MARTENSITIC STAINLESS STEEL WITH EXCELLENT WELD CHARACTERISTICS, AND MARTENSITIC STAINLESS STEEL MATERIAL

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.