Classifications

• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
  • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
  • C22C38/52—Ferrous alloys, e.g. steel alloys containing chromium with nickel with cobalt
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
  • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
  • C22C38/46—Ferrous alloys, e.g. steel alloys containing chromium with nickel with vanadium
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
  • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
  • C22C38/54—Ferrous alloys, e.g. steel alloys containing chromium with nickel with boron

Definitions

• This invention relates to steam turbine rotor materials for use in thermal electric power generation.
• High-temperature rotor materials for use in steam turbine plants for thermal electric power generation include CrMoV steel and 12Cr steel. Of these, the use of CrMoV steel is restricted to plants having a steam temperature up to 566°C because of its limited high-temperature strength. On the other hand, rotor materials based on 12Cr steel have more excellent high-temperature strength than CrMoV steel and can hence be used in plants having a steam temperature up to 593°C. However, if the steam temperature exceeds 593°C, such rotor materials have insufficient high-temperature strength and cannot be easily used for steam turbine rotors.
• the present inventors made intensive investigations in order to improve high-temperature strength by using 12Cr steel as a basic material and adding carefully selected alloying elements thereto, and have now invented new steam turbine rotor materials for high-temperature applications which have excellent high-temperature properties.
• inventive material (3) The reasons for content restrictions in the inventive material (3) are described below. However, the same explanations as those given in connection with the inventive material (1) are omitted. Here, the reason why no Ni is added as contrasted with the inventive materials (1) and (2) is explained.
• inventive material (4) has the same composition as the inventive material (2), except that no Ni is added similarly to the aforesaid inventive material (3).
• inventive material (3) has already been described in connection with the inventive materials (1) and (2) and are hence omitted here.
• test materials were prepared by melting the components in a 50 kg vacuum high-frequency furnace. These test materials were hot-forged at a heating temperature of 1,200°C and then subjected to the following heat treatment. The heat treatment was carried out by hardening the test materials under conditions which simulated the central part of an oil-quenched rotor having a drum diameter of 1,200 mm, and then tempering them at a temperature which had been determined so as to give a 0.2% yield strength of about 68-74 kgf/mm 2 .
• inventive materials (1) and comparative materials are shown in Table 2. Although there is little difference in the results of room-temperature tension tests, the elongation and reduction in area of comparative material Nos. 10, 14 and 19 are lower than those of the inventive materials (1). With respect to impact properties, comparative material Nos. 8-11, 14-17, 19 and 20 show lower values, revealing that the toughness of these comparative materials is lower than that of the inventive materials (1). Moreover, this table shows the rupture times obtained in creep rupture tests performed at a test temperature of 650°C and a stress of 15 kgf/mm 2 . It is evident from these results that the creep rupture strength of the inventive materials (1) is much more excellent than that of all comparative materials except No. 10.
• compositions of inventive materials used for testing purposes are summarized in Table 3.
• the compositions of inventive materials (2) are substantially the same as those of the inventive materials (1), except that the content of Mn is reduced as compared with the inventive materials (1).
• all test materials were prepared by melting the components in a 50 kg vacuum high-frequency furnace. These test materials were hot-forged at a heating temperature of 1,200°C and then subjected to the following heat treatment. The heat treatment was carried out by hardening the test materials under conditions which simulated the central part of an oil-quenched rotor having a drum diameter of 1,200 mm, and then tempering them at a temperature which had been determined so as to give a 0.2% yield strength of about 68-74 kgf/mm 2 .
• compositions of materials used for testing purposes are summarized in Table 5.
• the compositions of inventive materials (3) are substantially the same as those of the inventive materials (1), except that Ni is completely eliminated from the inventive materials (1).
• all test materials were prepared by melting the components in a 50 kg vacuum high-frequency furnace. These test materials were hot-forged at a heating temperature of 1,200°C and then subjected to the following heat treatment. The heat treatment was carried out by hardening the test materials under conditions which simulated the central part of an oil-quenched rotor having a drum diameter of 1,200 mm, and then tempering them at a temperature which had been determined so as to give a 0.2% yield strength of about 68-74 kgf/mm 2 .
• inventive materials (3) and the inventive materials (1) used for comparative purposes are shown in Table 6. It is evident from this table that there is little difference in the results of room-temperature tension tests. With respect to impact properties, the inventive materials (3) show somewhat lower impact values than the corresponding inventive materials (1), because they have a lower Ni content. However, similarly to the inventive materials (2) having a lower Mn content, such reductions are slight and unworthy of serious consideration. On the other hand, a comparison of the creep rupture strengths reveals that, as a result of the elimination of Ni, the inventive materials (3) show a distinct improvement in creep rupture strength over the respective inventive materials (1).
• compositions of materials used for testing purposes are summarized in Table 7.
• the compositions of inventive materials (4) are substantially the same as those of the inventive materials (3), except that the content of Mn is reduced as compared with the inventive materials (3).
• all test materials were prepared by melting the components in a 50 kg vacuum high-frequency furnace. These test materials were hot-forged at a heating temperature of 1,200°C and then subjected to the following heat treatment. The heat treatment was carried out by hardening the test materials under conditions which simulated the central part of an oil-quenched rotor having a drum diameter of 1,200 mm, and then tempering them at a temperature which had been determined so as to give a 0.2% yield strength of about 68-74 kgf/mm 2 .
• inventive materials (5) were derived from some typical inventive materials (1) to (4) by adding B thereto.
• inventive materials (5) Nos. 51 to 58 are based on the compositions of inventive material (1) Nos. 3 and 4, inventive material (2) Nos. 21 and 22, inventive material (3) Nos. 34 and 35, and inventive material (4) Nos. 41 and 42, except that B is added to the respective base materials.
• inventive materials (1) to (4) all test materials were prepared by melting the components in a 50 kg vacuum high-frequency furnace. These test materials were hot-forged at a heating temperature of 1,200°C and then subjected to the following heat treatment.
• the heat treatment was carried out by hardening the test materials under conditions which simulated the central part of an oil-quenched rotor having a drum diameter of 1,200 mm, and then tempering them at a temperature which had been determined so as to give a 0.2% yield strength of about 68-74 kgf/mm 2 .
• inventive materials (6) were derived from some typical inventive materials (1) to (5) by replacing part or all of Hf and/or part of Fe with Nd.
• inventive materials (6) Nos. 61 to 68 are based on the compositions of inventive material (1) No. 3, inventive material (2) No. 21, inventive material (3) No. 34, inventive material (4) No. 41, and inventive material (5) Nos. 52, 54, 56 and 58, except that part or all of Hf and/or part of Fe are replaced with Nd in the respective base materials.
• further comparative materials (sample Nos. 71 and 72) were provided by adding Nd to inventive material Nos.
• test materials were prepared by melting the components in a 50 kg vacuum high-frequency furnace. These test materials were hot-forged at a heating temperature of 1,200°C and then subjected to the following heat treatment. The heat treatment was carried out by hardening the test materials under conditions which simulated the central part of an oil-quenched rotor having a drum diameter of 1,200 mm, and then tempering them at a temperature which had been determined so as to give a 0.2% yield strength of about 68-74 kgf/mm 2 .
• the steam turbine rotor materials for high-temperature applications in accordance with the present invention have excellent high-temperature strength and are hence useful as high-temperature steam turbine rotor materials for use in hypercritical-pressure electric power plants having a steam temperature higher than 593°C.
• the present invention is useful in further raising the operating temperature of the current hypercritical-pressure electric power plants to afford a saving of fossil fuels and, moreover, to reduce the amount of carbon dioxide evolved.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Turbine Rotor Nozzle Sealing (AREA)

Applications Claiming Priority (5)

Publications (2)

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Cited By (3)

Citations (4)

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• 1997
  • 1997-08-20 JP JP22324397A patent/JP3245097B2/ja not_active Expired - Fee Related
  • 1997-12-12 CZ CZ982849A patent/CZ284998A3/cs unknown
  • 1997-12-12 WO PCT/JP1997/004580 patent/WO1998030727A1/fr not_active Application Discontinuation
  • 1997-12-12 EP EP97947913A patent/EP0896071A4/fr not_active Withdrawn

Patent Citations (4)

Non-Patent Citations (2)

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