Ni base alloy pipe stock and method for manufacturing the same

Abstract

A Ni base alloy pipe stock having a chemical composition comprising, by mass %, C≦0.04%, Si≦0.50%, Mn: 0.01 to 6.0%, P≦0.03%, S≦0.01%, Cr: 15 to 30%, Ni: more than 45% to not more than 60%, Mo: 0 to 18%, W: 0 to 36%, with Mo(%)+0.5W(%): more than 1.5% to not more than 18%, Cu: 0.01 to 1.5%, Al≦0.01% and N: 0.0005 to 0.20%, and the balance substantially being Fe, with 1380−5000P−100S−4400C≧1300, Ni+10(Mo+0.5W)+100N≦200, (Ni−50)+10(N−0.1)−2(Cr−25)−5(Mo+0.5W−6)+12≧0, can be manufactured into a seamless pipe by use of a Mannesmann piercing and rolling mill because of its excellent inner surface properties. The resulting seamless pipe has excellent mechanical properties and moreover has excellent corrosion resistance in a sour gas environment, and thus, the Ni base alloy pipe stock can be used as a pipe stock for oil country tubular goods and line pipes and further as a pipe stock for various structural members of nuclear power plants and chemical industrial plants.

1 - 19 . (canceled)  
   
   
       20 . A Ni base alloy pipe stock, having a chemical composition comprising, by mass %, C: not more than 0.04%, Si: not more than 0.50%, Mn: 0.01 to 6.0%, P: not more than 0.03%, S: not more than 0.01%, Cr: 15 to 30%, Ni: more than 45% to not more than 60%, Mo: 0 to 18%, W: 0 to 36%, with Mo(%)+0.5W(%): more than 1.5% to not more than 18%, Cu: 0.01 to 1.5%, Al: not more than 0.10% and N: 0.0005 to 0.20%, and the balance being substantially Fe, with values of T GBm , P sr  and P σ  represented by the following equations (1) to (3) being not more than 1300, not more than 200 and not less than 0, respectively, and moreover being subjected to piercing and rolling by a Mannesmann piercing and rolling mill:  
         T   GBm =1380−5000 P −100 S− 4400 C   (1),    P   sr =Ni+10(Mo+0.5W)+100N  (2),    P   σ =(Ni−50)+10(N−0.1)−2(Cr−25)−5(Mo+0.5W−6)+12  (3),  
     wherein each element symbol in the equations (1) to (3) represents the content by mass % of the element concerned.  
   
   
       21 . The Ni base alloy pipe stock according to  claim 20 , wherein the content of Mn is 0.01 to 1.0% by mass %.  
   
   
       22 . A Ni base alloy pipe stock according to  claim 20 , which further contains an element or elements of one or more groups selected from the groups (a) to (d) listed below in lieu of part of Fe: 
 (a): one or more selected from among V: 0.001 to 0.3%, Nb: 0.001 to 0.3%, Ta: 0.001 to 1.0%, Ti: 0.001 to 1.0%, Zr: 0.001 to 1.0% and Hf: 0.001 to 1.0% by mass %;    (b): B: 0.0001 to 0.015% by mass %;    (c): Co: 0.3 to 5.0% by mass %;    (d): one or more selected from among Mg: 0.0001 to 0.010%, Ca: 0.0001 to 0.010%, La: 0.0001 to 0.20%, Ce: 0.0001 to 0.20%, Y: 0.0001 to 0.40%, Sm: 0.0001 to 0.40%, Pr: 0.0001 to 0.40% and Nd: 0.0001 to 0.50% by mass %.    
   
   
       23 . The Ni base alloy pipe stock according to  claim 22 , wherein the content of Mn is 0.01 to 1.0% by mass %.  
   
   
       24 . The Ni base alloy pipe stock according to  claim 20 , which further has the value of fn represented by the following equation (4) being not more than 0.3:  
         fn={P /(0.025 H− 0.01)} 2   +{S /(0.015 H− 0.01)} 2   (4),  
     wherein P and S represent contents, by mass %, of P and S in the pipe stock, respectively, and H represents the pipe expansion ratio represented by the ratio of the outer diameter of the pipe stock to the diameter of a steel stock billet.  
   
   
       25 . The Ni base alloy pipe stock according to  claim 21 , which further has the value of fn represented by the following equation (4) being not more than 0.3:  
         fn={P /(0.025 H− 0.01)} 2   +{S /(0.015 H− 0.01)} 2   (4),  
     wherein P and S represent contents, by mass %, of P and S in the pipe stock, respectively, and H represents the pipe expansion ratio represented by the ratio of the outer diameter of the pipe stock to the diameter of a steel stock billet.  
   
   
       26 . The Ni base alloy pipe stock according to  claim 22 , which further has the value of fn represented by the following equation (4) being not more than 0.3:  
         fn={P /(0.025 H− 0.01)} 2   +{S /(0.015 H− 0.01)} 2   (4),  
     wherein P and S represent contents, by mass %, of P and S in the pipe stock, respectively, and H represents the pipe expansion ratio represented by the ratio of the outer diameter of the pipe stock to the diameter of a steel stock billet.  
   
   
       27 . The Ni base alloy pipe stock according to  claim 23 , which further has the value of fn represented by the following equation (4) being not more than 0.3:  
         fn={P /(0.025 H− 0.01)} 2   +{S /(0.015 H− 0.01)} 2   (4),  
     wherein P and S represent contents, by mass %, of P and S in the pipe stock, respectively, and H represents the pipe expansion ratio represented by the ratio of the outer diameter of the pipe stock to the diameter of a steel stock billet.  
   
   
       28 . A Ni base alloy seamless pipe, manufactured by use of the Ni base alloy pipe stock according to  claim 20 .  
   
   
       29 . A Ni base alloy seamless pipe, manufactured by use of the Ni base alloy pipe stock according to  claim 21 .  
   
   
       30 . A Ni base alloy seamless pipe, manufactured by use of the Ni base alloy pipe stock according to  claim 22 .  
   
   
       31 . A Ni base alloy seamless pipe, manufactured by use of the Ni base alloy pipe stock according to  claim 23 .  
   
   
       32 . A Ni base alloy seamless pipe, manufactured by use of the Ni base alloy pipe stock according to  claim 24 .  
   
   
       33 . A Ni base alloy seamless pipe, manufactured by use of the Ni base alloy pipe stock according to  claim 25 .  
   
   
       34 . A Ni base alloy seamless pipe, manufactured by use of the Ni base alloy pipe stock according to  claim 26 .  
   
   
       35 . A Ni base alloy seamless pipe, manufactured by use of the Ni base alloy pipe stock according to  claim 27 .  
   
   
       36 . A method for manufacturing a Ni base alloy pipe stock, comprising piercing and rolling a billet, which satisfies the chemical compositions according to  claim 20 , by use of a Mannesmann piercing and rolling mill.  
   
   
       37 . The method for manufacturing a Ni base alloy pipe stock according to  claim 36 , wherein the piercing and rolling by the Mannesmann piercing and rolling mill is performed in a condition where the value of fn represented by the following equation (4) is not more than 0.3:  
         fn={P /(0.025 H− 0.01)} 2   +{S /(0.015 H− 0.01)} 2   (4),  
     wherein P and S represent contents, by mass %, of P and S in the pipe stock, respectively, and H represents the pipe expansion ratio represented by the ratio of the outer diameter of the pipe stock to the diameter of the steel stock billet.  
   
   
       38 . A Ni base alloy seamless pipe, manufactured by use of the Ni base alloy pipe stock manufactured by the method according to  claim 36 .  
   
   
       39 . A Ni base alloy seamless pipe, manufactured by use of the Ni base alloy pipe stock manufactured by the method according to  claim 37.