Cr-Containing Steel Superior in Heat Fatigue Charateristics

Abstract

The present invention provides Cr-containing steel superior in heat fatigue characteristics, that is, Cr-containing steel superior in heat fatigue characteristics, characterized by containing, by mass %, C: 0.01% or less, N: 0.015% or less, Si: 0.8 to 1.0%, Mn: 0.2 to 1.5%, P: 0.03% or less, S: 0.01% or less, Ni: 0.2% or less, Cu: 0.2% or less, Cr: 13 to 15%, Mo: 0.1% or less, Nb: 0.3 to 0.5%, Ti: 0.05 to 0.2%, V: 0.01 to 0.2%, Al: 0.015 to 1.0%, and B: 0.0002 to 0.0010%, satisfying (Nb+1.9×Ti)/(C+N)≦50, and having a balance of Fe and unavoidable impurities, wherein a 0.2% yield strength at 800° C. after aging at 800° C. for 100 hours or more is 20 MPa or more and a drawability value at 200° C. is 35% or more and wherein a soluble Nb amount+soluble Ti amount after aging at 800° C. for 100 hours or more is 0.08% or more.

1 . Cr-containing steel superior in heat fatigue characteristics, characterized by containing, by mass %,
 C: 0.01% or less,   N: 0.015% or less,   Si: 0.8 to 1.0%,   Mn: 0.2 to 1.5%,   P: 0.03% or less,   S: 0.01% or less,   Ni: 0.2% or less,   Cu: 0.2% or less,   Cr: 13 to 15%,   Mo: 0.1% or less,   Nb: 0.3 to 0.55%,   Ti: 0.05 to 0.2%,   V: 0.01 to 0.2%,   Al: 0.015 to 1.0%, and   B: 0.0002 to 0.0010%,   
       satisfying (Nb+1.9×Ti)/(C+N)≦50, and having a balance of Fe and unavoidable impurities. 
     
     
         2 . Cr-containing steel superior in heat fatigue characteristics as set forth in  claim 1 , characterized in that a 0.2% yield strength at 800° C. after aging at 800° C. for 100 hours or more is 20 MPa or more and a drawability value at 200° C. is 35% or more. 
     
     
         3 . Cr-containing steel superior in heat fatigue characteristics as set forth in  claim 1 , characterized in that a soluble Nb amount+soluble Ti amount after aging at 800° C. for 100 hours or more is 0.08% or more. 
     
     
         4 . Cr-containing steel superior in heat fatigue characteristics as set forth in  claim 1 , characterized by satisfying Mn/Ti≧3.