JP2000256770A - LOW THERMAL EXPANSION Ni BASE SUPERALLOY - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a low thermal expansion Ni base superalloy having a linear expansion coefficient equal to that of 12Cr steel and also having high temp. strength and corrosion resistance and oxidation resistance similar to those of an austenitic heat resistant alloy. SOLUTION: This superalloy has a compsn. contg., by weight, <=0.15% C, <=1% Si, <=1% Mn, 5 to <10% Cr, one or >= two kinds among Mo, W and Re so as to satisfy Mo+1/2(W+Re): 10 to 25%, one or two kinds among 0.2 to 2% Al, 0.5 to 4.5% Ti, <=10% Fe, <=0.02% B and <=0.2% Zr, in which the atomic % of Al+Ti is controlled to 2.5 to 7.0%, and consisting of the balance Ni with inevitable impurities.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a low thermal expansion Ni-base superalloy, and more particularly to a low thermal expansion Ni-base superalloy having high strength and excellent corrosion and oxidation resistance.

[0002]

2. Description of the Related Art Conventionally, high-temperature bolts used for members of a pressure vessel heated to a high temperature, such as a cabin of a steam turbine and a gas turbine device, include ferrite-based 12Cr steel (C: 0.12%, Si: 0.04%, Mn: 0.7%, P: 0.1%,
Ni: 0.4%, Cr: 10.5%, Mo: 0.5%, Cu: 0.03%,
V: 0.2%, W: 1.7%, Nb: 0.1%, Fe: balance) and austenitic heat-resistant alloy (Cr: 10.5%, Mn: 0.4%,
Al: 1.4%, Ti: 2.4%, Sl: 0.3%, C: 0.06%, Z
r: 0.06%, B: 0.003%, Ni: balance of Nimonic alloy 8
0A, Cr: 18%, Co: 20%, Mo: 3%, Ti: 2.6%, F
e: 16%, C: 0.05%, Ni: Refractaloy26) is used.

In recent years, the steam temperature has been further increased in order to improve the thermal efficiency of the steam turbine, and high-temperature bolts have been used under increasingly severe conditions.
When the above materials are used for high-temperature bolts under such severe conditions, ferritic 12Cr steel is low in cost and excellent in manufacturability, but the high-temperature strength is insufficient when the steam temperature and the like are higher than now. Austenitic heat-resistant alloys have higher corrosion resistance and oxidation resistance and higher high-temperature strength than ferritic 12Cr steel, but have a large linear expansion coefficient, so steam leakage due to insufficient bolt tightening force. In addition to the above-mentioned problems, there is a problem that thermal fatigue occurs, and this is a serious problem when used for members used at higher temperatures.

As a low thermal expansion Ni-base super heat resistant alloy having excellent corrosion resistance and oxidation resistance, C: 0.2% or less, Si: 1% or less, M
n: 1% or less, Cr: 10 to 24%, 1 of Mo and W
Mo + 1 / 2W: 5-17%, Al: 0.
5 to 2%, Ti: 1 to 3%, Fe: 10% or less, B:
Contains one or two of 0.02% or less and Zr: 0.2% or less, and if necessary, Co: 5% or less, Nb:
Japanese Patent Application Laid-Open No. 9-157779 discloses a composition containing 1.0% or less and the balance consisting of Ni and inevitable impurities, and a similar substance is disclosed in Japanese Patent Application Laid-Open No. 8-85838.

As an alloy having a low linear expansion coefficient, Inconel 783 (Cr: 3.21%, Mn: 0.08%, Al: 5.4), an Invar alloy developed as a member for a jet engine, is used.
%, Ti: 0.2%, Si: 0.07%, C: 0.03%, B: 0.003%
%, Fe: 24.5%, Ni: 28.2%, Co: 35.3%, N in Comparative Example
o.2) is known. This alloy is Fe @ Ni-Co
Although the Curie point is adjusted by the balance of the above and has a low linear expansion coefficient in a ferromagnetic state, there is a problem that the corrosion resistance is insufficient when this alloy is used for a steam turbine or the like.

[0006]

SUMMARY OF THE INVENTION The present invention provides a 12Cr
It is an object of the present invention to provide a low-thermal-expansion Ni-base superalloy having a linear expansion coefficient equivalent to that of steel and having the same high-temperature strength, corrosion resistance, and oxidation resistance as the austenitic heat-resistant alloy.

[0007]

Means for Solving the Problems In order to solve the above-mentioned problems, the present inventors have made intensive studies on low thermal expansion Ni-base superalloys.
When the value represented by o + 1/2 (W + Re) is 10 or more, a target coefficient of thermal expansion is obtained. At this time, Cr for increasing the coefficient of thermal expansion must be 20% or less; Further, when Mo + 1/2 (W + Re) is set to a value exceeding 17, and when Cr is set to less than 10%, the thermal expansion coefficient is further reduced. Even if Cr is lower than the conventional Ni-based heat-resistant alloy, there is a problem of steam oxidation in steam. The present invention has been made based on the finding that there is no such element.

That is, in the low thermal expansion Ni-base superalloy of the present invention, C: 0.15% or less, Si: 1% or less, M
n: 1% or less, Cr: 5 to less than 10%, one or more of Mo, W and Re: Mo + 1/2 (W + Re):
10-25%, Al: 0.2-2%, Ti: 0.5-
One or two of 4.5%, Fe: 10% or less, B: 0.02% or less and Zr: 0.2% or less, and if necessary, one or two of Nb and Ta Nb + 1/2
Ta: 1.5% or less, and if necessary, C
o: contains 5% or less, and when Nb and Ta are not contained, the atomic% of Al + Ti is set to 2.5 to 7.0%, and Nb, T
atomic% of Al + Ti + Nb + Ta when a is contained
Is set to 2.5 to 7.0%, and the balance consists of Ni and inevitable impurities.

In addition, one or more of the above Mo, W and Re is Mo + 1/2 (W + Re): 10 to 25.
% "Means that one or more of Mo, W and Re are M
This means that it is calculated in the formula of o + 1/2 (W + Re) to be in the range of 10 to 25%. In addition, the above “Nb
One or two of Ta and Nb + 1 / 2Ta: 1.5
% Or less "means that 1.5% or less of one or two of Nb and Ta is calculated by the following formula: Nb + 1 / 2Ta: 1.5% or less.
It means the following.

Further, in the low thermal expansion Ni-base superalloy of the present invention, C: 0.15% or less, Si: 1% or less, M:
n: 1% or less, Cr: 5 to 20%, Mo, W and Re
Mo + 1/2 (W + Re): 17
Ultra-25%, Al: 0.2-2%, Ti: 0.5-4.
5%, Fe: 10% or less, B: 0.02% or less, and Z
r: contains one or two kinds of 0.2% or less, and if necessary, one or two of Nb and Ta is Nb + 1
1.5% or less in / 2Ta, and if necessary,
Co: contains 5% or less, and when Nb and Ta are not contained, the atomic% of Al + Ti is set to 2.5 to 7.0%, and Nb,
When Ta is contained, the atomic percentage of Al + Ti + Nb + Ta is set to 2.5 to 7.0%, and the balance is made up of Ni and unavoidable impurities.

In the low thermal expansion Ni-base superalloy of the present invention, C: 0.15% or less, Si: 1% or less, Mn:
1% or less, Cr: 5 to 20%, 1 of Mo, W and Re
Mo + 1/2 (W + Re): 10-2
5%, Al: 0.2 to less than 0.4%, Ti: 0.5 to
One or two of 4.5%, Fe: 10% or less, B: 0.02% or less, and Zr: 0.2% or less, and if necessary, one or two of Nb and Ta Seed Nb
+ 1 / 2Ta contains 1.5% or less, and if necessary, Co: 5% or less, and when Nb and Ta are not contained, the atomic% of Al + Ti is 2.5 to 7.0%. And N
When b and Ta are contained, the atomic percentage of Al + Ti + Nb + Ta is set to 2.5 to 7.0%, and the balance consists of Ni and inevitable impurities.

Further, in the low thermal expansion Ni-base superalloy of the present invention, C: 0.15% or less, Si: 1% or less, Mn:
1% or less, Cr: 5 to 20%, 1 of Mo, W and Re
Mo + 1/2 (W + Re): 10-2
5%, Al: 0.2 to 2.0%, Ti: more than 3.5 to 4.
5%, Fe: 10% or less, B: 0.02% or less, and Z
r: contains one or two kinds of 0.2% or less, and if necessary, one or two of Nb and Ta is Nb + 1
1.5% or less in / 2Ta, and if necessary,
Co: contains 5% or less, and when Nb and Ta are not contained, the atomic% of Al + Ti is set to 2.5 to 7.0%, and Nb,
When Ta is contained, the atomic percentage of Al + Ti + Nb + Ta is set to 2.5 to 7.0%, and the balance is made up of Ni and unavoidable impurities.

The low thermal expansion Ni-base superalloy of the present invention comprises:
The low thermal expansion Ni-base superalloy has an average coefficient of expansion from room temperature to 700 ° C. of 14.0 × 10 ⁻⁶ / ° C. or less.

[0014]

Next, the reasons for specifying the component compositions as described above in the present invention will be described. C: 0.15% or less C is an element that combines with Ti, Nb, Cr, and Mo to form carbides, enhances high-temperature strength, and prevents crystal grains from becoming coarse. If the content is more than 0.15%, the hot workability deteriorates.
15% or less. Desirably, it is 0.10% or less.

Si: 1% or less Si is an element added not only as a deoxidizing agent but also for improving the oxidation resistance. However, if it exceeds 1%, the ductility is reduced. , Its content is 1% or less. Desirably, it is 0.5% or less. Mn: 1% or less Mn is added as a deoxidizing agent like Si, but 1%
If added in excess of, not only the high-temperature oxidation characteristics will deteriorate, but also the precipitation of the η phase (Ni ₃ Ti) which impairs the ductility will be promoted, so the content is made 1% or less. Desirably 0.5
% Or less.

Cr: 5 to 20% Cr is an element which forms a solid solution with the austenite phase and is contained for improving high-temperature oxidation and corrosion. In order to maintain sufficient high-temperature oxidation resistance and corrosion characteristics, it is desirable to increase the amount, but since it is an element that increases the coefficient of thermal expansion,
From the viewpoint of thermal expansion, a smaller amount is desirable. At around 650 to 700 ° C., which is the intended use temperature of the present invention, the amount of Cr is preferably 5 to 20% in order to obtain a desired coefficient of thermal expansion. In order to obtain a lower coefficient of thermal expansion, the amount of Cr should be 5-1.
5% is desirable, and in order to obtain a lower coefficient of thermal expansion, the Cr content is desirably 5 to less than 10%.

Mo + 1/2 (W + Re): 10 to 25% Mo, W and Re are elements which are dissolved in the austenite phase to increase the high-temperature strength and lower the coefficient of thermal expansion by solid solution strengthening. . In order to obtain the desired thermal expansion coefficient of the present invention, one or two of these elements must be used.
At least 10% of the sum of Mo + 1/2 (W + Re) of more than one kind is required. If this total exceeds 25%, not only the hot workability is reduced, but also the embrittled phase is precipitated and the ductility is reduced. Therefore, the content of Mo + 1/2 (W + Re) is set to 10 to 25%. Further, in order to obtain a lower coefficient of thermal expansion, it is desirable that Mo + 1/2 (W + Re) is more than 17 to 25%.

Ti: 0.5-4.5% Ti combines with Ni to form a γ 'phase, strengthening the γ' phase, lowering the coefficient of thermal expansion, and aging precipitation hardening of the γ 'phase. Is an element to be contained in order to promote. In order to obtain this effect, it is necessary to contain 0.8% or more. However, if 4.5% or more is contained, the embrittlement phase η phase (Ni ₃
Since Ti) results in precipitation and leads to a decrease in ductility, the content is set to 0.5 to 4.5%. In order to obtain a sufficient strength and a low coefficient of thermal expansion at the intended use temperature of 700 ° C. of the present invention, the content is preferably more than 3.5% and 4.5% or less.

Al: 0.2 to 2.0% Al is the most important element that combines with Ni to form a γ 'phase and strengthens precipitation, and is therefore included. If this content is less than 0.2%, the precipitation of the γ 'phase is not sufficient, and if a large amount of Ti, Nb and Ta are present, the γ' phase is unstable and the η phase and δ phase are precipitated. If the content exceeds 2.0%, the hot workability decreases, and forging into a part becomes impossible.
2 to 2.0%. A desirable range is from 0.2 to less than 0.4%.

Fe: 10% or less Fe is an impurity contained by using an inexpensive scrap or an inexpensive mother alloy containing Fe such as W or Mo as a raw material in order to reduce the cost of the alloy. Since it is an element which lowers and increases the coefficient of thermal expansion, it is desirable that the amount is small, but if it is 10% or less, the effect on the high-temperature strength and the coefficient of thermal expansion is negligible. . It is preferably at most 5%, more preferably at most 2%.

B: 0.02% or less, Zr: 0.2% or less B and Zr segregate at the crystal grain boundaries to increase the creep strength, and B has the effect of suppressing the precipitation of the η phase in an alloy containing a large amount of Ti. Therefore, it is an element to be contained for this purpose. However, if it is contained excessively, the hot workability is reduced and Zr impairs the creep characteristics. Therefore, the content of B is set to 0.02% or less, and the content of Zr is decreased. 0.2% or less. Co: 5% or less Co is a solid solution in the alloy and increases the high-temperature strength. Therefore, Co is an element to be contained. However, its effect is smaller than other elements, and it is expensive. The content is 5% or less.

Nb + 1 / 2Ta: 1.5% or less Nb and Ta are elements that form a γ ′ phase (Ni ₃ (Al, Nb, Ta)) which is a precipitation strengthening phase of a Ni-base superalloy. ′
In addition to strengthening the phase, it has the effect of preventing the γ 'phase from becoming too large, so it is an element to be contained.However, if too much is contained, the δ phase (Ni ₃ (Nb, Ta)) precipitates. The content is 1.5% at Nb + 1 / 2Ta.
%. A desirable range is 1.0% or less. Ni: Remaining Ni is a main element that forms austenite as a matrix, and is an element that improves heat resistance and corrosion resistance. It is also an element that forms the γ 'phase, which is a precipitation strengthening phase.

Al + Ti: 2.5-7.0% by atomic%,
Al + Ti + Nb + Ta: 2.5 to 7.0% in atomic% Since Al, Ti, Nb and Ta are constituent elements of the γ ′ phase, if sufficient Ni is present, the precipitation volume of the γ ′ phase The ratio is proportional to the sum of the atomic percentages of these elements. Since the high-temperature strength is proportional to the volume ratio of the γ 'phase, the high-temperature strength increases in proportion to the sum of these elements. Therefore, in order to exhibit sufficient strength intended by the present invention, 2.
5% or more is necessary, but if it exceeds 7.0%, the volume ratio of the γ 'phase becomes too large and the hot workability is remarkably reduced. 0%. Desirably, it is 3.5 to 6.0% in atomic%.

Other elements Mg, Ca, P, S and Cu are as follows: Mg: 0.03% or less, Ca: 0.03% or less, P: 0.05% or less, S:
When the content is 001% or less and Cu: 2% or less, the characteristics of the low thermal expansion Ni-based superalloy of the present invention are not reduced.

The low thermal expansion Ni-base superalloy of the present invention can be manufactured by a method similar to a conventional Ni-base superalloy. After the solution heat treatment at 950 ° C. or more, the heat treatment is performed in one-stage aging (700 to 850 ° C.) and two-stage aging (1
(Stage: 800-900 ° C, second stage: 700-800 ° C)
Both are valid.

[0026]

Next, embodiments of the present invention will be described. Table 1 below
Was melted using a vacuum induction furnace having a capacity of 50 kg, and a 50 kg ingot was cast. The casting surface of these ingots was removed by turning, and then at 1150 ° C for 1 hour.
After the homogenizing heat treatment for 5 hours, the bar was forged into a 60 mm square bar. After heating these forged rods at 1100 ° C. for 2 hours and then cooling them with water, they are subjected to solution heat treatment at 750 ° C. for 16 hours.
An aging treatment by heating for hr was performed. Test specimens were cut out from these heat-treated materials and subjected to the following various tests.
It was shown to.

The coefficient of thermal expansion was measured using a thermomechanical analyzer TMA manufactured by Rigaku Denki using quartz as a standard sample, and by a differential expansion method at a temperature rising rate of 5 ° C./min from room temperature to 70 ° C.
The average coefficient of thermal expansion up to 0 ° C. was measured. The test piece used was φ
5 × L19. The high-temperature tensile test was performed at 700 ° C. in accordance with the JIS high-temperature tensile test method, using a tensile test piece with a flange having a parallel portion of 6 mm. The creep rupture test was performed using a test piece having a parallel portion of 6.4 mm at 700 ° C. under a load stress of 34.
The test was performed at 3 MPa. The steam oxidation test, which is a problem for steam turbine members, is 10 mm wide, 10 mm long, and 5 m thick.
A test was conducted at a temperature of 600 ° C. for 100 hours using a test piece of m, and the oxidation increase after the test was measured. The test environment was a normal pressure, a steam concentration of 83%, and a steam flow rate of 7.43 ml / s.

[0028]

[Table 1]

[0029]

[Table 2]

From these results, all of the examples of the present invention have an average coefficient of thermal expansion from room temperature to 700 ° C. of 14.0.
× 10 ⁻⁶ / ° C. or less, and the tensile strength at 700 ° C. was 890 to 1118 MPa. Further, the creep rupture life was 791-2880 hr, and the steam oxidation weight increase was 0.05-0.21 mg / cm ² . on the other hand,
Comparative Example 1 was a ferritic 12Cr steel having a low average coefficient of thermal expansion of 12.4 × 10 ⁻⁶ / ° C., but had a significantly lower high-temperature tensile strength than that of the inventive example. Comparative Example 2,
No. 3 is Nimonic 80A and Refractaloy 26, which are known as high-temperature bolt materials, and their average thermal expansion coefficients are 14.5 × 10 ⁻⁶ / ° C. and 16.1 × 10 ^{−6, respectively.}
/ ° C, which is larger than that of the present invention. Comparative Example 4
And Comparative Example 5 were Inconel 783 and Incoloy 909, which had average thermal expansion coefficients equal to or lower than those of the inventive examples, but had poorer steam oxidation properties than those of the inventive examples.

Comparative Example 6 is an alloy in which the Al content exceeds the upper limit of the present invention and the total amount of Al + Ti also exceeds the upper limit of the present invention. However, cracks occur in the material by water cooling during the solution treatment of heat treatment. did. In Comparative Example 7, although the total amount of Al + Ti exceeded the upper limit of the present invention, cracks occurred in the material during water cooling during the solution treatment, as in Comparative Example 6.
No further evaluation was possible. Comparative Example 8 was an alloy having a larger amount of Cr and a smaller value of Mo + 1/2 (W + Re) than the present invention, and had a large average coefficient of thermal expansion of 14.1 × 10 ⁻⁶ / ° C. Comparative Example 9 shows that Mo + 1/2 (W + Re)
This alloy had poor forgeability, and cracks occurred during forging, and subsequent evaluation was not possible. Comparative Example 10 was made of Al
Since the total amount of + Ti was lower than that of the present invention and the precipitation amount of the γ 'phase was not sufficient, the high-temperature strength was smaller than that of the present invention.

[0032]

The low thermal expansion Ni-base superalloy of the present invention has an average thermal expansion coefficient of 14.0.times.
It is almost the same as 12Cr steel at 10 ^-6 / ° C or less, has a creep rupture life of 791-2880 hr and a steam oxidation increase of 0.05-0.21 mg / cm ² , and has a high temperature almost similar to that of the austenitic heat-resistant alloy. It has an excellent effect of having strength, corrosion resistance and oxidation resistance. Also,
The low thermal expansion Ni-base superalloy of the present invention leads to an improvement in the reliability of a thermal power plant by being applied to bolts, blades and disks of steam turbines, gas turbines and jet engines, boiler tubes of heating equipment, pressure machines and the like. It has an excellent effect.

Continued on the front page (72) Inventor Hisataka Kawai 2-1-1 Shinama, Araimachi, Takasago-shi, Hyogo Prefecture Inside Takasago Works, Mitsubishi Heavy Industries, Ltd. (72) Yoshikuni Tsunoya 2-1-1 Shinama, Araimachi, Takasago-shi, Hyogo Prefecture Inside the Takasago Research Laboratory, Mitsubishi Heavy Industries, Ltd. (72) Ryuichi Yamamoto 2-1-1, Shinhama, Araimachi, Takasago City, Hyogo Prefecture Inside the Takasago Research Laboratory, Mitsubishi Heavy Industries, Ltd. (72) Inventor Shunji Noda 4-26, Wakinoshima-cho, Tajimi-shi, Gifu Prefecture 11 (72) Inventor Susumu Isobe 12 Lions Mansion Iraka Garden 12 Takikawacho, Showa-ku, Nagoya-shi, Aichi Prefecture (72) Inventor Michio Okabe 137 Asahi Momodai, Chita-shi, Aichi Prefecture

Claims (14)

[Claims] C .: 0.15% or less, Si: 1% or less, Mn:
1% or less, Cr: 5 to less than 10%, Mo, W and Re
Mo + 1/2 (W + Re): 10 or more
-25%, Al: 0.2-2%, Ti: 0.5-4.5
%, Fe: 10% or less, B: 0.02% or less, and Z
r: contains one or two kinds of 0.2% or less, and Al + T
A low thermal expansion Ni-base superalloy characterized in that the atomic% of i is 2.5 to 7.0% and the balance consists of Ni and unavoidable impurities. 2. C: 0.15% or less, Si: 1% or less,
Mn: 1% or less, Cr: 5 to less than 10%, one or more of Mo, W and Re are Mo + 1/2 (W + R
e): 10-25%, Al: 0.2-2%, Ti: 0.
5 to 4.5%, Fe: 10% or less, B: 0.02% or less, and Zr: 0.2% or less.
Further, one or two of Nb and Ta are replaced with Nb + 1 / 2T
a: A low thermal expansion Ni-base superalloy containing 1.5% or less, wherein the atomic percentage of Al + Ti + Nb + Ta is 2.5 to 7.0%, and the balance is composed of Ni and unavoidable impurities. 3. C: 0.15% or less, Si: 1% or less,
Mn: 1% or less, Cr: 5 to 20%, Mo, W and R
Mo + 1/2 (W + Re): 1 or more of e
More than 7 to 25%, Al: 0.2 to 2%, Ti: 0.5 to
One or two of 4.5%, Fe: 10% or less, B: 0.02% or less, and Zr: 0.2% or less.
Low thermal expansion Ni, wherein the atomic% of + Ti is 2.5 to 7.0%, and the balance is Ni and unavoidable impurities.
Base superalloy. 4. C: 0.15% or less, Si: 1% or less,
Mn: 1% or less, Cr: 5 to 20%, Mo, W and R
Mo + 1/2 (W + Re): 1 or more of e
More than 7 to 25%, Al: 0.2 to 2%, Ti: 0.5 to
One or two of 4.5%, Fe: 10% or less, B: 0.02% or less, and Zr: 0.2% or less. Further, one or two of Nb and Ta are Nb + 1 / 2Ta:
A low thermal expansion Ni-base superalloy containing 1.5% or less, wherein the atomic percentage of Al + Ti + Nb + Ta is 2.5 to 7.0%, and the balance is Ni and unavoidable impurities. 5. C: 0.15% or less, Si: 1% or less,
Mn: 1% or less, Cr: 5 to 20%, Mo, W and R
Mo + 1/2 (W + Re): 1 or more of e
0 to 25%, Al: 0.2 to less than 0.4%, Ti: 0.
5 to 4.5%, Fe: 10% or less, B: 0.02% or less, and Zr: 0.2% or less.
The atomic percentage of Al + Ti is 2.5-7.0%, and the balance N
A low thermal expansion Ni-base superalloy comprising i and unavoidable impurities. 6. C: 0.15% or less, Si: 1% or less,
Mn: 1% or less, Cr: 5 to 20%, Mo, W and R
Mo + 1/2 (W + Re): 1 or more of e
0 to 25%, Al: 0.2 to less than 0.4%, Ti: 0.
5 to 4.5%, Fe: 10% or less, B: 0.02% or less, and Zr: 0.2% or less.
Further, one or two of Nb and Ta are replaced with Nb + 1 / 2T
a: A low thermal expansion Ni-base superalloy containing 1.5% or less, wherein the atomic percentage of Al + Ti + Nb + Ta is 2.5 to 7.0%, and the balance is composed of Ni and unavoidable impurities. 7. C: 0.15% or less, Si: 1% or less,
Mn: 1% or less, Cr: 5 to 20%, Mo, W and R
Mo + 1/2 (W + Re): 1 or more of e
0 to 25%, Al: 0.2 to 2.0%, Ti: more than 3.5 to 4.5%, Fe: 10% or less, B: 0.02% or less, and Zr: 0.2% or less Containing one or two kinds, A
The atomic% of l + Ti is 2.5-7.0%, and the balance Ni
And low thermal expansion N characterized by comprising unavoidable impurities
i-base superalloy. 8. C: 0.15% or less, Si: 1% or less,
Mn: 1% or less, Cr: 5 to 15%, Mo, W and R
Mo + 1/2 (W + Re): 1 or more of e
0 to 25%, Al: 0.2 to 2.0%, Ti: more than 3.5 to 4.5%, Fe: 10% or less, B: 0.02% or less, and Zr: 0.2% or less One or two of Nb and Ta, and one or two of Nb and Ta
a: A low thermal expansion Ni-base superalloy containing 1.5% or less, wherein the atomic percentage of Al + Ti + Nb + Ta is 2.5 to 7.0%, and the balance is composed of Ni and unavoidable impurities. 9. The low thermal expansion Ni-base superalloy according to claim 1, wherein a part of the Ni is replaced by 5% or less of Co. 10. The Mo + 1/2 (W + Re) is greater than 17
The low thermal expansion Ni-base superalloy according to any one of claims 1, 2 and 5 to 9, characterized in that it is 25%. 11. The low thermal expansion Ni-base superalloy according to claim 3, wherein the Cr is 5% to less than 10%. 12. The low thermal expansion Ni-base according to claim 1, wherein the Al content is 0.2 to less than 0.4%. Super alloy. 13. The method according to claim 1, wherein the Ti content is more than 3.5% to 4.5%.
13. The low thermal expansion Ni-base superalloy according to claim 12. 14. The low thermal expansion Ni-base superalloy according to claim 1, wherein an average coefficient of expansion from room temperature to 700 ° C. is 14.0 × 10 ⁻⁶ / ° C. or less. Item 4. The low thermal expansion Ni-base superalloy according to the above item.