JP3510606B2 - High and low pressure integrated turbine rotor and method of manufacturing the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a turbine rotor and a method for manufacturing the same, and more particularly to a high and low pressure integrated turbine rotor used for a steam turbine used in thermal power generation and the like and a method for manufacturing the same. .

[0002]

2. Description of the Related Art Conventionally, as one of turbine rotors for steam turbines for thermal power generation, there has been known a high / low pressure integrated turbine rotor using a material integrated from a high pressure portion to a low pressure portion. The steam turbine is exposed to high-temperature and high-pressure steam on the steam inlet side, but the temperature and pressure of the steam decrease as it approaches the end, and the steam turbine is exposed to steam whose volume has expanded significantly. Therefore, in the high pressure portion, the length of the turbine blade is short, and the stress applied to the turbine rotor is relatively small, so that the diameter of the turbine rotor may be small. On the other hand, in the low pressure portion, in order to receive the force of a large amount of steam, the length of the turbine blade must be increased to increase the diameter of the turbine rotor, and the stress applied to the turbine rotor becomes large. Therefore, as the characteristics required for the high-low pressure integrated turbine rotor, high-temperature strength is required in the high-pressure portion, and particularly excellent creep strength is required, while mechanical strength at room temperature and excellent toughness are required in the low-pressure portion.

Conventionally, examples of heat-resistant steels used in high-low pressure integrated turbine rotors include low alloy CrMoV steels and high Cr 12Cr steels (Japanese Patent Laid-Open No. 165359/1985).
JP-A-62-103345) has been exclusively used. Then, a method has been proposed in which a turbine rotor material is processed by using a CrMoV type steel, and the turbine rotor is divided into a high pressure portion and a low pressure portion and subjected to heat treatment under different conditions to obtain a turbine rotor having both creep characteristics and toughness. ing. For example, in Japanese Patent Laid-Open No. 195068/1993, a high temperature portion of the turbine rotor material is heated to a temperature higher than that of the low pressure portion to quench it, and then the entire turbine rotor material is tempered at a predetermined temperature to obtain an excellent high temperature. A method of obtaining a high-low pressure integrated turbine rotor having both creep strength and toughness is disclosed.

Further, in JP-A-8-176671, the turbine rotor material is standardized at 1000 to 1150 ° C., transformed into pearlite, further standardized at 920 to 950 ° C., and then the high pressure part and the low pressure part are heated at different temperatures. A method of obtaining a high-low pressure integrated turbine rotor having both excellent high temperature creep characteristics and toughness by quenching and then tempering the entire turbine rotor material is disclosed.

However, in recent years, further improvement in energy efficiency has been demanded, and the steam temperature introduced into the turbine tends to become higher and higher, and the amount of steam generated accompanying this tends to increase. Therefore, the characteristics required for the turbine rotor have become more severe.
Therefore, conventional low-alloy steel turbine rotors are insufficient in high-temperature mechanical properties in the high-pressure part, especially in terms of creep strength, and it has become necessary to develop materials that can be used at higher steam temperatures. .

Further, in the low pressure portion of the turbine rotor, there has been a demand for a material having a higher toughness and a higher toughness than ever before. Although using 12Cr steel, which is a high-grade material, can solve these material problems, it takes a long time to manufacture the material, so that it is not possible to meet urgent needs and there is a drawback that the cost is increased. .

Therefore, in order to construct a high-pressure and low-pressure integrated turbine of low cost and high performance in a short delivery time, an inexpensive low-alloy steel is used, and a high- and low-pressure integrated type excellent in high-temperature mechanical characteristics, particularly creep strength, in the high-pressure portion. Development of turbine rotors is desired. However, a high-low pressure integrated turbine rotor made of low alloy steel having the above characteristics has not been obtained.

[0008] Conventionally, CrMoV steel, which is a low alloy steel, has been used by quenching from a temperature of about 950 ° C. Increasing the quenching temperature suppresses the precipitation of soft pro-eutectoid ferrite phase and promotes solid solution of strengthening elements to increase the material strength, but it causes a new problem of creep embrittlement. I couldn't. Also,
Attempts have been made to suppress embrittlement by adding various alloying elements and devising heat treatment methods, but satisfactory results have not yet been obtained.

Further, when the quenching temperature is raised, there is a problem that the crystal grains are coarsened and the toughness of the material is deteriorated. From this point as well, the quenching temperature cannot be raised to 1,000 ° C. or higher. As described above, the high-temperature strength and brittleness of CrMoV steel include the difficulty that the heat treatment conditions contradict each other in manufacturing.

[0010]

Therefore, the present invention optimizes the material components and raises the quenching temperature of the high pressure portion,
A material that has higher creep rupture characteristics in the smooth creep test than the high pressure part of the conventional high / low pressure integrated rotor material, yet is less prone to creep embrittlement, and has high toughness in both the high pressure part and low pressure part that is equal to or higher than that of conventional materials. The present invention intends to provide a turbine rotor composed of this novel heat-resistant steel.

The inventors of the present invention have already made a major improvement by optimizing the material components and increasing the quenching temperature of the high-pressure portion, so that in the smooth creep test, higher creep than the high-pressure portion of the conventional high-low pressure integrated rotor material can be obtained. We have proposed a low-alloy heat-resistant steel that has fracture characteristics, is less prone to creep embrittlement, and has high toughness equivalent to or better than conventional materials in both the high-pressure and low-pressure parts. (Japanese Patent Application 2000-031002)

In the above proposal, it was found that impurities have a great influence on high temperature characteristics, especially creep embrittlement characteristics, and not only prescribed alloy blending but also phosphorus, sulfur, copper, aluminum, arsenic, tin and antimony. By suppressing harmful trace impurity elements such as such as possible, it is possible to quench from high temperatures of 980 ° C or higher, high toughness, high temperature characteristics, and low alloy heat resistant steel that is particularly resistant to creep embrittlement. The manufacturing method and a turbine rotor made of the low alloy heat resistant steel were proposed.

Further, the inventors of the present invention found that in a low alloy heat resistant steel mainly intended to be used as a high pressure turbine rotor material, there is a close relationship between creep embrittlement and crystal grain size. It was shown that creep embrittlement can be avoided by controlling the diameter within an appropriate range. (Japanese Patent Application No. 2001-61842)

By the way, in order to refine the crystal grains to a grain size within an appropriate range, it is general to take measures such as strong forging, rapid heat treatment, or repeated heat treatment. Since it is possible to perform strong forging and rapid heating for relatively small members, it is relatively easy to maintain the target crystal grains, but for large members such as turbine rotors, forging and upsetting during the material forging process. There is no other way but to repeatedly perform the heat treatment and the heat treatment, and the process takes a long time, so that the cost is inevitably increased and it is practically difficult to adopt.

The present invention has been made in view of the above circumstances, and includes the toughness of a high pressure portion, the strength characteristics and toughness of a low pressure portion, and the like.
After securing the necessary characteristics as a high-low pressure integrated rotor,
The object of the present invention is to obtain a high-strength member having excellent high-temperature characteristics even in the surface layer portion and the central portion of a large-sized material even in a high-pressure portion, in particular, creep embrittlement resistance.

[0016]

As a result of intensive studies to solve the above-mentioned problems, the inventors of the present invention have been able to avoid inclusion in the metallographic structure, which has been conventionally regarded as a factor of lowering strength and toughness. Focusing on the pro-eutectoid ferrite phase, it was found that creep embrittlement can be avoided while securing strength and toughness by positively utilizing the pro-eutectoid ferrite phase if it is a specific component system.

However, in a large member such as a turbine rotor, the cooling condition differs between the surface layer portion and the central portion, and if a cooling condition that precipitates an appropriate amount of pro-eutectoid ferrite near the surface layer portion is adopted, the central portion will be There was a problem that a larger amount of proeutectoid ferrite was deposited than necessary. Further, particularly in a material in which the quenching temperature is increased to form a solid solution with a matrix strengthening element to increase the strength, the crystal grains are likely to become coarse, and thus there is a possibility of causing creep embrittlement.

Therefore, in the heat treatment process of a material having a predetermined alloy component, the high-pressure portion is quenched from a high temperature region while controlling the cooling rate to precipitate a predetermined amount of pro-eutectoid ferrite phase, and the low-pressure portion is conventionally formed. After heating to a temperature equal to or higher than that, by cooling with a method with a large cooling effect, it has excellent creep strength in the high pressure part,
The present invention has been completed by finding that it is possible to obtain a high-low pressure integrated turbine rotor that does not particularly cause creep embrittlement and has high toughness in the low pressure portion.

In the high-low pressure integrated turbine rotor of the present invention, the portion (high-pressure portion) used for high-pressure steam is 600 ° C.
It has excellent high temperature characteristics such that the creep rupture time in the smooth creep rupture test under the condition of stress of 176 MPa is 2,500 hours or more, and the creep rupture time in the notch creep rupture test under the same condition is 5,000 hours or more. It is a thing.

The portion (low pressure portion) used in the low pressure steam of the high and low pressure integrated turbine rotor of the present invention is 0.2%.
It has excellent toughness with a yield strength of 686 MPa or more and a Charpy impact absorption energy of 98 J or more.

As described above, the turbine rotor integrated with high pressure and low pressure according to the present invention has the characteristics of both excellent creep characteristics of the high pressure portion and excellent toughness of the low pressure portion.
The present inventor has verified the above characteristics by the examples described later. The test method and test results will be described in detail in (Example).

In the method for manufacturing a turbine rotor of high pressure and low pressure integrated type according to the present invention, a turbine rotor material made of an alloy steel having a specific composition is subjected to different heat treatments in a portion corresponding to the high pressure portion and a portion corresponding to the low pressure portion. Is the way to do it. That is, the portion corresponding to the high pressure portion of the turbine rotor material is heated to 980 ° C or more and 1100 ° C or less, and the portion corresponding to the low pressure portion of the turbine rotor material is 850 ° C or more 98
After heating below 0 ° C., the part of the turbine rotor material corresponding to the high pressure part is cooled to a predetermined temperature of 900 ° C. to 700 ° C. using one or more methods of fountain cooling or blast cooling, and then After air cooling for 5 minutes to 5 hours, 300
1 out of fountain cooling, blast cooling or oil cooling up to ℃
Cooling is performed by using a method of at least one kind, and the portion corresponding to the low pressure portion of the turbine rotor material is cooled by a method capable of obtaining speed and speed higher than oil quenching.

That is, in the turbine rotor manufacturing method of the present invention, the portion corresponding to the high pressure portion of the turbine rotor material is quenched from a high temperature and tempered at a high temperature, while the portion corresponding to the low pressure portion is compared. It employs a method of quenching from a relatively low temperature and tempering at a relatively low temperature.

By subjecting the portions corresponding to the high-pressure portion and the low-pressure portion to different heat treatments, the portion corresponding to the high-pressure portion is subjected to a creep rupture time in a smooth creep rupture test under the condition of 600 ° C. and a stress of 176 MPa. Of 2,500 hours or more, and has excellent high-temperature characteristics such that the creep rupture time in the notch creep rupture test under the same conditions is 5,000 hours or more, and the low-pressure part has a resistance of 0.
The 2% proof stress can be 686 MPa or more, and the Charpy impact absorption energy can have excellent toughness of 98 J or more.

The notch creep rupture strength of the high temperature characteristics will be described. Usually, when a stress is applied to a steel material, even at a relatively low stress, at a high temperature, plastic deformation is caused, but at a very gradual time, a plastic deformation is exhibited, and elongation is rapidly progressed. This phenomenon is the creep phenomenon (creep rupture phenomenon). This creep phenomenon is considered to be due to viscous flow at the grain boundaries and movement of dislocations within the crystal. In the high temperature creep rupture test, a constant static load is applied to a material for a long time at high temperature to measure the time until the material breaks. A round bar having a constant cross-sectional area is used as the test piece, and the measuring method is specified in JIS Z-2272. The JIS stipulates a smooth creep rupture test, and the test piece used is one that has been smoothly shaved and finished between the measurement points of the measurement portion.

On the other hand, in the notch creep rupture test,
Use test pieces with notches between the scores. The cross-sectional area of the measurement portion to be pulled (cross-sectional area of the notch bottom) is the same as in the smooth creep rupture test, and the stress is determined.
The diameter of the parallel part of the test piece (corresponding to the score of the test piece used for the smoothness test) is 1.2 times the diameter of the notch bottom, the notch has an opening angle of 60 °, and the radius of curvature of the notch bottom is 0.
It is 13 mm, and is cut perpendicular to the pulling direction. In the above-mentioned smooth creep rupture test, when tensile stress is applied, the distance between the gauge points gradually expands, and the distance between the gauge points becomes narrow, and eventually the fracture occurs. On the other hand, in the notch creep rupture test in which a notch is provided in the test piece, when the test piece is pulled, the stress that does not deform the notch works to surround the notch (so-called multiaxial stress), Fracture occurs without exhibiting an elongation phenomenon.

Generally, in a material having high ductility, the time until fracture occurs because the deformation is restrained by the notch becomes longer than that in the smooth creep rupture test, but depending on the type of steel, the embrittlement of the material gradually occurs during the creep rupture test. Then, the phenomenon in which cracks occur due to the generation of voids and their connection is accelerated, and some cause creep rupture. In this case, the notch creep rupture test causes the test piece to rupture in a shorter time than the smooth creep rupture test. Such a phenomenon is called notch weakening and can be used as an index showing creep embrittlement. That is, it is possible to clearly show the degree of creep embrittlement by performing a smooth creep rupture test and a notch creep rupture test under the same stress and temperature conditions and comparing the creep rupture times of both.

Since the turbine rotor is exposed to a high temperature for a long time in a stressed state during its operation, the deterioration of material strength over time becomes a problem. Conventionally, the quality of the material used for the turbine rotor has been evaluated only by the smooth high temperature creep rupture test stipulated in JIS, but the present inventors conducted a notch high temperature creep rupture test to obtain the high temperature strength characteristics of the material, In particular, a means for evaluating creep embrittlement characteristics has been found. By this means, for the turbine rotor material of the predetermined component, a comparative evaluation of the metal structure of the high-pressure part is a bainite single phase similar to the conventional material, and a composite structure of bainite phase mixed proeutectoid ferrite phase. It was clarified that creep embrittlement is suppressed in a material containing more than 10% and not more than 40% by volume of pro-eutectoid ferrite phase.

However, when cooling by the conventional method is adopted at the time of heat treatment of the high-pressure portion, a predetermined amount of pro-eutectoid ferrite phase should be precipitated at the central portion (diametrical central portion) of the turbine rotor material, where the cooling rate becomes slow. However, the proeutectoid ferrite phase is hard to precipitate in the surface layer because of the high cooling rate. Therefore, the present inventor has conducted extensive studies to solve this problem, and as a result, in cooling the high-pressure portion,
After cooling to 900 ° C. to 700 ° C. by using fountain cooling and / or blast cooling as a cooling means, then air cooling for 5 minutes to 5 hours, and then to 300 ° C. fountain cooling or blast cooling or oil By cooling using one or more types of cooling means, an appropriate amount of pro-eutectoid ferrite phase is precipitated at each position of the high pressure part of the large turbine rotor material (excluding the surface layer part to be finally cut). Made it possible.

In a part of the component system of the present invention, since the turbine rotor has a large diameter, the cooling rate becomes particularly slower than that of the high pressure portion. In some cases, 30% or less of ferrite phase was precipitated. However, both 0.2% proof stress and impact characteristics exceed the target values for the turbine rotor, and if the ferrite phase is 30% or less in volume%,
It was also clarified that there is substantially no problem as a material forming the low-pressure portion of the turbine rotor.

Based on the above research, the present invention has the following configurations.

That is, the invention described in claim 1 is a high-low pressure integrated turbine rotor in which a high-pressure portion and a low-pressure portion are integrally formed, and carbon: 0.20 to 0.35 in% by weight.
%, Silicon: 0.15% or less, manganese: 0.05 to 1.
0%, nickel: more than 0.3 % to 2.5%, chromium: 1.
0-3.0%, molybdenum: 0.5-1.5%, tungsten: 0.1-3.0%, vanadium: 0.1-0.
Contains 3%, phosphorus: 0.012% or less, sulfur: 0.005
% Or less, copper: 0.15% or less, aluminum: 0.01
% Or less, arsenic: 0.01% or less, tin: 0.01% or less,
Antimony: 0.003% or less, the balance of which is composed of iron containing unavoidable impurities, and the metal structure of the high-pressure part is a pro-eutectoid ferrite phase of more than 10% and 40% or less in volume%. It is a high-low pressure integrated turbine rotor characterized by comprising the balance bainite phase. With the above alloy composition
The nickel content exceeds 0.3% and 2.5%
The range is as follows.

The alloy used in the high and low pressure turbine rotor of the present invention is obtained by adding W to the conventional low alloy heat resistant steel for high and low pressure integrated rotors to improve the high temperature strength of the high pressure portion.
Here, when the improvement of the creep strength in the high temperature part is important, the content of tungsten is increased, and when the improvement of the toughness in the low temperature part is important, the content of tungsten is preferably small. And, the metallographic structure of the high pressure part is volume%
Is controlled so as to consist of more than 10% and not more than 40% of proeutectoid ferrite phase and the balance of bainite phase, thereby avoiding creep embrittlement in the high pressure part.

Next, the present invention is a high / low pressure integrated turbine rotor in which a high pressure portion and a low pressure portion are integrally formed, wherein carbon: 0.20 to 0.35% by weight, silicon: 0. 15%
Hereinafter, manganese: 0.05 to 1.0%, nickel: 0.
05-2.5%, chromium: 1.0-3.0%, molybdenum: 0.5-1.5%, tungsten: 0.1-3.0
%, Vanadium: 0.1 to 0.3%, cobalt: 0.1
.About.3.0%, phosphorus: 0.012% or less, sulfur: 0.
005% or less, copper: 0.15% or less, aluminum:
0.01% or less, arsenic: 0.01% or less, tin: 0.01
% Or less, antimony: 0.003% or less, the balance of which is composed of iron containing unavoidable impurities, and the metallographic structure of the high-pressure portion is more than 10% and 40% or less in volume% providing high and low pressure integrated type turbine rotor, comprising the bainite phase of the ferrite phase and the balance.

The alloy used in the turbine rotor described above is based on the above alloy with cobalt added to enhance high temperature strength and toughness. When importance is attached to the creep strength of the high-pressure portion, it is preferable to reduce the amount of nickel and the amount of manganese, but by adding cobalt in that amount, the balance of heat treatment characteristics and material characteristics can be maintained. This alloy is also controlled so that the metal structure of the high pressure part is composed of more than 10% and less than 40% by volume of proeutectoid ferrite phase and the balance of bainite phase, thereby avoiding creep embrittlement of the high pressure part. .

Next, a second aspect of the present invention is a high-low pressure integrated turbine rotor in which a high-pressure portion and a low-pressure portion are integrally formed, wherein carbon is 0.20 to 0.35% by weight. , Silicon: 0.15% or less, manganese: 0.05 to 1.0%,
Nickel: over 0.3 % to 2.5%, chromium: 1.0 to
3.0%, molybdenum: 0.5 to 1.5%, tungsten: 0.1 to 3.0%, vanadium: 0.1 to 0.3%
In addition, niobium: 0.01 to 0.15%, tantalum: 0.01 to 0.15%, nitrogen: 0.001 to 0.0
5%, boron: 0.001 to 0.015%, and at least one selected from phosphorus, 0.012% or less,
Sulfur: 0.005% or less, Copper: 0.15% or less, Aluminum: 0.01% or less, Arsenic: 0.01% or less, Tin:
0.01% or less, antimony: 0.003% or less, the balance being a composition consisting of iron containing unavoidable impurities, and the metallographic structure of the high-pressure portion exceeds 10% by volume% and 4
It is a high-low pressure integrated turbine rotor characterized by comprising 0% or less of proeutectoid ferrite phase and the balance of bainite phase. In the above alloy composition, the nickel content is 0.3
% To 2.5% or less.

The alloy used in the turbine rotor according to claim 2 aims to improve the creep strength in the high temperature portion, and the alloy used in the turbine rotor according to claim 1 further includes niobium, tantalum and nitrogen. , Or at least one of boron is added as a trace element to further improve the smooth creep property, and the metal structure of the high-pressure part is more than 10% by volume and 40% or less of the pro-eutectoid ferrite phase and the balance. To prevent creep embrittlement by controlling so that it consists of the bainite phase.

Next, the present invention is a high / low pressure integrated turbine rotor in which a high pressure portion and a low pressure portion are integrally formed, wherein carbon: 0.20 to 0.35% by weight and silicon: 0. 15%
Hereinafter, manganese: 0.05 to 1.0%, nickel: 0.
05-2.5%, chromium: 1.0-3.0%, molybdenum: 0.5-1.5%, tungsten: 0.1-3.0
%, Vanadium: 0.1 to 0.3%, cobalt: 0.1
To 3.0%, and further niobium: 0.01 to 0.15
%, Tantalum: 0.01 to 0.15%, nitrogen: 0.00
1 to 0.05%, boron: 0.001 to 0.015%, and at least one selected from phosphorus: 0.01
2% or less, sulfur: 0.005% or less, copper: 0.15% or less, aluminum: 0.01% or less, arsenic: 0.01%
Below, tin: 0.01% or less, antimony: 0.003%
It has the following composition, the balance of which is composed of iron containing unavoidable impurities, and the metal structure of the high-pressure portion is 10% by volume.
Providing high and low pressure integrated type turbine rotor, comprising the pro-eutectoid ferrite phase and the balance of bainite phase 40% or less than the.

The alloy used in the turbine rotor described above is the alloy of the turbine rotor described above in addition to at least one of niobium, tantalum, nitrogen, or boron.
This is to improve the creep strength in the high temperature part by adding a trace element of seeds. In particular, in addition to further improving the smooth creep characteristics, the metal structure of the high pressure part exceeds 10% by volume% and 40% or less. The creep embrittlement is avoided by controlling the proeutectoid ferrite phase and the balance of the bainite phase.

The invention according to claim 3 of the present invention is as follows.
In high-low pressure integrated type turbine rotor according to any preceding, wherein the average particle size of 0.5μm or less of carbon-nitride pro-eutectoid ferrite phase is characterized in that it is finely dispersed.

Next, the turbine rotor of the present invention is characterized in that the grain size number of the metal structure of the high-pressure portion is 3 or more and 6 or less.

The high-pressure portion of the high-low pressure integrated turbine rotor of the present invention has both high temperature creep characteristics, particularly excellent notch creep characteristics and excellent toughness. That is, the creep rupture time in the smooth creep rupture test under the condition of 600 ° C. and the stress of 176 MPa is 2,500 hours or more (conventional material: 2,000 hours or less), and the creep in the notch creep rupture test under the same conditions. It has excellent high temperature characteristics with a breaking time of 5,000 hours or more.

Further, the high temperature creep property is a material judged by using the creep rupture time ratio in order to prevent creep embrittlement in addition to the length of the smooth creep rupture time. That is, the creep rupture time ratio, which is indicated by the ratio of the creep rupture time in the notch creep rupture test and the creep rupture time in the smooth creep rupture test, is at least 2.0 or more, preferably 2.5 or more in the high pressure part, More preferably, it is 3.0 or more.

Further, the portion used in the low pressure steam of the turbine rotor of the high and low pressure integrated type according to the present invention has a 0.2% proof stress of 68.
It has an excellent toughness of 6 MPa or more and a Charpy impact absorption energy of 98 J or more.

As described above, the high-low pressure integrated turbine rotor having both excellent creep strength and toughness is
It was first introduced by the present invention.

Next, the method for manufacturing a turbine rotor according to the present invention is a method for manufacturing a high-low pressure integrated turbine rotor in which a high pressure portion and a low pressure portion are integrally formed, and has a predetermined composition. The part corresponding to the high pressure part of the turbine rotor material is 980
After heating to 850 ° C. or more and 1100 ° C. or less and heating the portion corresponding to the low pressure portion of the turbine rotor material to 850 ° C. or more and less than 980 ° C., the portion corresponding to the high pressure portion of the turbine rotor material is 900 ° C. to 700 ° C. Up to a predetermined temperature of at least one of fountain cooling or blast cooling, followed by air cooling for 5 minutes to 5 hours, and then 300
1 out of fountain cooling, blast cooling or oil cooling up to ℃
This is a manufacturing method in which cooling is performed by at least one kind of cooling means, and the portion corresponding to the low pressure portion of the turbine rotor material is cooled by the cooling means that can obtain a speed higher than oil quenching.

The method of manufacturing the turbine rotor of the present invention is
High and low pressure integrated turbine in which the pressure part and the low pressure part are integrally formed
When manufacturing a rotor,
The part corresponding to the high pressure part of the bin rotor material is 980 ℃ or more
Low temperature of the turbine rotor material by heating below 1100 ℃
The part corresponding to the part is heated above 850 ° C and below 980 ° C
After that, the part corresponding to the high pressure part of the turbine rotor material
Cooling the fountain from 900 ℃ to a predetermined temperature of 700 ℃
Alternatively, cooling is performed by one or more cooling means among blast cooling.
And then air cool for 5 minutes to 5 hours, then to 300 ° C
One or more of fountain cooling, blast cooling or oil cooling
Of the turbine rotor material
In the part corresponding to the low pressure part, the speed faster than oil quenching can be obtained.
High and low pressure integrated turbine rotor cooled by cooling means
A method of manufacturing the turbine rotor materials, carbon in weight percent: 0.20 to 0.35%, silicon: 0.15% or less, Mn: 0.05% to 1.0%, nickel: 0. Three
% To 2.5%, chromium: 1.0 to 3.0%, molybdenum: 0.5 to 1.5%, tungsten: 0.1 to 3.0.
%, Vanadium: 0.1-0.3%, phosphorus: 0.0
12% or less, sulfur: 0.005% or less, copper: 0.15%
Hereinafter, aluminum: 0.01% or less, arsenic: 0.01
% Or less, tin: 0.01% or less, antimony: 0.003
% Or less, and the balance is an alloy steel having a composition consisting of iron containing unavoidable impurities. With the above alloy composition
The nickel content exceeds 0.3% and 2.5%
The range is as follows.

Next, the present invention provides a method of manufacturing a high-low pressure integrated type turbine rotor described previously, the turbine rotor materials, carbon in weight percent: from 0.20 to 0.35%, silicon: 0.15 % Or less, manganese: 0.05 to 1.0%,
Nickel: 0.05 to 2.5%, chromium: 1.0 to 3.
0%, molybdenum: 0.5 to 1.5%, tungsten:
0.1-3.0%, vanadium: 0.1-0.3%, cobalt: 0.1-3.0%, phosphorus: 0.012% or less, sulfur: 0.005% or less, copper : 0.15% or less, Aluminum: 0.01% or less, Arsenic: 0.01% or less,
A method for manufacturing a high-low pressure integrated turbine rotor, characterized in that an alloy steel having a composition of tin: 0.01% or less, antimony: 0.003% or less, and the balance being iron containing unavoidable impurities. To provide .

Next, a method of manufacturing a turbine rotor according to the present invention comprises a high pressure / low pressure integrated type in which a high pressure portion and a low pressure portion are integrally formed.
It has a specified composition when manufacturing a turbine rotor.
980 as the high pressure part of the turbine rotor material
The turbine rotor material is heated to a temperature between ℃ and 1100 ℃
The part corresponding to the low pressure part of 850 ℃ or more and less than 980 ℃
After heating, it corresponds to the high pressure part of the turbine rotor material.
The part to be sprayed from 900 ℃ to a predetermined temperature of 700 ℃.
By one or more cooling means of water cooling or wind cooling
And then air-cooling for 5 to 5 hours, then 300
1 out of fountain cooling, blast cooling or oil cooling up to ℃
The turbine rotor is cooled by one or more cooling means.
The part corresponding to the low pressure part of the material is faster than oil quenching.
High and low pressure integrated turbine cooled by the obtained cooling means
A method of manufacturing a rotor, wherein the turbine rotor material is carbon: 0.20 to 0.35% by weight and silicon: 0.
15% or less, manganese: 0.05 to 1.0%, nickel: more than 0.3 % to 2.5%, chromium: 1.0 to 3.0
%, Molybdenum: 0.5 to 1.5%, tungsten:
0.1-3.0%, vanadium: 0.1-0.3%, niobium: 0.01-0.15%, tantalum:
0.01-0.15%, nitrogen: 0.001-0.05
%, Boron: contains 0.001 to 0.015%, and phosphorus: 0.012% or less, sulfur: 0.005% or less, copper: 0.15% or less, aluminum : 0.01% or less, arsenic: 0.01% or less, tin:
A method for producing a high-low pressure integrated turbine rotor, comprising: an alloy steel having a composition of 0.01% or less, antimony: 0.003% or less, and the balance being iron containing unavoidable impurities. . In the above alloy composition,
Kell content is in the range of more than 0.3% and less than 2.5%
is there.

Next, the present invention provides the high-low pressure integrated turbine rotor manufacturing method described above, wherein the turbine rotor material is carbon: 0.20 to 0.35% by weight and silicon: 0.15 by weight. % Or less, manganese: 0.05 to 1.0%,
Nickel: 0.05 to 2.5%, chromium: 1.0 to 3.
0%, molybdenum: 0.5 to 1.5%, tungsten:
0.1 to 3.0%, vanadium: 0.1 to 0.3%, cobalt: 0.1 to 3.0%, and niobium: 0.
01-0.15%, tantalum: 0.01-0.15%,
Nitrogen: 0.001-0.05%, Boron: 0.001-
Containing at least one selected from 0.015%, phosphorus: 0.012% or less, sulfur: 0.005% or less,
Copper: 0.15% or less, Aluminum: 0.01% or less,
Arsenic: 0.01% or less, tin: 0.01% or less, antimony: 0.003% or less, and a balance characterized by being an alloy steel having a composition of iron containing unavoidable impurities. A method for manufacturing a low-pressure integrated turbine rotor is provided.
It

The reason why the portion corresponding to the high pressure portion of the turbine rotor is heated to a high temperature is to sufficiently melt the alloying elements. On the other hand, the reason why the low pressure part of the turbine rotor is heated to a temperature lower than that of the high pressure part is to make the crystal grains fine and increase the toughness.

According to the method for manufacturing a high-low pressure integrated turbine rotor, by cooling the turbine rotor material as described above, the portion corresponding to the high-pressure portion of the turbine rotor material becomes 10% by volume in the bainite phase. Controlled to a metallographic structure containing more than 40% of proeutectoid ferrite phase, the part corresponding to the low pressure part of the turbine rotor material contains bainite single phase or bainite phase containing 30% or less of proeutectoid ferrite phase by volume. Controlled by. Then, after cooling, the parts corresponding to the high-pressure part and the low-pressure part are reheated and held (tempering process) at predetermined temperatures set, respectively, and adjusted to obtain predetermined material characteristics. Later, it is used as a material for a high-pressure integrated turbine rotor.

[0053]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to the following embodiments. First, the reason for limiting each component range in the alloy used in the present invention will be described.

Carbon (C): Carbon has the effects of ensuring hardenability during heat treatment and enhancing material strength. It also forms carbides and / or carbonitrides and contributes to the improvement of creep rupture strength at high temperatures. In this alloy system, the material strength is not sufficient if the content is less than 0.20%, so the lower limit is made 0.20%. On the other hand, if the carbon content is too high, the toughness decreases, and during use at high temperature, the carbides and / or carbonitrides agglomerate and coarsen, causing a decrease in creep rupture strength and creep embrittlement. Therefore, the upper limit of the carbon content is 0.35%. A particularly preferable range is 0.22 to have both material strength and toughness.
It is 0.30%.

Silicon (Si): Silicon has an effect as a deoxidizing material, but on the other hand, it embrittles the base material. Since silicon comes from steelmaking raw materials, in order to make silicon extremely low, it is necessary to select raw materials carefully, resulting in high cost.
Content up to 0.15% is acceptable. The preferred range is 0.
It is 10% or less.

Manganese (Mn): Manganese acts as a deoxidizer and has an effect of preventing hot cracking during forging. It also has the effect of enhancing the hardenability during heat treatment.
However, as the manganese content increases, the creep rupture strength deteriorates, so the maximum amount was made 1.0%. However, in order to suppress the manganese content to less than 0.05%, careful selection of raw materials and an excessive refining process are required, resulting in high cost, so the minimum amount is made 0.05%. Therefore, the range of manganese content is 0.05 to 1.0%, preferably 0.1%.
5 to 0.9%.

Nickel (Ni): Nickel enhances the hardenability during heat treatment and improves the tensile strength and proof stress.
In particular, it has the effect of increasing toughness. If the content is less than 0.3%, the effect is not recognized. On the other hand, however, the long-term creep rupture strength decreases with the addition of nickel. In the alloy used for the turbine rotor of the present invention, the hardenability and toughness are not expected to be improved by the addition of nickel, and conversely, in order to eliminate the adverse effect of nickel on the long-term creep rupture strength, the upper limit of the nickel content is set to 2 It was decided to keep it below 0.5%.

Chromium (Cr): Chromium enhances the hardenability during heat treatment, forms carbides and / or carbonitrides, contributes to the improvement of creep rupture strength, and dissolves in the matrix to improve the oxidation resistance. To do. It also has the effect of strengthening the matrix itself and improving creep rupture strength. If the chromium content is less than 1.0%, the effect is not sufficient, and if the chromium content exceeds 3.0%, the creep rupture strength is rather lowered. Therefore, the content range of chromium is 1.0 to 3.0%, preferably 2.0 to 2.5.
%.

Molybdenum (Mo): Molybdenum has the effects of enhancing the hardenability during heat treatment and improving the creep rupture strength by forming a solid solution in the matrix or in the carbide and / or carbonitride. If the content is less than 0.5%, the effect is not sufficiently observed, and if the content exceeds 1.5%, the toughness is rather lowered and the cost becomes high. Therefore, the content of molybdenum is set to 0.5 to 1.5%, preferably 0.9 to 1.3%.

Vanadium (V): Vanadium has the effect of enhancing the hardenability during heat treatment and forming a carbide and / or carbonitride to improve the creep rupture strength.
If the content is less than 0.1%, a sufficient effect cannot be obtained. Further, if the content exceeds 0.3%, the creep rupture strength rather decreases. Therefore, the content of vanadium is set to 0.1 to 0.3%, preferably 0.21 to 0.28%.

Tungsten (W): Tungsten forms a solid solution in the matrix or in the carbide and has the effect of improving the creep rupture strength. If the content is less than 0.1%, a sufficient effect cannot be obtained. If the content exceeds 3.0%, segregation may occur, and a ferrite phase is likely to appear, resulting in a decrease in strength. Therefore, when tungsten is used, its content is suitably 0.1 to 3.0%.

Cobalt (Co): Like nickel, cobalt enhances the hardenability during heat treatment, improves tensile strength and proof stress, and particularly has the effect of enhancing toughness. Also, unlike nickel, addition of 3.0% or less does not adversely affect the creep strength characteristics. Therefore, it is effective in balancing mechanical strength, creep strength and toughness. If the amount of cobalt added is less than 0.1%, no effect is exhibited, and if it exceeds 3.0%, the precipitation of carbides is promoted and the creep characteristics deteriorate. Therefore, the allowable content range of cobalt is 0.1% to 3.0%. It is more preferably 0.5 to 2.2%.

Niobium (Nb): Niobium enhances hardenability and forms carbides and / or carbonitrides to improve creep rupture strength. Further, it has an effect of suppressing the growth of crystal grains at the time of heating at high temperature and contributing to homogenization of the structure. If the addition amount is less than 0.01%, the effect is not recognized, and if it exceeds 0.15%, significant segregation occurs during solidification of the steel ingot, or toughness is significantly reduced. Therefore, the allowable content of niobium is set to 0.01% to 0.15%. Preferably it is 0.05 to 0.10% of range.

Tantalum (Ta): Tantalum, like niobium, has the effects of enhancing hardenability and forming carbides and / or carbonitrides to improve creep rupture strength. If the addition amount is less than 0.01%, the above effect is not observed, and if it exceeds 0.15%, significant segregation occurs during solidification of the steel ingot, or toughness is significantly reduced. Therefore, the allowable content of tantalum is 0.01% to 0.15%.
And It is preferably in the range of 0.05 to 0.1%.

Nitrogen (N): Nitrogen has the effect of forming a carbonitride by combining with carbon and an alloying element to contribute to the improvement of creep rupture strength. The addition amount is 0.001
If it is less than 0.1%, the above effect is not observed because carbonitride cannot be generated, and if it exceeds 0.05%, the carbonitride aggregates and coarsens for a long time, so that sufficient creep strength can be obtained. Absent. Therefore, the allowable content of nitrogen is 0.00
It was set to 1% to 0.05%. Preferably 0.005 to 0.
It is in the range of 01%.

Boron (B): Boron has the effects of enhancing the hardenability and the grain boundary strength to contribute to the improvement of creep rupture strength. If the addition amount is less than 0.001%, the above effect is not observed, and if it exceeds 0.015%, the hardenability is rather deteriorated. Therefore, the allowable content of boron is set to 0.001% to 0.015%. Preferably it is 0.003 to 0.010% of range.

Next, phosphorus, sulfur, copper, which are harmful impurities,
Aluminum, arsenic, tin and antimony will be described. It is arguable that lower levels of these impurities are preferable for the mechanical properties of steel. However, it is generally only phosphorus and sulfur that are inevitably introduced from steel-making raw materials that have an allowable content limit as impurities in steel materials. Since phosphorus and sulfur make the steel material brittle, the allowable amount is set for most steel types, but it is set at a considerably high level due to the difficulty of refining.

The inventors have used CrMo for turbine rotors.
As a result of diligent research aimed at improving the high temperature characteristics of V steel, especially the notch creep rupture strength, it was found that trace impurities have a great influence on the notch creep rupture strength. Further, it was found that not only phosphorus and sulfur but also copper, aluminum, arsenic, tin, antimony, and the like are adversely affected as the trace impurities. Until now, it was only recognized that trace impurities should be vaguely low, and the specific allowable amount has not been clarified. However, the present inventors have examined these impurities in detail, and found that the temperature is 600 ° C. Stress 178 MPa
Rupture time in the notch creep rupture test under the conditions
With the goal of 000 hours or more, it was decided to specifically show the allowable amounts of these contents.

Phosphorus (P), Sulfur (S): Both phosphorus and sulfur are impurities brought from the steelmaking raw material, and are harmful impurities that form phosphide or sulfide in the steel material and significantly reduce the toughness of the steel material. Is. The research conducted by the present inventors has revealed that the high temperature characteristics are also adversely affected. Phosphorus easily segregates, and secondarily causes carbon segregation to embrittle the material. In particular, it has been found that embrittlement is greatly affected when high stress is applied for a long time at high temperature.

Since the burden on the steel making process is increased when the content of phosphorus or sulfur is extremely reduced, the breaking time in the notch creep rupture test under the conditions of temperature: 600 ° C. and stress of 178 MPa is targeted for a breaking time of 5,000 hours or more. As a result of obtaining the upper limits, the upper limit of the content of phosphorus was 0.012%, and the upper limit of sulfur was 0.005%. More preferably, phosphorus is 0.010% or less and sulfur is 0.002% or less.

Copper (Cu): Copper diffuses along the crystal grain boundaries in the steel material to embrittle the material. In particular, it deteriorates the high temperature characteristics. From the result of the notch creep rupture test, the upper limit of the copper content was 0.15%. It is more preferably 0.04% or less.

Aluminum (Al): Aluminum is mainly brought from the deoxidizing material in the steel making process, and forms oxide-based inclusions in the steel material to embrittle the material. From the result of the notch creep rupture test, the upper limit of the content of aluminum was set to 0.01%. It is more preferably 0.005% or less.

Arsenic (As), Tin (Sn), Antimony (Sb): Arsenic, tin and antimony are often mixed from the steelmaking raw material, and both are precipitated along the grain boundaries of the crystals to reduce the toughness of the material. It is a thing. In particular, when these elements are heated to a high temperature, the agglomeration at the grain boundaries becomes remarkable, and the alloy rapidly becomes brittle. From the results of the notch creep rupture test, the upper limits of the content of these impurities are 0.01% for arsenic and 0.1% for tin.
01% and antimony were 0.003%. More preferably, arsenic is 0.007% or less, tin is 0.007% or less,
Antimony is 0.0015% or less.

(Manufacturing Method of High-Low Pressure Integrated Turbine Rotor) Next, a manufacturing method of the high-low pressure integrated turbine rotor of the present invention will be described.

In the method of manufacturing the high-low pressure integrated turbine rotor according to the present invention, as described above, the base material is first melted so as to have a predetermined alloy composition. The method for reducing the trace impurities is not particularly limited, and any known refining method including careful selection of raw materials can be used.

Next, a molten alloy having a predetermined composition is cast into a steel ingot by a known method, and subjected to a predetermined forging / forming process to obtain a turbine rotor material.

Next, the turbine rotor material is heat-treated in two sections, that is, the portion corresponding to the high pressure portion and the portion corresponding to the low pressure portion of the turbine rotor. In order to perform the heat treatment in the two sections, a heat-resistant partition is provided between the spaces in which the respective parts of the heat treatment furnace are housed, the inside of the heat treatment furnace is divided into two chambers, and each chamber is independently heated. It can be achieved by controlling.

The turbine rotor material is housed in the heat treatment furnace constructed as described above, and the portion corresponding to the high pressure portion is 9
Heat to a temperature of 80 ° C. or higher and 1100 ° C. or lower. Further, the portion corresponding to the low pressure portion is heated to a temperature of 850 ° C or higher and lower than 980 ° C. If the high pressure part is not heated to 980 ° C or higher, the high temperature creep strength will be insufficient, and if the heating temperature exceeds 1100 ° C, the facility will be restricted and the cost will be reduced and the toughness will be reduced. The heating temperature range of the portion to be heated was 980 ° C or higher and 1100 ° C or lower. If the low-pressure portion is not heated to 850 ° C or higher, solid solution of carbide does not proceed, resulting in insufficient strength and toughness, and if heated to 980 ° C or higher, the crystal grains become coarse and toughness is reduced. The heating temperature range for the part is 850 ° C or higher and 980
The temperature was set to ℃ or below.

Next, the portion corresponding to the high pressure portion of the turbine rotor material heated to the above temperature range is from 900 ° C to 7 ° C.
The water is cooled to a predetermined temperature of 00 ° C using one or more cooling means of fountain cooling or blast cooling, and then air-cooled for 5 minutes to 5 hours, and then cooled to 300 ° C with fountain cooling or blast cooling or Among the oil cooling, at least one cooling means is used for cooling, and a portion corresponding to a low pressure portion of the turbine rotor material is cooled by a cooling means capable of obtaining a speed higher than oil quenching. Examples of the cooling means capable of cooling at a speed higher than the oil quenching include oil cooling, water cooling, and fountain cooling.

The temperature control in the heat treatment method of the present invention is supposed to be carried out at a position corresponding to the outermost surface layer portion in the product shape of the final product. Since the turbine rotor material at the time of heat treatment has a surplus of approximately 30 to 200 mm, the temperature is controlled at the position which is the outermost layer of the product excluding the surplus. In temperature control, a method of directly measuring the temperature at the control position, a method of managing the temperature at another position by grasping the correspondence relationship between the control position and another location of the turbine rotor material in advance, and obtaining in advance It is possible to freely select the method of managing the discharge amount / discharge speed of the cooling medium, the discharge time, etc. based on the existing data and the heat calculation simulation.

Controlling the cooling pattern in this way is
This is to precipitate the proeutectoid ferrite phase in an amount within the proper range. Depending on the amount of various alloy components within the scope of the present invention and the size of the turbine rotor material, the temperature at which air cooling is started, the time for air cooling, and the cooling rate before and after that are appropriately combined within the range specified by the present invention. As a result, a target amount of pro-eutectoid ferrite phase can be obtained.

Then, the rotor material that has been subjected to the above-mentioned quenching treatment is subjected to tempering to adjust the crystal structure and to adjust its mechanical properties. This tempering treatment has a 0.2% proof stress value of 58 in the portion corresponding to the high pressure portion.
Aiming to obtain the characteristics of 8 to 686 MPa, the value of 0.2% proof stress is 686 to
The goal is to obtain a characteristic of 784 MPa. Specifically, 600 ° C to 750 ° C for the portion corresponding to the high pressure portion.
It is preferable that tempering is performed at a temperature of ℃ and tempering is performed at a temperature of 550 ° C to 700 ° C for a portion corresponding to the low pressure portion.

The tempering treatment is not limited to once, but is not limited to two.
You may repeat it more than once. By performing such a series of heat treatments, it is possible to obtain a high-low pressure integrated turbine rotor in which the portions corresponding to the high pressure portion and the low pressure portion each have predetermined mechanical characteristics.

Next, the microstructure of the high-low pressure integrated turbine rotor of the present invention will be described with reference to FIG. Figure 1
FIG. 4 is a view showing a microscope image of a high pressure portion of a turbine rotor according to the present invention.

The microstructure of the high- and low-pressure integrated turbine rotor of the present invention, which has been subjected to the heat treatment as described above, is such that the high-pressure portion has a bainite phase containing proeutectoid ferrite phase of more than 10% and less than 40% by volume. The low-pressure portion is controlled to a bainite single phase or a bainite phase containing a pro-eutectoid ferrite phase of 30% or less in volume%. Moreover, since the alloy of the present invention has good hardenability, the pro-eutectoid ferrite phase precipitates at a temperature lower than that of ordinary steel and is more finely dispersed than the ordinary pro-eutectoid ferrite phase.

Further, since it contains a large amount of carbon / nitride forming elements such as tungsten and molybdenum, when the pro-eutectoid ferrite phase is tempered, it has an average grain size of 0.5 μm or less as shown in FIG. Fine carbon / nitride finely precipitates in the pro-eutectoid ferrite phase. Generally, the pro-eutectoid ferrite phase is soft, and if it is precipitated in a large amount, 0.2% proof stress and creep rupture strength will be reduced. However, in the turbine rotor according to the present invention, since carbon / nitride is finely dispersed in this pro-eutectoid ferrite phase, it has strength properties comparable to those of the bainite phase. This is a major feature of the turbine rotor according to the present invention. In addition,
The proportion of the ferrite phase in the microstructure can be determined by a commonly used image analyzer.

On the other hand, the precipitation of the above-described pro-eutectoid ferrite phase makes the metal structure of the turbine rotor finer than the original austenite crystal grain size, which is a major factor in suppressing creep embrittlement. Has become. In the present invention, the crystal grains are finer than the crystal grains of the original austenite, and proeutectoid ferrite grains and bainite grains (the size thereof corresponds to the size of the austenite grains at the time when the proeutectoid ferrite is completely deposited). It is preferable that the average size of () is 3 to 6 in terms of grain size number. If the grain size number is less than 3, there is a risk of creep embrittlement due to excessively coarse grains. Further, if the grain size number exceeds 6, the fine grain becomes too fine and the high temperature strength may be lowered. Therefore, a suitable crystal grain size is in the range of 3 to 6 in the grain size number, and more preferably in the range of 3.2 to 4.5.

The term "grains" as used herein means that the boundaries between the bainite phase and the pro-eutectoid ferrite phase, the boundaries between the pro-eutectoid ferrite phases, and the boundaries between the prior austenite grains transformed into the bainite phase are defined as the crystal grain boundaries. The area surrounded by the crystal grain boundaries.

Here, a method for measuring the crystal grain size of the crystal grains will be described. For the grain size measurement method, see JI
SG 0551 (1998) stipulates “method for testing austenite grain size of steel” and JIS G 0552 (1998) stipulates “method for testing ferrite grain size of steel”. The low alloy heat resistant steel of the present invention is quenched from a high temperature in the austenite stable region to precipitate a pro-eutectoid ferrite phase and present a metal structure in which a ferrite phase and a bainite phase are mixed. Therefore, in the present invention, it is rational to define the crystal grain size for the composite structure in which the ferrite phase and the bainite phase are mixed. As defined above, the boundary between the bainite phase and the pro-eutectoid ferrite phase, the boundary between the pro-eutectoid ferrite phases,
The boundaries between the former austenite grains transformed into the bainite phase are defined as grain boundaries, and the size of the portion surrounded by these grain boundaries is defined as the grain size. Grain size is measured according to JIS G 05
52 (1998) "Mixed grain case" specified in "Steel ferrite grain size test method" shall be applied. That is, the crystal grains appearing on the corroded surface of the test piece are photographed in a micrograph and determined by using the determination method based on the intersecting line segment (particle size). The smaller the grain size number, the larger the grain size.

[0090]

The present invention will be described in more detail with reference to the following examples, but the following examples do not limit the content of the present invention.

Example 1 In order to study the effects of heat treatment conditions, the amount of pro-eutectoid ferrite phase and the grain size on the material properties of the high pressure part of the turbine rotor, an alloy material having an alloy number 1 shown in Table 1 was used. After various heat treatments,
2% proof stress, Charpy impact absorption energy and 600 ° C
The creep rupture time at -176 MPa was measured for the smooth sample and the notched sample, and the creep rupture time ratio was calculated based on the measured value.

Table 2 shows the quenching temperature and cooling method for each sample. The results of the above measurements are shown in Table 3.
In each test of this example, a turbine rotor material having a barrel diameter of 1200 mm (corresponding to the high-pressure portion) is assumed, and the heat treatment is performed at the center portion (diameter direction) of the turbine rotor high-pressure portion when each is cooled. The position of the center) was simulated.

As shown in Tables 2 and 3, comparing sample No. 1A (comparative material), sample No. 1B, and sample No. 1D in which the heat treatment conditions other than the quenching temperature were aligned, the quenching temperature was 95.
The sample at 0 ° C (Sample No. 1A) does not meet the target values for both smooth creep strength and notch creep strength, whereas the sample for which the quenching temperature was raised to 980 ° C or higher (Sample No. 1B,
Sample No. 1D) shows that the smooth creep strength and the notch creep strength both exceed the target values, and the 0.2% proof stress, impact absorption energy, and creep rupture time ratio also exceed the target values.

These target values are stress 1 at 600 ° C.
The creep rupture time in the smooth creep rupture test under the condition of 76 MPa is 2,500 hours or more, and the creep rupture time in the notch creep rupture test under the same condition is 5,000 hours or more. Further, the 0.2% proof stress is 686 MPa or more, the Charpy impact absorption energy is 98 J or more, and the creep rupture time ratio in the high pressure part is at least 2.0 or more, preferably 2.5 or more, more preferably 3. It is 0 or more.

Next, comparing the samples of sample No. 1C (comparative material), sample No. 1D, sample No. 1E, sample No. 1F, and sample No. 1G (comparative material) with the quenching temperature kept constant at 1050.degree. The influence of the amount of ferrite phase and the grain size on the material properties becomes clear. That is, the sample of Sample No. 1C, which has a metal structure containing no proeutectoid ferrite phase and has a grain size number smaller than 3.0 (indicating coarse grains), has a smooth creep rupture time longer than that of the other samples. It is excellent, but the notch creep rupture time is short, and the creep rupture time ratio is much less than 2.0, which shows that the material may cause creep embrittlement. In addition, sample number 1G in which the amount of pro-eutectoid ferrite phase exceeds 40%
Sample No. 2 could not secure 0.2% proof stress, and the smooth creep rupture time did not reach the target value. On the other hand, sample number 1D, sample number 1E, sample number 1 in which the amount of pro-eutectoid ferrite phase is in the range of more than 10% and 40% or less in volume%
In the sample of F, all the material properties exceeded the target value as the alloy material used for the high pressure part of the turbine rotor.

From the above, the quenching temperature is set to 980 ° C. or higher in order to satisfy the target values of the excellent material properties aimed at by the present invention as an alloy material for use in the high pressure portion of the high / low pressure integrated turbine rotor. It is understood that it is necessary to set the amount of pro-eutectoid ferrite phase to more than 10% and 40% or less in volume%.

Example 2 In Table 1, the materials used in Example 2 (alloy numbers 1 to 3) and comparative materials (alloy numbers 4 to 5) were used.
The chemical composition of In addition, assuming a turbine rotor material with a barrel diameter of 1200 mm (corresponding to the high-pressure portion) and a turbine rotor material with a barrel diameter of 2000 mm (corresponding to the low-pressure portion), the center portion of the turbine rotor (diameter center) when each cooling is performed. Part) and the surface layer part were simulated and heat treated to prepare a sample. Table 4 shows the quenching temperature and cooling method for each sample.

Then, the measurement results of the amount of pro-eutectoid ferrite phase, the grain size number, the 0.2% proof stress, the Charpy impact absorbed energy, and the creep rupture time (smooth sample and notched sample) at 600 ° C.-176 MPa for each of the above samples,
Table 5 shows the creep rupture time ratio calculated based on the creep rupture time of the smooth sample and the notched sample.

As shown in Table 5, by subjecting the sample using the alloy having the composition range defined by the present invention to the appropriate heat treatment within the range defined by the present invention, the high-pressure part is formed in the central part of the turbine rotor material and Both surface layer volume% exceeds 10% and 40
% Or less of the pro-eutectoid ferrite phase was obtained, and as a result, the crystal grain size number was controlled to 3.5 or more. Also, 0.2
% Yield strength, Charpy impact absorption energy and 600 ° C-
The creep rupture time at 176 MPa (smooth sample and notched sample) and the creep rupture time ratio all exceeded the target values for the high-pressure part, and it can be seen that the material has excellent material properties that have never been seen before.

On the other hand, with respect to the sample prepared assuming the low pressure part, there is no proeutectoid ferrite phase in the surface layer part, and in some samples, 30% or less by volume% of the proeutectoid ferrite phase is precipitated in the central part. ing. However, regardless of the presence or absence of the precipitation of the pro-eutectoid ferrite phase, the 0.2% proof stress and the Charpy impact absorbed energy are the target values (0.2% proof stress: 686 MPa or more, the Charpy impact absorbed energy: 98J or more).

On the other hand, in the sample using the alloy No. 4 in which the amount of carbon or vanadium is below the component range specified by the present invention, a large amount of pro-eutectoid ferrite phase is precipitated in both the high pressure part and the low pressure part, and 0.2 % Proof strength, impact energy absorption, and creep strength (smooth test and notch test) are below the target values. In the sample using the alloy No. 5 in which the amount of carbon, the amount of silicon, the amount of manganese, the amount of chromium, and the amount of tungsten exceed the component range, the target value of the impact absorption energy cannot be reached in both the high pressure portion and the low pressure portion. It is suggested that the creep rupture time ratio of the high pressure portion is much lower than the target value of 2.0, and creep embrittlement occurs.

As described above, the high-low pressure integrated turbine rotor having an alloy composition and a metal structure satisfying the requirements of the present invention has excellent high-temperature creep strength in the high-pressure portion, does not cause creep embrittlement, and has a low pressure. It was confirmed that the part had both excellent strength and toughness.

Example 3 Next, Table 6 shows the chemical composition of the alloy (alloy numbers 6 and 7) used in Example 3. In Example 3, the alloy of Alloy No. 2 of Example 2 was used as a base, and an alloy to which cobalt was further added was used.

Alloy No. 6 aims to further improve the high temperature creep strength in the high pressure portion of the turbine rotor.
The amount of nickel and the amount of manganese of the alloy No. 2 are reduced and cobalt is added instead. The alloy of sample No. 7 is based on the alloy of sample No. 2 described above with the aim of improving the toughness of the high pressure part and the low pressure part of the turbine rotor material while maintaining the high temperature creep strength of the high pressure part to some extent. The amount was slightly increased and cobalt was added.

Samples using the above alloys have a body diameter of 1200
mm rotor material (equivalent to high pressure part) and body diameter 2000
Assuming a rotor material (corresponding to a low-pressure portion) of mm, heat treatment was performed by simulating the positions of the center portion (center portion in the diametrical direction) and the surface layer portion of each rotor when subjected to each cooling. Table 7 shows the respective quenching temperatures and cooling methods.

Next, the results of measurement of the amount of pro-eutectoid ferrite phase, grain size number, 0.2% proof stress, Charpy impact absorbed energy and creep rupture time (smooth sample and notched sample) at 600 ° C.-176 MPa, and Table 8 shows the creep rupture time ratio calculated based on the creep rupture time of the smooth sample and the notched sample.

As shown in Table 8, a sample using an alloy in the composition range defined by the present invention is subjected to an appropriate heat treatment within the range defined by the present invention, whereby the high-pressure part becomes a central part and a surface layer part of the material. In both cases, a pro-eutectoid ferrite phase of more than 10% and not more than 40% in volume% was obtained, and as a result, the crystal grain size number was also 3.
It can be seen that it is controlled to 5 or more.

Further, in the materials of the present invention shown in Table 8, 0.2%
Proof strength, Charpy impact absorption energy and 600 ℃ -1
The creep rupture time at 76 MPa (smooth sample and notched sample) and the creep rupture time ratio all exceeded the target values of the high-pressure part, and it can be seen that the material has excellent material properties that have never been obtained. Particularly, the sample symbols 2A and 2 in Table 5 shown above.
Compared with B, the creep rupture time of Samples 6A and 6B using Alloy No. 6 was longer in both the smoothing test and the notch test, and the change of the components centering on the addition of cobalt effectively acted to improve the creep characteristics. Suggesting that

On the other hand, the sample prepared assuming the low pressure part
0.2% proof stress without proeutectoid ferrite phase, Charpy impact absorption energy target value (0.2%) required for low pressure part
The yield strength is 686 MPa or more, and the Charpy impact absorption energy is 98 J or more). Compared with the sample symbols 2A, 2B, 2C and 2D in Table 5 shown above, the impact absorption energies of the samples 7A, 7B, 7C and 7D using the alloy No. 7 show large values at all parts. , It is suggested that the change of the composition centering on the addition of cobalt effectively acts to improve the toughness.

From the above, the high-low pressure integrated turbine rotor having an alloy composition satisfying the requirements of the present invention has excellent high-temperature creep strength in the high-pressure portion, does not cause creep embrittlement, and has excellent strength in the low-pressure portion. It was confirmed that the material had both toughness and toughness. It was also confirmed that the addition of cobalt has an effect of improving the creep characteristics in the high pressure part and an effect of improving the toughness in the low pressure part.

Example 4 Next, Table 9 shows the chemical composition of the alloy used in Example 4. In Example 4, an alloy based on alloy No. 1 of Example 2 shown in Table 1 and further added with one or more of niobium, tantalum, nitrogen, or boron was used.

Alloy No. 8 was obtained by adding niobium and nitrogen to the above alloy No. 1 in order to further improve the high temperature creep strength of the high pressure portion. The alloy of sample No. 9 was obtained by adding niobium, tantalum and nitrogen to the alloy of alloy No. 1 above in order to further improve the high temperature creep strength of the high pressure part. The alloy of sample No. 10 was obtained by adding niobium and boron to the alloy of alloy No. 1 above in order to further improve the high temperature creep strength of the high pressure portion. The alloy of sample No. 11 is obtained by adding tantalum and boron to the alloy of alloy No. 1 above in order to further improve the high temperature creep strength of the high pressure portion.

For each of the above samples, a turbine rotor material having a barrel diameter of 1200 mm (corresponding to a high pressure portion) and a barrel diameter of 200
Assuming a turbine rotor material of 0 mm (corresponding to the low pressure portion), heat treatment was performed by simulating the center portion (center portion in the diameter direction) and the surface layer portion of the rotor when each cooling was performed.
Table 10 shows the quenching temperature and cooling method for each sample.

Next, the measurement results of the amount of pro-eutectoid ferrite phase, the grain size number, the 0.2% proof stress, the Charpy impact absorbed energy and the creep rupture time (smooth sample and notched sample) at 600 ° C.-176 MPa, and a smooth sample were obtained. Table 11 shows the creep rupture time ratio calculated based on the creep rupture time of the notched sample.

As shown in Table 11, by subjecting the sample in the composition range defined by the present invention to an appropriate heat treatment within the range defined by the present invention, both the center portion and the surface layer portion of the turbine rotor in the high pressure portion are increased in volume. %, A proeutectoid ferrite phase of more than 10% and 40% or less was obtained, and as a result, it can be seen that the grain size index number is also controlled to 3.5 or more.

Further, the 0.2% proof stress, the Charpy impact absorbed energy, the creep rupture time at 600 ° C. and 176 MPa (smooth sample and notched sample), and the creep rupture time ratio are all higher than the target values of the high pressure part. It can be seen that it does not have excellent material properties.

Particularly, the sample symbols 1A and 1B in Table 3 shown above.
Compared with the sample No. 8, the sample Nos. 8A and 8B using the alloy No. 8, the sample Nos. 9A and 9B using the alloy No. 9, and the sample No. 10A using the alloy No. 10 The creep rupture time of the sample of 10B and the samples of sample numbers 11A and 11B using the alloy of alloy number 11 are long in both the smoothing test and the notch test.
It is shown that the appropriate addition of one or more of tantalum, nitrogen and boron is effective in improving the creep characteristics.

On the other hand, in the sample prepared assuming the low pressure part, there is no pro-eutectoid ferrite phase and 0.2% proof stress and the Charpy impact absorbed energy are the target values (0.
2% proof stress: 686 MPa or more, Charpy impact absorption energy: 98 J or more).

From the above, the high-low pressure integrated turbine rotor satisfying the requirements of the present invention has excellent high-temperature creep strength in the high-pressure portion, does not cause creep embrittlement, and has excellent strength and toughness in the low-pressure portion. It was confirmed that it was a combination. It was also confirmed that the addition of at least one of niobium, tantalum, nitrogen, and boron can improve the creep characteristics in the high-pressure portion in the turbine rotor of the present invention.

Example 5 Next, Table 12 shows the chemical composition of the alloy used in Example 5. In Example 5, based on the alloy No. 6 of Example 3 shown in Table 6, an alloy to which any one or more of niobium, tantalum, nitrogen and boron was appropriately added was used.

Alloy No. 12 was obtained by adding niobium, tantalum and nitrogen to the above alloy No. 6 in order to further improve the high temperature creep strength of the high pressure portion.
Alloy No. 13 is an alloy of Alloy No. 6 to which tantalum and boron have been added in order to further improve the high temperature creep strength of the high pressure portion. Alloy No. 14 aims to further improve the high temperature creep strength of the high pressure part,
It is the above alloy No. 6 with niobium, tantalum and boron added.

Assuming a rotor material having a barrel diameter of 1200 mm (corresponding to a high pressure portion) and a rotor material having a barrel diameter of 2000 mm (corresponding to a low pressure portion) using the above alloys, the center portion (diameter direction) of the rotor when subjected to each cooling Heat treatment was performed by simulating the position of the center part) and the surface layer part. Table 13 shows the quenching temperature and cooling method for each sample.

The amount of pro-eutectoid ferrite phase in each of the above samples,
Creep calculated based on the measurement results of grain size number, 0.2% proof stress, Charpy impact absorbed energy and creep rupture time (smooth sample and notch sample) at 600 ° C.-176 MPa, and creep rupture time of smooth sample and notch sample Table 14 shows the breaking time ratio.

As shown in Table 14, by subjecting a sample having an alloy composition within the range specified by the present invention to an appropriate heat treatment within the range specified by the present invention, in the high pressure part, the central part and the surface layer of the turbine rotor material are It was confirmed that the proeutectoid ferrite phase of more than 10% and not more than 40% in volume% was obtained in both parts, and as a result, the grain size degree number was controlled to 3.5 or more.

Further, in the sample produced assuming a high pressure part, 0.2% proof stress, Charpy impact absorbed energy and creep rupture time at 600 ° C.-176 MPa (smooth sample and notched sample), creep rupture time ratio are all high pressure. It exceeds the target value of the part, and it can be seen that it has excellent material properties that have never been obtained.

Particularly, the sample symbols 6A and 6B in Table 8 shown above.
Compared with the sample of No. 12, the alloys of Sample Nos. 12A and 12B using the alloy of Alloy No. 12, the samples Nos. 13A and 13B using the alloy of Alloy No. 13 and the sample No. 14A using the alloy of Alloy No. 14, The creep rupture time of the 14B sample is long in both the smoothing test and the notch test, and it is shown that the addition of at least one of niobium, tantalum, nitrogen, and boron is effective in improving the creep characteristics. ing.

On the other hand, in the sample prepared assuming the low pressure part,
There is no proeutectoid ferrite phase, 0.2% proof stress, Charpy impact absorbed energy is the target value (0.2
% Yield strength: 686 MPa or more, Charpy impact absorption energy: 98 J or more).

From the above, the high and low pressure integrated turbine rotor of the present invention has excellent high temperature creep strength in the high pressure portion,
Moreover, it was confirmed that creep embrittlement did not occur and that the low pressure portion had both excellent strength and toughness. It was also confirmed that the creep property can be further improved by adding at least one of niobium, tantalum, nitrogen, and boron to the alloy containing cobalt.

[0129]

As described in detail above, the high and low pressure integrated turbine rotor of the present invention has a carbon content of 0.20 in weight%.
.About.0.35%, silicon: 0.15% or less, manganese: 0.
05-1.0%, nickel: more than 0.3 % -2.5%, chromium: 1.0-3.0%, molybdenum: 0.5-1.5
%, Tungsten: 0.1 to 3.0%, vanadium:
Containing 0.1 to 0.3%, phosphorus: 0.012% or less, sulfur: 0.005% or less, copper: 0.15% or less, aluminum: 0.01% or less, arsenic: 0.01% or less ,tin:
0.01% or less, antimony: 0.003% or less, the balance being a composition consisting of iron containing unavoidable impurities, and the metallographic structure of the high-pressure portion exceeds 10% by volume% and 4
Since the composition is composed of 0% or less of the pro-eutectoid ferrite phase and the balance of the bainite phase, the turbine rotor has excellent strength and high temperature creep characteristics in the high pressure portion and excellent strength and toughness in the low pressure portion. Therefore, it can be used in a steam turbine having a large capacity at a higher temperature, and a power plant with high energy efficiency can be realized, which is extremely useful.

Next, in the high / low pressure integrated turbine rotor of the present invention, if an alloy containing 0.1 to 3.0% by weight of cobalt is adopted, the creep characteristics are improved in the high pressure part and the toughness is improved in the low pressure part. The improvement effect of can be obtained.

Next, in the high and low pressure integrated turbine rotor of the present invention, niobium: 0.01 to 0.15%, tantalum: 0.01 to 0.15%, nitrogen: 0.001 to 0.0
If an alloy containing at least one selected from the group consisting of 5% and boron: 0.001 to 0.015% is adopted, it is possible to obtain the effect of improving the creep characteristics in the high pressure part.

Next, in the high-low pressure integrated turbine rotor of the present invention, 0.1 to 3.0% by weight of cobalt, niobium: 0.01 to 0.15%, tantalum: 0.01 to 0.
15%, nitrogen: 0.001-0.05%, boron: 0.0
If an alloy containing at least one selected from the range of 01 to 0.015% is adopted, it is possible to obtain the effect of improving the toughness in the low pressure portion and the effect of further improving the creep characteristics in the high pressure portion. .

Further, according to the method for manufacturing a high-low pressure integrated turbine rotor of the present invention, the portion corresponding to the high-pressure portion of the turbine rotor material having a predetermined composition is 980 ° C. or higher 1100.
After heating the portion corresponding to the low pressure portion of the turbine rotor material to 850 ° C. or higher and lower than 980 ° C., the portion corresponding to the high pressure portion of the turbine rotor material is heated to 90 ° C. or lower,
Cooling to a predetermined temperature of 0 ° C to 700 ° C by one or more cooling means of fountain cooling or blast cooling, followed by air cooling for 5 minutes to 5 hours, and then to 300 ° C fountain cooling or blast cooling or oil. Since the cooling is performed by one or more cooling means, and the portion corresponding to the low pressure portion of the turbine rotor material is cooled by the cooling means capable of obtaining a speed higher than oil quenching, the high pressure portion is 980 ° C. or higher. It is possible to easily manufacture a high-low pressure integrated turbine rotor that does not cause creep embrittlement even when quenched from a high temperature range of 1100 ° C. or less.

Further, it is possible to easily obtain a high / low pressure integral type turbine rotor having a low pressure portion having an excellent 0.2% proof stress, a high Charpy impact value and an excellent toughness.

[0135]

[Table 1]

[0136]

[Table 2]

[0137]

[Table 3]

[0138]

[Table 4]

[0139]

[Table 5]

[0140]

[Table 6]

[0141]

[Table 7]

[0142]

[Table 8]

[0143]

[Table 9]

[0144]

[Table 10]

[0145]

[Table 11]

[0146]

[Table 12]

[0147]

[Table 13]

[0148]

[Table 14]

[Brief description of drawings]

FIG. 1 is a photomicrograph of a high and low pressure integrated turbine rotor material according to the present invention.

[Explanation of symbols]

1 Proeutectoid ferrite phase 2 Bainite phase 3 grain boundaries 4 Charcoal / Nitride

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification symbol FI F01D 5/28 F01D 5/28 (56) References JP 2002-256378 (JP, A) JP 9-194946 (JP, A) JP 9-268343 (JP, A) JP 60-17016 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) C22C 38/00-38/60 C21D 9 / 28

Claims (5)

(57) [Claims] 1. A high / low pressure integrated turbine rotor in which a high pressure part and a low pressure part are integrally formed, wherein carbon: 0.20 to 0.35% by weight and silicon: 0.15.
% Or less, manganese: 0.05 to 1.0%, nickel:
More than 0.3 % to 2.5%, chromium: 1.0 to 3.0%, molybdenum: 0.5 to 1.5%, tungsten: 0.1
3.0%, containing vanadium: 0.1 to 0.3%, phosphorus:
0.012% or less, sulfur: 0.005% or less, copper: 0.
15% or less, aluminum: 0.01% or less, arsenic:
0.01% or less, tin: 0.01% or less, antimony:
It has a composition of 0.003% or less, the balance being iron containing unavoidable impurities, and the metallographic structure of the high-pressure part is more than 10% by volume and 40%.
A high-low pressure integrated turbine rotor comprising the following proeutectoid ferrite phase and the balance bainite phase. 2. A high-low pressure integrated turbine rotor in which a high-pressure portion and a low-pressure portion are integrally formed, wherein carbon: 0.20 to 0.35% by weight and silicon: 0.15
% Or less, manganese: 0.05 to 1.0%, nickel:
More than 0.3 % to 2.5%, chromium: 1.0 to 3.0%, molybdenum: 0.5 to 1.5%, tungsten: 0.1
3.0%, vanadium: 0.1 to 0.3%, niobium: 0.01 to 0.15%, tantalum: 0.01
~ 0.15%, nitrogen: 0.001-0.05%, boron:
Contains at least one selected from 0.001 to 0.015%, phosphorus: 0.012% or less, sulfur: 0.0
05% or less, copper: 0.15% or less, aluminum: 0.
01% or less, arsenic: 0.01% or less, tin: 0.01% or less, antimony: 0.003% or less, with the balance being iron containing unavoidable impurities. Metal structure exceeds 10% by volume% and 40%
A high-low pressure integrated turbine rotor comprising the following proeutectoid ferrite phase and the balance bainite phase. 3. An average grain size of 0.1 in the proeutectoid ferrite phase.
The high-low pressure integrated turbine rotor according to claim 1 or 2 , wherein carbon / nitride having a size of 5 µm or less is finely dispersed. 4. When manufacturing a high / low pressure integrated turbine rotor in which a high pressure portion and a low pressure portion are integrally formed, a portion corresponding to the high pressure portion of a turbine rotor material having a predetermined composition is 980 ° C. or higher and 1100 ° C. or lower. After heating the portion corresponding to the low pressure portion of the turbine rotor material to 850 ° C. or higher and lower than 980 ° C., the portion corresponding to the high pressure portion of the turbine rotor material is
From a predetermined temperature of 00 ° C to 700 ° C, it is cooled by one or more cooling means of fountain cooling or blast cooling, and then air-cooled for 5 minutes to 5 hours and then to 300 ° C fountain cooling or blast cooling or oil. cooled by one or more cooling means of the cooling, the part corresponding to the low pressure portion of the turbine rotor material, manufacturing method of the high pressure and low pressure integrated type turbine rotor cooled by cooling means the rate of more than oil quenching is obtained met And the turbine rotor material, in wt% carbon: 0.20-
0.35%, silicon: 0.15% or less, manganese: 0.0
5 to 1.0%, nickel: more than 0.3% to 2.5%, black
Mu: 1.0-3.0%, Molybdenum: 0.5-1.5
%, Tungsten: 0.1 to 3.0%, vanadium:
0.1 to 0.3%, phosphorus: 0.012% or less, sulfur
Yellow: 0.005% or less, Copper: 0.15% or less, aluminum
Um: 0.01% or less, Arsenic: 0.01% or less, Tin:
0.01% or less, antimony: 0.003% or less
And the balance consists of iron with unavoidable impurities.
High and low pressure integrated turbine characterized by being made of alloy steel
Method of manufacturing rotor. 5. A high pressure part in which a high pressure part and a low pressure part are integrally formed.
When manufacturing a low-pressure integrated turbine rotor, it corresponds to the high-pressure part of a turbine rotor material with a specified composition.
The portion to be heated is heated to 980 ° C or higher and 1100 ° C or lower to
-The part corresponding to the low pressure part of the bin rotor material is 850 ° C or higher.
After heating to below 980 ° C., the portion corresponding to the high pressure portion of the turbine rotor material is
From 00 ° C. to a predetermined temperature of the 700 ° C. fountain cooling or
After cooling with one or more cooling means among blast cooling, then air- cooling for 5 minutes to 5 hours , and then fountain up to 300 ° C.
One or more of cooling, wind cooling, or oil cooling
Cooling means, the part corresponding to the low pressure part of the turbine rotor material is oil
Cooling by cooling means that can obtain a speed higher than quenching
A method of manufacturing a low-pressure integrated turbine rotor, comprising: using the turbine rotor material in carbon of 0.20% by weight.
0.35%, silicon: 0.15% or less, manganese: 0.0
5 to 1.0%, nickel: more than 0.3 % to 2.5%, chromium: 1.0 to 3.0%, molybdenum: 0.5 to 1.5
%, Tungsten: 0.1 to 3.0%, vanadium:
0.1 to 0.3%, and further niobium: 0.01 to
0.15%, tantalum: 0.01 to 0.15%, nitrogen:
0.001-0.05%, boron: 0.001-0.01
Contains at least one selected from the group consisting of 5% and phosphorus:
0.012% or less, sulfur: 0.005% or less, copper: 0.
15% or less, aluminum: 0.01% or less, arsenic:
0.01% or less, tin: 0.01% or less, antimony:
A method for manufacturing a high-low pressure integrated turbine rotor, comprising an alloy steel having a composition of 0.003% or less and the balance being iron containing unavoidable impurities.