Cr steel for structural use and method for producing the same

Abstract

To provide structural Cr-containing steel with excellent low-temperature toughness and impact toughness, with low costs as compared with stainless steel, and with sufficient corrosion resistance. Specifically, this is structural Cr-containing steel and a manufacturing method thereof, wherein the Cr-containing steel contains C of 0.002 to 0.02%; N of 0.002 to 0.02%; Si of 0.05 to 1.0%; Mn of 0.05 to 1.0%; P of 0.04% or less; S of 0.02% or less; Al of 0.001 to 0.1%; and Cr of 6.0 to 10.0%, further may contain Cu of 0.1 to 1.0%, further may contain at least one of: Ni of 0.1 to 1.0%; and Mo of 0.1 to 1.0%, and further may contain at least one of: Nb of 0.005 to 0.10%; and V of 0.005 to 0.20%, the balance are formed of Fe and unavoidable impurities, and the Cr-concentration in the surface layer of the steel is equal to or more than the value wherein 1% is subtracted from the Cr-concentration within the steel.

1 . Structural Cr-containing steel comprising: 
 0.002 to 0.02% by mass of C;    0.002 to 0.02% by mass of N;    0.05 to 1.0% by mass of Si;    0.05 to 1.0% by mass of Mn;    0.04% by mass or less of P;    0.02% by mass or less of S;    0.001 to 0.1% by mass; of Al    6.0 to 10.0% by mass of Cr, and    the balance being Fe and unavoidable impurities,    wherein the Cr-concentration in the surface layer of the steel is equal to or more than the value wherein 1% by mass is subtracted from the Cr-concentration within the steel.    
   
   
       2 . Structural Cr-containing steel according to  claim 1 , further comprising 0.1 to 1.0% by mass of Cu.  
   
   
       3 . Structural Cr-containing steel according to  claim 1 , further comprising at least one of: 
 0.1 to 1.0% by mass of Ni; and    0.1 to 1.0% by mass of Mo.    
   
   
       4 . Structural Cr-containing steel according to  claim 1 , further comprising at least one of: 
 0.005 to 0.10% by mass of Nb; and    0.005 to 0.20% by mass of V.    
   
   
       5 . A manufacturing method for structural Cr-containing hot-rolled steel comprising: 
 a step wherein a steel material comprising:    0.002 to 0.02% by mass of C;    0.002 to 0.02% by mass of N;    0.05 to 1.0% by mass of Si;    0.05 to 1.0% by mass of Mn;    0.04% by mass or less of P;    0.02% by mass or less of S;    0.001 to 0.1% by mass of Al;    6.0 to 10.0% by mass of Cr; and    the balance being Fe and unavoidable impurities, is formed into a steel strip by hot rolling after reheating; wherein the steel surface is removed by a removal depth of 10 to 200 μm by descaling.    
   
   
       6 . A manufacturing method for structural Cr-containing cold-rolled steel, wherein following said descaling processing according to  claim 5 , cold rolling, annealing cold-rolled steel, and pickling are performed.  
   
   
       7 . A manufacturing method for structural Cr-containing steel according to  claim 5 , wherein said steel material further comprising Cu of 0.1 to 1.0% by mass.  
   
   
       8 . A manufacturing method for structural Cr-containing steel according to  claim 5 , wherein said steel material further comprising at least one of: 
 0.1 to 1.0% by mass of Ni; and    0.1 to 1.0% by mass of Mo.    
   
   
       9 . A manufacturing method for structural Cr-containing steel according to  claim 5 , wherein said steel material further comprising at least one of: 
 0.005 to 0.10% by mass of Nb; and    0.005 to 0.20% by mass of V.    
   
   
       10 . Structural Cr-containing steel according to  claim 1 , wherein said steel is employed for freezing containers.  
   
   
       11 . A manufacturing method for structural Cr-containing hot-rolled steel according to  claim 5 , wherein said structural Cr-containing steel is employed for frame material of freezing containers.  
   
   
       12 . A manufacturing method for structural Cr-containing cold-rolled steel according to  claim 6 , wherein said structural Cr-containing steel is employed for external-wall material of freezing containers.  
   
   
       13 . A freezing container formed of said Cr-containing steel according to  claim 10 , wherein formation of said freezing container is made by forming and welding, and wherein the steel surface is coated with dry-paint film thickness of 10 μm or more.  
   
   
       14 . A freezing container formed of said Cr-containing steel manufactured with said manufacturing method according to  claim 11 , wherein formation of said freezing container is made by forming and welding, and wherein the steel surface is coated with dry-paint film thickness of 10 μm or more.  
   
   
       15 . Structural Cr-containing steel according to  claim 1 , wherein said steel is used for civil engineering and construction.  
   
   
       16 . A manufacturing method for structural Cr-containing hot-rolled steel according to  claim 5 , wherein said structural Cr-containing hot-rolled steel is used for civil engineering and construction.  
   
   
       17 . A manufacturing method for structural Cr-containing cold-rolled steel according to  claim 6 , wherein said structural Cr-containing steel is used for civil engineering and construction.  
   
   
       18 . Structural Cr-containing steel according to  claim 2 , further comprising at least one of: 
 0.1 to 1.0% by mass of Ni; and    0.1 to 1.0% by mass of Mo.    
   
   
       19 . Structural Cr-containing steel according to  claim 2 , further comprising at least one of: 
 0.005 to 0.10% by mass of Nb; and    0.005 to 0.20% by mass of V.    
   
   
       20 . Structural Cr-containing steel according to  claim 3 , further comprising at least one of: 
 0.005 to 0.10% by mass of Nb; and    0.005 to 0.20% by mass of V.    
   
   
       21 . Structural Cr-containing steel according to  claim 18 , further comprising at least one of: 
 0.005 to 0.10% by mass of Nb; and    0.005 to 0.20% by mass of V.