JP6911174B2 - Nickel-based alloy - Google Patents

Description

The present invention relates to Ni-based alloys used in various applications represented by chemical plants, natural gas pipes and containers.

Ni-based alloys, especially Ni-Cr-Mo-Nb alloys, have excellent corrosion resistance and are therefore used in harsh environments with strong corrosiveness. As described above, the Fe-based alloy is an alloy used in a harsh environment where there is a risk of corrosion. Therefore, the corrosion resistance of the surface is particularly important.

In order to fully utilize the corrosion resistance of the Ni—Cr—Mo—Nb alloy, a technique for forming a passivation film has been shown (see, for example, Patent Document 1). The surface condition is especially important because it is the surface that exerts the power of corrosion resistance. When the surface is viewed microscopically, it is composed of crystal grains. The surface of the crystal grains is sufficiently secured by a dense passivation film. However, the grain boundaries have a problem of being inferior in corrosion resistance. The reason is that in the Ni-Cr-Mo-Nb alloy, if the heat treatment conditions are inappropriate, precipitates containing Cr and Mo may be formed at the grain boundaries. A passivation film containing Ni, Cr, Mo, and O as main components and effective for corrosion resistance is difficult to be formed densely on the precipitate, which causes deterioration of corrosion resistance. Further sensitize and reduce corrosion resistance. That is, in the vicinity of the precipitate containing Cr and Mo, Cr and Mo of the base material diffuse into the precipitate, and a depletion layer of these elements is formed. Since Cr and Mo are elements effective for corrosion resistance, when the passivation film is dissolved in a corroded environment, corrosion occurs from the depletion layer of Cr and Mo, and the corrosion resistance is remarkably deteriorated.

To solve the above problems, a technique for providing a Ni-based alloy in which carbides do not exist by performing a solution heat treatment is disclosed (see, for example, Patent Document 2). In fact, according to this technology, it has excellent corrosion resistance at the stage of shipping from the factory. However, since Ni-based alloys are processed and used in pipelines, chemical plants, reaction vessels, etc., heat treatment may be performed through these processing and welding processes. At that time, if an inappropriate heat treatment is performed, precipitates containing Cr and Mo may be formed at the grain boundaries. Then, the above-mentioned mechanism impairs the intergranular corrosion resistance, the intergranular corrosion progresses, and in the worst case, it causes a serious problem of penetrating the material. As described above, it can be said that it is a very important technique to prevent carbides containing Cr and Mo, which are effective elements for corrosion resistance, from being formed at the grain boundaries.

In a Ni—Cr—Mo—Nb alloy containing 11 to 20% of Mo, a technique for preventing the formation of carbides containing Cr and Mo has been shown (see, for example, Patent Document 3). That is, it is a technique for preventing the formation of carbides containing Cr and Mo by precipitating NbC at the grain boundaries by performing an aging heat treatment at 600 to 800 ° C. for 1 to 200 hours. However, there is a problem that long-term aging heat treatment at 600 to 800 ° C. for 1 to 200 hours is required, and it is impractical to carry out after assembling a pipeline, a chemical plant, a reaction vessel and the like. In other words, it was an industrially inapplicable method. Moreover, there was no description about the size and density of NbC, and there was a question as to whether it would be stabilized by this technology.

A Ni-based alloy with excellent intergranular boundary fracture resistance has been proposed, which was developed under the condition that NbC does not precipitate, that is, after performing solution heat treatment to prepare a test piece and then evaluating it in an intergranular corrosion resistance test while applying strain. (See, for example, Patent Document 4). As described above, if the carbide is in a solution state, if an inappropriate heat treatment is performed after assembling it in a pipeline, a chemical plant, a reaction vessel, etc., precipitates containing Cr or Mo will be formed at the grain boundaries. There was a problem that it was sometimes formed and lacked practicality.

Further, a technique is disclosed in which a solution heat treatment is performed at 1000 to 1100 ° C. and a carbide is dissolved by quenching at 200 ° C./sec or higher (see, for example, Patent Document 5). Certainly, if that state can be realized, it can be said that corrosion resistance can be ensured. However, it is unrealistic to actually perform the heat treatment and quenching after assembling a pipeline, a chemical plant, a reaction vessel, etc., and there is a problem that it is not practical.

Japanese Unexamined Patent Publication No. 2015-183290 Japanese Unexamined Patent Publication No. 57-9861 Japanese Unexamined Patent Publication No. 7-11404 Japanese Unexamined Patent Publication No. 5-255787 Japanese Unexamined Patent Publication No. 5-140707

In view of the above-mentioned prior art, first, in order to control the precipitation containing Cr and Mo of the Ni-based alloy, the influence of the amount of C on the precipitation behavior of the carbide is clarified, and excellent intergranular corrosion resistance is brought out. It is an object of the present invention to provide a Ni-based alloy capable of producing a product.

The inventors have conducted diligent research to solve the above problems. We evaluated the products actually manufactured on the actual machine. That is, the slab manufactured by the continuous casting machine was hot-rolled to obtain a hot-rolled plate having a thickness of 6 mm, and then cold-rolled to produce a cold-rolled plate having a thickness of 4 mm. A 20 × 25 mm test piece was collected from the cold rolled plate, and the ratio of NbC, the ratio of M6C (M is mainly Mo, Ni, Cr, Si), and M23C6 (M is mainly Cr, Mo, Fe). The present invention was completed from the correlation between the ratio of (), the density of NbC, the size factor, and the result of the intergranular corrosion resistance test. That is, it has been found that high intergranular corrosion resistance can be maintained by suppressing the precipitation of M6C and M23C6 and effectively precipitating NbC. The present invention enables more accurate control by quantitatively clarifying the relationship between C concentration and temperature by analyzing the equilibrium phase diagram of a Ni-Cr-Mo-Nb-based multi-element alloy in detail. did.

In particular, in this alloy, the effect of adding Nb is extremely important and not only increases the strength but also is extremely important in preventing the sensitization state that deteriorates the intergranular corrosion resistance. The reason is that C binds to Nb to form NbC in order to keep Cr and Mo, which are important elements for keeping intergranular corrosion resistance in a good state, in a solid solution state. The present invention has been developed based on the above findings.

That is, the Ni-based alloy of the present invention has C: 0.005 to 0.03%, Si: 0.02-1%, Mn: 0.02-1%, P ≦ 0.03 in the following mass%. %, S: 0.005% or less, Cr: 18 to 24%, Mo: 8 to 10%, Nb: 2.5 to 5.0%, Al: 0.05 to 0.4%, Ti: 1% Below, Fe: 5% or less, N: 0.02% or less, the balance Ni and unavoidable impurities, and in the above C concentration range, the ratio of (Nb, Ti) C carbide to all carbides is 90%. As described above, at 2000 ×% C + 890 ≦ T (temperature ° C.) ≦ 1030, the number of (Nb, Ti) C carbides is 6000 to 100,000 (pieces / mm ² ) (however, -30 × T + 37220 ≦ (Nb, Ti). ) The number of C carbides (pieces / mm ² ) ≤ -7.7 x T ² +15700 x T-7866000) .

In the Ni-based alloy of the present invention, the range of T (temperature ° C.) is preferably 2000 ×% C + 890 ≦ T (temperature ° C.) ≦ 980.

In the Ni-based alloy of the present invention, N: 0.002 to 0.02% is a preferred embodiment.

In the Ni-based alloy of the present invention, it is preferable that the size of the (Nb, Ti) C carbide is 0.03 to 3 μm.

In the Ni-based alloy of the present invention, it is preferable that the degree of corrosion is less than 1.5 mm / y in the ASTM G28 Method A test.

The Ni-based alloy of the present invention preferably has a degree of corrosion of less than 1.5 mm / y in the ASTM G28 Method A test after being heat-treated at 500 to 800 ° C. for 1 to 20 hours.

By forming (Nb, Ti) C carbides, precipitation of Cr and Mo carbides can be suppressed. As a result, the intergranular corrosion resistance can be maintained in a good state, so that the decrease in intergranular corrosion resistance can be suppressed even by the heat treatment performed at the alloy shipping destination, and the material used in an extremely harsh environment can be used. It will be possible to provide.

It is a graph which shows the equilibrium state diagram in the Ni-based alloy of this invention, and shows the relationship between temperature and carbon content (mass%). It is a graph which shows the relationship between the number of (Nb, Ti) C carbides (piece / mm ^{2) in the Ni-based alloy of this invention, and the heat treatment temperature.}

Hereinafter, the reason for limiting the component range of the present invention will be described. In addition,% is mass% (mass%).

C: 0.005 to 0.03%
C is an element useful for maintaining the strength of the alloy. Therefore, 0.005% is required. However, in the heat treatment process and the heat-affected zone during welding, carbides are precipitated by combining with Cr and Mo. Cr and Mo are elements that are effective for maintaining corrosion resistance, and a depletion layer is formed around the precipitate, impairing intergranular corrosion resistance. Therefore, C was set to 0.03% or less. Therefore, it was set to 0.005 to 0.03%. It is preferably 0.007 to 0.028%, more preferably 0.01 to 0.02%, and even more preferably 0.01 to 0.018%.

Si: 0.02-1%
Si is an effective element for deoxidation and 0.02% is required. However, since it is also an element that promotes the formation of M6C and M23C6 and lowers the intergranular corrosion resistance, it is necessary to suppress it to 1% or less. Therefore, it was set to 0.02-1%.

Mn: 0.02-1%
Mn is an effective element for deoxidation and 0.02% is required. However, if it exceeds 1%, MnS is likely to be formed and the pitting corrosion resistance is deteriorated. Therefore, it is set to 0.02 to 1%.

P ≤ 0.03%
P is an element harmful to hot workability, and it is desirable to reduce it as much as possible. Therefore, it was set to 0.03% or less.

S: 0.005% or less S is an element harmful to hot workability like P, and it is desirable to reduce it as much as possible. Therefore, it was set to 0.005% or less.

Cr: 18-24%
Cr is an important element for forming a passivation film and maintaining corrosion resistance. Base material Cr
The concentration should be 18% or more. However, excessive content makes it easy to precipitate M23C6 (M is mainly Cr, Mo, Fe). When it exceeds 24%, this tendency becomes remarkable, and it is specified as 18 to 24% in order to reduce the corrosion resistance. It is preferably 20 to 23%, more preferably 21 to 22.8%.

Mo: 8-10%
Mo is an important element for forming a non-conducting film and maintaining corrosion resistance. The Mo concentration of the base material needs to be 8% or more. However, the excessive content is defined as 8 to 10% because M6C (M is mainly Mo, Ni, Cr, Si) is likely to be precipitated, and the strength is increased and the workability is deteriorated. It is preferably 8.1 to 9.0%, more preferably 8.2 to 8.7%.

Nb: 2.5-5.0%
Nb is an element that enhances strength. Furthermore, since it binds to carbon to form NbC, it has an important effect of preventing the bond between Mo and Cr and carbon. Therefore, it also has a role of enhancing intergranular corrosion resistance. However, if it is 5% or more, the ductile development temperature will decrease, and hot working will not be possible. Therefore, it was set in the range of 2.5 to 5.0%. It is preferably 3 to 4.8%, more preferably 3.5 to 4.5%.

Al: 0.05 to 0.4%
Al is an important element for deoxidation and desulfurization. 0.05% is required to deoxidize and desulfurize and satisfy the range of the present invention, S: 0.005% or less. Additions in excess of 0.4% may result in the formation of alumina clusters. Therefore, it is defined as 0.05 to 0.4%. It is preferably 0.1 to 0.35%, more preferably 0.15 to 0.33%.

Ti: 1% or less Ti is an effective element for increasing the strength, and like Nb, Ti combines with carbon to form TiC and prevents the formation of carbides of Cr and Mo. Therefore, since it has the property of enhancing intergranular corrosion resistance, it is added in the range of 1% or less.

Fe: 5% or less Fe may be added to reduce the production cost, but it is set to 5% or less in order to reduce the corrosion resistance when the Fe concentration in the passivation film increases. It is preferably 4.8% or less, more preferably 4.7% or less.

N: 0.02% or less N needs to be kept as low as possible in order to form TiN that clusters and causes surface defects. Therefore, it was set to 0.02% or less. On the other hand, in order to develop strength and corrosion resistance, the minimum amount of addition is preferable, and 0.002% or more is preferable. More preferably, it is 0.002 to 0.015%. The N concentration was precisely controlled in AOD or VOD by blowing nitrogen gas or adding ferrochrome nitride.

Basically, the alloy of the present invention is a Ni-based alloy. The reason is as follows. Since Ni is a precious metal, it has better corrosion resistance than Fe. Unlike Fe, hydroxide Fe (OH) ₂ is not generated in the passivation film, so that the passivation film is dense and has a high protective effect. Further, since the Ni-based alloy has a higher content of alloying elements that can be solid-solved than the Fe-based alloy, it can contain more elements such as Cr and Mo that enhance the corrosion resistance. Therefore, in order to form a protective film having excellent corrosion resistance on the surface of the base material, it is necessary to use a Ni-based alloy. Further, the unavoidable impurities referred to in the present invention are Cu, Co, W, Ta, V, B and H.

The reason why the ratio of (Nb, Ti) C carbide is required to be 90% or more with respect to all carbides in the above C concentration range (C: 0.005 to 0.03%) will be described. This is because the degree of corrosion cannot be achieved to be less than 1.5 mm / y in the ASTM G28 Method A test unless the precipitation ratio of M6C and M23C6 is suppressed to less than 10%.

At 2000 ×% C + 890 ≦ T (temperature ° C.) ≦ 1150, the ratio of −30 × T + 37220 ≦ (Nb, Ti) C carbide number (pieces / mm ² ) ≦ -7.7 × T ² +15700 × T-7866000 The principles contained in are experimentally verified and derived from consistency with the equilibrium phase diagram. This is because if the conditions are satisfied, the ratio of (Nb, Ti) C carbides becomes 90% or more, and the degree of corrosion can be achieved to be less than 1.5 mm / y in the ASTM G28 Method A test. Furthermore, in the range of 10 ⁴ × C% + 950 Temperature 30 ° C. higher than the boundary of, M6C and M23C6 is dissolved, because the NbC remains partially, 1.5 mm in ASTM G28 Method A test after stress relief annealing / This is because less than y can be achieved.

It is extremely important to correctly obtain the number distribution of the above (Nb, Ti) C carbides. First, after heat treatment at the temperature, it is necessary to quickly cool and maintain the state at that temperature. Therefore, it is cooled at 50 ° C./sec or higher. The 4 mm thick cold rolled plate thus produced was cut into a size of 10 × 10 mm. The cross section perpendicular to the rolling direction was wet-polished, then electrolytically polished, and observed using an FE-SEM to obtain the result. Furthermore, the composition of carbides was identified by quantitative analysis.

The necessity that PRE value = Cr% + 3.3Mo% + 16N% is 50 or more will be explained. The PRE value was set to 50 or more in order to form a dense non-conducting film on the surface. Although not particularly limited, it is preferable to leave it in the air for 4 days or to perform a passivation treatment in order to obtain a dense passivation film.

The need for the size of the (Nb, Ti) C carbide to be 0.03 to 3 μm will be explained. If the dispersion is finer than 0.03 μm, the crystal grains become finer due to the pinning effect, which lowers the cold workability. On the other hand, if it is larger than 3 μm, a dense passivation film is not formed on the precipitate, so that it becomes a starting point of corrosion and there is a risk of inducing crevice corrosion. Therefore, it was set to 0.03 to 3 μm. More preferably, it is 0.1 to 2 μm.

By satisfying the scope of the above invention, the degree of corrosion can be satisfied to be less than 1.5 mm / y in the ASTM G28 Method A test. In some cases, the alloy may be heat treated at 500 to 800 ° C. for 1 to 20 hours in order to remove the strain introduced during processing or welding. By satisfying the scope of the above invention, the degree of corrosion can be satisfied to be less than 1.5 mm / y in the ASTM G28 Method A test. It is preferably less than 1.3 mm / y, more preferably less than 1.2 mm / y, and even more preferably less than 1 mm / y.

If Hodokose hot rolled in ^{10 4 × C% + 950~2000 ×} % C + 890 ℃, as described above, it is possible to more effectively precipitate (Nb, Ti) C carbides, 10 ⁴ × C% + 950~ It is specified that hot rolling is performed at 2000 ×% C + 890 ° C.

Raw materials such as scrap, Ni, Cr, and Mo were melted in an electric furnace, and oxygen was blown by AOD (Argon Oxygen Decarburization) and / or VOD (Vacum Oxygen Decarburization) to decarburize. Thereafter, Al and limestone was charged performs Cr reduction, further limestone and fluorite were _{charged, CaO-SiO 2 -Al 2 O} 3 -MgO-F slag was formed by deoxidation onto the molten alloy, desulfurization Was done. The SiO ₂ concentration in the slag was controlled to 10% or less. The molten alloy refined in this way was cast by a continuous casting machine to obtain a slab.

Then, the slab was hot-rolled with a stickel mill and then cold-rolled to produce a cold-rolled plate having a plate thickness of 4 mm. Table 1 shows the chemical composition of the manufactured alloy, and Table 2 shows the measurement conditions and evaluation results. The numerical values shown in parentheses in Tables 1 and 2 indicate that they are outside the scope of the present invention.
Here, the evaluation method is specified.
(1) Fluorescent X-ray analysis was performed. However, C and S were based on the combustion gravimetric method, and O was based on the inert gas impulse melting infrared absorption method.
(2) The hot rolling temperature was measured with a radiation thermometer after the finish rolling of the stickel mill and before water cooling.
(3) Number distribution of (Nb, Ti) C: It is extremely important to correctly obtain the number distribution of (Nb, Ti) C carbides. First, after heat treatment at the temperature, it is necessary to quickly cool and maintain the state at that temperature. Therefore, it is cooled at 50 ° C./sec or higher. The 4 mm thick cold rolled plate thus produced was cut into a size of 10 × 10 mm. The cross section parallel to the rolling direction was mirror-polished and then observed using an FE-SEM to obtain the result. The area used for measurement is 1 mm ² .
(4) The composition of carbide was determined by quantitative analysis by EDS.
(5) The size of (Nb, Ti) C was determined by FE-SEM as described above. The sizes shown in Table 2 are represented by the average size as a representative value.
(6) Evaluation of Intergranular Corrosion Resistance: The annual corrosion depth (mm / y) was evaluated by the ASTM G28 Method A test.
(7) SR (Stress Release) was strain-removing annealing, and was heat-treated at 600 ° C. × 5 hr. This is a reproduction of the heat treatment performed at the destination of the alloy, which causes a decrease in intergranular corrosion resistance.

Examples are shown in Table 2 to clarify the effects of the present invention. In addition, FIG. 1 shows an equilibrium phase diagram created from the results of this study. In the equilibrium state diagram of FIG. 1, the 10 ⁴ × C% + 950 of the claims 5 boundary (1), the 2000 ×% C + 890 and boundaries (2). Further, in Table 2, the ASTM G28 Method A test is specified as Test I, and the ASTM G28 Method A test after strain annealing is specified as Test II.

No. which is an example of the invention. Nos. 1 to 3 are regions where the hot rolling temperature is between the boundary (1) and (2) shown in FIG. 1 and (Nb, Ti) C is precipitated, but the annealing temperature is between the boundary (1) and 1150 ° C. Since it is a region between, Test I satisfies less than 1.5 mm / y and is good (◯). Furthermore, No. The annealing temperatures of 1 and 3 are in the region where C is easily dissolved because the heat treatment is performed within a temperature range 30 ° C. higher than the boundary (1), but (Nb, Ti) C remains, so the test It is also good (〇) in II. However, although the value of the degree of corrosion is within the range, it can be seen that it was high.

No. In Nos. 4 to 7, hot rolling was performed within the range sandwiched between the boundaries (1) and (2), and the subsequent heat treatment was also appropriate, so that the results of Tests I and II were both good (◯).

No. In No. 8, since the amount of C was lower than the lower limit of 0.005%, the strength was lowered. Further, since the amount of Cr is lower than the lower limit of 18% and N is 0.001%, which is lower than the lower limit, the corrosion resistance is low and the PRE is 50 or less. Further, since the hot rolling end temperature and the annealing temperature are above the boundary (1) and below 1150 ° C., C is in a solid solution state. Therefore, since M6C and M23C6 are solid-solved, (Nb, Ti) C is 95%, but the number is as small as ^{100 / mm 2.} Therefore, both Tests I and II exceeded 1.5 mm / y.

No. In No. 9, since the hot rolling end temperature and the annealing temperature are above the boundary (1) and the annealing temperature exceeds 1150 ° C., (Nb, Ti) C is in a completely solid solution state and does not precipitate. Therefore, both Tests I and II exceeded 1.5 mm / y.

No. In No. 10, the amount of C% is as high as 0.032%, the boundary (1) is 1270 ° C., and the boundary (2) is 954 ° C. Since the hot rolling end temperature is 920 ° C., it is lower than the boundary (2), so that M6C is precipitated after hot rolling. Since the annealing temperature is 1100 ° C. and is between the boundaries (1) and (2), (Nb, Ti) C is likely to precipitate. Therefore, the ratio of (Nb, Ti) C is about 30%, and the ratio of (Nb, Ti) C is as small as ^{5,000 / mm 2.} As a result, both Tests I and II exceed 1.5 mm / y.

No. In No. 11, the amount of C is 0.005%, which is the lower limit, the boundary (1) is 1000 ° C., and the boundary (2) is 900 ° C. Since the hot rolling end temperature is 1070 ° C. and is above the boundary (1), the amount of C after hot rolling is in a solid solution state. On the other hand, the annealing temperature is 780 ° C., and M6C and M23C6 are precipitated. Therefore, the ratio of (Nb, Ti) C is as small as 5%, and the ratio of (Nb, Ti) C is ^{as small as 200 pieces / mm 2.} As a result, both Tests I and II exceed 1.5 mm / y. Further, since the N value exceeded the upper limit value of 0.024%, TiN clusters were generated and nozzle blockage occurred in continuous casting.

No. No. 12 has a low intensity because the amount of C is lower than the lower limit of 0.005%, and the boundary (1) is 980 ° C. and the boundary (2) is 896 ° C. Since both the hot rolling end temperature and the annealing temperature are lower than the boundary (2), M6C and M23C6 are deposited. The ratio of (Nb, Ti) C is as small as 5%, and the ratio of (Nb, Ti) C is ^{as small as 200 pieces / mm 2.} Furthermore, the PRE is also 50 or less, and as a result, both Tests I and II exceed 1.5 mm / y.

No. Reference numeral 13 is a component in which the amounts of C, Si, and Mo exceed the upper limits, and M6C is abundant and easily precipitated. The boundary (1) is 1190 ° C., the boundary (2) is 938 ° C., the hot rolling temperature is 1100 ° C., and the annealing temperature is 900 ° C., MC is precipitated after hot rolling, and M6C and M23C6 are precipitated after annealing. Since a large amount of M6C is precipitated depending on the components and annealing conditions, the ratio of (Nb, Ti) C is low, and the number of (Nb, Ti) C is as small ^{as 20 / mm 2.} As a result, both Tests I and II exceed 1.5 mm / y.

No. No. 14 has a low strength because the amount of C is equal to or less than the lower limit value and is the lowest in the examples. The boundary (1) is 960 ° C, the boundary (2) is 892 ° C, the hot rolling end temperature is above the boundary (2) and within 30 ° C from the boundary (2), and the annealing temperature is below the boundary (2). (Nb, Ti) C does not precipitate. As a result, both Tests I and II exceed 1.5 mm / y.

High intergranular corrosion resistance that can be used for a long time in a harsh environment with strong intergranular corrosion resistance by suppressing the decrease in intergranular corrosion resistance even by the heat treatment performed at the alloy shipping destination. It is promising because it can produce Ni-based alloys.

Claims (6)

In the following mass%, C: 0.005 to 0.03%, Si: 0.02 to 1%, Mn: 0.02 to 1%, P ≦ 0.03%, S: 0.005% or less, Cr: 18 to 24%, Mo: 8 to 10%, Nb: 2.5 to 5.0%, Al: 0.05 to 0.4%, Ti: 1% or less, Fe: 5% or less, N: It consists of 0.02% or less, the balance Ni and unavoidable impurities, and in the above C concentration range, the ratio of (Nb, Ti) C carbide is 90% or more with respect to all carbides, and 2000 ×% C + 890 ≦ T. When (temperature ° C.) ≤ 1030, the number of the (Nb, Ti) C carbides is 6000 to 100,000 (pieces / mm ² ) (however, -30 × T + 37220 ≦ (Nb, Ti) number of C carbides (pieces / mm). ² ) A Ni-based alloy characterized in that (excluding the range of ≦ −7.7 × T ^{2 +15700 × T-7866000).} The Ni-based alloy according to claim 1, wherein the range of T (temperature ° C.) is 2000 ×% C + 890 ≦ T (temperature ° C.) ≦ 980. The Ni-based alloy according to claim 1 or 2, wherein N: 0.002 to 0.02%. The Ni-based alloy according to any one of claims 1 to 3, wherein the size of the (Nb, Ti) C carbide is 0.03 to 3 μm. The Ni-based alloy according to any one of claims 1 to 4, wherein the degree of corrosion is less than 1.5 mm / y in the ASTM G28 Method A test. The Ni group according to any one of claims 1 to 5, wherein the degree of corrosion is less than 1.5 mm / y in the ASTM G28 Method A test after heat treatment at 500 to 800 ° C. for 1 to 20 hours. alloy.

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