Use of alloy steel for making high-strength, seamless steel tubes

Abstract

An alloy steel, includes 0.12 to 0.25 wt. % C, 0.40 wt. % or less Si, 1.20 to 1.80 wt. % Mn, 0.025 wt. % or less P, 0.010 wt. % or less S, 0.01 to 0.06 wt. % Al, 0.20 to 0.50 wt. % Cr, 0.20 to 0.50 wt. % Mo, 0.03 to 0.10 wt. % V, 0.20 wt. % or less Cu, 0.02 wt. % or less N, 0.30 to 1.00 wt. % W, and the balance iron and incidental impurities, for making high-strength, weldable seamless steel tubes for structural application, through a hot rolling process and subsequent quenching and tempering.

What is claimed is:  
     
         1 . An alloy steel, comprising, by weight percent,  
       
         
           
                 
                 
                 
               
                     
                     
                 
                     
                     
                 
                     
                   C 
                   0.12-0.25% 
                 
                     
                   Si 
                   ≦0.40% 
                 
                     
                   Mn 
                   1.20-1.80% 
                 
                     
                   P 
                    ≦0.025% 
                 
                     
                   S 
                    ≦0.010% 
                 
                     
                   Al 
                   0.01-0.06% 
                 
                     
                   Cr 
                   0.20-0.50% 
                 
                     
                   Mo 
                   0.20-0.50% 
                 
                     
                   V 
                   0.03-0.10% 
                 
                     
                   Cu 
                   ≦0.20% 
                 
                     
                   N 
                   ≦0.02% 
                 
                     
                   W 
                   0.30-1.00% 
                 
                     
                     
                 
                     
                   
                    
                   
                 
                     
                     
                 
             
                
                
               
               
                
                
                
                
                
                
                
                
                
                
                
                
                
                
                
               
            
           
         
       
       for making high-strength, weldable seamless steel tubes for structural application, through a hot rolling process and subsequent quenching and tempering.  
     
     
         2 . The alloy steel of  claim 1  having at least 0.50 wt. % W.  
     
     
         3 . The alloy steel of  claim 1  having 0.20 wt. % or less Ni.  
     
     
         4 . The alloy steel of  claim 1  having less than 0.15 wt. % Ni.  
     
     
         5 . The alloy steel of  claim 1  having 0.10 wt. % or less Ni.  
     
     
         6 . The alloy steel of  claim 1  having 0.14 to 0.20 wt. % C.  
     
     
         7 . A high-strength, weldable seamless structural tube made through a hot-rolling process and subsequent quenching and tempering, comprising an alloy steel containing, by weight percent,  
       
         
           
                 
                 
                 
               
                     
                     
                 
                     
                     
                 
                     
                   C 
                   0.12-0.25% 
                 
                     
                   Si 
                   ≦0.40% 
                 
                     
                   Mn 
                   1.20-1.80% 
                 
                     
                   P 
                    ≦0.025% 
                 
                     
                   S 
                    ≦0.010% 
                 
                     
                   Al 
                   0.01-0.06% 
                 
                     
                   Cr 
                   0.20-0.50% 
                 
                     
                   Mo 
                   0.20-0.50% 
                 
                     
                   V 
                   0.03-0.10% 
                 
                     
                   W 
                   0.30-1.00% 
                 
                     
                   Ni 
                   0.00-0.20% 
                 
                     
                   Cu 
                   ≦0.20% 
                 
                     
                   N 
                   ≦0.02% 
                 
                     
                     
                 
                     
                   
                    
                   
                 
                     
                     
                 
             
                
                
               
               
                
                
                
                
                
                
                
                
                
                
                
                
                
                
                
                
               
            
           
         
       
     
     
         8 . The structural tube of  claim 7 , wherein the alloy steel contains at least 0.50 wt. % W.  
     
     
         9 . The structural tube of  claim 7 , wherein the alloy steel contains less than 0.15 wt. % of Ni.  
     
     
         10 . The structural tube of  claim 7 , wherein the alloy steel contains 0.10 wt. % or less Ni.  
     
     
         11 . The structural tube of  claim 7 , wherein the alloy steel contains 0.14 to 0.20 wt. % C.