Ferritic stainless steel

Abstract

Provided is a ferritic stainless steel including, as a ferritic stainless steel used in a separator for a fuel cell, a base material including, in weight %, C: 0.003% to 0.012%, N: 0.003% to 0.015%, Si: 0.05% to 0.15%, Mn: 0.3% to 0.8%, Cr: 20% to 24%, Mo; 0.1% to 0.4%, Nb: 0.1% to 0.7%, Ti: 0.03% to 0.1%, and the remainder being Fe and inevitable impurities. A first scale layer including chromium oxide is formed on a surface of the base material, and a second scale layer including chromium oxide and manganese oxide is formed on a surface of the first scale layer. A silicon content included in each of the first scale layer and the second scale layer is 0.2 weight % or less, and the following formula is satisfied: Nb+Mn≧8Si where Nb, Mn and Si are weight % amounts of corresponding components, respectively.

1 . A ferritic stainless steel used for a separator for a fuel cell, comprising a base material including, in weight %, C: 0.003% to 0.012%, N: 0.003% to 0.015%, Si: 0.05% to 0.15%, Mn: 0.3% to 0.8%, Cr: 20% to 24%, Mo; 0.1% to 0.4%, Nb: 0.1% to 0.7%, Ti: 0.03% to 0.1%, and the remainder being Fe and inevitable impurities,
 wherein a first scale layer including chromium oxide is formed on a surface of the base material, and a second scale layer including chromium oxide and manganese oxide is formed on a surface of the first scale layer,   a silicon content included in each of the first scale layer and the second scale layer is 0.2 weight % or less, and   the following formula is satisfied:   formula: Nb+Mn≧8Si (Nb, Mn and Si are weight % amounts of corresponding components, respectively).   
     
     
         2 . The ferritic stainless steel of  claim 1 , wherein a thickness of the second scale layer is ⅔ or greater of a thickness of the whole scale layer. 
     
     
         3 . The ferritic stainless steel of  claim 2 , comprising a third scale layer including niobium oxide formed between the base material and the first scale layer.