JPH05230599A - Steam turbine rotor material - Google Patents

Abstract

PURPOSE:To obtain a steam turbine rotor material. CONSTITUTION:This steam turbine rotor material is (1) a steam turbine rotor material produced by providing a composition consisting of, by weight ratio, 0.25-0.34% carbon, <=0.1% silicon, 0.7-1.1% manganese, 0.5-1% nickel, 1-1.4% chromium, 1-1.3% molybdenum, 0.2-0.3% vanadium, and iron with inevitable impurities, using vacuum deoxidation process at the time of ingoting, and further applying oil quenching at the time of hardening and (2) a steam turbine rotor material produced by providing a composition which contains, by weight ratio, 0.25-0.34% carbon, <=0.1% silicon, 0.7-1.1% manganese, 0.5-1% nickel, 1-1.4% chromium, 1-1.3% molybdenum, and 0.2-0.3% vanadium and has <=8 embrittlement parameter value represented by [10X(phosphorus content) + 5X(antimony content) + 4X(tin content) + (arsenic content)]X100 and also has the balance iron, using a vacuum deoxidation process at the time of ingoting, and further applying oil quenching at the time of hardening.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a steam turbine rotor material,
In particular, it relates to a steam turbine rotor material for thermal power generation.

[0002]

2. Description of the Related Art CrMoV steel, which is mainly used as a high-pressure rotor, can be cited as a rotor material used in a steam turbine plant for thermal power generation. However, this material is componently in order to secure high temperature strength, especially creep rupture strength. The Ni content is suppressed to 0.5% or less, and the heat treatment is performed by performing a relatively slow quenching process called forced air cooling.

For this reason, this rotor material has excellent creep rupture properties, but on the other hand, its toughness is inferior and it is 50%.
FATT (Fracture Appearance Trasition Temperatu
re; impact transition temperature) is high, and the turbine cannot be rotated unless the temperature inside the turbine rises sufficiently, so there is a problem that the startup time becomes long. In particular, in recent years, it has become necessary to take an operating form that meets the power demand even in a thermal power plant, and the demand for shortening the start-up time has become stronger because the plant frequently repeats starting and stopping.

[0004]

Therefore, the present invention intends to provide a new CrMoV steel-based rotor material in which the creep rupture strength of a high-pressure rotor is maintained as it is and the toughness is improved to shorten the start-up time. It is what

[0005]

As a result of earnest research, the inventors of the present invention have invented a new rotor material having excellent toughness and creep rupture strength equivalent to that of the current CrMoV high pressure rotor material. It was

That is, the present invention is: (1) Carbon: 0.25 to 0.34%, silicon: 0.1% or less, manganese: 0.7 to 1.1%, nickel: 0.5 by weight. -1%, chromium: 1-1.4%, molybdenum: 1-1.3%, vanadium: 0.2-0.3% and inevitable impurities and iron. A steam turbine rotor material, which is manufactured by using oil quenching when used. (2) By weight, carbon: 0.25 to 0.34%, silicon: 0.1% or less, manganese: 0.7 to 1.1%, nickel: 0.5 to 1%, chromium: 1 to 1. 1.4%, molybdenum: 1 to 1.3%, vanadium: 0.2 to 0.3%, represented by {(10 × phosphorus amount + 5 × antimony amount + 4 × tin amount + deflecting amount)} × 100 The steam turbine material is characterized in that the embrittlement parameter value is 8 or less and the balance is iron, and the product is manufactured by using a vacuum carbon deoxidizing method for ingot formation and further applying oil quenching during quenching. .. Is.

[0007]

The present inventors have invented a high-pressure rotor material having excellent toughness that cannot be obtained conventionally by carefully selecting the components of the CrMoV steel high-pressure rotor material. The reasons for limiting the components in the rotor material of the present invention will be described below.
Hereinafter,% of the components means% by weight.

C: C improves the hardenability and at the same time C
It forms carbides of r and Mo and contributes to improvement of high temperature strength.
However, if it is less than 0.25%, sufficient yield strength and creep rupture strength cannot be obtained, and if it exceeds 0.34%, excessive carbides are formed and the toughness decreases, so 0.25 to 0.34%.
And

Si: Si is an element necessary as a deoxidizing agent, but it is not always necessary in the rotor material of the present invention which employs the vacuum carbon deoxidizing method as the agglomeration method, and rather the reaction of vacuum carbon deoxidizing is performed. In order to promote it, it is preferable that the content is low, and Si is 0.1% or less because it promotes deterioration of toughness and embrittlement.

Mn: Mn is useful as an element for improving hardenability and is effective in improving toughness. If it is less than 0.7%, the effect is not sufficient, and if it exceeds 1.1%, the toughness decreases, so the content is made 0.7 to 1.1%.

Ni: Ni has an effect of improving hardenability and a strong effect of improving toughness. If it is less than 0.5%, its effect is small, and if it exceeds 1%, the high temperature strength, particularly the creep rupture strength is lowered.

Cr: Cr forms a carbide, is effective in improving high temperature strength, and is also effective in improving toughness. 1
%, Sufficient strength and toughness cannot be obtained, and 1.4%
If it exceeds, the toughness and the creep rupture strength are lowered.
Therefore, it is set to 1 to 1.4%.

Mo: Mo forms carbides and is effective in improving creep rupture strength at high temperatures. It is also effective in improving toughness. If it is less than 1%, a sufficient effect cannot be obtained, and if it exceeds 1.3%, it causes embrittlement during use.

V: V forms carbide and strongly contributes to the improvement of creep rupture strength, but if it is less than 0.2%, a sufficient effect cannot be obtained, and if it exceeds 0.3%, toughness is deteriorated. 0.2 to 0.3%.

P, Sb, Sn, As: These are elements that promote temper embrittlement, and it is desirable that they are as low as possible. In particular, tempering embrittlement parameter value {(10P +
When 5Sb + 4Sn + As) × 100} is 8 or less, temper embrittlement becomes a slight sign.

[0016]

EXAMPLES The present invention will be described below based on examples. (Example 1) In the test, the test materials shown in Table 1 were melted using a 50 kg vacuum melting furnace, and after forging corresponding to 3S, heat treatment was performed and each test was performed. The heat treatment was carried out by simulating a heat cycle corresponding to the center portion and the surface portion of the rotor material having a body diameter of 1200 φ when oil-cooled or forced air cooling. The quenching temperature was 955 ° C., and the tempering temperature was adjusted in the range of 670 to 705 ° C. so that the 0.2% proof stress was 60 to 65 kgf / mm ² .

Table 2 shows the result of the mechanical test of the simulated heat treated material corresponding to the center. From this result, it is understood that the material of the present invention has excellent toughness as compared with the comparative material. That is, the 50% FATT of the material of the present invention is less than 60 ° C., whereas the comparative material has a high value of 60 ° C. or higher, and the impact value of the material of the present invention is 3.0 kgf-m or more, whereas the comparative material Is as low as 2.6 kgf-m or less. The excellent toughness of the material of the present invention was achieved for the first time by the effect of reducing Si, the effect of oil cooling with a high cooling rate, and further by carefully selecting the component range. In this example, since a small amount of the material was dissolved, vacuum carbon deoxidation was simulated only by reducing Si. However, in Example 2 described later, the effect of vacuum carbon deoxidation was confirmed with a material equivalent to an actual machine.

FIG. 1 shows the results of creep rupture test of the surface phase simulated material. In FIG. 1, the abscissa is the Larson-Miller parameter, which is a value determined by the temperature and the rupture time, and the ordinate is the rupture stress when a creep rupture test is performed. From these results, it is understood that the rotor material of the present invention has excellent creep rupture strength equivalent to that of the comparative material and the conventionally used high-pressure rotor material.

Table 3 shows the results of the embrittlement test conducted at 450 ° C to 500 ° C. As is clear from this table, the material of the present invention exhibits excellent temper embrittlement characteristics.

[Table 1]

[Table 2]

[Table 3]

(Embodiment 2) A model rotor (maximum body diameter 120
0φ) was prototyped and confirmed. This model rotor uses the vacuum carbon deoxidation method for the agglomeration method and employs oil cooling for the quenching treatment. It was manufactured by a method different from forced air cooling.

Table 4 shows the chemical composition of the model rotor material corresponding to the actual machine of the rotor material of the present invention in comparison with the actual example of the conventional high-pressure rotor material. In addition, Table 5 shows the mechanical properties of the rotor together with actual examples of conventional high-pressure rotors. As is clear from this result, the toughness of the rotor material of the present invention is dramatically improved as compared with the conventional high-pressure rotor.

[Table 4]

[Table 5]

[0022]

The high-pressure rotor material of the present invention has good toughness without impairing the conventional excellent high-temperature strength, in particular, creep rupture strength. Therefore, the start-up time of the turbine can be shortened. It has become possible to operate a thermal power plant that can respond to changes in power demand.

[Brief description of drawings]

FIG. 1 is a diagram showing creep rupture strength of a rotor material of the present invention.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yusaku Takano 5-717-1, Fukahori-cho, Nagasaki-shi, Nagasaki Sanhishi Heavy Industries Ltd. Nagasaki Research Institute (72) Inventor Yorima Takeda 5-chome, Fukahori-cho, Nagasaki-shi, Nagasaki Prefecture 717-1 Sanbishi Heavy Industries Ltd. Nagasaki Research Institute (72) Inventor Takeshi Kondo 1-1, Atsunouracho, Nagasaki City, Nagasaki Prefecture Mitsubishi Heavy Industries Ltd. Nagasaki Shipyard (72) Inventor Kitajiro Kitagawa Tobata, Kitakyushu City, Fukuoka Prefecture Ward Ward 46-59 Nakahara Masakinohama 59 Japan Cast & Forged Steel Co., Ltd. (72) Inventor Katsuo Kaku Tobata-ku, Kitakyushu-shi, Fukuoka Kamo Nakahara Masakinoha 46 59 Japan Cast & Forged Steel Co., Ltd. (72) Inventor Takashi Koga Fukuoka, Kitakyushu, Tobata-ku, Oita 46-59, Nakahara Sakinohama Nippon Cast and Forged Steel Co., Ltd.

Claims (2)

[Claims] 1. A weight ratio of carbon: 0.25 to 0.34.
%, Silicon: 0.1% or less, manganese: 0.7 to 1.
1%, nickel: 0.5 to 1%, chromium: 1 to 1.4
%, Molybdenum: 1 to 1.3%, vanadium: 0.2 to
A steam turbine rotor material comprising 0.3% and inevitable impurities and iron, which is manufactured by using a vacuum carbon deoxidizing method for ingot formation and further applying oil quenching during quenching. 2. A weight ratio of carbon: 0.25 to 0.34.
%, Silicon: 0.1% or less, manganese: 0.7 to 1.
1%, nickel: 0.5 to 1%, chromium: 1 to 1.4
%, Molybdenum: 1 to 1.3%, vanadium: 0.2 to
0.3%, and the embrittlement parameter value represented by {(10 × phosphorus amount + 5 × antimony amount + 4 × tin amount + definition amount)} × 100 is 8 or less, and the balance is iron, and vacuum is applied to the ingot formation. A steam turbine material characterized by being manufactured by using a carbon deoxidizing method and applying oil quenching during quenching.