JP2001049398A - High toughness heat resistant steel, and manufacture of turbine rotor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high toughness heat resistant steel excellent in creep rupture strength at high temperature as well as in tensile strength and toughness at relatively low temperature and suitable for use as a stock for a high- and low-pressure integrated type turbine rotor. SOLUTION: The steel has a composition consisting of, by weight ratio, 0.05 to 0.30% C, >0 to 0.20% Si, >0 to 1.0% Mn, 8.0 to 14.0% Cr, 0.5 to 3.0% Mo, 0.10 to 0.50% V, 1.5 to 5.0% Ni, 0.01 to 0.50% Nb, 0.01 to 0.08% N, 0.001 to 0.020% B, 0.1 to 2.0% Re, and the balance Fe with inevitable impurities. A steel ingot for a tubine rotor element body is manufactured from the high toughness heat resistant steel with the above composition by using an electroslag remelting process. The turbine rotor element body is heated to 950 to 1,120 deg.C, hardened, and then tempered at 550 to 740 deg.C one or more times and formed into a turbine rotor.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-toughness heat-resistant steel which is suitable as a material for a high-low pressure integrated turbine rotor and has excellent tensile strength and toughness at a relatively low temperature and excellent creep rupture strength at a high temperature. The present invention relates to a method of manufacturing a high-low pressure integrated turbine rotor suitable for a large-capacity, high-efficiency power plant using high-toughness heat-resistant steel.

[0002]

2. Description of the Related Art Generally, in a steam turbine rotor,
A steam turbine is formed by mechanically connecting a plurality of different turbine rotors according to the used steam conditions.
For example, as a turbine rotor material for a high temperature / high pressure side (for example, 550 to 600 ° C.), CrMoV steel as specified in ASTM-A470 (Class 8) and JP-B-60-54385 are disclosed. Such 12Cr steel is used as a low-temperature, low-pressure side (eg, 400 ° C or lower) turbine rotor material.
2. As specified in ASTM-A471 (Class 2-7)
NiCrMoV steel containing more than 5% Ni is used.

[0003] On the other hand, in the case of a relatively small steam turbine, from the viewpoint of miniaturization and simplification of the mechanism, a high-low pressure integrated turbine rotor in which the high pressure side to the low pressure side are integrally formed of the same material is used. I have.

[0004]

As materials for high-low pressure integrated turbine rotors, the above-mentioned CrMoV steel and N
Although iCrMoV steel is used, when the high-low pressure integrated turbine rotor is made of these materials, there are the following problems.

[0005] Although CrMoV steel has excellent creep rupture strength at a high temperature of about 550 ° C., it is not sufficiently satisfactory in tensile strength and toughness in a low temperature range. Therefore Cr
When a high-low pressure integrated turbine rotor is made of MoV steel, it is necessary to reduce the acting stress of the low-pressure part in order to prevent ductile fracture and brittle fracture. However, there is a problem that the capacity of the power plant is prevented from increasing.

Recently, in order to improve the efficiency of the power plant, the steam at the turbine inlet is further heated to a high temperature (about 600 ° C.).
There is a demand for increasing the pressure, in which case the CrMoV steel lacks high-temperature creep rupture strength. This problem can be solved by using 12Cr steel with excellent creep rupture strength.However, since 12Cr steel is not a material that is sufficiently satisfactory in terms of toughness, it can be used for blades that can be mounted on low-pressure paragraphs like CrMoV steel. There is a problem in that the size is limited, and increase in the capacity of the power plant is hindered.

On the other hand, NiCrMoV steel has excellent tensile strength and toughness in a low temperature range, but is not satisfactory in creep rupture strength. Therefore, when a high-low pressure integrated turbine rotor is made of NiCrMoV steel, the high temperature of the turbine inlet steam must be limited due to insufficient strength of the high-pressure portion, which hinders improvement in efficiency of the power plant. There is.

As described above, in the conventional high / low pressure integrated turbine rotor, it is intended to increase the capacity and efficiency of the steam turbine by using high-temperature steam and installing a long low-pressure last stage blade. There were great restrictions on the case.

The present invention has been made in view of the above-mentioned problems, and has high tensile strength and toughness at a relatively low temperature and excellent creep rupture strength at a high temperature, which are suitable as materials for a high-low pressure integrated turbine rotor. An object of the present invention is to provide a tough heat-resistant steel and to provide a method for manufacturing a turbine rotor suitable for a large-capacity and high-efficiency power plant using the high-toughness heat-resistant steel.

[0010]

According to a first aspect of the present invention, C: 0.05 to 0.30% and Si: more than 0% by weight.
0.20% or less, Mn: more than 0% and 1.0% or less, Cr: 8.
0-14.0%, Mo: 0.5-3.0%, V: 0.10-0.50%,
Ni: 1.5 to 5.0%, Nb: 0.01 to 0.50%, N: 0.01 to
High toughness heat resistant steel containing 0.08%, B: 0.001 to 0.020%, Re: 0.1 to 2.0%, the balance being Fe and inevitable impurities.

A second aspect of the present invention provides a method for manufacturing a fuel cell, comprising:
0.07 to 0.25%, Si: more than 0% and 0.20% or less, Mn:
More than 0% and 1.0% or less, Cr: 9.0 to 13.0%, Mo:
0.7 to 2.5%, V: 0.10 to 0.40%, Ni: 1.5 to 4.0
%, Nb: 0.01 to 0.30%, N: 0.01 to 0.06%, B: 0.00
3 to 0.015%, Re: 0.1 to 1.2%, the balance being Fe
And a high-toughness heat-resistant steel characterized by being composed of unavoidable impurities.

A third aspect of the present invention relates to a method for producing a C:
0.09 to 0.20%, Si: more than 0% and 0.20% or less, Mn:
More than 0% and 1.0% or less, Cr: 9.5 to 12.0%, Mo:
0.9-2.0%, V: 0.15-0.30%, Ni: 2.0-3.0
%, Nb: 0.03 to 0.20%, N: 0.02 to 0.04%, B: 0.00
5 to 0.012%, Re: 0.1 to 1.2%, the balance being Fe
And a high-toughness heat-resistant steel characterized by being composed of unavoidable impurities.

[0013] A fourth aspect of the present invention relates to a method for producing C:
0.05 to 0.30%, Si: more than 0% and 0.20% or less, Mn:
More than 0% and 1.0% or less, Cr: 8.0 to 14.0%, Mo:
0.1-2.0%, W: 0.3-5.0%, V: 0.10-0.50%,
Ni: 1.5 to 5.0%, Nb: 0.01 to 0.50%, N: 0.01 to
High toughness heat-resistant steel containing 0.08%, B: 0.001 to 0.020%, and Re: 0.1 to 2.0%, with the balance being Fe and unavoidable impurities.

[0014] A fifth aspect of the present invention relates to a C:
0.07 to 0.25%, Si: more than 0% and 0.20% or less, Mn:
More than 0% and 1.0% or less, Cr: 9.0 to 13.0%, Mo:
0.2-1.5%, W: 0.5-3.0%, V: 0.10-0.40%,
Ni: 1.5 to 4.0%, Nb: 0.01 to 0.30%, N: 0.01 to
High toughness heat-resistant steel containing 0.06%, B: 0.003 to 0.015%, and Re: 0.1 to 1.2%, with the balance being Fe and unavoidable impurities.

According to a sixth aspect of the present invention, C:
0.09 to 0.20%, Si: more than 0% and 0.20% or less, Mn:
More than 0% and 1.0% or less, Cr: 9.5 to 12.0%, Mo:
0.5-1.2%, W: 1.0-2.5%, V: 0.15-0.30%,
Ni: 2.0 to 3.0%, Nb: 0.03 to 0.20%, N: 0.02 to
High toughness heat-resistant steel containing 0.04%, B: 0.005 to 0.012%, and Re: 0.1 to 1.2%, with the balance being Fe and unavoidable impurities.

[0016] A seventh aspect of the present invention provides a method for manufacturing a semiconductor device, comprising:
The high toughness heat-resistant steel according to any one of the first to sixth claims, wherein the high toughness is 0.5 to 6.0%.

According to an eighth aspect of the present invention, there is provided a turbine rotor element comprising the high toughness heat-resistant steel according to any one of the first to seventh aspects, wherein the element is heated to 950 to 1120 ° C. Quenching and then 550-740 ° C
Is a method for manufacturing a turbine rotor, wherein tempering is performed once or more.

According to a ninth aspect of the present invention, a heating temperature at the time of quenching is 1030 to 1120 ° C. for a portion corresponding to a high pressure portion or a medium pressure portion of the turbine rotor body, and a portion corresponding to a low pressure portion. 950-1030 ° C., the method of manufacturing a turbine rotor according to the eighth aspect.

According to a tenth aspect of the present invention, at least one tempering requires a heating temperature of 630 to a portion corresponding to a high pressure portion or a medium pressure portion of the turbine rotor body.
~ 740 ℃, 550 ~ 630 for low pressure part
The method for manufacturing a turbine rotor according to the eighth or ninth aspect, wherein the method is characterized in that the temperature is ℃.

According to an eleventh aspect of the present invention, there is provided a method for manufacturing a turbine rotor according to any one of the eighth to tenth aspects, wherein the turbine rotor body is formed by any one of the first to seventh aspects. It is formed from a steel ingot manufactured from the high toughness heat-resistant steel according to the above-described method by electroslag remelting.

First, the reasons for limiting the composition range of the high toughness heat-resistant steel of the present invention will be described. In the following description,% representing the composition is a weight ratio unless otherwise specified. C combines with Cr, Nb, V and the like to form a carbide, contributes to precipitation strengthening, and is an indispensable element for improving hardenability and suppressing the formation of δ ferrite. In order to secure the desired creep rupture strength, it is necessary to add 0.05% or more. However, if 0.30% or more is added, the coarsening of the carbide is promoted, and the creep rupture strength in a long time is lowered. The content is set to 0.05 to 0.30%. Preferably 0.07 to 0.25
%, More preferably 0.09 to 0.20%.

Si is added as a deoxidizing material at the time of melting,
If it is added in a large amount, part of it will remain in the steel as an oxide, and the toughness will be reduced.
Mn is an element added as a deoxidizing / desulfurizing agent during dissolution, but if added in a large amount, the creep rupture strength is reduced.

Cr improves oxidation resistance and corrosion resistance and contributes to solid solution strengthening and precipitation strengthening.
It is an indispensable element as a constituent element of the type precipitate,
If the amount is less than 8.0%, the above-mentioned effect is small. Meanwhile, 14.
If it exceeds 0%, δ ferrite which is harmful to toughness and creep rupture strength is likely to be formed.
0 to 14.0%. Preferably it is 9.0-13.0%, more preferably 9.5-12.0%.

Mo is necessary as a solid solution strengthening element and a constituent element of carbides, but its effect is small if added less than 0.5%. On the other hand, if it exceeds 3.0%, the toughness is greatly reduced, and δ ferrite is easily formed, so the content is made 0.5 to 3.0%. Preferably 0.7
~ 2.5%, more preferably 0.9 ~ 2.0%.

It should be noted that W, which will be described later, has almost the same action, and when W is added, it is necessary to reduce the amount of Mo added. When adding W, the amount of Mo added is 0.1
%, The effect as a solid solution strengthening element and a carbide element is small. On the other hand, when it exceeds 2.0%, toughness is greatly reduced and δ ferrite is easily formed. Therefore, the amount of Mo added when added together with W is 0.1 to
2.0%. Preferably it is 0.2-1.5%, more preferably 0.5-1.2%.

V contributes to solid solution strengthening and formation of fine V carbonitride. At an addition amount of 0.10% or more, these fine precipitates precipitate mainly on the martensite lath boundary during creep and suppress the recovery, but when it exceeds 0.50%, δ ferrite is easily formed. If the addition amount is less than 0.10%, both the solid solution amount and the precipitation amount are small and the above-mentioned effects cannot be obtained, so the content is set to 0.10 to 0.50%. Preferably 0.10
0.40.40%, more preferably 0.15 to 0.30%.

Ni is an element which greatly improves the hardenability and toughness and suppresses the precipitation of δ-ferrite, but its effect is small if added less than 1.5%. Meanwhile, 5.
If it exceeds 0%, the creep resistance is reduced, so the content is made 1.5 to 5.0%. Preferably 1.5-4.0%,
More preferably, it is 2.0 to 3.0%.

Nb bonds with C and N to form Nb (C,
N) is an element that contributes to precipitation dispersion strengthening by forming a fine carbonitride, but if it is less than 0.01%, the above-mentioned effects cannot be obtained because the precipitation density is low. On the other hand, if it exceeds 0.50%, undissolved coarse Nb (C, N) is easily generated,
In order to reduce ductility and toughness, its content is 0.01 to 0.50
%. Preferably 0.01 to 0.30%, more preferably 0.1%.
It is 0.20% from 03.

N contributes to precipitation strengthening by forming nitrides or carbonitrides, and N remaining in the parent phase also contributes to solid solution strengthening. I can't get it. On the other hand, if it exceeds 0.08%, coarsening of the nitride or carbonitride is promoted, and the creep resistance is reduced and the ductility and toughness are reduced.
01 to 0.08%. Preferably it is 0.01 to 0.06%, more preferably 0.02 to 0.04%.

B is an element which, when added in a small amount, promotes the precipitation of precipitates at the crystal grain boundaries and enhances the high-temperature long-term stability of the carbonitride. However, if less than 0.001%, the effect cannot be obtained. On the other hand, if the content exceeds 0.020%, the toughness is significantly reduced, and the hot workability is further impaired.
~ 0.020%. Preferably it is 0.003 to 0.015%, more preferably 0.005 to 0.012%.

Re contributes to the improvement of creep rupture strength as a solid solution strengthening element, delays the diffusion of various alloying elements when used at high temperature, and contributes to the improvement of long-term stability. However, the addition of less than 0.1% results in these effects. Can not be obtained.
On the other hand, if it exceeds 2.0%, the toughness is greatly reduced,
The added amount is 0.1 to 2.0%. Preferably 0.1 to 1.
2%.

W contributes as a solid solution strengthening element and a carbide element, and further contributes to the formation of an intermetallic compound composed of Fe, Cr and W. Therefore, W is added when higher creep rupture strength is required. If the content is less than 0.3%, these effects cannot be obtained. On the other hand, if the content is more than 5.0%, δ ferrite is easily formed, and the toughness and the heat embrittlement property are remarkably reduced. . Preferably it is 0.5-3.0%, more preferably 1.0-2.5%.

Co is an element that contributes to solid solution strengthening and further suppresses the formation of δ ferrite, and is added as necessary. These effects cannot be obtained with the addition of less than 0.5%,
On the other hand, if it exceeds 6.0%, the workability is impaired, so its content is made 0.5 to 6.0%.

It is desirable to reduce as much as possible the impurities incidentally added when the above components and the main component Fe are added. Next, the reason for limiting the heat treatment conditions of the method for manufacturing the turbine rotor of the present invention will be described.

[0035] Quenching is a heat treatment necessary for imparting excellent strength to the turbine rotor element. If the heating temperature is lower than 950 ° C, austenitization is not sufficient and quenching becomes impossible. On the other hand, when the temperature exceeds 1120 ° C, austenite crystal grains are significantly coarsened, and the ductility is reduced.
The heating temperature is 950 to 1120 ° C. Since the creep rupture strength is important in the high pressure part or the medium pressure part of the rotor element, various precipitates are sufficiently dissolved by quenching in a high heating temperature range of 1030 to 1120 ° C. It is desirable to cause fine re-precipitation by tempering. In the low-pressure portion of the rotor body, tensile strength and toughness at relatively low temperatures are important, so that
It is desirable to refine the crystal grains by quenching in a low heating temperature range of 1030 ° C.

Tempering is a heat treatment that needs to be performed one or more times to adjust the turbine rotor body to a desired strength. However, if the heating temperature is lower than 550 ° C., a sufficient tempering effect cannot be obtained, and Toughness cannot be obtained. On the other hand, if the temperature exceeds 740 ° C, the desired strength cannot be obtained, so the heating temperature is set to 550 to 740 ° C. Since the creep rupture strength is important in the high pressure part or the medium pressure part of the rotor body, tempering in a high temperature range of 630 to 740 ° C is performed at least once and the solid solution is formed by quenching. It is desirable that the substance be sufficiently reprecipitated. In the low-pressure part of the rotor element, tensile strength and toughness at relatively low temperature are important, so that the temperature is 550 to 630 ° C.
It is desirable to perform tempering at least once in a low heating temperature range to achieve both desired tensile strength and excellent toughness. Next, the reason why the steel ingot constituting the turbine rotor body is manufactured by using the electroslag remelting method in the method for manufacturing the turbine rotor of the present invention will be described.

In a large-sized material typified by a rotor for a steam turbine, segregation of added elements and unevenness of a solidified structure are liable to occur when the steel ingot is solidified. In particular, when various elements are added in order to improve the material properties, the tendency of segregation in the center of the steel ingot increases, and the ductility and toughness in the center of the rotor element tend to decrease. The steel ingot constituting the turbine rotor body according to the method for manufacturing a turbine rotor of the present invention can be manufactured by a normal method represented by vacuum carbon deoxidation or the like.
It is preferable to use electroslag remelting to obtain a clean steel ingot.

The properties of the steel and turbine rotor according to the present invention, such as tensile strength, toughness, ductility, and creep rupture strength, can be evaluated by the following tensile test, Charpy impact test, creep rupture test, and the like.

The tensile test is a material test for the purpose of determining the tensile strength, proof stress, elongation, drawing, etc. of the test material. Tensile strength and proof stress indicate the tensile strength of the test material, and elongation and drawing indicate the ductility of the test material. The larger the value of each, the better the properties.

In the Charpy impact test, the impact value of the test material, FA
This is a material test for the purpose of obtaining TT (ductility-brittle transition temperature determined from the fracture surface area of the impact test piece) and the like. In general, the term “impact value” refers to characteristics at room temperature (20 ° C.). The impact value indicates how hard it is to break when an impact force is applied, that is, toughness.
Larger values indicate better properties. Further, the impact value of the steel and turbine rotor test material according to the present invention changes depending on the temperature, and even in the same test material, the impact value is large in a high temperature region, and the fracture surface exhibits a ductile fracture surface. Conversely, in a low temperature region, the impact value is small, and the fracture surface exhibits a brittle fracture surface. In the intermediate temperature range, a ductile fracture surface and a brittle fracture surface are mixed. The area ratio of both fractured surfaces is calculated, and a temperature that is exactly 50% -50% is obtained, and this temperature is defined as FATT. Therefore, the smaller the value of FATT, the higher the toughness.

The creep rupture test is a material test aimed at obtaining the creep rupture strength and the like of the test material. The creep rupture strength is a characteristic corresponding to the creep rupture time, and the longer the creep rupture time, the higher the creep rupture strength. In addition, the creep rupture strength (105-hour rupture strength, 105-hour rupture strength,
Etc.).

[0042]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described with reference to embodiments. (Example 1) In Example 1, the influence of the chemical composition will be particularly described.

FIGS. 1 and 2 show the chemical compositions of 70 kinds of samples used as test materials. Of these, Examples M1 to M45 shown in FIG. 1 are steels having a chemical composition range of the high toughness heat-resistant steel according to the present invention. In the comparative example shown in FIG. 2, S1 is CrMoV steel specified in ASTM-A470, and S2 is AS
NiCrMoV steel and S3 specified in TM-A470
No. 60-54385, which is a 12Cr steel disclosed in
S3 and S3 are steels used for the high-temperature turbine rotor, and S2 is steel used for the low-temperature turbine rotor. Further, among the comparative examples shown in FIG. 2, S4 to S25 are steels whose chemical compositions do not fall within the scope of the present invention.

These test materials were melted and cast in a 50 kg vacuum high-frequency induction electric furnace, heated to 1200 ° C., press-forged, and forged into round bars having a diameter of 60 mm. Thereafter, each round bar was subjected to a tempering heat treatment. The conditions of the heat treatment were as follows: Examples M1 to M45 and Comparative Examples S4 to S45.
For 25, HM1 (hardened at 1030 ° C, 630 ° C
Tempering), and in Comparative Examples S1 to S3, H shown in FIG.
From S1 to HS3.

A test piece was cut out from the thus obtained round bar test material and subjected to a tensile test, a Charpy impact test and a creep rupture test at room temperature. The tensile strength, 0.02% proof stress, elongation, drawing, FATT at 590 ° C. The 105-hour breaking strength was determined. The results are shown in FIG. 4 for the example and in FIG. 5 for the comparative example.

First, among the comparative examples, S1 to S3 used for the current turbine rotor are compared. The 105-hour breaking strength is highest in S3, followed by S1 and S2. For FATT, S2 is the lowest, followed by S3 and S1. The tensile strength and the 0.02% proof stress of S3 are the highest, followed by S2 and S1. Therefore, from these results, "S1 is a material having excellent creep rupture strength but inferior in tensile strength and toughness", "S2 is a material having very excellent toughness and excellent in tensile strength, but inferior in creep rupture strength", "S3 Can be said to be a material that has very excellent tensile strength and creep rupture strength, but never excellent toughness.

Next, Example M1 which is a test material according to the present invention
To M45 and Comparative Examples S1 to S3. With respect to the tensile strength and the 0.02% proof stress, Examples M1 to M45 all show values exceeding those of Comparative Example S3, indicating that they have extremely excellent tensile strength. On the other hand, in FATT, Examples M1 to M45 all show values equal to or lower than Comparative Example S2, indicating that they have extremely excellent toughness. Also, in the creep rupture strength,
Examples M1 to M45 all show values higher than Comparative Example S1, and some also show values equivalent to Comparative Example S3, indicating that they have extremely excellent creep rupture strength. In the elongation and the drawing, the examples M1 to M45 show almost the same values as the comparative examples S1 to S3, indicating that they have sufficient ductility.

That is, the high toughness heat-resistant steel according to the present invention comprises:
It has higher tensile strength and toughness than steel conventionally used as a steam turbine rotor, and has excellent creep rupture strength exceeding that of CrMoV steel and approaching that of 12Cr steel.

In Comparative Examples S4 to S25, which are steels whose chemical composition does not fall within the range of the present invention, no test material having excellent tensile strength, toughness and creep rupture strength is found. That is, S4, S5, S6, S7, S8, S10, S
13, S14, S16, S17, S18, S20, S22, and S24 have low creep rupture strengths, and S9, S11, S12, S15, S17,
S19, S21, S23 and S25 have low toughness, and S4 and S16 have low tensile strength. From these results, it is clear that by adjusting the composition of the steel to the range of the chemical composition of the present invention, a high toughness heat-resistant steel having excellent tensile strength, toughness and creep rupture strength can be obtained.

(Embodiment 2) In Embodiment 2, the influence of the heat treatment will be particularly described. As a material, M1, M32, and M42 are used in the embodiment of FIG. 1 which is the high toughness heat-resistant steel according to the present invention.
Samples 1 to HM10 (Example) and HS4 to HS7 (Comparative Example) were heat-treated to obtain test materials. Here, HM1
To HM10 are heat treatment conditions in the method for manufacturing a turbine rotor according to the present invention, and HS4 to HS7 are not heat treatment conditions in the method for manufacturing a turbine rotor according to the present invention.

A test piece was cut out from the test material thus obtained, and subjected to a tensile test, a Charpy impact test and a creep rupture test at room temperature. Tensile strength, 0.02% proof stress, elongation, drawing, FATT, 105 hours at 590 ° C. for 105 hours The breaking strength was determined. FIG. 6 shows the result.

The heat treatment conditions HM1 (hardened at 1030 ° C.
(Tempering at 630 ° C.) described in Example 1 that excellent tensile strength, toughness, and creep rupture strength can be obtained in the high-toughness heat-resistant steel according to the present invention.
10 is described.

HM2 is obtained by adding a second tempering at 475 ° C. to HM1 (quenched at 1030 ° C. and tempered at 630 ° C.). Compared to the case where heat treatment HM1 is performed,
It can be seen that the heat treatment HM2 significantly increases the 0.02% proof stress in any of the materials M1, M32, and M42, and hardly changes the FATT and the creep rupture strength. That is, the second tempering has an effect of increasing the tensile strength, and it is more preferable to perform the second tempering when manufacturing the rotor material.

HM3 is obtained by lowering the quenching temperature to 1000 ° C. with respect to HM1 (quenched at 1030 ° C. and tempered at 630 ° C.). As compared with the case where the heat treatment HM1 is performed, the heat treatment HM3 reduces the creep rupture strength in any of the materials M1, M32, and M42, but the tensile strength and
It can be seen that the 0.02% proof stress hardly changes, and the FATT greatly decreases. That is, by performing the quenching in a low heating temperature range of 950 to 1030 ° C., it is possible to realize excellent toughness suitable as a characteristic of a low pressure portion of a high / low pressure integrated steam turbine rotor body.

HM4 is obtained by increasing the quenching temperature to 1070 ° C with respect to HM1 (quenched at 1030 ° C and tempered at 630 ° C). Compared with the case where the heat treatment HM1 is performed, the heat treatment HM3 increases the FATT in any of the materials M1, M32, and M42, but hardly changes the tensile strength and the 0.02% proof stress, and increases the creep rupture strength. You can see that. That is, by performing quenching in a high heating temperature range of 1030 to 1120 ° C., it is suitable as a characteristic of a high-pressure portion or a medium-pressure portion of a high-low pressure integrated steam turbine rotor body.
Excellent creep rupture strength can be realized.

HM5 is obtained by lowering the tempering temperature to 600 ° C. with respect to HM1 (quenching at 1030 ° C., tempering at 630 ° C.). Compared with the case where the heat treatment HM1 is performed, the heat treatment HM5 slightly reduces the creep rupture strength and slightly increases the FATT in any of the materials M1, M32, and M42, but increases the tensile strength and the 0.02% proof stress. It can be seen that it rises. That is, by performing the tempering in a low heating temperature range of 550 to 630 ° C., it is possible to realize an excellent tensile strength suitable as a characteristic of a low pressure portion of a high / low pressure integrated steam turbine rotor element.

HM6 is obtained by raising the tempering temperature to 660 ° C. with respect to HM1 (quenching at 1030 ° C. and tempering at 630 ° C.). Compared with the case where the heat treatment HM1 is performed, the heat treatment HM6 decreases the tensile strength and the 0.02% proof stress in any of the materials M1, M32, and M42, but slightly decreases the FATT and increases the creep rupture strength. You can see that. In other words, by performing tempering in a high heating temperature range of 630 to 740 ° C., it is possible to realize excellent creep rupture strength suitable for high-pressure or medium-pressure parts of a high-low pressure integrated steam turbine rotor element. it can.

HM7 is obtained by lowering the quenching temperature to 1000 ° C. and further lowering the tempering temperature to 600 ° C. with respect to HM1 (quenching at 1030 ° C., tempering at 630 ° C.). Heat treatment H
Compared with the case where M1 is applied, the heat treatment HM7 reduces the creep rupture strength of any of the materials M1, M32 and M42, but greatly reduces the FATT and greatly increases the tensile strength and the 0.02% proof stress. I understand. That is, by performing quenching in a low temperature range of 950 to 1030 ° C. and further performing tempering in a low heating temperature range of 550 to 630 ° C., it is suitable as a characteristic of a low-pressure portion of a high-low pressure integrated steam turbine rotor element. Excellent tensile strength and toughness can be realized.

HM8 is obtained by increasing the quenching temperature to 1070 ° C and further increasing the tempering temperature to 660 ° C with respect to HM1 (quenching at 1030 ° C, tempering at 630 ° C). Heat treatment H
Compared with the case where M1 was applied, the tensile strength and the tensile strength of any of the materials M1, M32 and M42 were increased by the heat treatment HM8.
It can be seen that the 0.02% proof stress decreases and the FATT increases, but the creep rupture strength greatly increases. That is, by performing quenching in a high temperature range of 1030 ° C. to 1120 ° C. and further performing tempering in a high heating temperature range of 630 to 740 ° C., the characteristics of the low-pressure portion of the high-low pressure integrated steam turbine rotor element are suitable. And very excellent creep rupture strength can be realized.

HM9 is obtained by adding a second tempering at 475 ° C. to HM7 (quenched at 1000 ° C. and tempered at 600 ° C.). Compared to the case where heat treatment HM7 is performed,
It can be seen that the heat treatment HM9 significantly increases the 0.02% proof stress in any of the materials M1, M32, and M42, and hardly changes the FATT and the creep rupture strength. That is, the quenching is performed in a low temperature range of 950 to 1030 ° C., the tempering is performed in a low heating temperature range of 550 to 630 ° C., and the second tempering is further performed to reduce the low pressure of the high-low pressure integrated steam turbine rotor body. Very good tensile strength and toughness suitable for the properties of the part can be realized.

HM10 is obtained by subjecting HM8 (quenched at 1070 ° C., tempered at 660 ° C.) to a second tempering at 475 ° C. Compared to the case where heat treatment HM8 is performed,
It can be seen that the heat treatment HM10 increases the proof stress by 0.02% in any of the materials M1, M32, and M42, and hardly changes the FATT and the creep rupture strength. That is, quenching is performed in a high temperature range of 1030 to 1120 ° C and tempering is performed in 63
When applied at a high heating temperature range of 0 to 740 ° C, it maintains very good creep rupture strength, which is suitable for the high-pressure part of the high-low pressure integrated steam turbine rotor element even after the second tempering. Is done.

When Comparative Examples HS4 to HS7, which are heat treatment conditions that do not fall within the scope of the method for manufacturing a turbine rotor according to the present invention, were applied, tensile strength, toughness, and creep rupture were observed in all of the materials M1, M32, and M42. No excellent strength was observed. That is, when HS4 was applied, the tensile strength, toughness, and creep rupture strength were all low.
Alternatively, when HS6 is applied, ductility and ductility are low, and when HS7 is applied, tensile strength and creep rupture strength are low.

From these results, by adjusting the heat treatment conditions to the range of the method for manufacturing the turbine rotor according to the present invention, it is possible to obtain a very excellent tensile strength and excellent tensile strength in the low-pressure portion, which is suitable for a high-low pressure integrated turbine rotor. It is clear that a rotor element having toughness and excellent creep rupture strength in the high pressure part can be obtained.

(Embodiment 3) In Embodiment 3, the effect of manufacturing the steel ingot forming the turbine rotor body by using the electroslag remelting method will be described.

FIG. 7 shows the chemical compositions of four types of samples used as test materials. These are all steels in the composition range of the high-toughness heat-resistant steel according to the present invention. Example E1 has almost the same chemical composition as Comparative Example V1, and Example E2 has almost the same chemical composition as Comparative Example V2. Have. Of these, Example E
Regarding 1 and E2, after melting in an electric furnace, casting into an electrode mold for electroslag remelting, then performing electroslag remelting using the ingot as a consumable electrode to produce a steel ingot, and heating to 1200 ° C. Press forging, 1000
A rotor partial model of mmφ × 800 mm was obtained. On the other hand, Comparative Example V
With respect to 1 and V2, after melting in an electric furnace, vacuum carbon deoxidation was performed to produce a steel ingot, and the steel ingot was heated to 1200 ° C. and press forged to obtain a rotor partial model of 1000 mmφ × 800 mm. These four types of rotor partial models were quenched at 1030 ° C and tempered at a heating temperature of 630 ° C.

A test piece was cut out from the surface layer and the center of the test material thus obtained, and subjected to a tensile test, a Charpy impact test and a creep rupture test at room temperature. The tensile strength, 0.02% proof stress, elongation, drawing, FATT At 590 ° C
The 105-hour breaking strength was determined. FIG. 8 shows the result.

In Examples E1 and E2, the tensile strength, the 0.02% proof stress, the elongation, the drawing, the FATT, and the creep rupture strength of the surface layer portion and the central portion are almost the same. On the other hand, in Comparative Examples V1 and V2, the tensile strength, the 0.02% proof stress, and the creep rupture strength of the surface layer portion and the central portion are almost the same, but the elongation and the reduction decrease in the central portion, and the FATT increases in the central portion. There is a tendency. This tendency is remarkable in V2 in which more alloying elements are added. In other words, especially when a large amount of alloying elements are added, the ingot forming the turbine rotor body using the high toughness heat-resistant steel according to the present invention is manufactured by using the electroslag remelting method, so that the surface layer portion and the central portion are manufactured. It is clear that a homogeneous rotor body having no difference in tensile strength, ductility, toughness and creep rupture strength can be obtained.

[0068]

As apparent from the above description, the present invention has a high creep rupture strength under high-temperature steam conditions and a high tensile strength and toughness even under relatively low-temperature steam conditions. It is possible to provide a high-toughness heat-resistant steel and a high-low pressure integrated turbine rotor using the high-toughness heat-resistant steel. This high-low pressure integrated turbine rotor can be used in a high-temperature steam environment and can be equipped with a long, low-pressure last stage blade, making it an unprecedented high-capacity, high-efficiency power plant with a high-low pressure integrated turbine. Becomes possible,
Industrially beneficial effects are brought about.

[Brief description of the drawings]

FIG. 1 is a table showing the composition of an example of a high toughness heat-resistant steel of the present invention.

FIG. 2 is a table showing the composition of a comparative example for the high toughness heat-resistant steel of the present invention.

FIG. 3 is a table showing heat treatment conditions for a test material.

FIG. 4 is a table showing the results of tensile tests and the like on the test materials of the examples.

FIG. 5 is a table showing the results of a tensile test and the like for a test material of a comparative example.

FIG. 6 is a table showing the results of tests on heat treatment conditions.

FIG. 7 is a table showing a composition of a test material for testing an electroslag remelting method.

FIG. 8 is a table showing results of tensile tests and the like of test materials manufactured by the electroslag remelting method and other methods.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (Reference) C22C 38/18 C22C 38/18 38/40 38/40 38/44 38/44 38/46 38/46 38 / 48 38/48 38/54 38/54 F01D 5/28 F01D 5/28 // C22B 9/18 C22B 9/18 (72) Inventor Masayuki Yamada 2-4 Suehirocho, Tsurumi-ku, Yokohama-shi, Kanagawa Prefecture Co., Ltd. F-term in Toshiba Keihin Works (reference) 3G002 EA06 4K001 AA42 BA23 FA01 GA14 4K042 AA25 BA01 BA02 BA14 CA02 CA07 CA08 CA09 CA10 CA13 CA15 DA01 DA02

Claims (11)

[Claims] 1. A weight ratio of C: 0.05 to 0.30%, Si: 0
%: 0.20% or less, Mn: more than 0% and 1.0% or less, Cr: 8.0-14.0%, Mo: 0.5-3.0%, V: 0.
10-0.50%, Ni: 1.5-5.0%, Nb: 0.01-0.50
%, N: 0.01 to 0.08%, B: 0.001 to 0.020%, Re:
A high toughness heat-resistant steel containing 0.1 to 2.0%, with the balance being Fe and unavoidable impurities. 2. C: 0.07 to 0.25% by weight, Si: 0 by weight ratio
%: More than 0.20%, Mn: more than 0% and 1.0% or less, Cr: 9.0-13.0%, Mo: 0.7-2.5%, V: 0.
10 to 0.40%, Ni: 1.5 to 4.0%, Nb: 0.01 to 0.30
%, N: 0.01 to 0.06%, B: 0.003 to 0.015%, Re:
A high toughness heat-resistant steel containing 0.1 to 1.2%, with the balance being Fe and unavoidable impurities. 3. A weight ratio of C: 0.09 to 0.20%, Si: 0
% To 0.20%, Mn: more than 0% to 1.0%, Cr: 9.5 to 12.0%, Mo: 0.9 to 2.0%, V: 0.
15-0.30%, Ni: 2.0-3.0%, Nb: 0.03-0.20
%, N: 0.02 to 0.04%, B: 0.005 to 0.012%, Re:
A high toughness heat-resistant steel containing 0.1 to 1.2%, with the balance being Fe and unavoidable impurities. 4. A weight ratio of C: 0.05 to 0.30%, Si: 0
%: 0.20% or less, Mn: more than 0% and 1.0% or less, Cr: 8.0-14.0%, Mo: 0.1-2.0%, W: 0.
3 to 5.0%, V: 0.10 to 0.50%, Ni: 1.5 to 5.0%,
Nb: 0.01 to 0.50%, N: 0.01 to 0.08%, B: 0.001 to
A high toughness heat-resistant steel containing 0.020% and Re: 0.1 to 2.0%, with the balance being Fe and unavoidable impurities. 5. C: 0.07 to 0.25% by weight, Si: 0 by weight ratio
%: 0.20% or less, Mn: more than 0% and 1.0% or less, Cr: 9.0-13.0%, Mo: 0.2-1.5%, W: 0.
5 to 3.0%, V: 0.10 to 0.40%, Ni: 1.5 to 4.0%,
Nb: 0.01 to 0.30%, N: 0.01 to 0.06%, B: 0.003 to
High toughness heat-resistant steel containing 0.015% and Re: 0.1 to 1.2%, with the balance being Fe and unavoidable impurities. 6. A weight ratio of C: 0.09 to 0.20%, Si: 0
% To 0.20%, Mn: more than 0% to 1.0%, Cr: 9.5 to 12.0%, Mo: 0.5 to 1.2%, W: 1.
0 to 2.5%, V: 0.15 to 0.30%, Ni: 2.0 to 3.0%,
Nb: 0.03 to 0.20%, N: 0.02 to 0.04%, B: 0.005 to
High toughness heat-resistant steel containing 0.012% and Re: 0.1 to 1.2%, with the balance being Fe and inevitable impurities. 7. The high-toughness heat-resistant steel according to claim 1, which contains 0.5 to 6.0% of Co by weight. 8. A turbine rotor element made of the high-toughness heat-resistant steel according to any one of claims 1 to 7, wherein the temperature is 950 to 1120 ° C.
And then quenched.
A method for manufacturing a turbine rotor, wherein tempering at 0 to 740 ° C is performed at least once. 9. The heating temperature at the time of quenching is set for a portion corresponding to a high pressure portion or a medium pressure portion of the turbine rotor body.
9. The method according to claim 8, wherein the temperature is 1030 to 1120 [deg.] C. and the temperature is 950 to 1030 [deg.] C. for a portion corresponding to a low pressure portion of the turbine rotor body. 10. The heating temperature of at least one tempering is 630 to 740 ° C. for a portion corresponding to a high pressure portion or a medium pressure portion of the turbine rotor body, and corresponds to a low pressure portion of the turbine rotor body. 550 to 630 ° C
The method for manufacturing a turbine rotor according to claim 8, wherein: 11. The turbine rotor body is formed from a steel ingot produced from the high toughness heat-resistant steel according to any one of claims 1 to 7 by an electroslag remelting method. 11. The method for manufacturing a turbine rotor according to any one of 10.