Precipitation hardening martensitic stainless steel, and steam turbine long blade, steam turbine, and power plant using the same
View Patent ↗The problem to be solved of the present invention is to provide a precipitation hardening martensitic stainless steel having excellent tissue stability, strength, toughness, and corrosion-resistance, requiring no sub-zero treatment, and having excellent productivity; and also a steam turbine long blade using the same. The problem is solved by providing a precipitation hardening martensitic stainless steel containing, by mass, 0.1% or less of C; 0.1% or less of N; 9.0% or more and 14.0% or less of Cr; 9.0% or more and 14.0% or less of Ni; 0.5% or more and 2.5% or less of Mo; 0.5% or less of Si; 1.0% or less of Mn; 0.25% or more and 1.75% or less of Ti; 0.25% or more and 1.75% or less of Al, and the rest is Fe and inevitable impurities; and a steam turbine long blade using the precipitation hardening martensitic stainless steel.
1. A precipitation hardening martensitic stainless steel comprising, by mass, 0.1% or less of C; 0.1% or less of N; 9.0% or more and 14.0% or less of Cr; 9.0% or more and 14.0% or less of Ni; 0.5% or more and 1.47% or less total of Mo with optional W; 0.5% or less of Si; 1.0% or less of Mn; 0.25% or more and 1.75% or less of Ti; 0.25% or more and 1.75% or less of Al; 1.0% or less of Co and the rest is Fe and inevitable impurities, and
a parameter A related to martensite transformation finish-temperature and a parameter B related to martensitic tissue stability satisfying the following specific range:
(Cr+2.2Si+1.1Mo+0.6W+4.3Al+2.1Ti)−(Ni+31.2C+0.5Mn+27N+1.1Co) A:
(125−4.0Cr−6.0Ni−3.0Mo+2.5Al−1.5W−3.5Mn−3.5Si−5.5Co−2.0Ti−221.5C−321.4N), and, B:
Specific range: 4.0≦A≦10.0 and 2.0≦B≦7.0.
2. The precipitation hardening martensitic stainless steel according to claim 1 , wherein the total amount of Al and Ti is 0.75% or more and 2.25% or less by mass.
3. The precipitation hardening martensitic stainless steel according to claim 1 , further comprising at least one member selected from Nb, V, and Ta wherein the total amount thereof is 0.5% or less by mass.
4. The precipitation hardening martensitic stainless steel according to claim 1 , further comprising, by mass, Re: 1.0% or less.
5. The precipitation hardening martensitic stainless steel according to claim 1 , wherein the inevitable impurities are at least one member selected from S, P, Sb, Sn, and As, the amounts thereof being, by mass, S: 0.5% or less, P: 0.5% or less, Sb: 0.1% or less, Sn: 0.1% or less, and As: 0.1% or less.
6. The precipitation hardening martensitic stainless steel according to claim 1 , wherein a temperature range of a solution treatment is 900 to 1000° C. and a temperature range of an aging treatment is 500 to 600° C.
7. A steam turbine long blade using the precipitation hardening martensitic stainless steel of claim 1 .
8. The steam turbine long blade according to claim 7 , wherein a Stellite plate made of a Co-based alloy is joined to a front end portion of the blade.
9. A turbine rotor comprising the steam turbine long blade of claim 7 .
10. A steam turbine comprising the turbine rotor of claim 9 .
11. A power plant comprising the steam turbine of claim 10 .