Seawater-resistant stainless clad steel

Abstract

A seawater-resistant stainless clad steel includes a cladding material made of stainless steel having a pitting index represented by Cr[mass %]+3.3Mo[mass %]+16N[mass %], of 35.0 or more and a microstructure in a surface portion thereof including, by area ratio, less than 2.0% of a σ phase, wherein dynamic friction coefficients in the rolling direction and in a direction at a right angle to the rolling direction determined in accordance with JIS K 7125 are both 0.05 or less.

1 - 5 . (canceled) 
     
     
         6 . A seawater-resistant stainless clad steel comprising a cladding material made of stainless steel having a pitting index represented by Cr[mass %]+3.3Mo[mass %]+16N[mass %], of 35.0 or more and a microstructure in a surface portion thereof including, by area ratio, less than 2.0% of a σ phase, wherein dynamic friction coefficients in the rolling direction and in a direction at a right angle to the rolling direction determined in accordance with JIS K 7125 are both 0.05 or less. 
     
     
         7 . The seawater-resistant stainless clad steel according to  claim 6 , wherein a crystal grain size of the cladding material determined in accordance with JIS G 0551 is 6.0 or more. 
     
     
         8 . The seawater-resistant stainless clad steel according to  claim 6 , wherein the cladding material has a chemical composition including, by mass %, B: 0.0010% to 0.0050%. 
     
     
         9 . The seawater-resistant stainless clad steel according to  claim 6 , wherein the stainless clad steel is manufactured by reheating a slab at a temperature of 900° C. to 1100° C., hot-rolling the reheated slab, and cooling the hot-rolled plate at a cooling rate of 0.2° C./s to 20° C./s without performing a normalizing treatment. 
     
     
         10 . The seawater-resistant stainless clad steel according to  claim 6 , wherein the stainless clad steel is manufactured by reheating a slab at a temperature of 950° C. to 1150° C., hot-rolling the reheated slab, performing a normalizing treatment on the hot-rolled plate under conditions of a heating temperature of 800° C. to 1000° C., and cooling the treated plate at a cooling rate of 1.0° C./s to 20° C./s. 
     
     
         11 . The seawater-resistant stainless clad steel according to  claim 7 , wherein the stainless clad steel is manufactured by reheating a slab at a temperature of 900° C. to 1100° C., hot-rolling the reheated slab, and cooling the hot-rolled plate at a cooling rate of 0.2° C./s to 20° C./s without performing a normalizing treatment. 
     
     
         12 . The seawater-resistant stainless clad steel according to  claim 8 , wherein the stainless clad steel is manufactured by reheating a slab at a temperature of 900° C. to 1100° C., hot-rolling the reheated slab, and cooling the hot-rolled plate at a cooling rate of 0.2° C./s to 20° C./s without performing a normalizing treatment. 
     
     
         13 . The seawater-resistant stainless clad steel according to  claim 7 , wherein the stainless clad steel is manufactured by reheating a slab at a temperature of 950° C. to 1150° C., hot-rolling the reheated slab, performing a normalizing treatment on the hot-rolled plate under conditions of a heating temperature of 800° C. to 1000° C., and cooling the treated plate at a cooling rate of 1.0° C./s to 20° C./s. 
     
     
         14 . The seawater-resistant stainless clad steel according to  claim 8 , wherein the stainless clad steel is manufactured by reheating a slab at a temperature of 950° C. to 1150° C., hot-rolling the reheated slab, performing a normalizing treatment on the hot-rolled plate under conditions of a heating temperature of 800° C. to 1000° C., and cooling the treated plate at a cooling rate of 1.0° C./s to 20° C./s.