Austenitic stainless steel and method for manufacturing same

Abstract

Disclosed is an austenitic stainless steel including, in percent by weight (wt %), 0.005 to 0.03% of C, 0.1 to 1% of Si, 0.1 to 2% of Mn, 0.01 to 0.4 of Cu, 0.01 to 0.2 of Mo, 6 to 9% of Ni, 16 to 19% of Cr, 0.01 to 0.2% of N, and the balance of Fe and inevitable impurities, wherein an austenitic stability parameter (ASP) value calculated by 551−462 (C+N)−9.2Si−8.1Mn−13.7Cr−29 (Ni+Cu)−18.5Mo is from 30 to 60, a [100*N]/[Ni+Cu] value is 1.4 or more, an average grain size is less than 5 μm, and a fraction (%) of grains with a grain size of 5 μm or more is less than 10%.

1 . An austenitic stainless steel comprising, in percent by weight (wt %), 0.005 to 0.03% of C, 0.1 to 1% of Si, 0.1 to 2% of Mn, 0.01 to 0.4 of Cu, 0.01 to 0.2 of Mo, 6 to 9% of Ni, 16 to 19% of Cr, 0.01 to 0.2% of N, and the balance of Fe and inevitable impurities,
 wherein an austenitic stability parameter (ASP) value calculated by 551−462(C+N)−9.2Si−8.1Mn−13.7Cr−29 (Ni+Cu)−18.5Mo is from 30 to 60,   a [100*N]/[Ni+Cu] value is 1.4 or more,   an average grain size is less than 5 μm, and a fraction (%) of grains with a grain size of 5 μm or more is less than 10%.   
     
     
         2 . The austenitic stainless steel according to  claim 1 , wherein the austenitic stainless steel has a tensile strength of 850 MPa or more. 
     
     
         3 . The austenitic stainless steel according to  claim 1 , wherein the austenitic stainless steel has a yield strength of 500 MPa or more. 
     
     
         4 . The austenitic stainless steel according to  claim 1 , wherein the austenitic stainless steel has an elongation of 25% or more. 
     
     
         5 . A method for manufacturing an austenitic stainless steel, the method comprising:
 preparing a slab by casting an austenitic stainless steel including, in percent by weight (wt %), 0.005 to 0.03% of C, 0.1 to 1% of Si, 0.1 to 2% of Mn, 0.01 to 0.4 of Cu, 0.01 to 0.2 of Mo, 6 to 9% of Ni, 16 to 19% of Cr, 0.01 to 0.2% of N, and the balance of Fe and inevitable impurities, wherein an austenitic stability parameter (ASP) value calculated by 551−462(C+N)−9.2Si−8.1Mn−13.7Cr−29(Ni+Cu)−18.5Mo is from 30 to 60, a [100*N]/[Ni+Cu] value is 1.4 or more, an average grain size is less than 5 μm, and a fraction (%) of grains with a grain size of 5 μm or more is less than 10%;   hot rolling, annealing, and acid pickling the slab, and cold-rolling a resultant steel sheet with a cold rolling reduction ratio of 60% or more; and   annealing the steel sheet in a temperature range of 800 to 850° C.   
     
     
         6 . The method according to  claim 5 , wherein the austenitic stainless steel has a tensile strength of 850 MPa or more. 
     
     
         7 . The method according to  claim 5 , wherein the austenitic stainless steel has a yield strength of 500 MPa or more. 
     
     
         8 . The method according to  claim 5 , wherein the austenitic stainless steel has an elongation of 25% or more.