Martensitic stainless steel with excellent weld characteristics, and martensitic stainless steel material

Abstract

This martensitic stainless steel contains, in terms of percent by mass: C: 0.003% to 0.03%; Si: 0.01% to 1.0%; Mn: 3.0% to 6.0%; P: 0.05% or less; S: 0.003% or less; Ni: 1.0% to 3.0%; Cr: 15.0% to 18.0%; Mo: 0% to 1.0%; Cu: 0% to 2.0%; Ti: 0% to 0.05%; N: 0.05% or less; Al: 0.001% to 0.1%; and O: 0.005% or less, with a remainder being Fe and inevitable impurities, wherein a total amount of C and N is in a range of 0.060% or less, γ max represented by the formula 1 is in a range of 80 or more, and γ pot represented by the formula 2 is in a range of 60 to 90. γ max =420×C %+470×N %+23×Ni %+9×Cu %+7×Mn %−11.5×Cr %−11.5×Si %−52×Al %+189  Formula 1 γ pot =700×C %+800×N %+10×(Mn %+Cu %)+20×Ni %−9.3×Si %−6.2×Cr %−9.3×Mo %−74.4×Ti %−37.2×Al %+63.2  Formula 2 Here, C %, N %, Ni %, Cu %, Mn %, Cr %, Si %, A1%, Mo %, and Ti % represent the contents (mass %) of the respective elements.

1 . A martensitic stainless steel with excellent weld characteristics comprising, in terms of percent by mass:
 C: 0.003% to 0.03%;   Si: 0.01% to 1.0%;   Mn: 3.0% to 6.0%;   P: 0.05% or less;   S: 0.003% or less;   Ni: 1.0% to 3.0%;   Cr: 15.0% to 18.0%;   Mo: 0% to 1.0%;   Cu: 0% to 2.0%;   Ti: 0% to 0.05%;   N: 0.05% or less;   Al: 0.001% to 0.1%; and   O: 0.005% or less,   with a remainder being Fe and inevitable impurities,   wherein a total amount of C and N is in a range of 0.060% or less, γ max  represented by the formula 1 is in a range of 80 or more, and γ pot  represented by the formula 2 is in a range of 60 to 90,
   γ max =420×C %+470×N %+23×Ni %+9×Cu %+7×Mn %−11.5×Cr %−11.5×Si %−52×Al %+189  Formula 1
 
   γ pot =700×C %+800×N %+10×(Mn %+Cu %)+20×Ni %−9.3×Si %−6.2×Cr %−9.3×Mo %−74.4×Ti %−37.2×Al %+63.2  Formula 2
 
   in which C %, N %, Ni %, Cu %, Mn %, Cr %, Si %, Al %, Mo %, and Ti % represent the contents (mass %) of the respective elements.   
     
     
         2 . The martensitic stainless steel with excellent weld characteristics according to  claim 1 ,
 wherein the martensitic stainless steel further comprises one or more selected from Nb, V: 0.5% or less, W: 1.0% or less, Co: 1.0% or less, B: 0.0050% or less, Ca: 0.0050% or less, Mg: 0.0030% or less, and REM: 0.10% or less, and   if Nb is included, γ pot  that is calculated by the formula 3 instead of the formula 2 is in a range of 60 to 90,
   γ pot =700×C %+800×N %+10×(Mn %+Cu %)+20×Ni %−9.3×Si %−6.2×Cr %−9.3×Mo %−3.1×Nb %−74.4×Ti %−37.2×Al %+63.2  Formula 3
 
   in which C %, N %, Mn %, Cu %, Ni %, Si %, Cr %, Mo %, Nb %, Ti %, and Al % represent the contents (mass %) of the respective elements.   
     
     
         3 - 5 . (canceled) 
     
     
         6 . A martensitic stainless steel material, wherein the martensitic stainless steel material has a composition according to  claim 1 , and the martensitic stainless steel material has a structure comprising 5% to 30% of a ferrite phase and 0% to 20% of a residual austenite phase with a remainder being a martensite phase. 
     
     
         7 . The martensitic stainless steel material according to  claim 6 , wherein a yield strength is in a range of 400 MPa to 800 MPa. 
     
     
         8 . A martensitic stainless steel material, wherein the martensitic stainless steel material has a composition according to  claim 2 , and the martensitic stainless steel material has a structure comprising 5% to 30% of a ferrite phase and 0% to 20% of a residual austenite phase with a remainder being a martensite phase. 
     
     
         9 . The martensitic stainless steel material according to  claim 8 , wherein a yield strength is in a range of 400 MPa to 800 MPa.