Ferrite stainless steel for use in producing urea water tank

Abstract

This ferrite stainless steel for use in producing a urea water tank includes: in terms of mass %, C: 0.05% or less; N: 0.05% or less; Si: 0.02 to 1.5%; Mn: 0.02 to 2%; Cr: 15 to 23%; and either one or both of Nb and Ti at a content within a range of 8(C+N) to 1% (herein, C and N represent the contents of C and N (expressed by mass %), respectively, and the numerical values shown in front of the atomic symbols represent constant numbers), with the remainder being iron and unavoidable impurities, wherein an effective amount of Cr expressed by any one of the following Equations (I), (II), and (III) is 15% or more (herein, the atomic symbols in Equations (I) to (III) represent the contents of the elements (expressed by mass %), and the numerical values shown in front of the atomic symbols represent constant numbers). Here, the effective amount of Cr=Cr+4Si−2Mn in the case where only Nb is contained, the effective amount of Cr=Cr+4Si−2Mn−10Ti in the case where only Ti is contained, and the effective amount of Cr=Cr+4Si−2Mn−(10Ti−3Nb) in the case where both of Nb and Ti are contained.

1 . A ferrite stainless steel for use in producing a urea water tank, comprising: in terms of mass %,
 C: 0.05% or less;   N: 0.05% or less;   Si: 0.02 to 1.5%;   Mn: 0.02 to 2%;   Cr: 15 to 23%; and   either one or both of Nb and Ti at a content within a range of 8(C+N) to 1% (herein, C and N represent the contents of C and N (expressed by mass %), respectively, and the numerical values shown in front of the atomic symbols represent constant numbers),   with the remainder being iron and unavoidable impurities,   wherein an effective amount of Cr expressed by any one of the following Equations (I), (II), and (III) is 15% or more (herein, the atomic symbols in Equations (I) to (III) represent the contents of the elements (expressed by mass %), respectively, and numerical values shown in front of the atomic symbols represent constant numbers),   in the case where only Nb is contained,
   the effective amount of Cr=Cr+4Si−2Mn  (I)
 
   in the case where only Ti is contained,
   the effective amount of Cr=Cr+4Si−2Mn−10Ti  (II)
 
   in the case where both of Nb and Ti are contained,
   the effective amount of Cr=Cr+4Si−2Mn−(10Ti−3Nb)  (III).
 
   
     
     
         2 . The ferrite stainless steel for use in producing a urea water tank according to  claim 1 ,
 which further comprises, in terms of mass %, one or more selected from Mo: 3% or less, Ni: 3% or less, Cu: 3% or less, V: 3% or less, and W: 5% or less.   
     
     
         3 . The ferrite stainless steel for use in producing a urea water tank according to  claim 1 ,
 which further comprises, in terms of mass %, one or more selected from Ca: 0.002% or less, Mg: 0.002% or less, and B: 0.005% or less.   
     
     
         4 . The ferrite stainless steel for use in producing a urea water tank according to  claim 1 ,
 wherein a content of C+N is in a range of 0.015% or more.   
     
     
         5 . The ferrite stainless steel for use in producing a urea water tank according to  claim 1 ,
 which further comprises, in terms of mass %, Al: 0.5% or less,   wherein Equations (IV) and (V) are fulfilled (herein, atomic symbols in Equations (IV) and (V) represent contents of the elements (expressed by mass %), and the numerical values shown in front of the atomic symbols represent constant numbers).
   Ti−3N≦0.03  (IV)
 
   10(Ti−3N)+Al≦0.5  (V)