr—Ni equivalent balance) 
                   5.0 to 7.5, 
                 
                     
                     
                 
             
                
               
               
                
                
                
                
                
                
                
                
                
                
                
                
                
               
            
           
         
         and having an impact toughness ranging over 50 J. 
       
     
     
         8 . The microalloyed martensitic stainless steel grade 403Cb of  claim 7 , wherein the microalloyed martensitic stainless steel grade 403Cb has a yield strength that ranges from 740 MPa to 800 MPa. 
     
     
         9 . The microalloyed martensitic stainless steel grade 403Cb of  claim 7 , wherein the microalloyed martensitic stainless steel grade 403Cb has a tensile strength that ranges from 880 MPa to 950 MPa. 
     
     
         10 . The microalloyed martensitic stainless steel grade 403Cb of  claim 7 , wherein a weight ratio of the nickel to the molybdenum is larger than 3. 
     
     
         11 . A turbine component comprising a microalloyed martensitic stainless steel grade 403Cb comprising, by weight percent: 
       
         
           
                 
                 
                 
               
                     
                     
                 
                     
                   carbon 
                   0.13 to 0.18 
                 
                     
                   manganese 
                   0.40 to 0.60 
                 
                     
                   silicon 
                   up to 0.50 
                 
                     
                   phosphorous 
                   up to 0.025 
                 
                     
                   sulfur 
                   up to 0.010 
                 
                     
                   nickel 
                   0.30 to 0.60 
                 
                     
                   chromium 
                   11.5 to 13.0 
                 
                     
                   molybdenum 
                   0.05 to 0.20 
                 
                     
                   niobium 
                   0.15 to 0.25 
                 
                     
                   vanadium 
                   up to 0.10 
                 
                     
                   iron 
                   balance 
                 
                     
                   CNB (Cr—Ni equivalent balance) 
                   5.0 to 7.5, 
                 
                     
                     
                 
             
                
               
               
                
                
                
                
                
                
                
                
                
                
                
                
                
               
            
           
         
         and wherein a weight ratio of the nickel to the molybdenum is larger than 3. 
       
     
     
         12 . The turbine component of  claim 11 , wherein the microalloyed martensitic stainless steel grade 403Cb has an impact toughness over 50 J. 
     
     
         13 . The turbine component of  claim 11 , wherein the microalloyed martensitic stainless steel grade 403Cb has a yield strength that ranges from 740 MPa to 800 MPa. 
     
     
         14 . The turbine component of  claim 11 , wherein the microalloyed martensitic stainless steel grade 403Cb has a tensile strength that ranges from 880 MPa to 950 MPa.