Oxidation resistant alloy

Abstract

The present invention relates to alloys used to prepare steel pipes i.e. tubes for use in chemical engineering applications. In particular, the invention relates to low carbon aluminium steel alloys and pipes made from such alloys. They may be used in plant such as ethylene cracker furnaces that need to be able to withstand elevated temperatures oxidation and carburisation for extended periods of time, the alloy been able to develop a pure, stable and continuous aluminium oxide layer on it surface when in service which is protective and anti-coking

1 . An alloy comprising:
 from 0.15 to 0.35 wt % carbon,   from 2.5 to 5.0 wt % aluminium,   from 40 to 45 wt % nickel,   from 25 to 35 wt % chromium,   from 0.50 to 1.50 wt % niobium and/or vanadium,   from 0.01 wt % to 0.25 wt % yttrium,   from 0.01 wt % to 0.25 wt % tungsten and/or tantalum,   from 0.01 wt % to 0.25 wt % in total of one or more of titanium and/or zirconium and/or hafnium,   up to 0.9 wt % manganese,   up to 0.9 wt % silicon, and   up to 0.10 wt % nitrogen,   with the balance of the composition being iron and incidental impurities.   
     
     
         2 . An alloy as claimed in  claim 1 , comprising:
 from 0.15 to 0.35 wt % carbon,   from 2.5 to 5.0 wt % aluminium,   from 40 to 45 wt % nickel, and/or cobalt   from 25 to 35 wt % chromium,   from 0.50 to 1.50 wt % niobium, and/or vanadium   from 0.01 wt % to 0.05 wt % yttrium,   from 0.05 wt % to 0.25 wt % of tungsten and/or tantalum,   from 0.04 wt % to 0.15 wt % in total of one or more of titanium and/or zirconium and/or hafnium,   an amount of up to 0.9 wt % manganese,   an amount of up to 0.6 wt % silicon, and   an amount of up to 0.10 wt % nitrogen,   with the balance of the composition being iron and incidental impurities.   
     
     
         3 . An alloy as claimed in  claim 1 , wherein carbon is present in an amount of from 0.20 wt % to 0.35 wt %. 
     
     
         4 . An alloy as claimed in  claim 1 , wherein aluminium is present in an amount of from 3.5 wt % to 4.5 wt %. 
     
     
         5 . An alloy as claimed in  claim 1 , or wherein nickel is present in an amount of from 42 wt % to 45 wt %. 
     
     
         6 . An alloy as claimed in  claim 1 , wherein chromium is present in an amount of from 28 wt % to 30 wt %. 
     
     
         7 . An alloy as claimed in  claim 1 , wherein niobium is present in an amount of from 0.80 wt % to 1.50 wt %. 
     
     
         8 . An alloy as claimed in  claim 1 , wherein silicon is present in an amount of from 0.3 wt % to 0.6 wt %. 
     
     
         9 . An alloy as claimed in  claim 1 , wherein manganese is present in an amount of from 0.4 wt % to 0.8 wt %. 
     
     
         10 . An alloy as claimed in  claim 1 , wherein tungsten is present in an amount of from 0.05 wt % to 0.15 wt %. 
     
     
         11 . An alloy as claimed in  claim 1 , wherein titanium is present in an amount of from 0.08 wt % to 0.15 wt %. 
     
     
         12 . An alloy as claimed in  claim 1 , wherein yttrium is present in an amount of from 0.01 wt % to 0.03 wt %. 
     
     
         13 . An alloy as claimed in  claim 1 , wherein nitrogen is present in an amount of from 0.03 wt % to 0.06 wt %. 
     
     
         14 . A steel pipe made from an alloy according to  claim 1 .