Low ductility alloy

Abstract

The present invention relates to a low ductility steel tube for use in chemical engineering applications. In particular, the invention relates to a high strength steel tube which has low ductility at elevated temperatures. Such tubes are typically used in chemical plants for transporting reactants and products. One such application includes the use in plants for producing hydrogen and methanol. The tubes could also be used when producing ethylene and other hydrocarbons.

1 . A steel pipe comprising:
 from 20.0 to 40.0 atomic % nickel,   from 20.0 to 40.0 atomic % chromium,   from 1.0 to 3.0 atomic % silicon,   from 0.5 to 2.5 atomic % carbon,   from 0.01 to 1.0 atomic % nitrogen,   from 0.01 to 0.90 atomic % niobium,   from 1.0 to 3.0 atomic % manganese, and   from 0.01 to 0.90 atomic % of one or more second carbide forming elements selected from: titanium, hafnium, zirconium, vanadium, tungsten, or molybdenum,   wherein:
 (a) a total amount of niobium and the one or more second carbide forming elements is from 0.50 to 0.91 atomic %; 
 (b) a total amount of carbon plus nitrogen is in the range of 1.2 to 3.0 atomic %; 
 (c) an amount of (nitrogen/carbon) is in the range 0.20 to 1.0, and 
 (d) an amount of [nitrogen/(the one or more second carbide forming elements plus niobium)] is in the range 0.2 to 1.1; 
 with the balance of the composition being iron and incidental impurities. 
   
     
     
         2 . A steel pipe as claimed in  claim 1 , wherein carbon is present in the range of from 1.5 to 2.5 atomic %. 
     
     
         3 . A steel pipe as claimed in  claim 1 , wherein nitrogen is present in an amount in the range of from 0.20 to 0.70 atomic %. 
     
     
         4 . A steel pipe as claimed in  claim 1 , wherein the amount of (nitrogen/carbon) is in the range of from 0.20 to 0.50 atomic %. 
     
     
         5 . A steel pipe as claimed in  claim 1 , wherein nickel is present in the range of from 25.0 to 35.0 atomic %. 
     
     
         6 . A steel pipe as claimed in  claim 5 , wherein nickel is present in an amount from 30.0 to 33.0 atomic %. 
     
     
         7 . A steel pipe as claimed in  claim 1 , wherein chromium is present in the range of from 20.0 to 30.0 atomic %. 
     
     
         8 . A steel pipe as claimed in  claim 7 , wherein chromium is present in an amount from 22.5 to 27.5 atomic %. 
     
     
         9 . A steel pipe as claimed in  claim 1 , wherein manganese is present in an amount in the range of from 1.0 to 2.0 atomic %. 
     
     
         10 . A steel pipe as claimed in  claim 1 , wherein titanium is present in the range of from 0.01 to 0.20 atomic %. 
     
     
         11 . A steel pipe as claimed in  claim 1 , wherein a time to rupture is at least 215 hours when tested at 1050° C. with 30 MPa Stress. 
     
     
         12 . A steel pipe as claimed in  claim 1 , wherein a time to rupture is at least 210 hours when tested at 1000° C. with 40 MPa Stress. 
     
     
         13 . A steel pipe as claimed in  claim 1 , wherein the total amount of niobium and the one or more second carbide forming elements is from 0.60 to 0.75 atomic %. 
     
     
         14 . A steel pipe as claimed in  claim 1 , wherein the total amount of carbon plus nitrogen is in the range of 1.5 to 2.5 atomic %. 
     
     
         15 . A steel pipe as claimed in  claim 1 , wherein the amount of [nitrogen/(the one or more second carbide forming elements plus niobium)] is in the range 0.4 to 1.0.