JPH05345922A - Production of high-pressure part and low-pressure part integrated type turbine rotor - Google Patents

Abstract

PURPOSE:To increase the size of a turbine rotor by heating a turbine rotor element body composed of a heat resistant steel with specific composition up to specific temp., separately applying hardening under respectively specified conditions, and then performing tempering under specific conditions. CONSTITUTION:A turbine rotor element body is constituted of a heat resistant steel which has a composition consisting of, by weight, 0.15-0.4% C, <=0.1% Si, 0.05-0.5% Mn, 1.5-2.5% Ni, 0.8-2.5% Cr, 0.8-2.5% Mo, 0.15-0.35% V, and the balance Fe with inevitable impurities and further satisfying at least one of the conditions in expressions I, II, III. At the time of hardening the above, heating is done up to 900-1000 deg.C, and then, the sect-ions to be high pressure part and medium pressure part of a steam turbine are hardened at a cooling velocity not higher than the velocity of air-blast quenching and also the section to be a low pressure part is hardened at a cooling velocity not lower than oil quenching velocity, respectively. Subsequently, tempering is done once or more at 550-700 deg.C. By this method, the high temp. creep strength in the high- pressure and medium-pressure part and the toughness in the low-pressure part can be improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for 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 one of generator turbines, a high-low pressure integrated turbine in which a high-pressure portion to a low-pressure portion are integrated is known, and a high-low pressure integrated turbine rotor is used for this turbine. .. This turbine rotor is exposed to steam pressures ranging from high pressure to low pressure at high temperatures, and its material is required to have both excellent high temperature creep characteristics and excellent low temperature toughness. Conventionally, Cr-Mo-V series low alloy steel has been developed as a high-low pressure integrated turbine rotor material, and further, for example, Japanese Patent Publication No. 54-19.
No. 370 and Japanese Patent Laid-Open No. 130502/1993 disclose a low alloy steel obtained by improving 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, as the high-low pressure integrated turbine rotor, a small one having a body diameter of about 1 m has been conventionally used, but in order to improve energy efficiency, for example, a large high-diameter body having a body diameter of 2 m is used. Development of a low-pressure integrated turbine rotor is desired.

[0003]

However, in order to increase the size of the high- and low-pressure integrated turbine rotor, it is necessary to increase the strength and toughness of the material, as compared with the conventional small rotor. This method is difficult to meet this demand. For example, even if a conventional heat treatment is performed using a Cr-Mo-V type low alloy steel that has been conventionally developed as a small high- and low-pressure integrated turbine rotor material, a high-temperature creep as a large high- and low-pressure integrated turbine rotor is obtained. There is a problem that strength or low temperature toughness is insufficient and sufficient performance cannot be obtained as a large-sized high-low pressure integrated turbine rotor material. 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-mentioned problems, the first invention of the method for manufacturing a high-low pressure integrated turbine rotor according to the present invention is C: 0.15 to 0.4 in weight%.
%, Si: 0.1% or less, Mn: 0.05 to 0.5%,
Ni: 1.5 to 2.5%, Cr: 0.8 to 2.5%, M
o: 0.8 to 2.5%, V: 0.15 to 0.35%, the balance consisting of Fe and unavoidable impurities, and (1), (2) and (3) shown below. When quenching a turbine rotor body made of heat-resistant steel that satisfies at least one of the conditions
To 1000 ° C. and quench the part corresponding to the high / intermediate pressure part in the operating environment of the steam turbine at a cooling speed equal to or lower than the airflow cooling, and the part corresponding to the low pressure part at a cooling speed equal to or higher than the oil cooling, and then The element body is tempered one or more times at 550 to 700 ° C. (Mn / Ni) ratio: 0.12 or less (1) (Si + Mn) / Ni ratio: 0.18 or less (2) (V + Mo) / (Ni + Cr) ratio: 0.45 to 0.7 (3)

In a second aspect of the invention, the portion corresponding to the high / medium pressure portion of the turbine rotor body made of the above heat resistant steel is 900-1.
030 ℃, 870 ~ 1000 ℃ for the low pressure part
Moreover, the part corresponding to the high and medium pressure parts is 2 more than the low pressure part.
It is characterized by heating to a high temperature of 0 to 80 ° C. and quenching, and then tempering the element body once or more at 550 to 700 ° C. In a third aspect of the invention, a portion corresponding to the high / medium pressure portion of the turbine rotor body made of the above heat-resistant steel is 900 to 1030 ° C., and a portion corresponding to the low pressure portion is 870 to 870.
At 1000 ° C, the part corresponding to the high / medium pressure part is heated to a temperature 20 to 80 ° C higher than that of the low pressure part.
The part corresponding to the medium pressure part is quenched at a cooling rate not higher than the wind cooling, and the part corresponding to the low pressure part is quenched at a cooling rate not lower than oil cooling, and then the element body is tempered at 550 to 700 ° C. one or more times. It is characterized by performing. A fourth aspect of the present invention is the composition of the above heat-resistant steel, further comprising Nb and Ta: 0.005% by weight.
.About.0.15% and W: 0.1 to 1.0%. A fifth aspect of the present invention is the composition of the above heat-resistant steel, further comprising 0.001 to 0.001 by weight of at least one of Ti, Al, Zr, B, Ca and a rare earth element.
It is characterized by containing 0.1%.

The turbine rotor body does not necessarily have to have the high pressure portion, the medium pressure portion, and the low pressure portion, and may have two or more of them. Further, when the cooling rate is changed between the high-medium pressure portion and the low-pressure portion, the cooling at the time of quenching applied to the portion corresponding to the low-pressure portion may be performed by a method having a cooling rate higher than oil cooling, for example, oil cooling, water cooling. The cooling at the time of quenching, which can be performed by cooling with a fountain, and which is applied to a 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, for example, by airflow cooling or air cooling. It can be carried out. 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.

[0007]

The high-low pressure integrated turbine rotor has different usage conditions depending on the parts, and thus the required properties also differ depending on the parts. Particularly, the high temperature creep strength is sufficiently high in the high pressure part and the intermediate pressure part. It is required, and it is required that the low pressure part has excellent low temperature toughness. by the way,
When the cooling rate during quenching is slow enough 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 becomes, the better the low temperature toughness becomes. ..

According to the method for manufacturing a high-low pressure integrated turbine rotor of the present invention, a well-known heat-resistant steel having a specific composition is used, and the turbine rotor body is cooled at the time of quenching by the high-medium pressure portion and the low-pressure portion. Since quenching is performed by changing the speed 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,
The turbine rotor body has improved hardenability due to the above composition, and by heat treatment it is sufficiently hardened to reach the center of the large diameter even in large rotors, improving low temperature toughness without impairing high temperature creep strength. be able to. Furthermore, at the time of quenching, the heating temperature prior to cooling,
By providing a difference between the high / medium pressure portion and the low pressure portion (hereinafter referred to as deviation heating), the above-mentioned operation is ensured.

Next, the conditions of the heat treatment applied to the turbine rotor body having the above composition and the reasons for limiting the heat treatment 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., low temperature toughness is poor. Since it will decrease, 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 and medium pressure part temperature-low pressure part temperature) 20 to 80 ° C When a difference in heating temperature between the high and medium pressure parts and the low pressure part is provided, 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 carbides are not completely dissolved, and if it exceeds 1000 ° C, the austenite crystal grains are coarsened and the low temperature toughness is lowered. Within the above range. 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.

Cooling Rate (In the Case of Deviation Cooling) In order to obtain good high temperature creep strength, the portion corresponding to the high / medium pressure portion is quenched at a cooling rate equal to or lower than the blast cooling. If this is cooled at a rate higher than the blast cooling, the amount of low-temperature transformed bainite structure increases, and sufficient high temperature creep strength cannot be obtained. Further, the portion corresponding to the low pressure portion is quenched at a cooling rate higher than oil cooling in order to obtain good low temperature toughness. If this is cooled at a cooling rate lower than that of oil cooling, a structure containing ferrite or high temperature transformation bainite is formed in the central part, and the low temperature toughness increases. 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.

[0011]

[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). 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
70 ° C, a portion corresponding to the low pressure part is heated to 930 ° C, and then, the cooling is performed at a cooling rate of 50 ° C / h assuming a cooling rate of the central portion when the actual turbine rotor body is cooled with a fountain, and then quenched. Was performed (deviation heating / uniform cooling).

Further, 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 9
The temperature corresponding to the low pressure part is 70 ° C., the part corresponding to the low pressure part is heated to 930 ° C., and the part corresponding to the high pressure part and the intermediate pressure part is 25 ° C. which is the center cooling rate when the actual turbine rotor body is forcedly cooled. The cooling rate was assumed to be the central portion when the water was cooled at a cooling rate of / h and the portion corresponding to the low pressure portion was cooled with a fountain.
Quenching was performed by cooling at a cooling rate of 0 ° 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). Note that 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 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.

[0014]

[Table 1]

[0015]

[Table 2]

[0016]

As described above, according to the method for manufacturing a high-low pressure integrated turbine rotor of the present invention, the turbine rotor element body having a specific composition is subjected to deviation heating as desired, and further deviation cooling is performed to quench it. The high temperature creep strength of the high and medium pressure portions is improved, the toughness of the low pressure portion is improved, the turbine rotor can be upsized, and the energy efficiency can be improved. Moreover, high reliability can be obtained by improving the material characteristics.

Front page continued (72) Inventor Masao Shiga 4026 Kujimachi, Hitachi City, Hitachi, Ibaraki Hitachi, Ltd., Hitachi Research Laboratory (72) Inventor Hiro Fukui 4026 Kujicho, Hitachi City, Ibaraki, Hitachi Research Institute, Ltd. (72) Inventor Toshimi Tan 3-1-1 Sachimachi, Hitachi City, Ibaraki Prefecture Hitachi Ltd. Hitachi factory (72) Inventor Ryoichi Kaneko 3-1-1, Sachimachi Hitachi City, Ibaraki Prefecture Stock Company Hitachi Ltd. Hitachi factory (72) Inventor Norio Morisada 2-832, Horiguchi, Katsuta City, Ibaraki Prefecture Hitachi Material Engineering Co., Ltd.

Claims (5)

[Claims] 1. C: 0.15 to 0.4% by weight, S
i: 0.1% or less, Mn: 0.05 to 0.5%, Ni:
1.5-2.5%, Cr: 0.8-2.5%, Mo:
0.8 to 2.5%, V: 0.15 to 0.35%, the balance consisting of Fe and inevitable impurities, and the conditions (1), (2) and (3) shown below. When quenching a turbine rotor body made of heat-resistant steel satisfying at least one of
After heating to 1000 ° C., the part corresponding to the high / medium pressure part in the operating environment of the steam turbine is quenched at a cooling speed not higher than the airflow cooling, and the part corresponding to the low pressure part is quenched at a cooling speed not lower than oil cooling. Method for manufacturing high- and low-pressure integrated turbine rotor characterized in that the element body is tempered at least once at 550 to 700 ° C. (Mn / Ni) ratio: 0.12 or less (1) (Si + Mn) / Ni ratio : 0.18 or less (2) (V + Mo) / (Ni + Cr) ratio: 0.45 to 0.7 (3) 2. A portion corresponding to the high / medium pressure portion of the turbine rotor body made of the heat-resistant steel according to claim 1 is 900-10.
30 ℃, 870 ~ 1000 ℃ for the low pressure part
Moreover, the part corresponding to the high and medium pressure parts is 2 more than the low pressure part.
A method for manufacturing a high-low pressure integrated turbine rotor, comprising heating to a high temperature of 0 to 80 ° C., quenching, and then tempering the element body once or more at 550 to 700 ° C. 3. A portion of the turbine rotor body made of the heat-resistant steel according to claim 1 corresponding to the high and medium pressure portions is 900 to 10.
30 ℃, 870 ~ 1000 ℃ for the low pressure part
Moreover, the part corresponding to the high and medium pressure parts is 2 more than the low pressure part.
0 to 80 ° C. are heated to a high temperature, the part corresponding to the high / medium pressure part is quenched at a cooling speed not higher than the wind cooling, and the part corresponding to the low pressure part is quenched at a cooling speed not lower than oil cooling, and then, A method for manufacturing a high-low pressure integrated turbine rotor, comprising tempering the element body at 550 to 700 ° C. one or more times. 4. The composition of the heat resistant steel further comprising Nb in a weight percentage.
And Ta: 0.005-0.15%, W: 0.1
The method for manufacturing a high-low pressure integrated turbine rotor according to claim 1, wherein the high-low pressure integrated turbine rotor contains 1.0% or more of 1.0%. 5. The composition of the heat-resisting steel, further comprising:
And Al, Zr, B, Ca, and at least one kind of rare earth element are contained in a total amount of 0.001 to 0.1%, and the high and low pressure integrated turbine rotor according to any one of claims 1 to 4 is contained. Manufacturing method