JPH02101143A - Structural material for turbine - Google Patents

Abstract

PURPOSE:To manufacture the title material having high creep rupture strength, tensile strength and toughness by incorporating specific ratios of C, Si, Mn, Ni, Cr, Mo, V, W, N, Nb and Ta into Fe. CONSTITUTION:A material contg., by weight, 0.05 to 0.30% C, <=1.0% (not including zero) Si, <=1.0%(not including zero) Mn, 1.5 to 3.5% Ni, 10 to 15% Cr, 0.5 to 2.0% Mo, 0.05 to 0.50% V, 0.5 to 2.0% W, 0.01 to 0.3% N, at least one kind of 0.01 to 0.5% Nb and Ta and the balance Fe with incidental impuri ties is prepd. In this way, the structural material having high creep rupture strength at about 400 to 500 deg.C and having high tensile strength and toughness at room temp. can be obtd.; the material is most preferable for a compressor for a high temp. and high pressure gas turbine or the like.

Description

Detailed Description of the Invention [Object of the Invention] (Industrial Field of Application) The present invention is used, for example, in compressor disks of gas turbines, and has particularly high creep-loveture strength at 400-500°C and high tensile strength at room temperature. and a structural material for a turbine having toughness.

(Prior Art) Currently, structural materials for turbines, such as compressor disks for gas turbines, are used according to ASTM 470 (
class 8) CI-Insite Li with excellent creep rupture strength at high temperatures as specified
Alloy materials such as AIS I 422) and austenitic steels have also been used.

In recent years, there has been a desire to improve the thermal efficiency of gas turbines from the viewpoint of energy conservation, and there has been a need to increase the temperature and pressure of combustion residue.

As gas turbines become higher in temperature and pressure, compressors also become larger in order to increase the pressure ratio.

Figure 1 is a partial sectional view showing an example of the configuration of a compressor. Specifically, it is necessary to lengthen the rotor blades 3 in the low pressure section (section a) and increase the temperature and pressure in the high pressure section (section b). Become.

In this case, the [temple tree disk 1] of the low pressure part (part a)
Since a higher tensile stress acts on the steel, high tensile strength and toughness at around room temperature are required from the viewpoint of preventing ductile and brittle fractures. On the other hand, in the high pressure section (section b), due to the high temperature, the compressor disk 1 is required to have high creep lumpure strength in the operating temperature range of 400 to 500'C. In FIG. 1, reference numeral 3 indicates a stationary blade, 4 indicates a disk tightening bolt, and 5 indicates a casing.

Conventional Cr-/MO/vm does not have enough tensile strength, toughness, and creep rubber strength to meet these requirements, so it is necessary to use other new materials.

(Problem to be Solved by the Invention) Examples of structural structures with creep rupture strength that are -b higher than Or-MO-V steel include N1-based alloys, Co-based alloys, Δ-stenite steels, and 12Ci-based martensitic steels. generally known. However, N-based alloys and Co1 alloys are undesirable in terms of hot workability, machinability, manufacturing cost, etc.

In addition, austenitic steel has a 2-lead p-strength at 400 to 500°C, which is not very high (<4).
Furthermore, it is undesirable due to the difference in thermal expansion with the blade. on the other hand,
Martesai 1 steel, which is a 12Cr steel, is considered to be a suitable structural material because it matches well with other components and has excellent tensile strength near room temperature.

Al5I4221 is known as a 12Cr-based multisite steel with excellent creep rupture strength at 400 to 500°C and tensile strength near room temperature.
5I422 steel has the disadvantage of having a low impact value near room temperature and being sensitive to notches.

The present invention was made in order to eliminate the above-mentioned drawbacks, and has a high creep temperature (・
- To provide a structural material for a turbine having strength and high tensile strength and toughness at room temperature.

"Structure of the Invention" (Means for Solving the Problems) The present invention is characterized by a weight ratio of C0.05 to 0.30%, Sl,
0% or less (including O), Mn'1.0 or less (
However, it does not contain O>, Ni' 1.5 to 3.5%
.

Cr 10-15%, Mo 0.5-2.0%,
V 0.05-0.50%, Wo, 5-2.0%, N
0.01-0.3%.

0.01 to 0.5% of at least one of Nb or Ta.

A structural material for a turbine characterized in that the remainder is made of an alloy consisting of Fe and incidental impurities.

This structural material for turbines has high creep rupture strength at 400 to 500° C. and high tensile strength and toughness at room temperature, and is extremely suitable for high-temperature and high-pressure compressors for gas turbines, for example.

(Function) The composition of the alloy constituting the structural material according to the present invention and the reason for limiting the composition ratio thereof will be explained below. na d3
, numbers are weight ratios.

C: 0.05-0.30% Carbon is an element necessary to improve hardenability and increase tensile strength, and also combines with niobium or tantalum in the alloy to form fine carbides. It is an effective element for increasing creep rupture strength.

If it is less than 0.05%, the above-mentioned curing will be poor;
If it exceeds 0%, carbides become coarse and toughness and ductility decrease, so the content is set at 0.05 to 0.30%.

Si: 1.0% or less (excluding O) Silicon is added as a deoxidizing agent during melting, but if added in large quantities, some of it will remain in the alloy as oxides, adversely affecting toughness. Therefore, it should be 1.0% or less.

Mn: 1.0% or less (excluding O) Manganese is added as a deoxidizing and desulfurizing agent during melting, and is an element that also improves hardenability. If added in a large amount, the toughness will decrease, so the content should be 1.0% or less.

Ni: 1.5 to 3.5% Nickel is an element effective in improving hardenability and improving strength and toughness at low temperatures.

If it is less than 1.5%, the effect is not sufficient, and if it is less than 3.5%.
If added in excess of 1.5 to 3, the high temperature strength will decrease.
．． Take 5%.

C+-: H) ~ 15% Chromium (J, an element effective in improving corrosion resistance and high-temperature strength. If it is less than 10%, the effect is not sufficient,
In addition, if it is added in excess of 15%, the δ-ferrite phase tends to form, reducing tensile strength and toughness.
Take 15%.

Mo: To 0.5・2. ()% Molybdenum is an effective element for improving creep-love ture strength through solid solution and precipitation strengthening effects. 05
If it is less than 20%, the effect will not be sufficient, and if it exceeds 20%, the effect will be saturated, and a large amount of carbide will precipitate, reducing the toughness. Ru.

V: 0.05 to 0.50% Vanadium is an effective element for combining with carbon and nitrogen to precipitate fine carbonitrides and improving creep rupture strength., 0.05 If it is less than %, it is not that effective.
If it is added in excess of 0.50%, the carbides will become coarse and the toughness will decrease.
%.

W: 0.5 to 2.0% Tungsten is an element that further improves creep rupture strength through solid solution strengthening. (), if it is less than 5%, the effect is not sufficient, and if it is added in excess of 2.0%, a ferrite phase will be formed, and the creep rupture strength a
3 and decreases toughness, so it is set at 0.5 to 2.0%.

N: 0.01-0.3% Nitrogen is an effective element for combining with carbon and niobium or tantalum in the alloy to form fine carbonitrides and improving crip rupture strength.

If it is less than 0.0%, the effect will not be sufficient, and if it is less than 0.3%, the effect will not be sufficient.
If added in excess of 0.01% to 0.3%, the elongation and toughness will decrease.

At least one of Nb or Ta: 0.01 to 0. , 5% Niobium or tantalum is an effective element for making crystal grains finer and improving toughness, and forming fine carbonitrides to improve creep-love ture strength. , 0.01
If the content is less than 0.0%, the effect will not be sufficient, and if it is added in excess of 0.5%, coarse carbides will be formed and the toughness will be reduced. Furthermore, the same effect can be obtained by adding both niobium and tantalum at the same time.

Incidental impurities other than [e] that are not included in -1- are, for example, P, S, etc., and the amount is such that it cannot be removed by ordinary metallurgical means, but it should be as small as possible. or desirable.

(Example) Next, the structural material for a turbine according to the present invention will be described with reference to an example of a complete tree disk.

Alloy steel having the chemical composition shown in Table 1 was melted in an electric arc furnace, subjected to deoxidation treatment and vacuum ingot formation, and then forged into a disk shape to produce a combrezzar disk-shaped element. .

(Hereinafter, blank space) The compressor disk body manufactured in this way has a diameter of 600 mm. It has a thickness of 200 ann, and is large enough to be used as a model of a part of an actual compressor disk. The compressor disk-shaped element bodies were subjected to the heat treatments shown in Table 2 to obtain Examples 1 to 3 and Comparative Examples 1 to 2.

(Hereinafter, blank space) Examples 1 to 3 constitute the compressor disk of the present invention. On the other hand, Comparative Example 1 is a CrMoV steel conventionally used for compressor disks, and Comparative Example 2 is Al5I422fI4, which is a typical 12Ci martensitic steel.

Test pieces were cut out from Examples 1 to 3 and Comparative Examples 1 to 2 thus obtained, and subjected to a tensile test, an impact test, and a creep rupture test.

Table 3 shows the results of the tensile test and Charpy impact test on the rod section.

(Hereinafter, blank space) /2 /Ll As is clear from Table 3, typical 12Cr-based maru-j
Comparative Example 2, which is made of steel, exhibits superior tensile strength and yield strength compared to Comparative Example 1, which is a conventional compressor disk material, but has a poor impact value.

F A -1'-T is almost the same and cannot be said to have superior toughness. On the other hand, Examples 1 to 3 constituting the compressor disk of the present invention have further improved tensile strength and yield strength, and impact value as compared to Comparative Example 2, which is a typical 12Cr martenzite steel. .

FA T-'r is also significantly superior. Example 1 of constructing a compressor disk of the present invention based on these results
~3 is understood to have strength and toughness near the shrinkage temperature of 4 minutes.

Table 4 shows the test temperature: 500°C2 load stress: 50KOf/m
1l12 and test temperature 470°C2 load stress 60Kg
This figure shows the results of two types of f/mm2 creep lag tests.

(Hereinafter, blank space) Table 1 - Examples 1 to 2 constituting the compressor disk of the present invention
3 shows an extremely superior rupture time compared to Comparative Example 1, which is a conventional compressor disk material, and Comparative Example 2, which is a typical 'J: 12 Cr-based marten-reite steel. From this result, it is understood that Examples 1 to 3 constituting the compressor disk of the present invention have sufficient creep rupture strength at 400 to 500°C.

In the above embodiment, the test was performed as a compressor disk cable, but the application of the structure VJ according to the present invention is not limited to compressor disks only, and for example, small gas turbine disks, etc. The roughness is forged into a cylindrical shape, and as shown in Figure 2, the high temperature part (0 part) is exposed to high temperature steam and the low temperature part (0 part) is exposed to low temperature steam.
High and low pressure integrated steam turbine rotor 6 having both parts d)
It can also be applied to structural materials for turbines such as.

[Effects of the Invention] According to the present invention, it is possible to provide a structural material for a turbine having high creep-love ture strength at 400-500'C and high tensile strength and toughness at palm temperature. If a compressor disk is formed using this structural material, long blades can be used in the low-pressure stage, and the high-pressure stage can be heated to high temperatures and pressures, making it possible to increase the pressure ratio of the compressor, which increases the This will have the effect of promoting efficiency.

[Brief explanation of drawings]

Figure 1 shows a combrella 4 applied with the structural material according to the present invention.
FIG. 2 is a schematic cross-sectional view showing a high-low pressure integrated steam turbine rotor. 1... Compressor disk 2... Moving blade 3... Stator blade 4... Tightening port 5... Casing 6... Turbine rotor a part... Low pressure part A part... High pressure part Part 0...High Temperature Department Part d...Low Temperature Department (8733) Agent Patent Attorney Yoshiaki Inomata (and others)
1 person)

Claims (1)

[Claims] By weight ratio, C0.05-0.30%, Si1.0% or less (however, 0 is not included), Mn1.0% or less (however,
0), Ni1.5-3.5%, Cr10-15
%, Mo0.5-2.0%, V0.05-0.50%,
W0.5-2.0%, N0.01-0.3%, at least one of Nb or Ta 0.01-0.5%, balance Fe
and incidental impurities.