Ferritic stainless steel with improved ridging resistance and its manufacturing method

Abstract

A ferritic stainless steel with improved ridging resistance is disclosed herein.According to a disclosed embodiment, the ferritic stainless steel with improved ridging resistance comprises, in percent by weight (wt %), 0.001 to 0.3% of C, 0.01 to 1.0% of Si, 0.1 to 3.0% of Mn, 10 to 15% of Cr, 0.001 to 0.3% of N, 0.03% or less of P, 1.0% or less of Ni, 1.0% or less of Cu, 1.0% or less of Al, 0.003% or less of Mo, 1.0% or less of Ti, the remainder of Fe, and other unavoidable impurities, and satisfies y s represented by the following formula (1) is 6 or more.γs=900C−30Si+12Mn+23Ni−17Cr−12Mo+12Cu−49Ti−52Al+950N+178   Equation (1)(wherein, C, Si, Mn, Ni, Cr, Mo, Cu, Ti, Al, and N represent the content (wt %) of each element)

1 . A ferritic stainless steel with improved ridging resistance comprising, in percent by weight (wt %), 0.001 to 0.3% of C, 0.01 to 1.0% of Si, 0.1 to 3.0% of Mn, 10 to 15% of Cr, 0.001 to 0.3% of N, 0.03% or less of P, 1.0% or less of Ni, 1.0% or less of Cu, 1.0% or less of Al, 0.003% or less of Mo, 1.0% or less of Ti, the remainder of Fe, and other unavoidable impurities, wherein γ S  represented by the following formula (1) is 6 or more.
   γ S =900C−30Si+12Mn+23Ni−17Cr−12Mo+12Cu−49Ti−52Al+950N+178   Formula (1)
 
 (wherein, C, Si, Mn, Ni, Cr, Mo, Cu, Ti, Al, and N represent the content (wt %) of each element) 
 
     
     
         2 . The ferritic stainless steel with improved ridging resistance according to  claim 1 , wherein a ferrite grain size is 15 μm or less. 
     
     
         3 . The ferritic stainless steel with improved ridging resistance according to  claim 1 , wherein a ridging height (Wt) is 10 μm or less, measured after 15% elongation at a thickness of 1.0 mm or less. 
     
     
         4 . A manufacturing method of a ferritic stainless steel with improved ridging resistance comprising:
 reheating a slab at a temperature of 1050 to 1250° C., the slab comprising, in percent by weight (wt %), 0.001 to 0.3% of C, 0.01 to 1.0% of Si, 0.1 to 3.0% of Mn, 10 to 15% of Cr, 0.001 to 0.3% of N, 0.03% or less of P, 1.0% or less of Ni, 1.0% or less of Cu, 1.0% or less of Al, 0.003% or less of Mo, 1.0% or less of Ti, the remainder of Fe, and other unavoidable impurities, wherein γ S  represented by the following formula (1) is 6 or more;   hot rolling the reheated slab; and   cold rolling and cold rolling annealing the hot rolled material;   wherein, in the reheating step, γ Wt (T), defined as austenite weight % at the temperature T, is controlled to satisfy the following formula (2).
   γ S =900C−30Si+12Mn+23Ni−17Cr−12Mo+12Cu−49Ti−52Al+950N+178   Formula (1)
 
   (wherein, C, Si, Mn, Ni, Cr, Mo, Cu, Ti, Al, and N represent the content (wt %) of each element)
   γ Wt (1200° C.)≥19%   Formula (2)
 
   
     
     
         5 . The manufacturing method of a ferritic stainless steel with improved ridging resistance according to  claim 4 , wherein the reheating step satisfies the following formula (3).
   γ s *γ Wt (1200° C.)≥114   Formula (3)
   
     
     
         6 . The manufacturing method of a ferritic stainless steel with improved ridging resistance according to  claim 4 , wherein the hot rolling step comprises finishing rolling at a temperature of 700 to 950° C. 
     
     
         7 . The manufacturing method of a ferritic stainless steel with improved ridging resistance according to  claim 4 , wherein after hot rolling step, hot rolling step further comprises hot rolling annealing at a temperature of 600 to 900° C.