Austenitic stainless steel excellent in fine blankability

Abstract

The newly proposed austenitic stainless steel has composition consisting of (C+½N) up to 0.060 mass %, Si up to 1.0 mass %, Mn up to 5 mass %, S up to 0.006 mass %, 15-20 mass % Cr, 5-12 mass % Ni, Cu up to 5 mass %, 0-3.0 mass % Mo and the balance being Fe except inevitable impurities under the condition that a value Md3O (representing a ratio of a strain-induced martensite) defined by the under-mentioned formula is controlled within a range of −60 to −10. Hardness increase of the steel sheet after being cold-rolled is preferably 20% or more as Vickers hardness. A metallurgical structure of the steel sheet is preferably adjusted to grain size number of #8 to #11 in a finish annealed state. The steel sheet is blanked with high dimensional accuracy, and a die life is also prolonged. Md 30 =551−462 (C+N)− 9.2 Si− 29 (Ni+Cu)− 8.1 Mn− 13.7 Cr− 18.5 Mo

1 . An austenitic stainless steel, which has an excellent property in fine blankability, consisting of (C+½N) up to 0.060 mass %, Si up to 1.0 mass %, Mn up to 5 mass %, S up to 0.006 mass %, 15-20 mass % Cr, 5-12 mass % Ni, Cu up to 5 mass %, optionally Mo up to 3.0 mass % and the balance being Fe except inevitable impurities, under the condition that a value Md 30  representing a ratio of a strain-induced martensite phase defined by the under-mentioned formula is within a range of −60 to −10.  
       Md 30 =551−462(C+N)−9.2Si−29(Ni+Cu)−8.1Mn−13.7Cr−18.5Mo  
     
     
         2 . The austenitic stainless steel according to  claim 1 , which is hardened 20% or more by Vickers hardness by cold-rolling after annealing and pickling.  
     
     
         3 . The austenitic stainless steel according to claims  1 , which has a metallurgical structure minimized to #8 to #10 by grain size number.