JPH09310156A - Steam turbine rotor material for high temperature use - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a steam turbine rotor material excellent in high temp. strength and applicable under the steam condition of >=593 deg.C as for Cr base steel. SOLUTION: This material has a compsn. contg., by weight, 0.05 to 0.13% carbon, 0.01 to 0.1% silicon, 0.01 to 1% manganese, 10 to 11.5% chromium, 0.1 to 0.3% vanadium, niobium and/or tantalum by 0.01 to 0.2% in total, 0.01 to 0.1% nitrogen, 0.01 to 0.5% molybdenum, 0.9 to 3% tungsten, 0.1 to 2% cobalt, and the balance iron with inevitable impurities.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high temperature steam turbine rotor material, and more particularly to the same material which can be advantageously applied as a steam turbine rotor material for thermal power generation.

[0002]

2. Description of the Related Art High-temperature rotor materials used in steam turbine plants for thermal power generation include CrMoV steel and 12C.
r Steel is an example. Among them, CrMoV steel is limited to a plant having a steam temperature up to 566 ° C. due to the limit of high temperature strength. On the other hand, rotor material made of 12Cr steel (for example, Japanese Patent Publication
0-4137) has higher high temperature strength than CrMoV steel, so it can be applied to a plant with a steam temperature up to 593 ° C., but the high temperature strength is insufficient for temperatures exceeding this. Therefore, application as a steam turbine rotor is difficult.

[0003]

SUMMARY OF THE INVENTION Accordingly, the present invention provides
An object of the present invention is to provide a high-temperature steam turbine rotor material excellent in high-temperature strength which is a Cr-based steel material and can be applied under a steam condition of 593 ° C. or higher.

[0004]

As a result of intensive studies, the inventors of the present invention have invented the following excellent high temperature steam turbine rotor material. That is, in the present invention, (1) weight ratio of carbon: 0.05 to 0.13%, silicon: 0.01 to 0.
1%, manganese: super 0.1-1%, chromium: 10-1
1.5%, vanadium: 0.1-0.3%, total of niobium and / or tantalum: 0.01-0.2%, nitrogen:
0.01-0.1%, molybdenum: 0.01-0.5
%, Tungsten: 0.9-3%, cobalt: 0.1
2%, unavoidable impurities and iron, which are characterized by high temperature steam turbine rotor material (hereinafter, this constituent material is abbreviated as material 1 of the present invention), (2) carbon by weight: 0.05
.About.0.13%, silicon: 0.01 to 0.1%, manganese: 0.01 to 0.1%, chromium: 10 to 11.5%,
Vanadium: 0.1-0.3%, total of niobium and / or tantalum: 0.01-0.2%, nitrogen: 0.01-
High temperature steam turbine characterized by comprising 0.1%, molybdenum: 0.01 to 0.5%, tungsten: 0.9 to 3%, cobalt: 0.1 to 2%, unavoidable impurities and iron. The rotor material (hereinafter, this constituent material is abbreviated as the present invention material 2) and (3) the weight ratio of boron: 0.001 to 0.
The high temperature steam turbine rotor material according to the above (1) or (2), characterized by containing 01% (hereinafter, this constituent material is abbreviated as the material 3 of the present invention).

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The reasons for limiting the components in the present invention materials 1 to 3 will be described below. However, unless specified as the present invention materials 1, 2, and 3, the present invention materials 1 to 3 are included in the description. In addition,% in the following description means weight%.

C: C forms carbonitrides together with N and contributes to the improvement of creep rupture strength. However, if it is less than 0.05%, a sufficient effect cannot be obtained, and if it exceeds 0.13%, carbonitrides agglomerate and coarsen during use to deteriorate high-temperature long-term strength. Therefore, the content is set to 0.05 to 0.13%. A particularly preferable range is 0.08 to 0.11%.

Si: Si is effective as a deoxidizer.
If the effect is less than 0.1%, it is not sufficient. In addition, Si
Reduces high temperature strength, especially creep rupture strength.
Therefore, in consideration of the application of the vacuum carbon deoxidizing method to the material of the present invention, the minimum addition necessary for steelmaking is made, and the range is 0.01 to 0.1%.

Mn: Mn is also an element useful as a deoxidizer, and has an action of suppressing the formation of δ ferrite.
However, the creep rupture strength deteriorates similarly to Ni described later. Therefore, it is not preferable to add more than 1%. In addition, Mn reduces the adverse effect of S mixed as an impurity by Mn.
Forming nS also has the effect of rendering it harmless. Therefore, addition of 0.01% or more is necessary. However, when considering the production in the steelmaking stage, it is more cost effective to manage scrap by more than 0.1% (amount exceeding 0.1%). Therefore, in the material 1 of the present invention, Mn is set to be more than 0.1 to 1%. Further, Mn is set to 0.01 to 0.1% in the material 2 of the present invention for the purpose of improving creep rupture strength and detoxifying S without considering the merit in scrap management.

Cr: Cr forms a carbide and contributes to the improvement of creep rupture strength. It also dissolves in the matrix to improve the oxidation resistance and strengthens the matrix itself to contribute to the improvement of the strength at high temperature and long time. . 10%
If it is less than the above range, the effect is not sufficient, and if it is added in an amount exceeding 11.5%, δ ferrite is likely to be formed, resulting in a decrease in strength and a deterioration in toughness. Therefore, 10
~ 11.5%. A particularly preferred range is 10.2-1
0.7%.

V: V becomes a carbonitride to improve creep rupture strength. If it is less than 0.1%, a sufficient effect cannot be obtained. Conversely, if the amount exceeds 0.3%, the creep rupture strength is rather lowered. Therefore, 0.
1 to 0.3%. A particularly preferred range is 0.18
0.23%.

Nb and / or Ta: Nb and / or Ta
Forms carbonitrides and contributes to improvement of high temperature strength. Also, contributing to the improvement of long-time Kukuripu breaking strength in the fine carbides (M ₂₃ C ₆₎ to precipitate at high temperatures. 0.01%
If the total amount exceeds 0.2%, the effect will not be obtained, and if the total amount exceeds 0.2%, Nb or T produced during the steel ingot production will be produced.
The carbonitride of a is heat treated (solution treatment: 980 to 1150).
(° C), it does not form a solid solution sufficiently in the matrix, and it coarsens during use to reduce long-term creep rupture strength. Therefore, the total amount of Nb and / or Ta is 0.01 to 0.2.
%. A particularly preferred range is 0.03 to 0.1%.

N: N forms carbonitrides together with C and alloy elements and contributes to improvement of high temperature strength. If it is less than 0.01%, sufficient carbonitride cannot be formed, so that sufficient creep rupture strength cannot be obtained. On the other hand, if the amount exceeds 0.1%, carbonitrides aggregate and grow over a long period of time, making it impossible to obtain sufficient creep rupture strength. Therefore, it is set to 0.01 to 0.1%. A particularly preferable range is 0.02 to 0.07%.

Mo: Mo forms a solid solution with W in the matrix to improve creep rupture strength. It is possible to add about 1.5% if Mo is added alone,
When W is added as in the case of the material of the present invention, W is more effective for improving the high-temperature strength, and when Mo and W are added in large amounts, δ ferrite is formed and the creep rupture strength is deteriorated. Therefore, from the balance with the added amount of W, 0.5%
The following additions are made. Further, W alone cannot exhibit sufficient high-temperature strength, so even a slight addition is necessary, and the amount is 0.01% or more. Therefore, the addition amount of Mo is set to 0.01 to 0.5%. A particularly preferred range is 0.1 to 0.4%.

W: W improves the creep rupture strength by forming a solid solution in the matrix together with Mo as described above. W is an element that has a stronger solid solution strengthening function than Mo and is effective. However, when a large amount is added, δ ferrite and a large amount of Laves phase are generated, and conversely, creep rupture strength is deteriorated. Therefore, in consideration of the balance with the addition amount of Mo, the addition amount is set to 0.9 to 3%. Particularly preferred range is 1.5
~ 2.5%.

Co: Co forms a solid solution in the matrix and suppresses the formation of δ ferrite. Also, the high temperature strength is not deteriorated unlike Ni. Therefore, when Co is added, it becomes possible to add more strengthening elements such as Cr, W, and Mo than when Co is not added. As a result, high creep rupture strength can be obtained. But,
Addition of an amount exceeding 2% accelerates the precipitation of carbides, which deteriorates the creep rupture strength on the long-term side. Further, as will be described later, in the material of the present invention, the addition of Co is indispensable for suppressing the formation of δ ferrite and ensuring the toughness because Ni which is usually added is completely excluded. The effect depends on the relationship with other elements, but in the case of the material of the present invention, addition of 0.1% or more is necessary. Therefore, 0.
The addition is 1-2%. Particularly preferred range is 0.8 to
It is 1.9%.

B: B has the effect of increasing the grain boundary strength.
This contributes to improvement in creep rupture strength. However, if added in a large amount, the hot workability deteriorates, and
The toughness decreases. If the amount is less than 0.001%, the effect of B cannot be sufficiently obtained. On the other hand, if the amount exceeds 0.01%, hot workability and toughness are reduced. Therefore, in the present invention material 3, the addition amount of B is 0.001 to 0.01.
%. A particularly preferred range is 0.003 to 0.007.
%.

In the material of the present invention, Ni which is usually added is not specified as a constituent element. However, this element is one of the important elements that influence the properties of the material such as the material of the present invention, and the reason will be described below. Ni is an element effective in improving toughness. It also has the effect of reducing the Cr equivalent to suppress the formation of δ ferrite. However, the addition of this element lowers the creep rupture strength, and therefore the addition to the minimum necessary amount is desired. In the present invention, Ni
Co is added as an element that exerts the effect of
Is replaced by Co. For this reason, Ni that adversely affects high temperature strength, especially creep rupture strength, is completely eliminated except for Ni which is unavoidably mixed in, and the material of the present invention aims to improve high temperature strength. However, it is a very important requirement of the present invention.

[0018]

EXAMPLES Hereinafter, specific examples of the present invention will be described to clarify the effects of the present invention.

(Example 1) An example of the material 1 of the present invention will be described below. Table 1 shows a summary of the chemical components of the materials used in the test. All materials were melted in a 50 kg vacuum high-frequency melting furnace and used as test materials. This test material was subjected to hot forging at a heating temperature of 1200 ° C., and then subjected to the following heat treatment. The heat treatment is a quenching process that simulates the center of a rotor with a body diameter of 1200φ when it is oil-cooled. Then, the tempering process has a 0.2% proof stress of about 62 to 68 kgf / m
The tempering temperature of each material was determined so as to be m ² .

Table 2 shows the mechanical properties and creep rupture strength of the invention material 1 and the comparative material. Although there is almost no difference in the results of the room temperature tensile test, the elongation and the reduction of the material of Comparative Material 9 are lower than those of the other materials. In terms of impact characteristics, the material numbers of the comparative materials are 9, 10, 11, 14, 1
6, 17, and 20 show low values, and it is clear that the toughness is lower than that of the material of the present invention. Further, Table 2 shows the creep rupture strength (extrapolated value) after 100,000 hours at 625 ° C.
Except for 0, the creep rupture strength of Inventive Material 1 is far superior to that of the Comparative Material.

[0021]

[Table 1]

[0022]

[Table 2]

(Example 2) An example of the material 2 of the present invention will be described below. Table 3 collectively shows the chemical components of the materials used in the test. All materials were melted in a 50 kg vacuum high-frequency melting furnace in the same manner as in Example 1 to obtain test materials. This test material is subjected to hot forging at a heating temperature of 1200 ° C.
Thereafter, the following heat treatment was performed. Heat treatment is 1200
A φ rotor is oil-cooled, and a quenching process that simulates the central part is performed, and then tempering is performed with a 0.2% proof stress of approximately 62%.
The tempering temperature of each material was determined so as to be about 68 kgf / mm ² .

Table 4 shows the mechanical properties and creep rupture strength of the invention material 2 and the invention material 1 for comparison. As is clear from Table 4, there is almost no difference in the results of the room temperature tensile test. However, in the impact characteristics, the material 2 of the present invention has
The impact value is slightly lower than that of the material 1 of the present invention due to the decrease in the amount. However, this decrease is small and not a problem. On the other hand, comparing the creep rupture strengths, it can be seen that the material 2 of the present invention has a significantly higher creep rupture strength than the material 1 of the present invention by lowering Mn.

[0025]

[Table 3]

[0026]

[Table 4]

(Example 3) An example of the material 3 of the present invention will be described below. Table 5 shows a summary of the chemical components of the materials used in the test. All materials were melted in a 50 kg vacuum high-frequency melting furnace in the same manner as in Examples 1 and 2 to prepare test materials. This test material was subjected to hot forging at a heating temperature of 1200 ° C., and then subjected to the following heat treatment. Heat treatment is body diameter 1
Quenching is performed by simulating the center part of a 200φ rotor when oil-cooled, and then tempering is performed by deciding the tempering temperature of each material so that the 0.2% proof stress is about 62 to 68 kgf / mm ^2. It was

Table 6 shows the mechanical properties and creep rupture strength of Inventive material 3 and Comparative invention material 1 and Inventive material 2 for comparison. As is clear from Table 6, there is almost no difference in mechanical properties between the three materials of the present invention material 1, the present invention material 2 and the present invention material 3. Comparing the creep rupture strengths, it can be seen that the inventive material 3 containing B has a significantly improved creep rupture strength as compared with the inventive material 1 and the inventive material 2, respectively. (31 of the invention material 3 is obtained by adding B to 3 of the invention material 1 of the same composition. Similarly, 32 of the invention material 3 is 4 of the invention material 3 and 3 of the invention material 3.
3 is 21 of the invention material 2, 34 of the invention material 3 is 22 of the invention material 2, 35 of the invention material 3 is 23 of the invention material 2, and B is added. )

[0029]

[Table 5]

[0030]

[Table 6]

[0031]

The high temperature steam turbine rotor material of the present invention has excellent high temperature strength, so that the steam temperature is 593 ° C.
It is useful as a high temperature steam turbine rotor material for ultra-supercritical power generation plants exceeding 100. According to the present invention, it can be said that the present ultra-supercritical power plant is useful for further raising the temperature, contributing to the saving of fossil fuels, and keeping the amount of generated carbon dioxide low.

Claims (3)

[Claims] 1. Carbon by weight ratio: 0.05 to 0.13%,
Silicon: 0.01-0.1%, Manganese: Super 0.1-
1%, chromium: 10 to 11.5%, vanadium: 0.1
~ 0.3%, sum of niobium and / or tantalum: 0.0
1 to 0.2%, nitrogen: 0.01 to 0.1%, molybdenum: 0.01 to 0.5%, tungsten: 0.9 to 3
%, Cobalt: 0.1 to 2%, unavoidable impurities, and iron. A high temperature steam turbine rotor material. 2. Carbon by weight ratio: 0.05 to 0.13%,
Silicon: 0.01 to 0.1%, manganese: 0.01 to
0.1%, chromium: 10 to 11.5%, vanadium:
0.1-0.3%, the sum of niobium and / or tantalum:
0.01-0.2%, nitrogen: 0.01-0.1%, molybdenum: 0.01-0.5%, tungsten: 0.9-
3%, cobalt: 0.1 to 2%, inevitable impurities, and iron. A high temperature steam turbine rotor material. 3. Boron: 0.001 to 0.01 by weight.
%, The high temperature steam turbine rotor material according to claim 1 or 2.