JPH05195068A - Manufacture of high-and low-pressure integrated turbine rotor - Google Patents

Abstract

PURPOSE:To manufacture a high-and low-pressure integrated turbine rotor, which makes strength and toughness high and can be used for the large scaled rotor. CONSTITUTION:The turbine rotor base stock is heated to parts corresponding to the high pressure part and middle pressure part as desirable so as to be higher than a part corresponding to the low pressure part and quenching is executed at cooling rate of oil cooling or above to the part corresponding to the low pressure part at the cooling rate of air blast cooling or lower to the parts corresponding to the high pressure part and the middle pressure part and, thereafter, one or more times of tempering is executed to the base stock at a prescribed temp. By this method, the material having excellent high temp. creep strength and low temp. toughness is obtd., and the application for the large scaled high-and low-pressure integrated turbine rotor is enabled, and energy efficiency can be improved by making the turbine rotor large in scale.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art As is well known, there are various types of turbine generators, and as one of them, a turbine generator having a single casing uses a high-low pressure integrated turbine rotor. This turbine rotor is exposed to steam pressure from high pressure to low pressure at high temperature, and its material is
It is required to have both excellent high temperature creep properties and excellent low temperature toughness. Conventionally, Cr-Mo-V type low alloy steel has been developed as a high-low pressure integrated turbine rotor material, and further, for example, Japanese Patent Publication No. 54-1937.
No. 0 discloses a low alloy steel improved on this type of material. When manufacturing a high-low pressure integrated turbine rotor, the turbine rotor body made of the above alloy steel is uniformly heated, and the entire body is oil-quenched, water-quenched, fountain-quenched, and then tempered. It is heat treated.
By the way, in the high-low pressure integrated turbine rotor described above,
Conventionally, a small one having a body diameter of about 1 m has been used, but in order to improve energy efficiency, development of a large-sized high-low pressure integrated turbine rotor having a body diameter of 2 m is desired.

[0003]

However, in order to increase the size of the high-low pressure integrated turbine rotor, it is required that the material has higher strength and higher toughness than the conventional small rotor, and thus the conventional rotor has been used. It is difficult to meet this demand with the conventional materials and manufacturing methods. For example, Cr-Mo, which has been previously developed as a compact high- and low-voltage integrated turbine rotor material
-Even if heat treatment of V-type low alloy steel is carried out by a conventional method, the high temperature and low pressure integrated turbine rotor lacks high temperature creep strength or low temperature toughness, and it has sufficient performance as a large high pressure and low pressure integrated turbine rotor material. Can't get The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for manufacturing a high-low pressure integral turbine rotor having both excellent high-temperature creep characteristics and excellent low-temperature toughness.

[0004]

In order to solve the above problems, the first invention of the method for manufacturing a high-low pressure integrated turbine rotor according to the present invention is to heat a turbine rotor body to a predetermined temperature to reduce the low pressure. The parts corresponding to the parts are quenched at a cooling speed of oil cooling or higher, and the parts corresponding to the high pressure part and the intermediate pressure part are cooled at a cooling speed of not higher than the airflow cooling, and then the element body is tempered one or more times at a predetermined temperature. It is characterized by performing. The turbine rotor body does not necessarily have to have each of the high pressure portion, the medium pressure portion, and the low pressure portion, and may have any two or more of them. Further, the heating temperature for quenching is appropriately selected according to the composition of the steel used for the turbine rotor body, the temperature required for austenitizing the steel. Also, the cooling applied to the low pressure part
A method having a cooling rate equal to or higher than oil cooling may be used, and for example, oil cooling, water cooling, or fountain cooling can be performed. Further, the cooling applied to the portion corresponding to the high and medium pressure portions may be performed by a method having a cooling rate equal to or lower than the airflow cooling, and for example, airflow cooling or air cooling can be performed. Next, the tempering temperature and the number of times thereof are appropriately selected according to the composition of the steel, the required tempering effect, and the like. A second aspect of the invention is to heat and quench the turbine rotor body in the first aspect of the invention so that the portions corresponding to the high pressure portion and the intermediate pressure portion have a higher temperature than the portions corresponding to the low pressure portion. Characterize.

According to a third aspect of the present invention, the turbine rotor body is, by weight%, C: 0.2 to 0.35%, Ni: 1.6 to 2.
4%, Cr: 1.2 to 2.5%, Mo: 0.9 to 1.5
%, V: 0.2 to 0.3%, the balance consisting of Fe and unavoidable impurities, and% by weight of the unavoidable impurities.
, Si: 0.1% or less, Mn: 0.1% or less, P:
The turbine rotor body is made of high-purity steel with an allowable content of 0.005% or less and S: 0.005% or less.
It is heated to 00 to 1000 ° C., the part corresponding to the low pressure part is quenched at a cooling speed of oil cooling or higher, and the parts corresponding to the high pressure part and the intermediate pressure part are quenched at a cooling speed not higher than the wind cooling, and then the element body is cooled. It is characterized by performing tempering at least once at 550 to 700 ° C.

According to a fourth aspect of the present invention, the turbine rotor body is, by weight%, C: 0.2 to 0.35%, Ni: 1.6 to 2.
4%, Cr: 1.2 to 2.5%, Mo: 0.9 to 1.5
%, V: 0.2 to 0.3%, the balance consisting of Fe and unavoidable impurities, and% by weight of the unavoidable impurities.
, Si: 0.1% or less, Mn: 0.1% or less, P:
It is made of high-purity steel having an allowable content of 0.005% or less and S: 0.005% or less, and the portions corresponding to the high pressure portion and the intermediate pressure portion of the turbine rotor body are 900 to 1030.
C., the part corresponding to the low pressure part is heated to 870 to 1000.degree. C. and the parts corresponding to the high pressure part and the intermediate pressure part are heated to 20 to 80.degree. The body is characterized by being tempered one or more times at 550 to 700 ° C.

According to a fifth aspect of the present invention, in the fourth aspect of the invention, a portion corresponding to a low pressure portion of the turbine rotor body is cooled at an oil cooling rate or higher, and portions corresponding to a high pressure portion and an intermediate pressure portion are blown air cooled or less. It is characterized by quenching at a cooling rate.

A sixth aspect of the invention is the composition of the high purity steel of the third to fifth aspects of the invention, further comprising Nb: 0.01-0.
It is characterized by containing 05%. In addition, the above-mentioned third
The unavoidable impurities in the sixth invention are not limited to the components whose contents are limited, and in addition to these, impurities that are usually unavoidably mixed may be included. Does not particularly limit the content, but it is desirable to reduce the content as much as possible.

[0009]

When the cooling rate during quenching is slower so that ferrite transformation does not occur (for example, about 5 ° C / h or more), the high temperature creep strength becomes better, and conversely, the faster the cooling rate during quenching, the lower temperature toughness. Will be good. Since the high-low pressure integrated turbine rotor has different usage conditions depending on the parts, the required properties also differ depending on the parts. Especially, it is necessary that the high temperature creep strength is sufficiently high in the high pressure part and the intermediate pressure part. In the low pressure part, it is required to have excellent low temperature toughness.

According to the method for manufacturing a high-low pressure integrated turbine rotor of the present invention, the high-to-medium pressure portion of the turbine rotor body,
Since the quenching is performed by changing the cooling rate according to the low pressure part as described above (hereinafter referred to as deviation cooling), sufficient high temperature creep strength is secured in the parts corresponding to the high and medium pressure parts,
On the other hand, excellent low temperature toughness is secured in the low pressure part. Also,
By providing a difference in the heating temperature prior to cooling between the high and medium pressure portions and the low pressure portion (hereinafter, referred to as deviation heating), the above-mentioned operation is ensured. In that case, it is desirable to heat so that the heating temperature of the high and medium pressure portions is higher by 20 to 80 ° C. than that of the low pressure portion. This means that if the temperature difference is less than 20 ° C,
This is because sufficient superiority cannot be obtained in the strength of the high and medium pressure portions and the toughness of the low pressure portion, and when the temperature exceeds 80 ° C, the production becomes difficult.

Further, by adopting a high-purity steel having a specific composition for the turbine rotor body, the hardenability is improved, and by heat treatment, even in a large-sized rotor, it is sufficiently hardened to reach the center of the large diameter. Therefore, the low temperature toughness can be improved without impairing the high temperature creep strength. Further, by suppressing the content of the unavoidable impurities to achieve high purification, the temper embrittlement susceptibility is improved and the deterioration over time can be suppressed.

Next, the reasons for limiting the component contents of this high-purity steel will be described below. In addition, in the following description, the content of each component is shown by weight%. C: 0.2 to 0.35% C needs to be contained in an amount of 0.2% or more in order to obtain desired tensile strength and proof stress, but if it exceeds 0.35%, toughness decreases, Further, since the carbide aggregates and coarsens to reduce the creep strength, the above range is set. Ni: 1.6 to 2.4% Ni is added to improve hardenability, strength, and toughness. However, if its content is less than 1.6%, its action is insufficient, and if it exceeds 2.4%, the high temperature creep strength is lowered, so the above range was made.

Cr: 1.2 to 2.5% Added for improving high temperature strength and toughness. However, if its content is less than 1.2%, its action is insufficient, and if it exceeds 2.5%, the effect is saturated, so the above range was made. Mo: Carbides are formed between 0.9 and 1.5% C and finely precipitate in the matrix ,
Improves strength at low and high temperatures and suppresses temper embrittlement. If the content is less than 0.9%, the effect is insufficient, and if the content exceeds 1.5%, not only the effect is saturated, but also the high temperature strength and toughness are deteriorated, so the above range And

V: 0.2 to 0.3% V forms carbides and improves high temperature strength. However,
If its content is less than 0.2%, its action is insufficient, and if it exceeds 0.3%, the high temperature creep strength and toughness are lowered, so the above range was made. Nb: 0.01 to 0.05 % Nb forms a carbide and enhances the high temperature strength, so it is added if desired. However, if the content is less than 0.01%,
Its action is insufficient, and if it exceeds 0.05%, eutectic type carbides are formed and the toughness is remarkably deteriorated.

Inevitable impurities (Si: 0.1% or less, Mn
: 0.1% or less, P: 0.005% or less, S: 0.0
05% or less) Si, Mn: 0.1% or less Si is usually used as a deoxidizing agent, and the content in that case is usually about 0.30 to 0.50%. When this amount of Si is contained, macrosegregation occurs in a large steel ingot. Further, if the Si content is high, the temper embrittlement susceptibility becomes extremely high, and the notch toughness is impaired. In the present invention, in order to avoid the above-mentioned adverse effects of Si, for example, Si
Vacuum C deoxidation is adopted instead of deoxidation. When performing vacuum C deoxidation, it is desirable to reduce the Si content as much as possible before the deoxidation. In the present invention, the permissible content of Si as an unavoidable impurity is set to 0.1% or less which is industrially possible. Limited M
n combines with S to form a non-metallic inclusion and reduces toughness. Further, Mn remaining in the steel promotes temper embrittlement similarly to Si, so it is desirable to reduce it as much as possible, and the allowable content of Mn as an unavoidable impurity is 0.1% or less that is industrially possible. Limited to. .

P: 0.005% or less P is an element that promotes temper embrittlement susceptibility, and it is desirable to reduce it as much as possible in order to obtain a material with little deterioration over time. Considering the current refining technology level. Then, the allowable content of P was limited to 0.005% or less. S: 0.005% or less S, in a large steel ingot, produces a non-metallic inclusion such as MnS in the steel even if it is contained in a small amount, and deteriorates the quality of the steel. Therefore, it is desirable to reduce S as much as possible. As with P, considering the current refining technology level, the allowable content of S is 0.005
Limited to less than%.

Other Inevitable Impurities In addition to the above inevitable impurities, inevitable impurities that deteriorate the steel quality are Cu, and as inevitable impurities that promote temper embrittlement, there are As, Sb, Sn, and the like.
It is preferable to reduce these unavoidable impurities as much as possible.
However, these unavoidable impurities are inevitably mixed with the raw materials and are difficult to remove by refining. Therefore, it is largely due to careful selection of raw materials, and from the viewpoint of steel quality improvement, Cu: 0.10%
Hereinafter, it is desirable to limit As: 0.008% or less, Sb: 0.01% or less, Sn: 0.005% or less.

Next, the special conditions for the heat treatment applied to the turbine rotor body having the above composition and the reasons for the limitation will be described. Quenching heating temperature Uniform heating : 900 to 1000 ° C. When uniformly heating the whole, if the austenitizing temperature is less than 900 ° C., sufficient high temperature creep strength cannot be obtained, and if it exceeds 1000 ° C., the low temperature toughness is low. Since it decreases, the above range is set. Deviation heating : High and medium pressure part 900 to 1030 ° C, low pressure part 87
0 to 1000 ° C (high-medium pressure part temperature-low pressure part temperature) 20 to 80 ° C When the heating temperature of the high and medium pressure parts and the low pressure part is different, the austenitizing temperature is 900 ° C in the high and middle pressure parts.
If it is less than 10%, sufficient high temperature creep strength cannot be obtained, and if it exceeds 1030 ° C., notch weakening at high temperature is recognized, so the above range is set. On the other hand, if the austenitizing temperature of the low pressure portion is less than 870 ° C, the low temperature toughness is lowered because the carbide is not completely solid-solved, and if it exceeds 1000 ° C, the austenite crystal grains are coarsened and the low temperature toughness is lowered. Within the above range. Incidentally, the austenitizing temperature of the high and medium pressure parts is higher than the austenitizing temperature of the low pressure part.
The temperature is selected in the range of 20 to 80 ° C. higher, but it is necessary to make a temperature difference of 20 ° C. or more in order to obtain the effect. Moreover, since the manufacturing is difficult when the temperature difference exceeds 80 ° C., the range of the temperature difference is limited to 20 to 80 ° C. Tempering temperature : 550 to 700 ° C. If the tempering temperature is less than 550 ° C., a sufficient tempering effect cannot be obtained, so that good toughness cannot be obtained.
If the temperature exceeds 00 ° C, the desired strength cannot be obtained, so the content is within the above range.

[0019]

[Examples] Sample steels (Nos. 1 to 3) having the compositions shown in Table 1 were melted in a vacuum melting furnace to melt a 50 Kg steel ingot. Each of the steel ingots was heated to 1200 ° C. and hot forged at a forging ratio of about 4 to form a turbine rotor body having a body diameter of 75 mm, and the following heat treatment was performed. As one method of the method of the present invention,
After the uniform heating, the parts corresponding to the high pressure part and the intermediate pressure part are cooled at a cooling rate of 25 ° C./h, which is assumed to be the cooling rate at the center when the actual turbine rotor body is forcedly cooled, The portion corresponding to the portion was cooled at a cooling rate of 50 ° C./h assuming the cooling rate of the central portion when the fountain was cooled, and quenching was performed with different cooling rates (uniform heating / deviation cooling). Further, as another method of the present invention, a portion corresponding to the high pressure portion and the intermediate pressure portion of the turbine rotor body is heated to 970 ° C., and a portion corresponding to the low pressure portion is heated to 930 ° C.
After that, quenching was performed by cooling at a cooling rate of 50 ° C./h, which is assumed to be the cooling rate of the central portion when the actual turbine rotor body was cooled with a fountain (deviation heating / uniform cooling).

As another method of the present invention, the portions corresponding to the high pressure portion and the intermediate pressure portion of the turbine rotor body are set to 97.
The temperature corresponding to 0 ° C. and the low pressure part is heated to 930 ° C., and the part corresponding to the high and medium pressure parts is further heated to 25 ° C., which is the center cooling rate when the actual turbine rotor body is forcedly cooled. The cooling rate was assumed to be 50 / h, and the cooling rate at the center was assumed to be 50 when the portion corresponding to the low pressure portion was cooled with a fountain.
Quenching was performed by cooling at a cooling rate of ° C / h (deviation heating / deviation cooling). As a comparative method, the turbine rotor body was uniformly heated to 950 ° C., and then the actual turbine rotor body was cooled at a cooling rate of 50 ° C./h, which is assumed to be the center cooling rate in the case of cooling with a fountain. Then, it was quenched (uniform heating / uniform cooling). Further, each element body was tempered at 650 ° C. for 20 hours after quenching.

Next, Table 2 shows the material test results of the sample steel after the heat treatment. As is clear from Table 2, according to the method of the present invention, the high temperature creep strength is improved in the high pressure portion and the toughness is improved in the low pressure portion as compared with the conventional method. Further, in the method of the present invention, the above-mentioned effect is more remarkable in the method of deviation heating / deviation cooling than in the method of uniform heating / deviation cooling or deviation heating / uniform cooling.

[0022]

[Table 1]

[0023]

[Table 2]

[0024]

As described above, according to the method of manufacturing a high-low pressure integrated turbine rotor of the present invention, the turbine rotor body is deviation-heated as desired, and further deviation-cooled to quench the steel body. The high temperature creep strength of the medium pressure part is improved, and the toughness of the low pressure part is improved, so that it can be applied to a large turbine rotor. Also, if the turbine rotor body is made of high-purity steel of a specific composition, this body is subjected to deviation heating or deviation cooling, quenching, and then tempering,
The effects of improving the high temperature creep strength and the low temperature toughness are further enhanced, and the temper embrittlement susceptibility is improved, so that deterioration over time can be suppressed.

Claims (6)

[Claims] 1. A turbine rotor body is heated to a predetermined temperature, a portion corresponding to a low pressure portion is cooled at an oil cooling rate or higher, and a portion corresponding to a high pressure portion and an intermediate pressure portion is cooled at a wind speed or less. Quenching, and then tempering the element body at a predetermined temperature one or more times. 2. The turbine rotor body is heated and quenched so that the portions corresponding to the high pressure portion and the intermediate pressure portion have a higher temperature than the portions corresponding to the low pressure portion. Method for manufacturing high-low pressure integrated turbine rotor described 3. The turbine rotor body, in wt%, C:
0.2 to 0.35%, Ni: 1.6 to 2.4%, Cr:
1.2-2.5%, Mo: 0.9-1.5%, V: 0.
2 to 0.3%, the balance consisting of Fe and inevitable impurities, of which in% by weight, Si:
0.1% or less, Mn: 0.1% or less, P: 0.005%
Hereinafter, S: 0.005% or less is made of high-purity steel with an allowable content of 900 to 100
It is heated to 0 ° C., the portion corresponding to the low pressure portion is quenched at an oil cooling rate or higher, and the portions corresponding to the high pressure portion and the intermediate pressure portion are quenched at a cooling rate not higher than the wind cooling, and then the element body is heated to 550.
High-low pressure integrated turbine rotor manufacturing method characterized by performing tempering at least once at 700 ° C. 4. The turbine rotor body, in wt%, C:
0.2 to 0.35%, Ni: 1.6 to 2.4%, Cr:
1.2-2.5%, Mo: 0.9-1.5%, V: 0.
2 to 0.3%, the balance consisting of Fe and inevitable impurities, of which in% by weight, Si:
0.1% or less, Mn: 0.1% or less, P: 0.005%
Hereinafter, S: composed of high-purity steel having an allowable content of 0.005% or less, a portion corresponding to the high pressure portion and the intermediate pressure portion of the turbine rotor body is 900 to 1030 ° C., and a portion corresponding to the low pressure portion is It is heated at 870 to 1000 ° C., and the parts corresponding to the high pressure part and the intermediate pressure part are heated to 20 to 80 ° C. higher than the low pressure part, and then quenched, and then the element body is once at 550 to 700 ° C. A method for manufacturing a high-low pressure integrated turbine rotor, characterized by performing the above tempering 5. A turbine rotor body is quenched by cooling a portion corresponding to a low pressure portion at an oil cooling rate or higher and a portion corresponding to a high pressure portion and a medium pressure portion at a cooling rate not higher than blast cooling. A method of manufacturing a high-low pressure integrated turbine rotor according to claim 4. 6. The composition of the high-purity steel for a turbine rotor body further contains Nb: 0.01 to 0.05% by weight, according to any one of claims 3 to 5. A method for manufacturing a high-low pressure integrated turbine rotor according to the description.