Nickel alloy and manufacturing method for the same

Abstract

A nickel alloy having an excellent corrosion resistance (hereinafter referred to as “nickel alloy”) used for pipes, structural materials and structural members, such as bolts or the like, in a nuclear power plant or in a chemical plant, and a manufacturing method for the same are provided. In the nickel alloy according to the present invention, an excellent corrosion resistance, in particular an excellent resistance against the IGSCC, is obtained by specifying the low angle boundary rate of 4% or more in the grain boundaries, along with the restriction of the chemical composition in the alloy, thereby making it possible to provide a nickel alloy which is most suitably used for pipes, structural materials and structural members, such as bolts or the like. Accordingly, the nickel alloy according to the present invention is widely applicable to structural members used in a nuclear station or in a chemical plant.

What is claimed is:  
     
         1 . Anickel alloy including, by mass %, C: 0.01-0.04%; Si: 0.05-1%; Mn: 0.05-1%; P: 0.015% or less; S: 0.015% or less; Cr: 25-35%; Ni: 40-70%; Al: 0.5% or less; Ti: 0.01-0.5%; and the balance Fe and impurities, wherein the crystal structure has a low angle boundary rate of 4% or more as for the grain boundaries.  
     
     
         2 . Anickel alloy including, by mass %, C: 0.01-0.05%; Si: 0.05-1%; Mn: 0.05-1%; P: 0.02% or less; S: 0.02% or less; Cr: 10-35%; Ni: 40-80%; Al: 2% or less; Ti: 0.5% or less; and the balance Fe and impurities, wherein the crystal structure has a low angle boundary rate of 4% or more as for the grain boundaries.  
     
     
         3 . A nickel alloy according to  claim 2 , further including at least one of Co: 2.5% or less; Cu: 1% or less; Nb+Ta: 3.15-4.15%; Mo: 8-10%; and V: 0.035% or less.  
     
     
         4 . A method for manufacturing a nickel alloy including, by mass %, C: 0.01-0.04%; Si: 0.05-1%; Mn: 0.05-1%; P: 0.015% or less; S: 0.015% or less; Cr: 25-35%; Ni: 40-70%; Al: 0.5% or less; Ti: 0.01-0.5%; and the balance Fe and impurities, said method comprising a step of cold working the alloy, wherein the final cold working is carried out at an area reduction rate of 60% or more.  
     
     
         5 . A method for manufacturing a nickel alloy including, by mass %, C: 0.01-0.05%; Si: 0.05-1%; Mn: 0.05-1%; P: 0.02% or less; S: 0.02% or less; Cr: 10-35%; Ni: 40-80%; Al: 2% or less; Ti: 0.5% or less; and the balance Fe and impurities, said method comprising steps of cold working the alloy, wherein the following two equations (1) and (2) are fulfilled:  
       Rd≧40   (1)  Rd× (0.1+1/exp( T/ 500))≧10   (2)  
       where Rd (%) is an area reduction rate in the final cold working, and T(° C.) is the temperature in the final solution treatment.  
     
     
         6 . A method for manufacturing a nickel alloy according to  claim 4  or  5 , wherein the cold working applied to the nickel alloy is the cold rolling.  
     
     
         7 . A method for manufacturing a nickel alloy according to  claim 5 , wherein said nickel alloy further includes at least one of Co: 2.5% or less; Cu: 1% or less; Nb+Ta: 3.15-4.15%; Mo: 8-10%; and V: 0.035% or less.  
     
     
         8 . A method for manufacturing a nickel alloy according to  claim 7 , wherein, the cold working applied to the nickel alloy is the cold rolling.