Duplex Stainless Steel

Abstract

A duplex stainless steel alloy which contains in weight %: Cr 25-35%, Ni 4-10%, Mo 1-6%, N 0.3-0.6%, Mn greater than 0-3%, Si max 1.0%, C max 0.06%, Cu and/or W and/or Co 0.1-10%, W 0.1-5%, balance Fe and normally occurring impurities wherein the ferrite content is 30-70%. The alloy has a yield point in tension being min 760 MPa.

1 . A duplex stainless steel alloy comprising:
 from about 0.1 weight % to about 5 weight % W;   optionally from about 0.1 weight % to about 5 weight % Cu;   optionally from about 0 weight % to about 3.5 weight % Co; and   the balance Fe and normally occurring impurities, wherein the ferrite content is 30 weight % to about 70 weight %, and the combination of W, optional Cu, and optional Co is from about 0.1 weight % to about 10 weight %, and the alloy has a yield point in tension being at least about 760 MPa.   
     
     
         2 . The alloy according to  claim 1 , wherein the alloy contains 0.1 weight % to about 5 weight % Cu. 
     
     
         3 . The alloy according to  claim 1 , wherein the alloy contains 0.1 weight % to about 3 weight % Cu. 
     
     
         4 . The alloy according to  claim 2 , wherein the alloy contains at least about 0.8% Cu. 
     
     
         5 . The alloy according to  claim 1 , wherein the alloy contains less than 0.15% Si and less than 0.05% C. 
     
     
         6 . The alloy according to  claim 1 , wherein the alloy contains less than 0.1% Si and less than 0.05% C. 
     
     
         7 . The alloy according to  claim 1 , wherein the alloy contains 0.40 weight % to about 0.55 weight % N. 
     
     
         8 . The alloy according to  claim 1 , wherein the alloy contains 1 weight % to about 3 weight % W. 
     
     
         9 . The alloy according to  claim 1 , wherein the following relationship is satisfied: 0.5(% W)+1 (% Mo)=2-10%. 
     
     
         10 . The alloy according to  claim 1 , wherein the following relationship is satisfied: 0.5(% W)+1(% Mo)=3-7%. 
     
     
         11 . The alloy according to  claim 1 , wherein the alloy contains less than 3.5 weight % Co. 
     
     
         12 . The alloy according to  claim 1 , wherein the alloy contains 28 weight % to about 33 weight % Cr. 
     
     
         13 . The alloy according to  claim 1 , wherein the alloy contains 5 weight % to about 1.5 weight % Mn. 
     
     
         14 . The alloy according to  claim 13 , wherein the alloy contains 5 weight % to about 9 weight % Ni. 
     
     
         15 . The alloy according to  claim 1 , wherein the alloy contains 35 weight % to about 55 weight % ferrite. 
     
     
         16 . The alloy according to  claim 1 , wherein the alloy is manufactured using a conventional metallurgical method. 
     
     
         17 . The alloy according to  claim 1 , wherein the alloy comprises a maximum of 1 weight % of further alloying additions in total. 
     
     
         18 . An article in the form of a tube, wire, strip, rod, sheet or bar, comprising the alloy according to  claim 1 . 
     
     
         19 . An article according to  claim 18 , wherein the article is made of the alloy according to  claim 1 . 
     
     
         20 . An article according to  claim 18 , wherein the alloy comprises a coating or a cladding of the article. 
     
     
         21 . An article comprising the alloy of  claim 1 , the article selected from the group consisting of an umbilical, a downhole, an integrated production unit, and a welding wire.