Low-cost austenitic stainless steel having high strength and high formability, and method for manufacturing same

Abstract

Disclosed are a low-cost austenitic stainless steel having high strength and high formability and a method for manufacturing same. The low-cost austenitic stainless steel having high strength and high formability according to an embodiment includes, greater than 0% and at most 0.08% of C, 0.2 to 0.25% of N, 0.8 to 1.5% of Si, 8.0 to 9.5% of Mn, 15.0 to 16.5% of Cr, greater than 0% and at most 1.0% of Ni, 0.8 to 1.8% of Cu, and the remainder of Fe and other unavoidable impurities and satisfies Expressions (1) to (4) below.Ni+0.47Mn+15N≥7.5  (1)23(C+N)+1.3 Si+0.24(Cr+Ni+Cu)+0.1Mn≥12  (2)551−462(C+N)−9.2Si−8.1Mn−13.7Cr−29(Ni+Cu)≤70  (3)11≤1+45C−5Si+0.09Mn+2.2Ni−0.28Cr−0.67Cu+88.6N≤17  (4)Here, C, N, Si, Mn, Cr, Ni, and Cu represent contents (wt %) of the elements, respectively.

1 . A low-cost austenitic stainless steel having high strength and high formability comprising, in percent by weight (wt %), greater than 0% and at most 0.08% of C, 0.2 to 0.25% of N, 0.8 to 1.5% of Si, 8.0 to 9.5% of Mn, 15.0 to 16.5% of Cr, greater than 0% and at most 1.0% of Ni, 0.8 to 1.8% of Cu, and the remainder of Fe and other unavoidable impurities and
 satisfying Expressions (1) to (4) below:
   Ni+0.47Mn+15N≥7.5  (1)
 
   23 (C+N)+1.3Si+0.24(Cr+Ni+Cu)+0.1Mn≥12  (2)
 
   551−462(C+N)−9.2Si−8.1Mn−13.7Cr−29(Ni+Cu)≤70  (3)
 
   11≤1+45C−5Si+0.09Mn+2.2Ni−0.28Cr−0.67Cu+88.6N≤17  (4)
 
   (wherein C, N, Si, Mn, Cr, Ni, and Cu represent contents (wt %) of the elements, respectively).   
     
     
         2 . The low-cost austenitic stainless steel according to  claim 1 , wherein a yield strength of a cold-rolled, annealed steel sheet is 400 MPa or more. 
     
     
         3 . The low-cost austenitic stainless steel according to  claim 1 , wherein an elongation of a cold-rolled, annealed steel sheet is 55% or more. 
     
     
         4 . The low-cost austenitic stainless steel according to  claim 1 , wherein a yield strength of a skin pass-rolled steel sheet is 800 MPa or more. 
     
     
         5 . The low-cost austenitic stainless steel according to  claim 4 , wherein an elongation of the skin pass-rolled steel sheet is 25% or more. 
     
     
         6 . A method for manufacturing a low-cost austenitic stainless steel having high strength and high formability, the method comprising:
 preparing a slab including, in percent by weight (wt %), greater than 0% and at most 0.08% of C, 0.2 to 0.25% of N, 0.8 to 1.5% of Si, 8.0 to 9.5% of Mn, 15.0 to 16.5% of Cr, greater than 0% and at most 1.0% of Ni, 0.8 to 1.8% of Cu, and the remainder of Fe and other unavoidable impurities and satisfying Expressions (1) to (4) below;   hot rolling the slab to prepare a hot-rolled steel sheet and hot annealing the hot-rolled steel sheet to prepare a hot-rolled, annealed steel sheet;   cold rolling the hot-rolled, annealed steel sheet to prepare a cold-rolled steel sheet and cold annealing the cold-rolled steel sheet at a temperature of 1050° C. or higher to prepare a cold-rolled, annealed steel sheet; and   skin pass rolling the cold-rolled, annealed steel sheet to prepare a skin pass-rolled steel sheet:
   Ni+0.47Mn+15N≥7.5  (1)
 
   23 (C+N)+1.3Si+0.24(Cr+Ni+Cu)+0.1Mn≥12  (2)
 
   551−462(C+N)−9.2Si−8.1Mn−13.7Cr−29(Ni+Cu)≤70  (3)
 
   11≤1+45C−5Si+0.09Mn+2.2Ni−0.28Cr−0.67Cu+88.6N≤17  (4)
 
   (wherein C, N, Si, Mn, Cr, Ni, and Cu represent contents (wt %) of the elements, respectively).   
     
     
         7 . The method according to  claim 6 , wherein the skin pass rolling is performed at a reduction ratio of 20% or more. 
     
     
         8 . The method according to  claim 6 , wherein the slab has a reduction of area of 50% or more at a high temperature of 800° C. or higher.