Precipitate hardening stainless steel and long blade using same for steam turbine
As a precipitate hardening stainless steel has excellent structure stability, strength, toughness, and corrosion resistance, requires no sub-zero treating and is excellent in terms of productivity, a long blade for a steam turbine uses the same. The following are provided: a precipitate hardening stainless steel, which comprises C at 0.05 mass % or less, N at 0.05 mass % or less, Cr at 10.0 mass % to 14.0 mass %, Ni at 8.5 mass % to 11.5 mass %, Mo at 0.5 mass % to 3.0 mass %, Ti at 1.5 mass % to 2.0 mass %, Al at 0.25 mass % to 1.00 mass %, Si at 0.5 mass % or less, and Mn at 1.0 mass % or less, and the balance is composed of Fe and inevitable impurities. The long blade for a steam turbine is composed of this precipitate hardening stainless steel.
1. A precipitate hardening stainless steel, which further comprises C at 0.05 mass % or less, N at 0.05 mass % or less, Cr at 10.0 mass % to 14.0 mass %, Ni at 8.5 mass % to 11.5 mass %, Mo at 0.5 mass % to 3.0 mass %, Ti at 1.5 mass % to 2.0 mass %, Al at 0.25 mass % to 1.00 mass %, Si at 0.5 mass % or less, Mn at 1.0 mass % or less, and W, wherein the total amount of Mo and W is equivalent to the amount of Mo in a case in which only Mo is added, and a balance composed of Fe and inevitable impurities.
2. The precipitate hardening stainless steel of claim 1 , which further comprises at least one member selected from Nb, V and Ta, at 0.5 mass % or less.
3. The precipitate hardening stainless steel of claim 1 , which further comprises Co at 1.0 mass % or less and Re at 1.0 mass % or less.
4. The precipitate hardening stainless steel of claim 1 , wherein the inevitable impurities include at least one member selected from S, P, Sb, Sn, and As, and the following conditions are satisfied: S: 0.5 mass % or less; P: 0.5 mass % or less; Sb: 0.1 mass % or less; Sn: 0.1 mass % or less; and As: 0.1 mass % or less.
5. The precipitate hardening stainless steel of claim 1 , wherein the stainless steel is subject to a solution treatment, a temperature range for the solution treatment is from 925° C. to 1025° C., the stainless steel is subject to an aging treatment, and a temperature range for the aging treatment is from 500° C. to 650° C.
6. A long blade for a steam turbine, wherein the precipitate hardening stainless steel of claim 1 is used.
7. A turbine rotor equipped with the long blade for a steam turbine of claim 6 .
8. A steam turbine equipped with the turbine rotor of claim 7 .
9. A steam turbine power plant equipped with the steam turbine of claim 8 .
10. A precipitate hardening stainless steel, which comprises C at 0.05 mass % or less, N at 0.05 mass % or less, Cr at 10.0 mass % to 14.0 mass %, Ni at 8.5 mass % to 11.5 mass %, Mo at 0.5 mass % to 3.0 mass %, Ti at 1.5 mass % to 2.0 mass %, Al at 0.25 mass % to 1.00 mass %, Si at 0.5 mass % or less, and Mn at 1.0 mass % or less, and the balance is composed of Fe and inevitable impurities;
wherein both parameter A for martensite finish temperature and parameter B for martensitic structure stability as defined below are satisfied:
Parameter A= 127.7−4.20Cr %−6.38Ni %−3.09Mo %−2.67Al %−14.7W %−3.41Mn %−3.57Si %−1.65Co %−2.32Ti %−221.5C %−321.4N %>2.5; and
Parameter B =(Cr %+2.2Si %+1.1Mo %+0.6W %+4.3Al %+2.1Ti %)/(Ni %+31.2C %+0.5Mn %+27N %+1.1Co %)<2.0.
11. The precipitate hardening stainless steel of claim 10 , which further comprises at least one member selected from Nb, V and Ta, at 0.5 mass % or less.
12. The precipitate hardening stainless steel of claim 10 , which further comprises Co at 1.0 mass % or less and Re at 1.0 mass % or less.
13. The precipitate hardening stainless steel of claim 10 , wherein the inevitable impurities include at least one member selected from S, P, Sb, Sn, and As, and the following conditions are satisfied: S: 0.5 mass % or less; P: 0.5 mass % or less; Sb: 0.1 mass % or less; Sn: 0.1 mass % or less; and As: 0.1 mass % or less.
14. The precipitate hardening stainless steel of claim 10 , wherein the stainless steel is subject to a solution treatment, a temperature range for the solution treatment is from 925° C. to 1025° C., the stainless steel is subject to an aging treatment, and a temperature range for the aging treatment is from 500° C. to 650° C.
15. A long blade for a steam turbine, wherein the precipitate hardening stainless steel of claim 10 is used.
16. A turbine rotor equipped with the long blade for a steam turbine of claim 15 .
17. A steam turbine equipped with the turbine rotor of claim 16 .
18. A steam turbine power plant equipped with the steam turbine of claim 17 .