Ferritic stainless steel with improved grain boundary erosion, and manufacturing method thereof

Abstract

Disclosed is a ferritic stainless steel with reduced grain boundary erosion. A ferritic stainless steel with reduced grain boundary erosion according to an embodiment includes, in percent by weight (wt %), 0.005 to 0.1% of C, 0.01 to 1.0% of Si, 0.01 to 1.5% of Mn, 13 to 18% of Cr, 0.005 to 0.1% of N, 0.005 to 0.2% of Al, 0.005 to 0.1% of Ni, 0.003% or less of Mo, 0.05% or less of P, 0.005% or less of S, and the remainder being Fe and impurities, and satisfies an Acl, defined by Formula (1) below, of 900 or more and 990 or less:Ac1=36Cr+90Si+76Mo+760Al+350−(800C+1300N+150Ni+50Mn)  Formula (1):(wherein C, N, Si, Mn, Cr, Ni, Al, Mn, and Mo represent a content (wt %) of each element).

1 . A ferritic stainless steel with reduced grain boundary erosion comprising, in percent by weight (wt %), 0.005 to 0.1% of C, 0.01 to 1.0% of Si, 0.01 to 1.5% of Mn, 13 to 18% of Cr, 0.005 to 0.1% of N, 0.005 to 0.2% of Al, 0.005 to 0.1% of Ni, 0.003% or less of Mo, 0.05% or less of P, 0.005% or less of S, and the remainder being Fe and impurities,
 wherein an Ac1, defined by Formula (1) below, is 900 or more and 990 or less:
   Ac1=36Cr+90Si+76Mo+760Al+350−(800C+1300N+150Ni+50Mn)  Formula (1):
 
   (wherein C, N, Si, Mn, Cr, Ni, Al, Mn, and Mo represent a content (wt %) of each element).   
     
     
         2 . The ferritic stainless steel according to  claim 1 , wherein the ferritic stainless steel comprises, in percent by weight (wt %), 0.4 to 1.0% of Mn and 0.1 to 0.15% of Al. 
     
     
         3 . A method of manufacturing a ferritic stainless steel with reduced grain boundary erosion, the method comprising:
 preparing a slab comprising, in percent by weight (wt %), 0.005 to 0.1% of C, 0.01 to 1.0% of Si, 0.01 to 1.5% of Mn, 13 to 18% of Cr, 0.005 to 0.1% of N, 0.005 to 0.2% of Al, 0.005 to 0.1% of Ni, 0.003% or less of Mo, 0.05% or less of P, 0.005% or less of S, and the remainder being Fe and impurities, and satisfying an Ac1, defined by Formula (1) below, of 900 or more and 990 or less;   reheating the slab;   rough-rolling the reheated slab and finish-rolling the rough-rolled steel material;   coiling the hot-rolled steel material;   continuous annealing the coiled steel material in a temperature range T(A) defined by Formula (2) below; and   acid-pickling the continuous annealed steel material,
   Ac1=36Cr+90Si+76Mo+760Al+350−(800C+1300N+150Ni+50Mn)  Formula (1):
 
   (wherein C, N, Si, Mn, Cr, Ni, Al, Mn, and Mo represent a content (wt %) of each element)
   870° C.≤T(A)≤(Ac1-10)° C.  Formula (2):
 
   
     
     
         4 . The method according to  claim 3 , wherein the slab comprises, in percent by weight (wt %), 0.4 to 1.0% of Mn and 0.1 to 0.15% of Al. 
     
     
         5 . The method according to  claim 3 , wherein the reheating is performed in a temperature range of 1,000 to 1,200° C. 
     
     
         6 . The method according to  claim 3 , wherein the finish rolling is performed in a temperature range of 800 to (Ac1-10)° C. 
     
     
         7 . The method according to  claim 3 , wherein the coiling is performed in a temperature range of 750 to (Ac1-10)° C. 
     
     
         8 . The method according to  claim 3 , wherein the continuous annealing is performed for 3 to 10 minutes.