Stainless clad steel with excellent corrosion resistance

Abstract

A stainless clad steel includes a stainless steel having Pitting Index of 35 or more as a cladding material, wherein the ratio of Cr concentration/Fe concentration in a passivation film portion of the above-described cladding material to Cr concentration/Fe concentration in a parent phase portion of the above-described cladding material is 1.20 or more and, in addition, the amount of precipitation of a σ (sigma) phase of the surface of the above-described cladding material is 2.0% or less on an area ratio basis.

1 - 3 . (canceled) 
     
     
         4 . A stainless clad steel comprising a stainless steel having Pitting Index represented by Formula (1) of 35 or more as a cladding material, wherein a ratio of Cr concentration (atomic percent)/Fe concentration (atomic percent) in a passivation film portion of the cladding material to Cr concentration (atomic percent)/Fe concentration (atomic percent) in a parent phase portion of the cladding material is 1.20 or more and, in addition, an amount of precipitation of a (sigma) phase of a surface of the cladding material is 2.0% or less on an area ratio basis,
   Pitting Index=(Cr+3.3Mo+16N)   (1)
   
       where Cr, Mo, and N indicate contents (percent by mass) of their respective elements, and no inclusion is specified to be 0. 
     
     
         5 . The stainless clad steel according to  claim 4 , when the average glossiness indicator Gs(60) calculated by Formula (2) of the cladding material is 60 or more, where the specular glossiness at a measurement angle of 60° defined in JIS Z 8741 is measured in a rolling direction (Gs(60) L ), in a direction perpendicular to the rolling direction (Gs(60) C ), and in a direction at an angle of 45 degrees with respect to the rolling direction (Gs(60) D ),
   Gs(60)=(Gs(60) L +2×Gs(60) D +Gs(60) C )/4   (2).
 
 
     
     
         6 . The stainless clad steel according to  claim 4 , wherein the average glossiness indicators Gs(60) L , Gs(60) C , Gs(60) D  and Gs(60) are 60 or more, where the specular glossiness is at a measurement angle of 60° as defined in JIS Z 8741. 
     
     
         7 . The stainless clad steel according to  claim 5 , wherein the average glossiness indicators Gs(60) L , Gs(60) C , Gs(60) D  and Gs(60) are 60 or more, where the specular glossiness is at a measurement angle of 60° as defined in JIS Z 8741.