Heat resistant ferritic steel

Abstract

There is provided a heat resistant ferritic steel, excellent in the weld crack resistance of the HAZ and creep strength. A high-Cr heat resistant ferritic steel is characterized by consisting of, by mass %, Si: more than 0.1% and not more than 1.0%, Mn: 2.0% or less, Co: 1 to 8%, Cr: 7 to 13%, V: 0.05 to 0.4%, Nb: 0.01 to 0.09%, either one or both of Mo and W: 0.5 to 4% as a total, B: 0.005 to 0.025%, Al: 0.03% or less, and N: 0.003 to 0.06%, and containing C in an amount satisfying Expression (1), the balance being Fe and impurities, and O, P and S as impurities being such that O: 0.02% or less, P: 0.03% or less, and S: 0.02% or less, respectively, 0.005≦C≦(−5/3)×B+0.085  (1) in which C and B represent the content of each element (mass %). Furthermore, the high-Cr heat resistant ferritic steel may contain one or more kinds selected from the group consisting of Nd, Ta, Ca and Mg.

1 . A high-Cr heat resistant ferritic steel characterized by consisting of, by mass %, Si: more than 0.1% and not more than 1.0%, Mn: 2.0% or less, Co: 1 to 8%, Cr: 7 to 13%, V: 0.05 to 0.4%, Nb: 0.01 to 0.09%, either one or both of Mo and W: 0.5 to 4% as a total, B: 0.005 to 0.025%, Al: 0.03% or less, N: 0.003 to 0.06%, Nd: 0.005 to 0.08% and containing C in an amount satisfying Expression (1), and the balance being Fe and impurities, and O, P and S as impurities being such that O: 0.02% or less, P: 0.03% or less, and S: 0.02% or less, respectively,
   0.005≦C≦(−5/3)×B+0.085  (1)   
     in which C and B represent the content of each element (mass %). 
   
   
       2 . The high-Cr heat resistant ferritic steel according to  claim 1 , characterized by containing, by mass %, Ta: 0.08% or less in place of part of Fe. 
   
   
       3 . The high-Cr heat resistant ferritic steel according to  claim 1 , characterized by containing, by mass %, either one or both of Ca: 0.02% or less and Mg: 0.02% or less in place of part of Fe. 
   
   
       4 . The high-Cr heat resistant ferritic steel according to  claim 1 , characterized by containing, by mass %, Ta: 0.08% or less, and either one or both of Ca: 0.02% or less and Mg: 0.02% or less in place of part of Fe.