Ferritic stainless steel and method of manufacturing the same

Abstract

The present disclosure relates to a ferritic stainless steel and fabrication method of a ferritic stainless steel comprising, by weight %, C: above 0 wt % to 0.01 wt % or less, Si: above 0 wt % to 0.5 wt % or less, Mn: above 0 wt % to 2.0 wt % or less, P: 0 wt % or more to 0.04 wt % or less, S: 0 wt % or more to 0.02 wt % or less, Cr: 12 wt % or more to 19 wt % or less, Mo: 0 wt % or more to 1.0 wt % or less, W: 2 wt % of more to 7 wt % or less, Ti: 0 wt % or more to 0.3 wt % or less, Nb: above 0 wt % to 0.6 wt % or less, N: above 0 wt % to 0.01 wt % or less, Al: 0 wt % or more to 0.1 wt % or less; and the balance of Fe and other inevitable impurities.

1 . A ferritic stainless steel comprising:
 by weight %, C: above 0 wt % to 0.01 wt % or less, Si: above 0 wt % to 0.5 wt % or less, Mn: above 0 wt % to 2.0 wt % or less, P: 0 wt % or more to 0.04 wt % or less, S: 0 wt % or more to 0.02 wt % or less, Cr: 12 wt % or more to 19 wt % or less, Mo: 0 wt % or more to 1.0 wt % or less, W: 2 wt % or more to 7 wt % or less, Ti: 0 wt % or more to 0.3 wt % or less, Nb: above 0 wt % to 0.6 wt % or less, N: above 0 wt % to 0.01 wt % or less, Al: 0 wt % or more to 0.1 wt % or less; and the balance of Fe and other inevitable impurities.   
     
     
         2 . The ferritic stainless steel according to  claim 1 , wherein Mo is 0.8 wt % or less, by weight %. 
     
     
         3 . The ferritic stainless steel according to  claim 2 , wherein a hot-annealed structure of the ferritic stainless steel comprises a sigma phase of 5% or less. 
     
     
         4 . The ferritic stainless steel according to  claim 1 , wherein W is 3 wt % or more to 6 wt % or less, by weight %. 
     
     
         5 . The ferritic stainless steel according to  claim 1 , wherein Mo wt %+0.83W wt % is 3.5 wt % or more to 5 wt % or less, by weight %. 
     
     
         6 . The ferritic stainless steel according to  claim 1 , wherein [(Ti wt %+1/2Nb wt %)/(C wt %+N wt %)] is 19.5 or more to 32 or less. 
     
     
         7 . The ferritic stainless steel according to  claim 1 , wherein ductile-brittleness transition temperature (DBTT) is 90° C. or less. 
     
     
         8 . The ferritic stainless steel according to  claim 1 , wherein the ferritic stainless steel satisfies the following equation: −184.6+3.2(Cr wt %)+27.5(Mo wt %)+4243.4(C wt %+N wt %)−295.6(Al wt %)+0.9[Nb wt %/(C wt %+N wt %)] 90. 
     
     
         9 . A fabrication method of a ferritic stainless steel comprising, by weight %, C: above 0 wt % to 0.01 wt % or less, Si: above 0 wt % to 0.5 wt % or less, Mn: above 0 wt % to 2.0 wt % or less, P: 0 wt % or more to 0.04 wt % or less, S: 0 wt % or more to 0.02 wt % or less, Cr: 12 wt % or more to 19 wt % or less, Mo: 0 wt % or more to 1.0 wt % or less, W: 2 wt % or more to 7 wt % or less, Ti: 0 wt % or more to 0.3 wt % or less, Nb: above 0 wt % to 0.6 wt % or less, N: above 0 wt % to 0.01 wt % or less, Al: 0 wt % or more to 0.01 wt % or less; and the balance of Fe and other inevitable impurities,
 wherein   the fabrication method of the ferritic stainless steel sheet comprises:   providing a slab;   heating the slab;   hot annealing;   cold annealing; and   cold rolling.   
     
     
         10 . The fabrication method of a ferritic stainless steel according to  claim 9 , wherein Mo is 0.8 wt % or less, by weight %. 
     
     
         11 . The fabrication method of a ferritic stainless steel according to  claim 9 , wherein W is 3 wt % or more to 6 wt % or less, by weight %. 
     
     
         12 . The fabrication method of a ferritic stainless steel according to  claim 9 , wherein:
 Mo wt %+0.83W wt % is 3.5 wt % or more to 5 wt % or less, by weight %.   
     
     
         13 . The fabrication method of a ferritic stainless steel according to  claim 9 , wherein:
 [(Ti wt %+1/2Nb wt %)/(C wt %+N wt %)] is 19.5 or more to 32 or less.   
     
     
         14 . The fabrication method of a ferritic stainless steel according to  claim 9 , wherein:
 ductile-brittleness transition temperature (DBTT) is 90° C. or less.   
     
     
         15 . The fabrication method of a ferritic stainless steel according to  claim 9 , wherein the ferritic stainless steel satisfies the following equation:
   −184.6+3.2(Cr wt %)+27.5(Mo wt %)+4243.4(C wt %+N wt %)−295.6(Al wt %)+0.9[Nb wt %/(C wt %+N wt %)]<90.
   
     
     
         16 . The fabrication method of a ferritic stainless steel according to  claim 9 , wherein grain size is ASTM No. 3 or more. 
     
     
         17 . The fabrication method of a ferritic stainless steel according to  claim 9 , wherein heating the slab has slab heating temperature that is 1180° C. or more to 1240° C. or less, with respect to slab temperature. 
     
     
         18 . The fabrication method of a ferritic stainless steel according to  claim 9 , wherein hot annealing has a hot-annealing temperature that is 1020° C. or more to 1070° C. or less, with respect to strip temperature. 
     
     
         19 . The fabrication method of a ferritic stainless steel according to  claim 9 , wherein cold annealing has a cold-annealing temperature that is 1030° C. or more to 1080° C. or less, with respect to strip temperature. 
     
     
         20 . The fabrication method of a ferritic stainless steel according to  claim 9 , wherein (cold-annealing temperature)/(hot-annealing temperature) is 1.0 or more to 1.1 or less, and wherein the cold-annealing temperature is the temperature in cold-annealing and the hot-annealing temperature is the temperature in hot annealing.