JPH07316721A - High and low pressure integrated type turbine rotor and its production - Google Patents

Abstract

PURPOSE:To provide a high and low pressure integrated type turbine rotor material having high tensile strength at relatively low temp. and high creep rupture strength at high temp. and capable of inhibiting secular change over a long period by specifying the chemical composition of a steel material. CONSTITUTION:This steel material has a composition consisting of, by weight, 0.10-0.35% C, <=0.3% Si, <=1.0% Mn, 1.0-2.0% Ni, 1.5-3.0% Cr, 0.9-1.3% Mo, 0.10-0.35% V, 0.01-0.15% Nb, 0.1-1.5% W, and the balance Fe with accompanying impurities, and-further, the contents of P, As, Sb, and Sn as the impurities are limited to <=0.005%, <=0.008%, <=0.004%, and =0.0080%, respectively. Moreover, the steel material of this composition is melted and formed into a primary steel ingot and then remelted by electroslag remelting, and the resultant secondary steel ingot is forged and heat-treated and formed into a product. By this method, the high and low pressure integrated type turbine rotor material, in which high strength at relatively low temp. and high creep rupture strength under high temp. conditions are provided and long-term deterioration in strength and toughness is inhibited and which is free from component segregation by ESR, can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high and low pressure integrated turbine rotor and a method for manufacturing the same.

[0002]

2. Description of the Related Art Generally, in a steam turbine, rotors made of different materials are used depending on steam conditions used. An example of a conventional steam turbine is shown in FIG. For example, in a large steam turbine, high temperature / high pressure side (for example, 566
As a rotor material used in the vicinity of 1), ASTM-
CrMoV steel having excellent creep rupture strength at high temperatures is used as specified in A470 (Class 8). Also, low pressure side (for example, 350 ° C or less)
The rotor material used in No. 2 is ASTM-A470.
2.5 as specified in (Class 2-7)
NiCrMoV steels with more than 1% Ni have been used. Then, rotors made of different materials corresponding to these steam conditions are mechanically joined to each other at the joining portion 3 to form a steam turbine and the generator 4 is rotated. Thus, in the conventional large steam turbine,
Since a plurality of rotors made of different materials are joined together to form a turbine, the manufacturing process is complicated, and the installation space for the entire turbine is widened, which is a factor of increasing plant cost.

On the other hand, a relatively small steam turbine (output 1
In a power generation facility of 00 MW or less), a high / low pressure integrated rotor is generally used in which a high pressure side to a low pressure side are constituted by a single rotor made of the same material. As a material for such a high and low pressure integrated rotor, a CrMoV is usually used.
Steel, NiCrMoV steel and 1CrMoVNiNb steel are used.

However, in a power generation facility with an output of more than 100 MW, the following problems occur when using a steam turbine composed of a high and low pressure integrated rotor. FIG. 7 shows an example of a steam turbine including a high-low pressure integrated rotor. In FIG. 7, the high pressure portion 1 of the steam turbine rotor is used in a high temperature environment exceeding 500 ° C., and the downstream side 5 of the high pressure portion 1 and the upstream vicinity 5 of the low pressure portion 2 are used in a temperature range of 350 to 450 ° C. Therefore, the CrMoV steel used in the past is not sufficiently satisfactory in terms of tensile strength and toughness.
Although the iCrMoV steel has excellent tensile strength, it lacks in creep rupture strength, and further has a problem that brittleness easily progresses in a temperature range of 350 ° C. or higher. On the other hand, 12Cr steel has already been developed as a rotor material having excellent creep rupture strength and toughness, and also excellent tensile strength in a low temperature range. However, 12Cr steel is expensive and is used as the rotor material. And there is a problem of causing an increase in manufacturing cost. For this reason, alloys for steam turbine rotors have been developed in which W is added to Ni, Cr, Mo, V, etc., and B and N are further added (Japanese Patent Laid-Open No. 63-157839).

[0005]

However, the output 1
In power generation facilities that exceed 00 MW, it is necessary to secure creep rupture strength in the high pressure part while suppressing the deterioration of strength (tensile strength and creep rupture strength) over time, and toughness and tensile strength in the low pressure part The present situation is that no high-low pressure integrated turbine rotor capable of suppressing the deterioration (brittleness) of specific toughness has been found. Therefore, the conventional rotor material has a problem that there is a large limitation in the case of attempting to improve the efficiency of the steam turbine by using high-temperature steam and mounting long low-pressure final stage blades.

Further, when it is used for a long time in a high temperature environment exceeding 500 ° C., the tensile strength and creep rupture strength decrease, and when it is used in the temperature range of 350 to 450 ° C., it becomes brittle. There was a problem of causing.

Further, in the low alloy steel, if the incidental impurity elements are reduced, the segregation of the components in the center of the steel ingot, in other words, the center of the rotor, in particular, the segregation of the C (carbon) component becomes remarkable. .

The present invention has been made in order to solve such a problem, and reduces the segregation of the components in the center of the rotor, and also provides a high tensile strength under relatively low temperature steam conditions and a high tensile strength under high temperature conditions. High-low pressure integrated turbine rotor having high creep rupture strength, which can be used for a long period of time while maintaining high tensile strength and creep rupture strength without causing an embrittlement phenomenon, and a manufacturing method thereof The purpose is to provide.

[0009]

The high and low pressure integrated turbine rotor according to claim 1 has a steel composition in a weight ratio,
C: 0.10 to 0.35%, Si: 0.3% or less, M
n: 1.0% or less, Ni: 1.0 to 2.0%, Cr:
1.5-3.0%, Mo: 0.9-1.3%, V: 0.
10 to 0.35%, Nb: 0.01 to 0.15%, W:
0.1 to 1.5% and the balance being Fe and incidental impurities, and the incidental impurities are P: 0.0 by weight.
05% or less, S: 0.001% or less, As: 0.008
% Or less, Sb: 0.004% or less, Sn: 0.008%
It is characterized by the following:

In the method for manufacturing a high-low pressure integrated turbine rotor according to claim 2, the composition of the steel is C: 0.10 to weight ratio.
0.35%, Si: 0.3% or less, Mn: 1.0% or less, Ni: 1.0 to 2.0%, Cr: 1.5 to 3.0
%, Mo: 0.9 to 1.3%, V: 0.10 to 0.35
%, Nb: 0.01 to 0.15%, W: 0.1 to 1.5
% And the balance being Fe and incidental impurities, and the incidental impurities are in a weight ratio of P: 0.005% or less,
S: 0.001% or less, As: 0.008% or less, S
b: 0.004% or less, Sn: 0.008% or less, a method of manufacturing a high-low pressure integrated turbine rotor, comprising: melting a steel material having the above-mentioned composition in a melting furnace to produce a primary steel. Ingot, a step of remelting and casting the primary steel ingot by the electroslag melting method (ESR) to form a secondary steel ingot, and forging the secondary steel ingot to form a rotor-shaped forged product And a step of annealing, quenching, and tempering the rotor-shaped forged product.

The high / low pressure integrated turbine rotor has aged strength (tensile strength and creep rupture strength) that decreases over time while ensuring creep rupture strength in the high pressure area, and toughness and tensile strength in the low pressure area over time. It is necessary to suppress the reduction (brittleness) of specific toughness. The present inventors have found that such required characteristics have a great influence on the type and amount of alloying elements and incidentally included impurities, and have investigated the optimum amount thereof. Moreover, when ESR is applied as a remelting method in addition to the usual melting and refining process, it is newly confirmed that the component segregation in the steel ingot central part, in other words, the rotor central part, in particular, the C (carbon) component segregation is greatly suppressed. Found in. In particular, in the ingot having the composition of the present invention, component segregation in the center of the rotor is relatively likely to occur. Therefore, by discovering a new effect of this ESR, the high-low pressure integrated turbine rotor of the present invention has extremely excellent characteristics. I was able to get it.

ESR is a method of melting a consumable electrode by electric resistance heat of molten slag and continuously solidifying it in a water-cooled copper mold. The following points are known as effects of the casting method using this ESR. 1) So-called V, in which non-metallic inclusions are trapped during solidification and V-type or inverted V-type segregation spots occur in the ingot
Segregation and inverse V segregation phenomena are suppressed and the solidified structure is improved.
2) The skin of the ingot becomes clean. 3) As a result of suppressing V segregation and reverse V segregation phenomena, removal of non-metallic inclusions becomes good. 4) Desulfurization and deoxidation can be easily performed by the refining action of slag.

When the high-low pressure integrated rotor is used in a high temperature environment exceeding 500 ° C., the fine carbides that contribute to the strengthening of the alloy material agglomerate and coarsen during use, and gradually stop contributing to the strengthening. Strength and creep rupture strength decrease. When used in the temperature range of 350 to 450 ° C,
Impurities contained in the alloy material are likely to collect at the crystal grain boundaries, so-called grain boundary segregation occurs, and the bonding force between the atoms at the grain boundaries is weakened, causing embrittlement over time. Based on the above findings, P (phosphorus) among impurities contained incidentally can be reduced to 0.
005% or less, S (sulfur) 0.001% or less, As
(Arsenic) is 0.008% or less, Sb (antimony) is 0.004% or less, and Sn (tin) is 0.008% or less, thereby significantly reducing the amount of grain boundary segregation, and
It was possible to significantly suppress the deterioration of strength and toughness over time during use. As a result, the long-term stability of the high / low pressure integrated rotor was secured, the life was extended, the risk of brittle fracture was prevented, and stable operation for a long time was enabled.

Further, among the alloying elements, it was found that three elements of Ni, Mo and W have a great influence on the material properties, and the optimum amount thereof was examined. Hereinafter, each element will be described. In addition, in the following description,% represents weight%. Ni (nickel); Nickel is an austenite forming element, and is effective in stabilizing the austenite phase during quenching and heating and preventing the formation of ferrite phase during quenching and cooling. Further, it is effective in increasing tensile strength and toughness. In order to obtain the tensile strength and toughness required for the high-low pressure integrated turbine rotor of the present invention, it is necessary to add more than 1.0%. However, if added over 2.0%,
On the contrary, since the creep rupture strength tends to decrease and embrittlement tends to be promoted, the addition amount is 1.0 to 2.0%. More preferably, it is 1.3 to 1.8%.

Mo (molybdenum): Molybdenum is an element effective for improving the hardenability of steel and for enhancing the tensile strength and creep rupture strength. In order to obtain the tensile strength and creep rupture strength required for the high-low pressure integrated turbine rotor of the present invention, the addition amount exceeding 0.9% is required. But,
On the other hand, if it exceeds 1.3%, not only the creep rupture strength lowers, but also the toughness lowers remarkably. In addition, the segregation of components in the central portion of the turbine rotor, particularly the segregation of C (carbon) components, is also noticeable. Therefore, 0.
It is in the range of 9 to 1.3%. More preferably 1.0 to
It is 1.2%.

Here, the C (carbon) component segregation refers to a phenomenon in which the C (carbon) component concentration varies depending on the site of the ingot. The ingot starts solidification from the outer peripheral portion or bottom of the ingot case (mold), and gradually solidifies toward the inside. The center and upper part solidify last. Although it depends on the component system of the material, in the material of the component system according to the present invention, the segregation phenomenon of the C component is easily seen in the center of the ingot. Specifically, this component segregation has a high concentration in the upper part of the central portion. If such component segregation occurs remarkably, the material properties may change and the specifications as a large rotor may not be satisfied. Therefore, in selecting the components, it is necessary to consider to reduce the component segregation as much as possible. Therefore, the degree of segregation of each steel type can be determined by actually manufacturing an ingot, analyzing the C content in the upper part and the lower part in the central part, and evaluating the ratio. In the present invention, when the amount of molybdenum exceeds 1.3%, the segregation of C (carbon) components becomes remarkable.

W (tungsten): Tungsten is an element effective in improving high temperature strength by solid solution strengthening. In order to exert its effect, 0.1% or more is required to be added. However, if added in excess of 1.5%, the toughness decreases, so the range is 0.1-1.5%. It is more preferably 0.2 to 0.8%.

The properties such as toughness, creep rupture strength and tensile strength according to the present invention can be evaluated by a tensile test, a Charpy impact test, a creep rupture test, etc. described below. Tensile test: Tensile strength of test material, 0.2
This is a material test for the purpose of obtaining% proof stress, elongation and drawing. The larger each value is, the better the characteristics are. By changing the temperature environment of the test piece, the tensile properties (tensile strength, 0.2% proof stress, elongation, drawing) at each temperature can be obtained.

The Charpy impact test is the impact value of the test material, F
This is a material test for the purpose of obtaining ATT (ductile / brittle transition temperature obtained from the fracture surface ratio of an impact test piece). In general, the term “impact value” refers to the characteristic at room temperature (20 ° C.). The impact value (hardness to break when an impact force is applied, that is, toughness) is similar to the tensile property, and the larger the value, the better the property. Also,
The test material according to the present invention changes in impact value depending on temperature,
Even with the same test material, the impact value is large in the high temperature region and the fracture surface shows a ductile fracture surface, but conversely, the impact value is small in the low temperature region and the fracture surface shows a brittle fracture surface. ing. In these intermediate temperature regions, ductile fracture surfaces and brittle fracture surfaces are mixed. The area ratios of both of these fracture surfaces are measured, and a temperature at which exactly 50% -50% is obtained, and this temperature is defined as FATT. Therefore, the smaller the FATT value, the higher the toughness.

The creep rupture test is a material test for the purpose of obtaining the creep rupture strength of the test material. Creep rupture strength is a characteristic that corresponds to creep rupture time,
The longer the creep rupture time, the higher the creep rupture strength.

Impurities and Ni, M contained incidentally
In addition to the optimum addition amounts of o and W, the present invention uses C, Si, M
It is composed of an Fe-based alloy having a specific composition component of n, Cr, V and Nb. The purpose of adding each of these components and the reasons for limiting the composition are as follows.

C (carbon): Carbon stabilizes the austenite phase during quenching and further forms carbides to enhance the tensile strength, but for that purpose, 0.10% or more is necessary. However, if it exceeds 0.35%, the carbide becomes excessive, which not only lowers the tensile strength but also lowers the toughness. Therefore, the amount of carbon is 0.10 to 0.35%. It is preferably 0.18 to 0.30%.

Si (silicon): Silicon is added as a deoxidizing agent at the time of melting, but if a large amount of this is added, a part of it remains in the steel as an oxide and adversely affects toughness. Therefore, the amount of silicon added is 0.3% or less.
It is preferably 0.1% or less.

Mn (manganese): Manganese is added as a deoxidizing / desulfurizing agent at the time of dissolution, but if a large amount of Mn is added, the toughness decreases, so the addition amount is 1.0% or less.
It is preferably 0.7% or less.

Cr (Chromium): Chromium is an element necessary for preventing oxidation and improving tensile strength and toughness. For this purpose, it is necessary to add 1.5% or more, but if it exceeds 3.0%, on the contrary, the toughness and tensile strength are lowered and the journal characteristics are lowered.
It is in the range of 5 to 3.0%. Preferably 1.8-2.5
%.

V (vanadium): Vanadium is an element effective for improving the hardenability of steel and enhancing the creep rupture strength. It is an effective element for improving strength. In addition, it is also effective in achieving a finer crystal grain. In order to exert the effect, 0.10% or more is required to be added, but if it exceeds 0.35%, the toughness and the tensile strength decrease, so the range is 0.10 to 0.35%. It is preferably 0.15 to 0.30%.

Nb (niobium); Niobium is an element effective in refining crystal grains. In order to exert its effect, it is necessary to add 0.01% or more. However, 0.
If added in excess of 15%, on the contrary, coarse carbonitrides are formed and the toughness is lowered, so it is in the range of 0.01 to 0.15%. It is preferably 0.02 to 0.10%.

[0028]

EXAMPLES Examples of the present invention will be described below together with comparative examples. The raw material formulations of Examples 1 to 14 are shown in Table 1, and the raw material formulations of Comparative Examples 1 to 18 are shown in Table 2. The mixing ratios of Examples 1 to 14 and Comparative Examples 1 to 18 were determined for the following reasons. Examples 1 to 5 are C and S for the purpose of improving creep rupture strength and toughness.
It is a steel type in which the amounts of i, Mn, Ni, Cr, V, Nb, and W are determined and the addition amount of Mo is changed. In Examples 6 to 9, the amounts of C, Si, Mn, Cr, Mo, V, Nb, and W were determined and the amount of Ni added was changed for the purpose of improving creep rupture strength and toughness and reducing component segregation. It is a steel grade. Example 1
0 to Example 14 are C, Si, Mn, Ni, Cr, for the purpose of improving creep rupture strength and toughness, and reducing component segregation.
It is a steel type in which the amounts of Mo, V and Nb are determined and the amount of W added is changed.

The composition of Comparative Example 1 corresponds to 1% CrMoV steel conventionally used for high temperature turbine rotors in thermal power plants. The composition of Comparative Example 2 is 3.5% NiCrM which is conventionally used in a low temperature turbine rotor for thermal power generation.
Corresponds to oV steel. Comparative Example 18 corresponds to 1% CrMoVNiNb steel used in a high / low pressure integrated rotor for a relatively small steam turbine (power generation facility with an output of 100 MW or less). In each case, the amounts of P, S, As, Sb, and Sn among the impurities contained incidentally are Examples 1 to 14.
It is a steel type that is more common than. Further, Comparative Examples 3 to 1
No. 7 is not used as a current turbine rotor material, but was manufactured to study the effects of Ni, Mo, and W in particular. That is, in Comparative Examples 3 to 8, the addition amount of Mo was varied beyond the upper and lower limits of the addition amount of Mo contained in Examples 1 to 5. Comparative Examples 9 to 13 are examples in which the addition amount of Ni was varied over the upper and lower limits of the addition amount of Ni contained in Examples 6 to 9. Comparative Example 14 to Comparative Example 17
Shows that the addition amount of W was varied over the upper and lower limits of the addition amount of W contained in Examples 10 to 14.

[0030]

[Table 1]

[Table 2] The raw materials of Examples and Comparative Examples, which were blended so as to have a predetermined alloy composition, were melted in a high frequency vacuum melting furnace and then cast into a mold to obtain an ingot. After the surface of this ingot was scraped off by machining, it was placed in a heavy oil furnace, heated to 1200 ° C. for press forging, and forged into a round bar having a diameter of 30 mm. Next, this round bar was subjected to pre-conditioning annealing, quenching and tempering. Table 3 shows the processing conditions. In Table 3, the pre-conditioning annealing removes the non-uniformity of the structure due to forging, dissolves the coarse undissolved carbide in the matrix, and improves the material properties after the subsequent quenching and tempering treatments. It has a role to let. For that purpose, it is effective to heat to as high a temperature as possible, so 1100 ° C., which is almost the upper limit in practical use, was selected.

The quenching heating adjusts the grain size of the material, and in order to carry out uniform fine precipitation of carbide in the tempering treatment, a carbide-forming element such as Cr, Mo, V is once solid-dissolved in the matrix. The working high-pressure rotor (Comparative Example 1) is carried out at 970 ° C. and the working low-pressure rotor (Comparative Example 2) is carried out at 840 ° C. However, since the steel of the present invention is a high-low pressure integrated turbine rotor, actual quench hardening of those rotors is performed. 930 ° C, which lies between the temperatures, was chosen as an example.

Quenching cooling is a cooling rate of about 100 at the center of a rotor of 1650 mmφ level, which is the maximum diameter of a general large-sized low-pressure rotor, when water spray cooling is performed.
℃ / h is adopted.

As with the quenching temperature, a tempering temperature of 650 ° C., which is between the working high pressure rotor of 670 ° C. and the working low pressure rotor of 600 ° C., was selected. Further, the tempering heating time was changed depending on each steel type, and the room temperature tensile strength was adjusted so as to reach the level of 87 to 90 kgf / mm ² required for the low pressure part. This is because the tensile strength is adjusted to a substantially constant level, and the proof stress, impact characteristics (particularly FATT: ductility-brittle fracture transition temperature) and creep rupture strength characteristics required for the high-low pressure integrated turbine rotor are comparatively evaluated. . Such comparative evaluation makes it possible to compare materials having different components.

[0034]

[Table 3] Each of the heat-treated test materials shown in Table 3 was machined into test pieces, and a tensile test, a Charpy impact test and a creep rupture test were performed. The results of the tensile test and the Charpy impact test are shown in Table 4, and the results of the creep rupture test are shown in Table 5. The tensile test was conducted at room temperature, and Table 4 also shows the elongation after breakage and the drawing. Further, the Charpy impact test was carried out at a plurality of temperatures ranging from room temperature to 200 ° C. to obtain FATT. Creep rupture test is 60
0 were performed over each of the stress of 14 kgf / mm ² and 17 kgf / mm ² at ° C..

[0035]

[Table 4]

[Table 5] From the above results, FIG. 1 shows the result of arranging FATT, creep rupture time and “segregation ratio” by Mo content, FIG. 2 shows the result by Ni content, and FIG. 3 shows the result by W content. Show.

Comparative Examples 1, 2, 3, 5, 6, 8, 1
8 and Examples 1 to 3, when the high-low pressure integrated turbine rotor was manufactured, C in the rotor central portion
In order to compare and evaluate the degree of segregation of (carbon), 500 kg ingots were produced for each and the C (carbon) content in the center was evaluated. The ratio of C (carbon)% in the upper part of the ingot to C (carbon)% in the lower part of the ingot is defined as "segregation ratio",
The results of "segregation ratio" of each material are shown in Table 6.

[0037]

[Table 6] Further, in order to see the effect of ESR on the component segregation, ESR steel ingots (ingots) of 2 tons were produced for each of Examples 1, 2 and 3 and the C (carbon) content in the central part was evaluated. As a result, the "segregation ratio" was 1.03 in Example 1, 1.06 in Example 2 and 1.07 in Example 3, and the effect of significantly reducing the component segregation was recognized as compared with the case of Table 6 in which ESR was not applied.

In order to compare and evaluate the deterioration of strength and the deterioration of toughness over time, Comparative Examples 1, 2, 18 and Example 2,
For 4, 7, 8, 11, 12, and 13, 1 at 600 ° C
A tensile test when heated for 0 ³ hours and 10 ⁴ hours and a Charpy impact test when heated at 400 ° C. for 10 ³ hours and 10 ⁴ hours were performed. The tensile test results are shown in Table 7 and FIG. 4, and the Charpy impact test results are shown in Table 8 and FIG. 5, respectively.

[0039]

[Table 7]

[Table 8] Consider these experimental results. The high-low pressure integrated turbine rotor of the present invention has high tensile strength under relatively low-temperature steam conditions and high creep rupture strength under high-temperature conditions, and maintains high tensile strength and creep rupture strength over a long period of time. As a preferable characteristic value because it can be used without causing an embrittlement phenomenon,
The following characteristic values can be mentioned. As initial values, tensile strength is 86 to 92 kgf / mm ² , 0.2% proof stress is 71 to 77 kgf / mm ² , elongation is 18% or more, drawing is 55% or more, and impact value is 6 kgf-m / cm. ² or more,
The FATT is preferably 70 ° C or lower. Also, 600 ° C x 1
Under the creep condition of 4 kgf / mm ² , the breaking time is 2500 hours or more, the elongation is 20% or more, and the drawing is 50%.
% Or more, preferably 600 ° C. × 17 kgf /
Under creep conditions of mm ² , the breaking time is 100
It is preferable that the elongation is 0% or more, the elongation is 20% or more, and the drawing is 50% or more.

Each of the examples satisfies the above characteristic values. Note that, among these characteristics, the tensile strengths are set to almost the same level by changing the tempering conditions in each test material, and therefore, all of the Examples have the same level. Along with that, the 0.2% proof stress is almost at the same level. Elongation and drawing are not significantly affected by the subtle differences in alloying elements, and all the test materials are at almost the same level. However, the impact value representing the toughness and the FATT characteristic are greatly affected by the type and amount of the added element. Especially Cr, Ni, Nb
Is effective in improving the toughness when the added amount is increased, and W and Mo reduce the toughness when the added amount is increased. Further, when the rotor is used for a long period of time, the amount of grain boundary segregation is remarkably reduced and the amount of impurities additionally contained must be limited to a very small amount in order to suppress aging embrittlement. On the other hand, since there are restrictions on the components from the viewpoint of creep rupture strength (time) and carbon component segregation, the preferred range of the components of the present invention is as follows.
Cr: 1.5-3.0%, Ni: 1.0%-
2.0%, Nb: 0.01% to 0.15%, W: 0.1
% -1.5%, Mo: 0.9% -1.3%, P: 0.005% or less as an incidental impurity, S: 0.001%
In the following, As: 0.008% or less, Sb: 0.004% or less, Sn: 0.008% or less, but the above-mentioned characteristic values are sufficiently satisfied within this range.

In Example 6, the impact value is relatively low, but it is considered that this is because the effective amount of Ni added for improving the toughness is smaller than that in the other Examples. The amount of Ni added in Example 14 was higher than that in Example 6, but the impact value was lower. It is considered that this is because the toughness was reduced due to the large amount of W added in Example 14. In Table 5, Comparative Examples 9, 10, 1
The creep rupture times of Nos. 1, 16 and 17 were rather superior to those of the examples of the present invention. Of these, Comparative Examples 9, 10 and 11 had a Ni addition amount of 1.0% or less. Therefore, in Comparative Examples 16 and 17, the W addition amount was 1.5% or more, so that neither the impact value indicating the toughness nor the FATT characteristic satisfied the above-mentioned characteristic values, and the toughness was low.

Next, the case where the contents of Mo, Ni and W are changed while suppressing the amounts of incidental impurities within the above-mentioned ranges will be described. First, Comparative Examples 1 to 8 and Examples 1 to 5 in which the amounts of incidental impurities are suppressed within the ranges described above and the Mo content is changed will be described. Table 4
From the test results shown in Example 1, Examples 1 to 5 according to the present invention show good tensile strength, proof stress, elongation, and drawing that are equal to or higher than those of Comparative Examples 1 to 8, and are relatively high. It has good mechanical properties at low temperatures. In particular, in each of the examples, the strength is remarkably improved as compared with Comparative Example 1, the FATT is low, and the toughness is improved. Next, Table 5
The test results shown in Table 1 show that Examples 1 to 5 according to the present invention have significantly better creep rupture times than Comparative Examples 2 to 8, and the conventional high pressure turbine rotor materials The characteristics are comparable to those of Comparative Example 1. Further, from the test results of Table 6, Examples 1 to 3 according to the present invention show a significantly smaller "segregation ratio" than Comparative Examples 6 and 8, and the conventional high pressures shown in Comparative Examples 1 and 2. The turbine rotor material and the low-pressure turbine rotor material have a small "segregation ratio" that is almost the same level as the problem, and the turbine rotor according to the present invention does not cause a problem regarding the segregation of components in manufacturing. Figure 1 shows these results as M
The content of Mo is 0.9.
It can be seen that in the range of up to 1.3%, any one of the characteristics of toughness, creep rupture time and "segregation ratio" is extremely excellent.

Next, Comparative Example 1 and Comparative Examples 9 to 13 and Examples 6 to 9 in which the Ni content is changed while suppressing the amounts of incidental impurities within the above-mentioned ranges will be described. From the test results shown in Table 4, also in Examples 6 to 9 according to the present invention, good tensile strength, yield strength and elongation equivalent to or higher than those of Comparative Example 1 and Comparative Examples 9 to 13 were obtained. , Squeezing, and it is understood that the mechanical properties at relatively low temperatures are well equipped. In particular, in all of Examples 6 to 9, the strength was remarkably improved as compared with Comparative Example 1, the FATT was also low, and the toughness was improved. Furthermore, in Examples 6 to 9, the FATT was lower than in Comparative Examples 9 to 11, and the toughness was significantly improved. Also,
From the test results shown in Table 5, Example 6 according to the present invention
Example 9 has a significantly better creep rupture time than Comparative Examples 12 and 13, and shows characteristics comparable to those of Comparative Example 1 which is a conventional rotor material for a high pressure turbine. . FIG. 2 summarizes these results by the Ni content. The Ni content is in the range of 1.0 to 2.0%, and both the toughness and the creep rupture time are extremely excellent. I understand.

Further, Comparative Example 1 and Comparative Examples 14 to 17 and Examples 10 to 14 in which the W content is changed by suppressing the amount of incidental impurities within the above ranges will be described. From the test results shown in Table 4, also in Examples 1 and 2 and Examples 10 to 14 according to the present invention, good tensile strength equal to or more than that of Comparative Example 1 and Comparative Examples 14 to 17 was obtained. It is understood that it exhibits strength, proof stress, elongation, squeeze and is well equipped with mechanical properties at relatively low temperatures. In particular, in each of Examples 1 and 2 and Examples 10 to 14, the strength is remarkably improved as compared with Comparative Example 1, the FATT is also low, and the toughness is improved. Furthermore, Examples 1 and 2 and Examples 10 to 1
No. 4 has a lower FATT than Comparative Examples 16 and 17, and the toughness is remarkably improved. In addition, from the test results shown in Table 5,
Examples 1 and 2 and Examples 10 to 14 according to the present invention have significantly better creep rupture times than Comparative Examples 14 and 15, and are conventional rotor materials for high pressure turbines. The characteristics are comparable to those of Comparative Example 1. FIG. 3 shows these results arranged by W content. The W content is in the range of 0.1 to 1.5%, the toughness,
It can be seen that all the characteristics of creep rupture time are extremely excellent.

From Table 7 and FIG. 4, which evaluated the decrease in tensile strength among the aged strength, Comparative Examples 1 and 2 show a large decrease in the tensile strength over time, and the comparative example is 600 ° C. × 10 ⁴ hours. 1
The tensile strength of the degradation of 5.3kgf / mm ^2, that of Comparative Example 2 showed a decrease in 8.6kgf / mm ^2. On the other hand, the amount of decrease in tensile strength in each example is 1 to 2 kgf / m.
m ^2, and has been greatly improved compared with the comparative example of conventional material. One of the features of the material of the present invention is that W is added. However, W not only enhances tensile strength and creep rupture strength by forming a solid solution with W, but also improves the stability of the structure at high temperature. It is thought that this has improved and suppressed the secular change in strength. In Comparative Example 1, the change in strength over time was larger than that in Comparative Example 2, but this is considered to be due to the difference in the Ni content. That is, Ni is an element that is extremely effective in increasing toughness, but is also an element that promotes strength reduction at high temperatures. In the present invention, since the upper limit of the Ni content is 2.0%, it is possible to suppress the secular change of the tensile strength together with the effect of the structural stability due to the addition of W.

From Table 8 and FIG. 5, which evaluated deterioration of toughness over time, Comparative Examples 1 and 2 had a large degree of embrittlement, and
By heating at 0 ° C. × 10 ⁴ hours, the FATT of Comparative Example 1 was 3
The FATT of 3 ° C. and Comparative Example 2 showed an increase of 57 ° C., respectively. On the other hand, the increase in FATT in the example is -3 to
It is +7, which is a great improvement over the comparative example of the conventional material. In the material of the present invention, the amount of P, S, As, Sb, and Sn among the impurities contained incidentally is extremely small, so that even if the rotor is used for a long time, the segregation amount of the grain boundaries of the impurities is remarkably large. It is considered that the amount is reduced and the aged embrittlement is suppressed. Comparative Example 2 had a larger degree of embrittlement than Comparative Example 1, but it is considered that this is due to the difference in the Ni content, as in the case of the strength reduction described above. That is, Ni is an extremely effective element for increasing the toughness, but 350 ° C
It is also an element that promotes embrittlement at around 450 ° C.
In the present invention, since the upper limit of the Ni content is 2.0%, the secular embrittlement is accompanied by the effect of suppressing the amount of grain boundary segregation due to the extremely small amount of impurities incidentally included. It was possible to keep it extremely small. As a result of the above consideration, Example 4 and Examples 6 to 9 show more preferable embodiments for the high-low pressure integrated turbine rotor of the present invention.

[0047]

According to the high-low pressure integrated turbine rotor of claim 1, C is 0.10 to 0.35%, Si is 0.3% or less,
Mn is 1.0% or less, Ni is 1.0 to 2.0%, Cr is 1.5 to 3.0%, Mo is 0.9 to 1.3%, and V is 0.
10 to 0.35%, Nb 0.01 to 0.15%, W 0.1 to 1.5%, and the balance Fe and incidental impurities, the amount of which is P, which is an incidental amount of impurities included in the Fe. To 0.0
05% or less, S 0.001% or less, As 0.008
% Or less, Sb 0.004% or less, Sn 0.008%
Since it has the following tensile strength and toughness, it is possible to use long blades on the low pressure stage side, and because it has high creep rupture strength, it can be used in high temperature steam environments and Strength (tensile strength and creep rupture strength) and toughness (embrittlement) can be suppressed. As a result, it can be used for a steam turbine of a power generation facility with an output exceeding 100 MW.

Since the method for manufacturing a high-low pressure integrated turbine rotor according to claim 2 has a step of remelting and casting a primary steel ingot by ESR to form a secondary steel ingot, segregation of components in the center of the rotor, especially C The segregation of (carbon) components can be greatly suppressed. As a result, a high-low pressure integrated turbine rotor having the above-mentioned characteristics is obtained.

[Brief description of drawings]

Figure 1: FATT, creep rupture time and "segregation ratio"
It is a figure which shows the result arrange | positioned by Mo content.

FIG. 2 is a diagram showing a result in which FATT and creep rupture time are arranged by Ni content.

FIG. 3 is a diagram showing a result of arranging FATT and creep rupture time by W content.

FIG. 4 is a diagram showing a relationship between a heating time at 600 ° C. and a tensile test.

FIG. 5 is a diagram showing a relationship between a heating time at 400 ° C. and a Charpy impact test.

FIG. 6 is a diagram for explaining an example of a conventional steam turbine.

FIG. 7 is a diagram for explaining an example of a steam turbine including a high-low pressure integrated rotor.

[Explanation of symbols]

1 ... High temperature / high pressure side, 2 ......... Low pressure side, 3 ...... Joining section, 4 ...... Generator, 5 ...... Downstream side of high pressure section and near upstream side of low pressure section.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location F01D 5/02 // B22D 23/10 590

Claims (2)

[Claims] 1. The composition of steel is C: 0.10 by weight ratio.
0.35%, Si: 0.3% or less, Mn: 1.0% or less, Ni: 1.0 to 2.0%, Cr: 1.5 to 3.0
%, Mo: 0.9 to 1.3%, V: 0.10 to 0.35
%, Nb: 0.01 to 0.15%, W: 0.1 to 1.5
% And the balance being Fe and incidental impurities, and the incidental impurities are in a weight ratio of P: 0.005% or less,
S: 0.001% or less, As: 0.008% or less, S
b: 0.004% or less, Sn: 0.008% or less, a high-low pressure integrated turbine rotor. 2. The composition of the steel is C: 0.10 by weight ratio.
0.35%, Si: 0.3% or less, Mn: 1.0% or less, Ni: 1.0 to 2.0%, Cr: 1.5 to 3.0
%, Mo: 0.9 to 1.3%, V: 0.10 to 0.35
%, Nb: 0.01 to 0.15%, W: 0.1 to 1.5
% And the balance being Fe and incidental impurities, and the incidental impurities are in a weight ratio of P: 0.005% or less,
S: 0.001% or less, As: 0.008% or less, S
b: 0.004% or less, Sn: 0.008% or less, a method of manufacturing a high-low pressure integrated turbine rotor, comprising: melting a steel material having the above composition in a melting furnace to produce a primary steel ingot. And a step of remelting and casting the primary steel ingot by an electroslag melting method to form a secondary steel ingot, and a step of forging the secondary steel ingot into a rotor-shaped forged product, It is characterized by comprising the steps of annealing, quenching and tempering a rotor-shaped forged product.