Stainless steel material having outstanding high-temperature strength, and a production method therefor

Abstract

Provided are a stainless steel having excellent high-temperature strength and a method of manufacturing the same, and more particularly, an austenitic stainless steel having excellent high-temperature and creep strength as well as excellent corrosion resistance able to be used in high-temperature corrosive environments such as power plants and a method of manufacturing the same. The stainless steel of the present invention may have a precipitation index of 1.5 to 2.5.

1 . A stainless steel with excellent high-temperature strength having a precipitation index of about 1.5 to about 2.5 expressed by the following Equation 1:
   (C/12+N/14)/(Nb/91+V/51): 1.5 to 2.5   [Equation 1]
   where carbon (C), nitrogen (N), niobium (Nb), and vanadium (V) denote contents (wt %) of corresponding components, respectively.   
     
     
         2 . The stainless steel with excellent high-temperature strength of  claim 1 , wherein the stainless steel comprises about 0.1 wt % to about 1.0 wt % of Nb and about 0.1 wt % to about 1.0 wt % of V. 
     
     
         3 . The stainless steel with excellent high-temperature strength of  claim 1 , wherein a content of V is about 10% or less than that of Nb in an atomic fraction in precipitates of the steel before being used. 
     
     
         4 . The stainless steel with excellent high-temperature strength of  claim 1 , wherein the stainless steel has a composition including about 0.01 to 0.1 wt % of carbon (C), about 0.1 to 1.0 wt % of silicon (Si), about 0.1 to 2.0 wt % of manganese (Mn), about 16 to 20 wt % of chromium (Cr), about 7 to 15 wt % of nickel (Ni), about 0.1 to 1.0 wt % of niobium (Nb), about 0.1 to 1.0 wt % of vanadium (V), about 0.1 to 0.3 wt % of cobalt (Co), about 2 to 5 wt % of copper (Cu), about 0.03 wt % or less of aluminum (Al), about 0.01 to 0.25 wt % of nitrogen (N), residual iron (Fe), and unavoidable impurities. 
     
     
         5 . A method of manufacturing a stainless steel with excellent high-temperature strength, the method comprising:
 heating a steel satisfying the composition of  claim 1 , and subjected to hot rolling and/or cold rolling to about 1200° C. or more, and   cooling the heated stainless steel at a cooling rate of about 10° C./s or more to a temperature of about 500° C. or less.   
     
     
         6 . The stainless steel with excellent high-temperature strength of  claim 2 , wherein a content of V is about 10% or less than that of Nb in an atomic fraction in precipitates of the steel before being used. 
     
     
         7 . The stainless steel with excellent high-temperature strength of  claim 2 , wherein the stainless steel has a composition of  claim 2 , wherein the stainless steel has a composition including about 0.01 to 0.1 wt % of carbon (C), about 0.1 to 1.0 wt % of silicon (Si), about 0.1 to 2.0 wt % of manganese (Mn), about 16 to 20 wt % of chromium (Cr), about 7 to 15 wt % of nickel (Ni), about 0.1 to 1.0 wt % of niobium (Nb), about 0.1 to 1.0 wt % of vanadium (V), about 0.1 to 0.3 wt % of cobalt (Co), about 2 to 5 wt % of copper (Cu), about 0.03 wt % or less of aluminum (Al), about 0.01 to 0.25 wt % of nitrogen (N), residual iron (Fe), and unavoidable impurities. 
     
     
         8 . A method of manufacturing a stainless steel with excellent high-temperature strength, the method comprising:
 heating a steel satisfying the composition of  claim 2 , and subjected to hot rolling and/or cold rolling to about 1200° C. or more, and   cooling the heated stainless steel at a cooling rate of about 10° C./s or more to a temperature of about 500° C. or less.