Cr-Al-Steel for High-Temperature Application

Abstract

The present invention relates to a product of ferritic stainless steel manufactured according to the process of this invention, which product has increased resistance to cyclic and continuous thermal load and oxidation at elevated temperatures and which has improved mechanical properties at said temperatures as well as use thereof in the form of wire, strip, foil and/or tube in high-temperature applications such as in catalytic converter applications, in heating and furnace applications and which has the following composition (in % by weight): less than 1% of Ni, 15-25% of Cr, 4.5-12% of Al, 0.5-4% of Mo, 0.01-1.2% of Nb, 0-0.5% of Ti, 0-0.5% of Y, Sc, Zr and/or Hf, 0-0.2% of one or more rare earth metals (REM) such as, for instance, Ce or La, 0-0.2% of C, 0-0.2% of N, with the balance iron and normally occurring impurities.

1 . Ferritic steel alloy comprising the following composition (in % by weight):
 less than 1% of Ni,   15-25% of Cr,   4.5-12% of Al,   0.5-4% of Mo,   0.01-1.2% of Nb,   0-0.5% of Ti,   0-0.5% of Y, Sc, Zr and/or Hf,   0-0.2% of one or more rare earth metals (REM),   0-0.2% of C,   0-0.2% of N,   with the balance iron and normally occurring impurities.   
     
     
         2 . Ferritic steel alloy according to  claim 1  wherein Mo entirely or partly is replaced by W. 
     
     
         3 . Ferritic steel alloy according to  claim 1  wherein it contains one or more rare earth metals (REM). 
     
     
         4 . Ferritic steel alloy according to  claim 1  wherein it contains at least 0.1% in total of Ti, Nb, Zr and/or Hf. 
     
     
         5 . Method of producing a ferritic steel alloy according to  claim 1  comprising coating a substrate alloy with Al or an alloy of Al, the substrate alloy having the following composition (in % by weight):
 less than 1% of Ni,   15-27% of Cr,   0-5% of Al,   0.5-5% of Mo,   0.01-2% of Nb,   0-0.5% of Ti,   0-0.5% of Y, Sc, Zr and/or Hf,   0-0.2% of one or more rare earth metals (REM),   0-0.2% of C,   0-0.2% of N,   with the balance iron and normally occurring impurities.   
     
     
         6 . Product in the form of wire, strip, foil and/or tube for use in high-temperature applications wherein it is produced from a ferritic steel alloy according to  claim 1 . 
     
     
         7 . Use of a ferritic steel alloy according to  claim 1  as a supporting material in catalytic converter applications. 
     
     
         8 . Use of a ferritic steel alloy according to  claim 1  in heating and furnace applications. 
     
     
         9 . Ferritic steel alloy according to  claim 1 , wherein the one or more rare earth metals (REM) is Ce or La. 
     
     
         10 . Method according to  claim 5 , wherein the one or more rare earth metals (REM) is Ce or La.