Steam turbine blade, and steam turbine and steam turbine power plant using the same

• US 6,398,504 B1
• Filed: 07/06/2000
• Issued: 06/04/2002
• Est. Priority Date: 07/09/1999
• Status: Expired due to Term

• Current Assignee: mitsubishi hitachi power systems, ltd. (Mitsubishi Heavy Industries, Ltd.)
• Original Assignee: Hitachi, Ltd.
• Inventors: Arai, Masahiko, Nakamura, Shigeyoshi, Onoda, Takeshi, Shiga, Masao
• Primary Examiner(s): Look, Edward K.
• Assistant Examiner(s): Nguyen, Ninh
• Application Number:
  US09/611,977
• Time in Patent Office: 698 Days
• Field of Search: 415/200, 415/199.5, 415/199.4, 415/216.1, 415/103, 416/241.R, 148/516, 148/335, 420/109
• US Class Current: 416/241.00R
• CPC Class Codes: B23K 35/3046 Co as the principal constituent
• CPC Class Codes: B23K 9/04 Welding for other purposes than joining, e.g. built-up welding
• CPC Class Codes: C22C 38/001 containing N
• CPC Class Codes: C22C 38/44 with molybdenum or tungsten
• CPC Class Codes: C22C 38/46 with vanadium
• CPC Class Codes: C22C 38/48 with niobium or tantalum
• CPC Class Codes: C22C 38/52 with cobalt
• CPC Class Codes: C22C 38/54 with boron
• CPC Class Codes: F01D 5/28 Selecting particular materials; Particular measures relating thereto; Measures against erosion or corrosion
• CPC Class Codes: F05D 2300/171 Steel alloys

Abstract

A steam turbine blade made of a martensite steel having high strength and high toughness, and a low pressure steam turbine and a steam turbine power generating plant using the steam turbine blades. The steam turbine blade is made of a martensite steel containing C of 0.13-0.40%; Si less than 0.5%; Mn less than 1.5%; Ni of 2-3.5%; Cr of 8-13%; Mo of 1.5-4%; at least one kind of Nb and Ta of 0.02-0.3% in total; V of 0.05-0.35; and N of 0.04-0.15%.

Claims

1. A steam turbine blade made of a martensite steel having a 20°

C. V-notch impact value, wherein said 20°

C. V-notch impact value is larger than a value (y) (kg·

m/cm²) calculated by an equation (y=−

0.44x+68) where (x) is a 20°

C. tensile strength (kg/mm²).

2. A steam turbine blade according to claim 1, which said blade having a blade length above 45 inches for a 3000 rpm turbine or a blade length above 37.5 inches for a 3600 rpm turbine, which is made of a martensite steel having a 20°

C. V-notch impact value larger than 6 kg·

m/cm² and a 20°

C. tensile strength larger than 140 kq/mm².

3. A steam turbine blade according to claim 2, which is made of a martensite steel containing C of 0.13-0.40%;

Si less than 0.5%;

Mn less than 1.5%;

Ni of 2-3.5%;

Cr of 8-13%;

Mo of 1.5-4%;

at least one kind of Nb and Ta of 0.02-0.3% in total;

V of 0.05-0.35; and

N of 0.04-0.15%, on the basis of weight.

4. A steam turbine power generating plant comprising a high pressure turbine, an intermediate pressure turbine and one or two low pressure turbines connected in tandem or cross, wherein blades in a final stage of said low pressure turbine are the steam turbine blades according to claim 1.

5. A steam turbine power generating plant comprising a set of a high pressure turbine and a low pressure turbine and a generator;

and a set of an intermediate pressure turbine and a low pressure turbine and a generator, said sets being connected in tandem or cross, wherein blades in a final stage of said low pressure turbines are the steam turbine blades according to claim 1.

6. A low pressure steam turbine comprising a rotor shaft;

rotor blades mounted on said rotor shaft;

fixed blades for guiding flow of steam to said rotor blades; and

a casing holding said fixed blades, wherein said rotor blades in a final stage are the steam turbine blades according to claim 1.

7. A low pressure steam turbine according to any one of claims 6 and 9, wherein said rotor shaft is made of a bainite steel having a 0.02% yield strength at room temperature above 80 kg/mm² in the central portion of said rotor shaft;

0.2% yield strength above 87.5 kg/mm² or a tensile strength above 92 kg/mm²; and

a FATT below −

5°

C. or a 20°

C. V-notch impact value above 10 kg·

m.

8. A low pressure steam turbine according to any one of claims 6 to 7, wherein said bainite steel is a forged steel containing C of 0.20-0.28%;

Si less than 0.15%;

Mn less than 0.25%;

Ni of 3.25-4.25%;

Cr of 1.6-2.5%;

Mo of 0.25-0.6%; and

V of 0.05-0.20%, on the basis of weight.

9. A low pressure steam turbine comprising a rotor shaft;

rotor blades mounted on said rotor shaft;

fixed blades for guiding flow of steam to said rotor blades; and

a casing holding said fixed blades, a rotating speed of the low pressure turbine being 3000 rpm or 3600 rpm, which comprises five stages of said rotor blades symmetrically arranged in both sides, and is of a double flow construction having said rotor blades in the first stages being mounted in a middle portions of said rotor shaft, and

said rotor blades in the final stages are the steam turbine blades according to clam 1.

10. A low pressure steam turbine blade, which is made of a martensite steel containing C of 0.19-0.40%;

Si less than 0.5%;

Mn less than 1.5%;

Ni of 2-3.5%;

Cr of 8-13%;

Mo of 1.5-4%;

at least one kind of Nb and Ta of 0.02-0.3% in total;

V of 0.05-0.35; and

N of 0.04-0.15%, on the basis of weight.

11. A low pressure steam turbine blade according to claim 10, wherein said martensite steel contains C of 0.25-0.40% and Mo of 1.5-2.0%;

or C of 0.19-0.40% and Mo of 3-4%, on the basis of weight and a 20°

C. tensile strength larger than 140 kg/mm².

12. A steam turbine power generating plant comprising a high pressure turbine, an intermediate pressure turbine and one or two low pressure turbines connected in tandem or cross, wherein blades in a final stage of said low pressure turbine are the steam turbine blades according to claim 10.

13. A steam turbine power generating plant comprising a set of a high pressure turbine and a low pressure turbine and a generator;

and a set of an intermediate pressure turbine and a low pressure turbine and a generator, said sets being connected in tandem or cross, wherein blades in a final stage of said low pressure turbines are the steam turbine blades according to claim 10.

14. A low pressure steam turbine comprising a rotor shaft;

rotor blades mounted on said rotor shaft;

fixed blades for guiding flow of steam to said rotor blades; and

a casing holding said fixed blades, wherein said rotor blades in a final stage are the steam turbine blades according to claim 10.

15. A low pressure steam turbine comprising a rotor shaft;

rotor blades mounted on said rotor shaft;

fixed blades for guiding flow of steam to said rotor blades; and

a casing holding said fixed blades, a rotating speed of the low pressure turbine being 3000 rpm or 3600 rpm, which comprises five stages of said rotor blades symmetrically arranged in both sides, and is of a double flow construction having said rotor blades in the first stages being mounted in a middle portions of said rotor shaft, and

said rotor blades in the final stages are the steam turbine blades according to claim 10.

16. A low pressure steam turbine blade according to claim 10, wherein said martensite steel contains at least one of Ti, Zr and Hf of less than 0.5% in total.

17. A low pressure steam turbine blade according to claim 10, wherein said martensite steel contains at least one of Al, Ca Mg, Y and rare-earth elements of less than 0.5% in total.

18. A steam turbine blade having a blade length above 45 inches for a 3000 rpm turbine or a blade length above 37.5 inches for a 3600 rpm turbine, which is made of a martensite steel containing C of 0.19-0.40%;

Si less than 0.5%;

Mn less than 1.5%;

Ni of 2-3.5%;

Cr of 8-13%;

at least one kind of Nb and Ta of 0.02-0.3% in total;

V of 0.05-0.35%; and

N of 0.04-0.15%, on the basis of weight and a 20°

C. tensile strength larger than 140 kg/mm².

19. A steam turbine blade having a blade length above 45 inches for a 3000 rpm turbine or a blade length above 37.5 inches for a 3600 rpm turbine, which is made of a martensite steel containing C of 0.19-0.40%;

Si less than 0.5%;

Mn less than 1.5%;

Ni of 2-3.5%;

Cr of 8-13%;

at least one kind of Nb and Ta of 0.02-0.3% in total;

V of 0.05-0.35%; and

N of 0.04-0.15%, on the basis of weight, wherein

a combination of said amount of C and said amount of Mo falls within a range formed by connecting to points A (0.21%, 1.5%), B(0.15%, 2.5%), C(0.15%, 3.2%) and D(0.25%, 4.0%) and a 20°

C. tensile strength larger than 140 kg/mm².