High Strength Austenitic Stainless Steel and Production Method Thereof

Abstract

An austenitic stainless steel including in weight % 0-0.4% C, 0-3% Si, 3-20% Mn, 10-30% Cr, 0-4.5% Ni, 0-3% Mo, 0-3% Cu, 0.05-0.5% N, 0-0.5% Nb, 0-0.5% Ti, 0-0.5% V, the balance of Fe and inevitable impurities. The content of at least one of the elements in the group of niobium (Nb), titanium (Ti) or vanadium (V) is more than 0.05% so that the total amount of niobium (Nb), titanium (Ti) and vanadium (V) contents is in the range of 0.05-0.5%. The grain size of the steel is less than 10 micrometer after annealing the cold deformed product and the difference between the yield strengths of the steel measured in transverse and parallel directions to the rolling direction is lower than 5%. Also, a method for producing the austenitic stainless steel.

1 . An austenitic stainless steel, comprising, in weight 0-0.4% C, 0-3% Si, 3-20% Mn, 10-30% Cr, 0-4.5% Ni, 0-3% Mo, 0-3% Cu, 0.05-0.5% N, 0-0.5% Nb, 0-0.5% Ti, 0-0.5% V, the balance Fe and inevitable impurities, wherein the content of at least one of the elements in the group consisting of niobium (Nb), titanium (Ti) and vanadium (V) is more than 0.05% so that the total amount of the niobium (Nb), titanium (Ti) and vanadium (V) contents is in the range of 0.05-0.5%, and after annealing of the cold deformed steel, the grain size is less than 10 micrometers and a difference between the yield strengths of the steel measured in transverse and parallel directions to the rolling direction is less than 5%. 
     
     
         2 . The austenitic stainless steel according to  claim 1 , wherein the grain size of the steel is less than 7 micrometers. 
     
     
         3 . The austenitic stainless steel according to  claim 1 , wherein the steel comprises 0-1.5% molybdenum. 
     
     
         4 . The austenitic stainless steel according to  claim 1 , wherein the steel comprises 0.05-0.30% Nb. 
     
     
         5 . The austenitic stainless steel according to  claim 1 , wherein the steel comprises 0.05-0.30% Ti. 
     
     
         6 . The austenitic stainless steel according to  claim 1 , wherein the steel comprises 0.05-0.30% V. 
     
     
         7 . A method for producing an austenitic stainless steel, comprising, in weight %, 0-0.4% C, 0-3% Si, 3-20% Mn, 10-30% Cr, 0-4.5% Ni, 0-3% Mo, 0-3% Cu, 0.05-0.5% N, 0-0.5% Nb, 0-0.5% Ti, 0-0.5% V, the balance of Fe and inevitable impurities, wherein the content of at least one of the elements in the group consisting of niobium (Nb), titanium (Ti) and vanadium (V) is more than 0.05% so that the total amount of niobium (Nb), titanium (Ti) and vanadium (V) is in the range of 0.05-0.5%, the method comprising cold deforming the steel with a reduction degree of at least 50% and annealing the steel, wherein after annealing, the steel has a grain size of less than 10 micrometers, and the difference between the yield strengths of the steel measured in transverse and parallel directions to the rolling direction is lower than 5%. 
     
     
         8 . The method according to  claim 7 , wherein the steel is annealed at a temperature of 700-1050° C. for 1-400 seconds. 
     
     
         9 . The method according to the  claim 7  or  8 , wherein the deformation is cold rolling. 
     
     
         10 . The austenitic stainless steel according to  claim 1 , wherein the grain size of the steel is less than 5 micrometers. 
     
     
         11 . The austenitic stainless steel according to  claim 1 , wherein the steel comprises 0-0.5% molybdenum. 
     
     
         12 . The austenitic stainless steel according to  claim 1 , wherein the steel comprises 0.05-0.20% Nb. 
     
     
         13 . The austenitic stainless steel according to  claim 1 , wherein the steel comprises 0.05-0.20% Ti. 
     
     
         14 . The austenitic stainless steel according to  claim 1 , wherein the steel comprises 0.05-0.20% V. 
     
     
         15 . The method according to  claim 8 , wherein the steel is annealed for 1-200 seconds.