US2013315776A1PendingUtilityA1

Duplex stainless steel

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Assignee: YAMADA KENTAPriority: Feb 14, 2011Filed: Feb 10, 2012Published: Nov 28, 2013
Est. expiryFeb 14, 2031(~4.6 yrs left)· nominal 20-yr term from priority
Inventors:Kenta YamadaHiroyuki NagayamaMasahiko HamadaDaisuke MotoyaHisashi Amaya
C22C 38/005C22C 38/44C22C 38/02C22C 38/42C22C 38/58C22C 38/002C22C 38/54C22C 38/46C22C 38/04C22C 38/001C22C 38/06C21D 6/004C21D 6/005C21D 7/13C21D 8/0226C21D 2211/001C21D 2211/004C21D 2211/005
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Claims

Abstract

A duplex stainless steel, which can suppress precipitation of a σ phase under high heat input welding, is excellent in SCC resistance under high-temperature chloride environments and has a high strength. The duplex stainless steel includes a chemical composition containing, in mass percent, C: at most 0.030%, Si: 0.20 to 1.00%, Mn: at most 8.00%, P: at most 0.040%, S: at most 0.0100%, Cu: more than 2.00% and at most 4.00%, Ni: 4.00 to 8.00%, Cr: 20.0 to 28.0%, Mo: 0.50 to 2.00%, N: 0.100 to 0.350%, and sol. Al: at most 0.040%, the balance being Fe and impurities, and satisfying Expression (1) and Expression (2); a structure having a ferrite rate of at least 50%; and a yield strength of at least 550 MPa or more: 2.2Cr+7Mo+3Cu>66   (1) Cr+11Mo+10Ni<12(Cu+30N)   (2)

Claims

exact text as granted — not AI-modified
1 . A duplex stainless steel comprising:
 a chemical composition containing, in mass percent, C: at most 0.025% Si: 0.20 to 1.00%, Mn: at most 8.00%, P: at most 0.040%, S: at most 0.0100%, Cu: more than 2.00% and at most 4.00%, Ni: 4.00 to 8.00%, Cr: 20.0 to 28.0%, Mo: 0.50 to 2.00%, N: 0.100 to 0.350%, and sol. Al: at most 0.040%, the balance being Fe and impurities, and satisfying Expression (1) and Expression (2);   a structure having a ferrite rate of at least 50%; and   a yield strength of at least 550 MPa:
   2.2Cr+7Mo+3Cu>66   (1)
 
   Cr+11Mo+10Ni<12(Cu+30N)   (2)
 
   
       where a content (mass percent) of each element in the steel is substituted into a symbol of each element in Expression (1) and Expression (2). 
     
     
         2 . (canceled) 
     
     
         3 . The duplex stainless steel according to  claim 1 , wherein
 the chemical composition contains V: at most 1.50%, instead of part of the Fe.   
     
     
         4 . The duplex stainless steel according to  claim 1 , wherein
 the chemical composition contains at least one type selected from the group consisting of Ca: at most 0.0200%, Mg: at most 0.020%, and B: at most 0.0200%, instead of part of the Fe.   
     
     
         5 . The duplex stainless steel according to  claim 1 , wherein
 the chemical composition contains rare earth metal: at most 0.2000%, instead of part of the Fe.   
     
     
         6 . The duplex stainless steel according to  claim 3 , wherein
 the chemical composition contains at least one type selected from the group consisting of Ca: at most 0.0200%, Mg: at most 0.020%, and B: at most 0.0200%, instead of part of the Fe.   
     
     
         7 . The duplex stainless steel according to  claim 3 , wherein
 the chemical composition contains rare earth metal: at most 0.2000%, instead of part of the Fe.   
     
     
         8 . The duplex stainless steel according to  claim 4 , wherein
 the chemical composition contains rare earth metal: at most 0.2000%, instead of part of the Fe.   
     
     
         9 . The duplex stainless steel according to  claim 6 , wherein
 the chemical composition contains rare earth metal: at most 0.2000%, instead of part of the Fe.

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