WO2023199902A1 - Alloy material - Google Patents

Abstract

Provided is an alloy material that has sufficient creep strength in a high temperature environment and is capable of attaining both excellent resistance to stress relaxation cracking and excellent resistance to welding hot cracking. The alloy material according to the present disclosure contains, in mass%, 0.050-0.100 % of C, 1.00 % or less of Si, 1.50 % or less of Mn, 0.035 % or less of P, 0.0015 % or less of S, 19.00-23.00 % of Cr, 30.00-35.00 % of Ni, 0.100 % or less of N, 0.15-0.70 % of Al, 0.15-0.70 % of Ti, and 0.0010-0.0050 % of B, with the remainder consisting of Fe and impurities. The alloy material satisfies formulae (1) and (2).　(1): 0.60<AL+Ti<1.20 (2): 1.12≤Ti/Al

Description

Alloy material

The present disclosure relates to an alloy material, and more particularly, to an alloy material that can be used in a high-temperature environment.

Alloy materials used in steam reformers, ethylene cracking furnaces, heating furnace tubes for petroleum refining and petrochemical plants, polycrystalline silicon manufacturing equipment, etc. are used in high-temperature environments of 500 to 1000°C. Therefore, alloy materials used in such high-temperature environments are required to have high creep strength and excellent corrosion resistance in high-temperature environments. Alloy 800, Alloy 800H, and Alloy 800HT are known as alloy materials used in such high-temperature environments.

Alloy 800, Alloy 800H, and Alloy 800HT contain large amounts of Cr and Ni. Therefore, these alloy materials are known to have excellent corrosion resistance at high temperatures. These alloy materials further contain Al and Ti. Therefore, a gamma prime (γ') phase (Ni ₃ (Al, Ti)) is generated in the alloy material during use in a high-temperature environment. Due to precipitation strengthening by the γ' phase, these alloy materials have excellent creep strength.

However, in Alloy 800, Alloy 800H, and Alloy 800HT, weld hot cracking is likely to occur in the weld heat-affected zone (HAZ) during welding. Furthermore, as introduced in Non-Patent Documents 1 and 2, stress relaxation cracking may occur in these alloy materials during use in a high-temperature environment. Therefore, alloy materials having the same chemical composition as Alloy 800, Alloy 800H, and Alloy 800HT are required to have excellent weld hot cracking resistance and excellent stress relaxation cracking resistance.

In order to improve the stress relaxation cracking resistance of the above-mentioned alloy materials, methods such as limiting the total content of Al and Ti, and performing heat treatment after welding have been proposed. However, if the total content of Al and Ti is limited, sufficient creep strength cannot be obtained. Furthermore, when heat treatment is performed after welding, the construction cost may increase, or heat treatment may not be possible after welding due to equipment design.

A technique for increasing stress relaxation cracking resistance of an alloy material containing Al and Ti is disclosed in International Publication No. 2018/066579. This document focuses on the γ' phase that forms in alloy materials during use in high-temperature environments in order to achieve excellent stress relaxation cracking resistance in high-temperature environments. In this document, the chemical composition of the alloy material is adjusted to generate an appropriate amount of γ' phase during use in high temperature environments. Patent Document 1 states that this provides excellent stress relaxation cracking resistance during use in a high-temperature environment.

International Publication No. 2018/066579

Hans van Wortel: “Control of Relaxation Cracking in Austenitic High Temperature Components”, CORROSION 2007 (2007), NACE, Paper No. 07423 Richard Colwell and Cathleen Shargay: “Alloy 800H: Material and fabrication challenges associated with the mitigation of stress relaxation cracking”, ASME Pressure Vessels & Piping Conference 2020, Pap er No. 2020-21842

The alloy material described in Patent Document 1 also provides excellent stress relaxation cracking resistance in a high-temperature environment. However, excellent stress relaxation cracking resistance in high temperature environments may be achieved by other means. Further, in Patent Document 1, there is no study on achieving both excellent stress relaxation cracking resistance and excellent welding hot cracking resistance.

An object of the present disclosure is to provide an alloy material that has sufficient creep strength in a high-temperature environment and is capable of achieving both excellent stress relaxation cracking resistance and excellent welding hot cracking resistance.

The alloy material according to the present disclosure is
The chemical composition is in mass%,
C: 0.050-0.100%,
Si: 1.00% or less,
Mn: 1.50% or less,
P: 0.035% or less,
S: 0.0015% or less,
Cr: 19.00-23.00%,
Ni: 30.00-35.00%,
N: 0.100% or less,
Al: 0.15-0.70%,
Ti: 0.15-0.70%,
B: 0.0010-0.0050%,
Nb: 0 to 0.30%,
Ta: 0 to 0.50%,
V: 0-1.00%,
Zr: 0-0.10%
Hf: 0-0.10%,
Cu: 0 to 1.00%,
Mo: 0-1.00%,
W: 0-1.00%,
Co: 0-1.00%,
Ca: 0-0.0200%,
Mg: 0 to 0.0200%,
Rare earth elements: 0 to 0.1000%, and
The remainder consists of Fe and impurities,
Formulas (1) and (2) are satisfied.
0.60<Al+Ti<1.20 (1)
1.12≦Ti/Al (2)
Here, each element symbol in formulas (1) and (2) is substituted with the content of the corresponding element in the chemical composition of the alloy material in mass %.

The alloy material according to the present disclosure has sufficient creep strength in a high-temperature environment, and is capable of achieving both excellent stress relaxation cracking resistance and excellent welding hot cracking resistance.

FIG. 1 is a diagram for explaining the mechanism by which stress relaxation cracking occurs during use in a high-temperature environment in an alloy material whose chemical composition contains each element within the range of this embodiment.

The present inventors first developed an alloy material that has sufficient creep strength in a high-temperature environment and is capable of achieving both excellent stress relaxation cracking resistance and excellent welding hot cracking resistance, from the viewpoint of chemical composition. We conducted a study from As a result, the present inventors found that, in mass %, C: 0.050 to 0.100%, Si: 1.00% or less, Mn: 1.50% or less, P: 0.035% or less, S: 0.0015% or less, Cr: 19.00 to 23.00%, Ni: 30.00 to 35.00%, N: 0.100% or less, Al: 0.15 to 0.70%, Ti: 0 .15-0.70%, B: 0.0010-0.0050%, Nb: 0-0.30%, Ta: 0-0.50%, V: 0-1.00%, Zr: 0- 0.10%, Hf: 0 to 0.10%, Cu: 0 to 1.00%, Mo: 0 to 1.00%, W: 0 to 1.00%, Co: 0 to 1.00%, An alloy material with a chemical composition of Ca: 0 to 0.0200%, Mg: 0 to 0.0200%, rare earth elements: 0 to 0.1000%, and the balance being Fe and impurities can be used in a high temperature environment. It was considered that there is a possibility of having sufficient creep strength, as well as having excellent stress relaxation cracking resistance and excellent welding hot cracking resistance.

The present inventors further investigated means for increasing the creep strength in a high-temperature environment in an alloy material having the above-mentioned chemical composition. As a result, it was found that in an alloy material in which the content of each element in the chemical composition is within the above-mentioned range, if the following formula (1) is satisfied, the creep strength in a high-temperature environment is sufficiently increased.
0.60<Al+Ti<1.20 (1)
Here, each element symbol in formula (1) is substituted with the content of the corresponding element in the chemical composition of the alloy material in mass %.

The present inventors further investigated how to achieve both excellent stress relaxation cracking resistance and excellent weld hot cracking resistance. Specifically, the present inventors first investigated the mechanism by which stress relaxation cracking occurs when an alloy material having the above-mentioned chemical composition is used in a high-temperature environment. As a result, the present inventors obtained the following findings.

FIG. 1 is a diagram for explaining the mechanism by which stress relaxation cracking occurs during use in a high-temperature environment in an alloy material in which the content of each element in the chemical composition is within the range of this embodiment. The horizontal axis in FIG. 1 indicates time. The vertical axis in FIG. 1 indicates the amount of elongation or strain. Curve CRD0 in FIG. 1 shows creep rupture elongation. A curve IS0 indicates the amount of strain accumulated in Cr-deficient regions within crystal grains due to creep deformation.

In general, alloy materials used in high-temperature environments are subjected to solution treatment during the manufacturing process of the alloy material, so that precipitates in the alloy material are dissolved in solid solution. Since precipitates are sufficiently dissolved in the alloy material during the manufacturing process, a γ' phase is generated during use in a high-temperature environment. Precipitation strengthening by the γ' phase provides high creep strength.

When such an alloy material is used in a high-temperature environment, as shown in FIG. 1, the creep rupture elongation CRD0 gradually decreases over time from the initial stage of use in the high-temperature environment. On the other hand, the above-mentioned γ' phase is generated inside the alloy material from the beginning of use in a high-temperature environment (that is, from the beginning of the stress relaxation process).

During use of the alloy material in a high-temperature environment, not only the above-mentioned γ' phase but also TiC is generated. Due to the formation of TiC, a Cr-depleted region is generated near the grain boundaries. In the Cr-deficient region, the strength is lower than in other regions within the grain. Therefore, creep strain tends to concentrate in the Cr-deficient region during the stress relaxation process. Dislocations that constitute strain are trapped in TiC within the Cr-depleted region. As time passes, the amount of TiC generated in the Cr-deficient region increases. Therefore, the amount of dislocations trapped in TiC also increases. Therefore, the amount of creep strain IS0 in the Cr-depleted region also increases. At time t0 when the increased creep strain IS0 exceeds the creep rupture elongation CRD0, stress relaxation cracking occurs in the alloy material.

As described above, an increase in the amount of creep strain that causes stress relaxation cracking occurs in the Cr-deficient region, and the Cr-depleted region occurs due to the formation of TiC. Therefore, the present inventors considered that TiC influences stress relaxation cracking more than the γ' phase. Therefore, the present inventors focused on TiC in the alloy material during the stress relaxation process.

The present inventors first thought that it would be sufficient to suppress the formation of TiC during the stress relaxation process. In order to suppress TiC, the Ti content in the alloy material may be reduced. However, if the Ti content does not satisfy formula (1), sufficient γ' phase will not be generated during use in a high temperature environment. In this case, sufficient creep strength cannot be obtained in a high temperature environment.

Therefore, the present inventors reversed their thinking and came up with the idea of generating a certain amount of TiC in the alloy material before use in a high-temperature environment, rather than suppressing the generation of TiC. Then, stress relaxation cracking resistance was investigated using such an alloy material. As a result, it was found that stress relaxation cracking resistance was improved.

If the alloy material contains a certain amount of TiC before being used in a high-temperature environment, a certain amount of TiC will be generated during the manufacturing process of the alloy material. Due to this pinning effect of TiC, the crystal grains in the alloy material become fine. If the crystal grains in the alloy material are fine, the creep rupture elongation increases from CRD0 to CRD1.

Furthermore, at the initial stage of the stress relaxation process, TiC is generated in the Cr-deficient region, as in the previous case. However, TiC already exists in a certain amount in the alloy material before use in a high temperature environment. Therefore, the production of TiC is saturated at the initial stage of the stress relaxation process. Then, after the generation of TiC is saturated, the TiC that has already been generated becomes coarse. As TiC becomes coarser, dislocations trapped in TiC are removed from TiC. As a result, the amount of creep strain accumulated in the Cr-deficient region decreases. Therefore, the amount of creep strain accumulated in the Cr-depleted region becomes a curve like IS1 in FIG.

The peak of the creep strain amount IS1 is formed at the initial stage of the stress relaxation process. The peak time of the creep strain amount IS1 corresponds to the time when the production of TiC is saturated. At the initial stage of the stress relaxation process, the creep rupture elongation CRD1 is higher than the peak of the creep strain amount IS1. Once the creep strain amount IS1 exceeds the peak, it gradually decreases over time. Therefore, the time at which creep rupture elongation CRD1 and creep strain amount IS1 intersect is later than time t0. As a result, stress relaxation cracking resistance increases.

Furthermore, as described above, when the alloy material contains a certain amount of TiC, the crystal grains in the alloy material become fine. Therefore, the welding hot cracking resistance during welding construction is also improved. Therefore, it is possible to achieve both excellent stress relaxation cracking resistance and excellent welding hot cracking resistance.

Note that if the crystal grains become fine, the creep strength may decrease. However, as described above, the alloy material already contains a certain amount of TiC, and during use in a high-temperature environment, not only the γ' phase but also TiC is generated. The TiC that was already present and the TiC that is newly generated during use in a high temperature environment precipitation strengthens the alloy material. Therefore, sufficient creep strength can be maintained in high-temperature environments.

Based on the above findings, the present inventors have developed a method that has sufficient creep strength in a high-temperature environment and enables both excellent stress relaxation cracking resistance and excellent weld hot cracking resistance. We investigated the appropriate amount of TiC in the alloy material. As a result, we obtained the following knowledge.

In an alloy material in which the content of each element in the chemical composition is within the above-mentioned range, in order to generate a certain amount of TiC, the Ti content must be higher than the Al content. Specifically, the Ti content and the Al content are made to satisfy formula (2).
1.12≦Ti/Al (2)
Here, each element symbol in formula (2) is substituted with the content of the corresponding element in the chemical composition of the alloy material in mass %.

If the content of each element in the chemical composition is within the above range and satisfies formulas (1) and (2), an appropriate amount of TiC is present in the alloy material. In this case, stress relaxation cracking resistance can be improved, and welding hot cracking resistance during welding work can also be improved. Furthermore, during use in a high-temperature environment, sufficient creep strength can be obtained due to the formation of the γ' phase and TiC.

The alloy material according to this embodiment, which was completed based on the above findings, has the following configuration.

[1]
The chemical composition is in mass%,
C: 0.050-0.100%,
Si: 1.00% or less,
Mn: 1.50% or less,
P: 0.035% or less,
S: 0.0015% or less,
Cr: 19.00-23.00%,
Ni: 30.00-35.00%,
N: 0.100% or less,
Al: 0.15-0.70%,
Ti: 0.15-0.70%,
B: 0.0010-0.0050%,
Nb: 0 to 0.30%,
Ta: 0 to 0.50%,
V: 0-1.00%,
Zr: 0 to 0.10%,
Hf: 0-0.10%,
Cu: 0 to 1.00%,
Mo: 0-1.00%,
W: 0-1.00%,
Co: 0-1.00%,
Ca: 0-0.0200%,
Mg: 0 to 0.0200%,
Rare earth elements: 0 to 0.1000%, and
The remainder consists of Fe and impurities,
satisfies formula (1) and formula (2),
Alloy material.
0.60<Al+Ti<1.20 (1)
1.12≦Ti/Al (2)
Here, each element symbol in formulas (1) and (2) is substituted with the content of the corresponding element in the chemical composition of the alloy material in mass %.

[2]
The alloy material according to [1], further comprising:
When the Ti content in mass % in the residue obtained by electrolytic extraction is defined as [Ti] _R , formula (3) is satisfied,
Alloy material.
0.050<[Ti] _R <0.72Ti-0.01(Ti/Al)-0.11 (3)
Here, each element symbol in formula (3) is substituted with the content of the corresponding element in the chemical composition of the alloy material in mass %.

[3]
The alloy material according to [1] or [2],
Nb: 0.01-0.30%,
Ta: 0.01 to 0.50%,
V: 0.01-1.00%,
Zr: 0.01~0.10%
Hf: 0.01-0.10%,
Cu: 0.01 to 1.00%,
Mo: 0.01-1.00%,
W: 0.01-1.00%,
Co: 0.01 to 1.00%,
Ca: 0.0001-0.0200%,
Mg: 0.0001 to 0.0200%, and
Rare earth elements: 0.001 to 0.1000%,
Containing one or more elements selected from the group consisting of
Alloy material.

Hereinafter, the alloy material of this embodiment will be explained in detail. Note that "%" regarding elements means mass % unless otherwise specified.

[Characteristics of the alloy material of this embodiment]
The alloy material of this embodiment has the following characteristics.
(Feature 1)
Chemical composition, in mass%, C: 0.050 to 0.100%, Si: 1.00% or less, Mn: 1.50% or less, P: 0.035% or less, S: 0.0015% or less , Cr: 19.00-23.00%, Ni: 30.00-35.00%, N: 0.100% or less, Al: 0.15-0.70%, Ti: 0.15-0. 70%, B: 0.0010 to 0.0050%, Nb: 0 to 0.30%, Ta: 0 to 0.50%, V: 0 to 1.00%, Zr: 0 to 0.10%, Hf: 0-0.10%, Cu: 0-1.00%, Mo: 0-1.00%, W: 0-1.00%, Co: 0-1.00%, Ca: 0-0 .0200%, Mg: 0 to 0.0200%, rare earth elements: 0 to 0.1000%, and the balance consists of Fe and impurities.
(Feature 2)
The chemical composition of feature 1 further satisfies formula (1).
0.60<Al+Ti<1.20 (1)
Here, each element symbol in formula (1) is substituted with the content of the corresponding element in the chemical composition of the alloy material in mass %.
(Feature 3)
The chemical composition of feature 1 further satisfies formula (2).
1.12≦Ti/Al (2)
Here, each element symbol in formula (2) is substituted with the content of the corresponding element in the chemical composition of the alloy material in mass %.

The alloy material of this embodiment satisfies the characteristics 1 to 3 described above. Therefore, the alloy material of this embodiment has sufficient creep strength in a high-temperature environment, and can achieve both excellent stress relaxation cracking resistance and excellent welding hot cracking resistance. Features 1 to 3 will be explained below.

[(Feature 1) Regarding chemical composition]
The chemical composition of the alloy of this embodiment contains the following elements.

C: 0.050-0.100%
Carbon (C) increases the creep strength of alloy materials in high-temperature environments. If the C content is less than 0.050%, the above effects cannot be sufficiently obtained even if the contents of other elements are within the range of this embodiment.
On the other hand, if the C content exceeds 0.100%, M ₂₃ C ₆ type Cr carbides are generated at the grain boundaries even if the contents of other elements are within the range of this embodiment. In this case, Cr-deficient regions are generated at grain boundaries. Therefore, the stress relaxation cracking resistance of the alloy material decreases.
Therefore, the C content is 0.050-0.100%.
The preferable lower limit of the C content is 0.053%, more preferably 0.055%, still more preferably 0.057%, and still more preferably 0.060%.
A preferable upper limit of the C content is 0.095%, more preferably 0.090%, still more preferably 0.085%, and still more preferably 0.080%.

Si: 1.00% or less Silicon (Si) is unavoidably contained. In other words, the Si content is over 0%. Si deoxidizes the alloy during the steelmaking process. Si further increases the oxidation resistance of the alloy material in high temperature environments. As long as even a small amount of Si is contained, the above effects can be obtained to some extent even if the contents of other elements are within the range of this embodiment. However, if the Si content exceeds 1.00%, the weld hot cracking resistance will decrease even if the other element contents are within the ranges of this embodiment. Therefore, the Si content is 1.00% or less.
The lower limit of the Si content is preferably 0.01%, more preferably 0.05%, even more preferably 0.10%, even more preferably 0.12%, and even more preferably 0.15%. %.
The preferable upper limit of the Si content is 0.90%, more preferably 0.80%, even more preferably 0.70%, still more preferably 0.65%, and even more preferably 0.60%. %, more preferably 0.55%, even more preferably 0.50%.

Mn: 1.50% or less Manganese (Mn) is unavoidably contained. That is, the Mn content is over 0%. Mn deoxidizes the welded portion of the alloy material during welding. Mn further stabilizes austenite. If even a small amount of Mn is contained, the above effects can be obtained to some extent. However, if the Mn content exceeds 1.50%, even if the contents of other elements are within the range of this embodiment, sigma phase (σ phase) is likely to be generated when used in a high temperature environment. . The σ phase reduces the toughness and creep ductility of the alloy material in a high temperature environment. Therefore, the Mn content is 1.50% or less.
The preferable lower limit of the Mn content is 0.01%, more preferably 0.05%, even more preferably 0.10%, still more preferably 0.40%, and even more preferably 0.50%. %, more preferably 0.60%.
A preferable upper limit of the Mn content is 1.45%, more preferably 1.40%, even more preferably 1.35%, still more preferably 1.30%, and even more preferably 1.25%. %, more preferably 1.20%.

P: 0.035% or less Phosphorus (P) is unavoidably contained. In other words, the P content is over 0%. P segregates at the grain boundaries of the alloy material during high heat input welding. If the P content exceeds 0.035%, even if the contents of other elements are within the ranges of this embodiment, the above-mentioned segregation occurs and stress relaxation cracking resistance decreases. Therefore, the P content is 0.035% or less.
It is preferable that the P content is as low as possible. However, excessive reduction in P content increases the manufacturing cost of the alloy material. Therefore, in consideration of normal industrial production, the lower limit of the P content is preferably 0.001%, more preferably 0.002%, and even more preferably 0.005%.
The upper limit of the P content is preferably 0.030%, more preferably 0.025%, even more preferably 0.020%, and still more preferably 0.015%.

S: 0.0015% or less Sulfur (S) is unavoidably contained. In other words, the S content is over 0%. S segregates at the grain boundaries of the alloy material during high heat input welding. If the S content exceeds 0.0015%, even if the contents of other elements are within the ranges of this embodiment, the above-mentioned segregation occurs and stress relaxation cracking resistance decreases. Therefore, the S content is 0.0015% or less.
It is preferable that the S content is as low as possible. However, excessive reduction in S content increases the manufacturing cost of the alloy material. Therefore, in consideration of normal industrial production, the preferable lower limit of the S content is 0.0001%, more preferably 0.0002%.
A preferable upper limit of the S content is 0.0012%, more preferably 0.0010%, still more preferably 0.0008%, and still more preferably 0.0006%.

Cr: 19.00-23.00%
Chromium (Cr) increases the corrosion resistance of alloy materials in high-temperature environments. If the Cr content is less than 19.00%, the above effects cannot be sufficiently obtained even if the contents of other elements are within the range of this embodiment. On the other hand, if the Cr content exceeds 23.00%, the stability of austenite will decrease in a high-temperature environment even if the contents of other elements are within the range of this embodiment. In this case, the creep strength of the alloy material decreases. Therefore, the Cr content is 19.00-23.00%.
The preferable lower limit of the Cr content is 19.20%, more preferably 19.40%, and even more preferably 19.60%.
A preferable upper limit of the Cr content is 22.50%, more preferably 22.00%, even more preferably 21.50%, still more preferably 21.00%, and even more preferably 20.50%. %, more preferably 20.00%.

Ni: 30.00-35.00%
Nickel (Ni) stabilizes austenite and increases the creep strength of the alloy material in high temperature environments. If the Ni content is less than 30.00%, the above effects cannot be sufficiently obtained even if the contents of other elements are within the range of this embodiment. On the other hand, if the Ni content exceeds 35.00%, the above effects are saturated. Furthermore, raw material costs increase. Therefore, the Ni content is 30.00-35.00%.
The preferable lower limit of the Ni content is 30.20%, more preferably 30.40%, even more preferably 30.60%, still more preferably 30.80%, even more preferably 31.20%. %, more preferably 31.40%, still more preferably 31.60%.
A preferable upper limit of the Ni content is 34.50%, more preferably 34.00%, still more preferably 33.50%, and even more preferably 33.00%.

N: 0.100% or less Nitrogen (N) is unavoidably contained. That is, the N content is more than 0%. N stabilizes austenite by forming a solid solution in the matrix (mother phase). Solid solution N further forms fine nitrides in the alloy material during use in high temperature environments. The fine nitrides strengthen the Cr-deficient region, thereby increasing the stress relaxation cracking resistance of the alloy material. Fine nitrides generated during use in high-temperature environments further increase creep strength through precipitation strengthening. If even a small amount of N is contained, the above effects can be obtained to some extent. However, if the N content exceeds 0.100%, coarse TiN will be produced even if the contents of other elements are within the range of this embodiment. Coarse TiN reduces the toughness of the alloy material. Therefore, the N content is 0.100% or less.
The preferable lower limit of the N content is 0.001%.
A preferable upper limit of the N content is 0.090%, more preferably 0.080%, even more preferably 0.070%, still more preferably 0.060%, and still more preferably 0.050%. %, more preferably 0.040%, still more preferably 0.030%, still more preferably 0.020%, still more preferably 0.010%.

Al: 0.15-0.70%
Aluminum (Al) deoxidizes alloy materials in the steel manufacturing process. Al further increases the oxidation resistance of the alloy material in high temperature environments. Furthermore, Al generates a γ' phase in a high-temperature environment, increasing the creep strength of the alloy material in a high-temperature environment. If the Al content is less than 0.15%, the above effects cannot be sufficiently obtained even if the contents of other elements are within the range of this embodiment.
On the other hand, if the Al content exceeds 0.70%, a large amount of γ' phase will be generated during the manufacturing process of the alloy material even if the content of other elements is within the range of this embodiment. In this case, hot workability during the manufacturing process of the alloy material decreases. Furthermore, if the Al content exceeds 0.70%, TiC will not be sufficiently produced. In this case, the crystal grains in the TiC alloy material do not become sufficiently fine. Therefore, during welding of the alloy material, the weld hot cracking resistance decreases in the weld heat affected zone of the alloy material. Furthermore, since the amount of Ti that satisfies formula (1) decreases, TiC, which undergoes precipitation strengthening at 700° C., decreases, and the creep strength of the alloy material does not increase sufficiently. Furthermore, TiC is not sufficiently produced at the initial stage of the stress relaxation process. Therefore, the stress relaxation cracking resistance in a high temperature environment decreases.
Therefore, the Al content is 0.15-0.70%.
The preferable lower limit of the Al content is 0.17%, more preferably 0.19%, still more preferably 0.21%, and still more preferably 0.23%.
A preferable upper limit of the Al content is 0.65%, more preferably 0.60%, even more preferably 0.57%, still more preferably 0.55%, and even more preferably 0.53%. %, more preferably 0.51%, still more preferably 0.45%, still more preferably 0.40%.
Note that the Al content is the so-called total Al content (mass %).

Ti: 0.15-0.70%
Titanium (Ti) combines with Ni and Al in a high-temperature environment to form a γ' phase, thereby increasing the creep strength of the alloy material in a high-temperature environment. If the Ti content is less than 0.15%, the above effects cannot be sufficiently obtained even if the contents of other elements are within the range of this embodiment. On the other hand, if the Ti content exceeds 0.70%, coarse TiC will be produced even if the contents of other elements are within the range of this embodiment. In this case, during welding of the alloy material, the weld hot cracking resistance is reduced in the weld heat affected zone of the alloy material. If the Ti content exceeds 0.70%, a large amount of γ' phase will be generated during the manufacturing process of the alloy material. In this case, hot workability during the manufacturing process of the alloy material decreases. Therefore, the Ti content is 0.15-0.70%.
The lower limit of the Ti content is preferably 0.17%, more preferably 0.19%, even more preferably 0.21%, and even more preferably 0.25%.
A preferable upper limit of the Ti content is 0.65%, more preferably 0.60%, even more preferably 0.59%, still more preferably 0.57%, and even more preferably 0.55%. %, more preferably 0.50%, still more preferably 0.45%.

B: 0.0010-0.0050%
Boron (B) segregates at grain boundaries in a high-temperature environment and increases grain boundary strength. Therefore, the stress relaxation cracking resistance of the alloy material is improved. If the B content is less than 0.0010%, the above effects cannot be sufficiently obtained even if the contents of other elements are within the range of this embodiment. On the other hand, if the B content exceeds 0.0050%, B promotes the formation of Cr carbides at grain boundaries even if the contents of other elements are within the ranges of this embodiment. In this case, the stress relaxation cracking resistance of the alloy material decreases. Therefore, the B content is 0.0010 to 0.0050%.
The lower limit of the B content is preferably 0.0012%, more preferably 0.0014%, and still more preferably 0.0015%.
A preferable upper limit of the B content is 0.0045%, more preferably 0.0040%, still more preferably 0.0035%, and still more preferably 0.0030%.

The remainder of the chemical composition of the alloy material according to this embodiment consists of Fe and impurities. Here, impurities are those that are mixed in from ores used as raw materials, scraps, or the manufacturing environment when alloy materials are manufactured industrially, and are not intentionally contained. It means what is permissible within a range that does not adversely affect the shape of the alloy material. Representative examples of impurities are Sn, As, Zn, Pb and Sb. The total content of these impurities is 0.1% or less.

[Optional Elements]
The chemical composition of the alloy material of this embodiment further includes:
In place of a part of Fe,
Nb: 0 to 0.30%,
Ta: 0 to 0.50%,
V: 0-1.00%,
Zr: 0-0.10%
Hf: 0-0.10%,
Cu: 0 to 1.00%,
Mo: 0-1.00%,
W: 0-1.00%,
Co: 0-1.00%,
Ca: 0-0.0200%,
Mg: 0 to 0.0200%,
Rare earth elements: 0 to 0.1000%,
It may contain one or more elements selected from the group consisting of.
These arbitrary elements will be explained below.

[Group 1: Regarding Nb, Ta, V, Zr and Hf]
The chemical composition of the alloy material according to this embodiment may further include one or more elements selected from the group consisting of Nb, Ta, V, Zr, and Hf in place of a part of Fe. All of these elements combine with C to form carbides and reduce solid solution C. This suppresses the formation of Cr carbides at grain boundaries in a high-temperature environment. Therefore, the formation of a Cr-deficient layer is suppressed. As a result, the stress relaxation cracking resistance of the alloy material in high-temperature environments is further enhanced.

Nb: 0-0.30%
Niobium (Nb) is an optional element and may not be included. That is, the Nb content may be 0%. When Nb is contained, that is, when the Nb content is more than 0%, Nb combines with C to form carbide. By generating carbide and fixing C, the amount of solid solution C in the alloy material is reduced. This suppresses the formation of Cr carbides at grain boundaries in a high-temperature environment. Therefore, the generation of Cr-deficient regions is suppressed. As a result, the stress relaxation cracking resistance of the alloy material increases. Furthermore, Nb forms fine nitrides in the alloy material together with N during use in a high temperature environment. The fine nitrides strengthen the Cr-deficient region, thereby increasing the stress relaxation cracking resistance of the alloy material. Fine nitrides generated during use in high-temperature environments further increase creep strength through precipitation strengthening. If even a small amount of Nb is contained, the above effects can be obtained to some extent.
However, if the Nb content exceeds 0.30%, even if the content of other elements is within the range of this embodiment, there will be no welding hot cracking in the weld heat affected zone of the alloy material during welding of the alloy material. Sexuality decreases. Therefore, the Nb content is 0-0.30%.
The lower limit of the Nb content is preferably 0.01%, more preferably 0.02%, even more preferably 0.05%, and still more preferably 0.08%.
A preferable upper limit of the Nb content is 0.25%, more preferably 0.20%, and still more preferably 0.15%.

Ta: 0~0.50%
Tantalum (Ta) is an optional element and may not be included. That is, the Ta content may be 0%. When Ta is contained, that is, when the Ta content is more than 0%, Ta combines with C to form carbide. By generating carbide and fixing C, the amount of solid solution C in the alloy material is reduced. This suppresses the formation of Cr carbides at grain boundaries in a high-temperature environment. Therefore, the generation of Cr-deficient regions is suppressed. As a result, the stress relaxation cracking resistance of the alloy material increases. If even a small amount of Ta is contained, the above effects can be obtained to some extent.
However, if the Ta content exceeds 0.50%, even if the contents of other elements are within the range of this embodiment, the welding heat-affected zone of the alloy material will be resistant to welding hot cracking during welding of the alloy material. Sexuality decreases. Therefore, the Ta content is 0 to 0.50%.
The lower limit of the Ta content is preferably 0.01%, more preferably 0.02%, even more preferably 0.05%, and still more preferably 0.08%.
A preferable upper limit of the Ta content is 0.45%, more preferably 0.40%, still more preferably 0.35%, and still more preferably 0.30%.

V: 0-1.00%
Vanadium (V) is an optional element and may not be included. That is, the V content may be 0%. When V is contained, that is, when the V content is more than 0%, V combines with C to form carbide. By generating carbide and fixing C, the amount of solid solution C in the alloy material is reduced. This suppresses the formation of Cr carbides at grain boundaries in a high-temperature environment. Therefore, the generation of Cr-deficient regions is suppressed. As a result, the stress relaxation cracking resistance of the alloy material increases. If even a small amount of V is contained, the above effects can be obtained to some extent.
However, if the V content exceeds 1.00%, even if the content of other elements is within the range of this embodiment, the welding heat-affected zone of the alloy material will be resistant to welding hot cracking during welding of the alloy material. Sexuality decreases. Therefore, the V content is 0-1.00%.
The lower limit of the V content is preferably 0.01%, more preferably 0.02%, still more preferably 0.04%, and even more preferably 0.06%.
The upper limit of the V content is preferably 0.80%, more preferably 0.50%, even more preferably 0.40%, even more preferably 0.35%, and even more preferably 0.30%. %.

Zr: 0-0.10%
Zirconium (Zr) is an optional element and may not be included. That is, the Zr content may be 0%. When Zr is contained, that is, when the Zr content is more than 0%, Zr combines with C to form carbide. By generating carbide and fixing C, the amount of solid solution C in the alloy material is reduced. This suppresses the formation of Cr carbides at grain boundaries in a high-temperature environment. Therefore, the generation of Cr-deficient regions is suppressed. As a result, the stress relaxation cracking resistance of the alloy material increases. If even a small amount of Zr is contained, the above effects can be obtained to some extent.
However, if the Zr content exceeds 0.10%, even if the content of other elements is within the range of this embodiment, the welding heat-affected zone of the alloy material will be resistant to welding hot cracking during welding work. Sexuality decreases. Therefore, the Zr content is 0-0.10%.
The lower limit of the Zr content is preferably 0.01%, more preferably 0.02%.
A preferable upper limit of the Zr content is 0.09%, more preferably 0.08%, still more preferably 0.07%, and still more preferably 0.06%.

Hf: 0-0.10%
Hafnium (Hf) is an optional element and may not be included. That is, the Hf content may be 0%. When Hf is contained, that is, when the Hf content is more than 0%, Hf combines with C to generate carbide. By generating carbide and fixing C, the amount of solid solution C in the alloy material is reduced. This suppresses the formation of Cr carbides at grain boundaries in a high-temperature environment. Therefore, the generation of Cr-deficient regions is suppressed. As a result, the stress relaxation cracking resistance of the alloy material increases. If even a small amount of Hf is contained, the above effects can be obtained to some extent.
However, if the Hf content exceeds 0.10%, even if the content of other elements is within the range of this embodiment, the welding heat-affected zone of the alloy material will be resistant to welding hot cracking during welding of the alloy material. Sexuality decreases. Therefore, the Hf content is 0-0.10%.
The lower limit of the Hf content is preferably 0.01%, more preferably 0.02%.
A preferable upper limit of the Hf content is 0.09%, more preferably 0.08%, still more preferably 0.07%, and still more preferably 0.06%.

[Group 2: About Cu, Mo, W and Co]
The chemical composition of the alloy material according to the present embodiment may further contain one or more elements selected from the group consisting of Cu, Mo, W, and Co in place of a part of Fe. All of these elements increase the creep strength of the alloy material in high temperature environments.

Cu: 0-1.00%
Copper (Cu) is an optional element and may not be included. That is, the Cu content may be 0%. When Cu is contained, that is, when the Cu content is more than 0%, Cu precipitates as a Cu phase within the grains during use of the alloy material in a high-temperature environment. This precipitation strengthening increases the creep strength of the alloy material. If even a small amount of Cu is contained, the above effects can be obtained to some extent.
However, if the Cu content exceeds 1.00%, the Cu phase will precipitate excessively within the crystal grains even if the contents of other elements are within the range of this embodiment. In this case, the difference in strength between the inside of the grain and the grain boundary becomes large. Therefore, stress relaxation cracking resistance decreases. Therefore, the Cu content is 0 to 1.00%.
The preferable lower limit of the Cu content is 0.01%, more preferably 0.02%, even more preferably 0.05%, still more preferably 0.10%, and still more preferably 0.15%. %, more preferably 0.20%.
The preferable upper limit of the Cu content is 0.90%, more preferably 0.80%, even more preferably 0.70%, even more preferably 0.60%, and even more preferably 0.55%. %, more preferably 0.50%.

Mo: 0-1.00%
Molybdenum (Mo) is an optional element and may not be included. That is, the Mo content may be 0%. When Mo is contained, that is, when the Mo content is more than 0%, Mo increases the creep strength of the alloy material through solid solution strengthening during use of the alloy material in a high-temperature environment. If even a small amount of Mo is contained, the above effects can be obtained to some extent.
However, if the Mo content exceeds 1.00%, intermetallic compounds such as the LAVES phase are generated within the crystal grains even if the contents of other elements are within the ranges of this embodiment. In this case, secondary induced precipitation hardening increases and the difference in strength between the inside of the grain and the grain boundary increases. Therefore, stress relaxation cracking resistance decreases. Therefore, the Mo content is 0 to 1.00%.
The preferable lower limit of the Mo content is 0.01%, more preferably 0.02%, even more preferably 0.03%, still more preferably 0.04%, even more preferably 0.05%. %, more preferably 0.10%, still more preferably 0.20%, still more preferably 0.30%.
The preferable upper limit of the Mo content is 0.90%, more preferably 0.80%, even more preferably 0.70%, still more preferably 0.65%, and even more preferably 0.60%. %.

W: 0-1.00%
Tungsten (W) is an optional element and may not be included. That is, the W content may be 0%. When W is contained, that is, when the W content is more than 0%, W increases the creep strength of the alloy material through solid solution strengthening during use of the alloy material in a high-temperature environment. If even a small amount of W is contained, the above effects can be obtained to some extent.
However, if the W content exceeds 1.00%, intermetallic compounds such as the LAVES phase are generated within the crystal grains even if the contents of other elements are within the ranges of this embodiment. In this case, secondary induced precipitation hardening increases and the difference in strength between the inside of the grain and the grain boundary increases. Therefore, stress relaxation cracking resistance decreases. Therefore, the W content is 0 to 1.00%.
The lower limit of the W content is preferably 0.01%, more preferably 0.02%, even more preferably 0.03%, even more preferably 0.04%, and even more preferably 0.05%. %, more preferably 0.10%.
The upper limit of the W content is preferably 0.90%, more preferably 0.80%, even more preferably 0.70%, even more preferably 0.65%, and even more preferably 0.60%. %, more preferably 0.50%.

Co: 0-1.00%
Cobalt (Co) is an optional element and may not be included. That is, the Co content may be 0%. When Co is contained, that is, when the Co content is more than 0%, Co stabilizes austenite and increases the creep strength of the alloy material in a high temperature environment. If even a small amount of Co is contained, the above effects can be obtained to some extent.
However, if the Co content exceeds 1.00%, the raw material cost will increase. Therefore, the Co content is 0 to 1.00%.
The preferable lower limit of the Co content is 0.01%, more preferably 0.02%, even more preferably 0.03%, still more preferably 0.05%, and even more preferably 0.10%. %.
A preferable upper limit of the Co content is 0.90%, more preferably 0.80%, even more preferably 0.70%, still more preferably 0.60%, and even more preferably 0.50%. %.

[Group 3: Regarding Ca, Mg and rare earth elements (REM)]
The chemical composition of the alloy material according to the present embodiment may further include one or more elements selected from the group consisting of Ca, Mg, and rare earth elements (REM) in place of a part of Fe. All of these elements improve the hot workability of the alloy material.

Ca: 0-0.0200%
Calcium (Ca) is an optional element and may not be included. That is, the Ca content may be 0%. When Ca is contained, that is, when the Ca content is more than 0%, Ca fixes O (oxygen) and S (sulfur) as inclusions and improves the hot workability of the alloy material. Ca further fixes S and suppresses grain boundary segregation of S. Therefore, during welding of the alloy material, the weld hot cracking resistance increases in the weld heat affected zone (HAZ) of the alloy material. If even a small amount of Ca is contained, the above effects can be obtained to some extent.
However, if the Ca content exceeds 0.0200%, even if the contents of other elements are within the range of this embodiment, the cleanliness of the alloy material decreases, and the hot workability of the alloy material decreases. do. Therefore, the Ca content is 0 to 0.0200%.
The lower limit of the Ca content is preferably 0.0001%, more preferably 0.0002%, even more preferably 0.0005%, and still more preferably 0.0010%.
The preferable upper limit of the Ca content is 0.0150%, more preferably 0.0100%, even more preferably 0.0080%, still more preferably 0.0050%, and still more preferably 0.0040%. %.

Mg: 0-0.0200%
Magnesium (Mg) is an optional element and may not be included. That is, the Mg content may be 0%.
When Mg is contained, that is, when the Mg content is more than 0%, Mg fixes O (oxygen) and S (sulfur) as inclusions and improves the hot workability of the alloy material. Mg further fixes S and suppresses grain boundary segregation of S. Therefore, during welding of alloy materials, the welding hot cracking resistance is improved in the HAZ of the alloy materials. If even a small amount of Mg is contained, the above effects can be obtained to some extent.
However, if the Mg content exceeds 0.0200%, even if the contents of other elements are within the range of this embodiment, the cleanliness of the alloy material decreases, and the hot workability of the alloy material decreases. do. Therefore, the Mg content is 0-0.0200%.
The preferable lower limit of the Mg content is 0.0001%, more preferably 0.0002%, even more preferably 0.0005%, and still more preferably 0.0010%.
A preferable upper limit of the Mg content is 0.0150%, more preferably 0.0100%, even more preferably 0.0080%, still more preferably 0.0050%, and still more preferably 0.0040%. %.

Rare earth elements: 0-0.1000%
Rare earth elements (REM) are optional elements and may not be included. That is, the REM content may be 0%. When REM is contained, that is, when the REM content is more than 0%, REM fixes O (oxygen) and S (sulfur) as inclusions and improves the hot workability of the alloy material. REM further fixes S and suppresses grain boundary segregation of S. Therefore, during welding of alloy materials, the welding hot cracking resistance is improved in the HAZ of the alloy materials. If even a small amount of REM is contained, the above effects can be obtained to some extent.
However, if the REM content exceeds 0.1000%, even if the contents of other elements are within the range of this embodiment, the cleanliness of the alloy material decreases, and the hot workability of the alloy material decreases. do. Therefore, the REM content is between 0 and 0.1000%.
The lower limit of the REM content is preferably 0.0001%, more preferably 0.0005%, even more preferably 0.0010%, and still more preferably 0.0020%.
A preferable upper limit of the REM content is 0.0800%, more preferably 0.0600%, and still more preferably 0.0400%.

REM in this specification contains at least one element of Sc, Y, and lanthanoids (La with atomic number 57 to Lu with atomic number 71), and the REM content means the total content of these elements. do.

[(Feature 2) Regarding formula (1)]
The chemical composition of the alloy material of this embodiment further satisfies formula (1).
0.60<Al+Ti<1.20 (1)
Here, each element symbol in formula (1) is substituted with the content of the corresponding element in the chemical composition of the alloy material in mass %.

Define F1=Al+Ti. F1 is an index of the amount of γ' phase produced. In the alloy material of this embodiment, a γ' phase is generated during use in a high temperature environment. This γ' phase increases the creep strength of the alloy material in high-temperature environments.

Even if the content of each element in the chemical composition is within the range of this embodiment, if F1 is 0.60 or less, a sufficient amount of γ' phase will not be generated in the alloy material in a high temperature environment. In this case, the creep strength of the alloy material in a high temperature environment decreases.
On the other hand, even if the content of each element in the chemical composition is within the range of this embodiment, if F1 is 1.20 or more, an excessive amount of γ' phase will be generated in the alloy material. In this case, the welding hot cracking resistance of the alloy material decreases. Therefore, F1 is greater than 0.60 and less than 1.20.

The lower limit of F1 is preferably 0.62, more preferably 0.64, even more preferably 0.66, still more preferably 0.68, and even more preferably 0.70.
The upper limit of F1 is preferably 1.15, more preferably 1.10, furthermore 1.05, still more preferably 1.00, still more preferably 0.95.

[(Feature 3) Regarding formula (2)]
The chemical composition of the alloy material of this embodiment further satisfies formula (2).
1.12≦Ti/Al (2)
Here, each element symbol in formula (2) is substituted with the content of the corresponding element in the chemical composition of the alloy material in mass %.

Define F2=Ti/Al. F2 is an index of stress relaxation cracking resistance of an alloy material in a high temperature environment.
In order to achieve both creep strength and stress relaxation cracking resistance in a high-temperature environment, in the alloy material of this embodiment, the Ti content is increased relative to the Al content. In this case, the alloy material contains a certain amount of TiC. Therefore, TiC makes the crystal grains in the alloy material finer. As a result, the creep rupture elongation of the alloy material in a high temperature environment increases. Furthermore, in the alloy material of this embodiment, by increasing the Ti content relative to the Al content, the generation of TiC is saturated at the initial stage of the stress relaxation process. After the production of TiC is saturated, the TiC becomes coarser over time. As a result, the amount of creep strain accumulated in the Cr-depleted region forms a peak at the initial stage of the stress relaxation process. Thereafter, the amount of creep strain decreases with the passage of time. As a result, stress relaxation cracking resistance in high-temperature environments increases. If F2 is less than 1.12, the above effects cannot be sufficiently obtained. Therefore, F2 is 1.12 or more.

The lower limit of F2 is preferably 1.13, more preferably 1.15, even more preferably 1.30, still more preferably 1.40, and still more preferably 1.50.
The upper limit of F2 is not particularly limited. From the viewpoint of increasing the oxidation resistance of the alloy material, the preferable upper limit of F2 is 4.00, more preferably 3.90, still more preferably 3.70, still more preferably 3.50, and Preferably it is 3.30.

[Preferred form of alloy material of this embodiment]
Preferably, the alloy material of the present embodiment satisfies Features 1 to 3, and further satisfies the following Feature 4.
(Feature 4)
When the Ti content in mass % in the residue obtained by the electrolytic extraction method is defined as [Ti] _R , formula (3) is satisfied.
0.050<[Ti] _R <0.72Ti-0.01(Ti/Al)-0.11 (3)
Here, each element symbol in formula (3) is substituted with the content of the corresponding element in the chemical composition of the alloy material in mass %.
Feature 4 will be explained below.

[(Feature 4) Regarding formula (3)]
[Ti] _R , which is the Ti content in the residue, is an index of the amount of TiC in the alloy material. In order to achieve both excellent stress relaxation cracking resistance and excellent weld hot cracking resistance, it is preferable that the amount of TiC and the amount of solid solution Ti in the alloy material are appropriate.

[Ti] If _R is higher than 0.050, some TiC is present in the alloy material before it is used in a high temperature environment. In this case, a pinning effect due to TiC can be obtained. Therefore, the crystal grains in the alloy material are refined. As a result, the creep rupture elongation of the alloy material in a high temperature environment increases. Furthermore, before using the alloy material in a high temperature environment, some amount of TiC is already present in the alloy material. Therefore, as explained above using FIG. 1, during high-temperature use, the production of TiC is saturated at the initial stage of the stress relaxation process. As a result, the amount of creep strain in the Cr-depleted region also forms a peak at the initial stage of the stress relaxation process. Thereafter, the amount of creep strain decreases with the passage of time. As a result, stress relaxation cracking of the alloy material in a high temperature environment is further suppressed.

On the other hand, if [Ti] _R is lower than F3 (=0.72Ti-0.01(Ti/Al)-0.11), the amount of TiC in the alloy material is appropriate and not too large. If an excessive amount of TiC exists in the alloy material, weld hot cracking due to TiC will occur during welding of the alloy material. In other words, if [Ti] _R is less than F3, the welding hot cracking resistance of the alloy material will further increase. Further, if an excessive amount of TiC exists in the alloy material, sufficient γ' phase will not be generated during use in a high temperature environment. In this case, creep strength does not increase in a high temperature environment. In other words, if [Ti] _R is less than F3, the creep strength of the alloy material will further increase. Therefore, preferably [Ti] _R is higher than 0.050 and lower than F3 (=0.72Ti-0.01(Ti/Al)-0.11).

A more preferable lower limit of [Ti] _R is 0.055, still more preferably 0.060, still more preferably 0.065, still more preferably 0.070, still more preferably 0.075. .
[Ti] A more preferable upper limit (F3) of _R is 0.72Ti-0.01(Ti/Al)-0.15, still more preferably 0.72Ti-0.01(Ti/Al)-0. 18, more preferably 0.72Ti-0.01(Ti/Al)-0.20.

[[Ti] _R measurement method]
[Ti] _R can be measured by the following electrolytic extraction method.
A test piece is taken from a position at least 1 mm deep from the surface of the alloy material. The size of the test piece is not particularly limited. The test piece is, for example, 10 mm in diameter x 70 mm in length.

The surface of the sampled test piece is polished by about 50 μm by preliminary electrolytic polishing to obtain a new surface. The electrolytically polished test piece is subjected to main electrolysis using an electrolytic solution (10% acetylacetone + 1% tetraammonium + methanol) at a current value of 270 mA. At this time, the electrolytic depth is about 31 μm. The electrolyte solution after main electrolysis is passed through a 0.2 μm filter to capture the residue. The obtained residue is subjected to acid decomposition, and the Ti mass (g) in the residue is determined by ICP (inductively coupled plasma) emission spectrometry. Furthermore, the mass (g) of the test piece before the main electrolysis and the mass (g) of the test piece after the main electrolysis are measured. Then, the value obtained by subtracting the mass of the test piece after main electrolysis from the mass of the test piece before main electrolysis is defined as the main electrolyzed base material mass (g). The Ti content (mass %) in the residue is determined by dividing the mass of Ti in the residue by the mass of the main electrolyzed base material. That is, [Ti] _R (mass %), which is the Ti content in the residue, is determined based on the following formula.
[Ti] _R = Ti mass in residue/base material mass x 100

[Effects of alloy materials]
The alloy material of this embodiment satisfies the characteristics 1 to 3 described above. As a result, the alloy material of this embodiment has sufficient creep strength in a high-temperature environment, and is capable of achieving both excellent stress relaxation cracking resistance and excellent weld cracking resistance. If the alloy material of this embodiment further satisfies feature 4, the creep strength and weld hot cracking resistance will further increase.

[Microstructure of alloy material]
The microstructure of the alloy material of this embodiment consists of austenite.

[Shape of alloy material]
The shape of the alloy material of this embodiment is not particularly limited. The alloy material may be an alloy tube or an alloy plate. The alloy material may be an alloy rod material. Preferably, the alloy material of this embodiment is an alloy tube.

[Method for manufacturing alloy material]
A method for manufacturing the alloy material of this embodiment that satisfies Features 1 to 4 will be described. The manufacturing method described below is an example of the manufacturing method of the alloy material of this embodiment. Therefore, the alloy material satisfying Features 1 to 4 may be manufactured by a manufacturing method other than the manufacturing method described below. However, the manufacturing method described below is a preferable example of the manufacturing method of the alloy material of this embodiment.

The method for manufacturing an alloy material of this embodiment includes the following steps.
(Process 1) Preparation process (Process 2) Hot processing process (Process 3) Cold processing process (Process 4) Heat treatment process

In the hot working step of step 2, the following condition 1 is satisfied.
(Condition 1)
The heating temperature T1 (° C.) during heating before hot working and the holding time t1 (minutes) at the heating temperature T1 are within the following range.
T1: 1100~1280℃
t1: 3-120 minutes

Furthermore, in the heat treatment step of step 4, the following condition 2 is satisfied.
(Condition 2)
The heat treatment temperature T2 (° C.) in the heat treatment step and the holding time t2 (minutes) at the heat treatment temperature T2 are within the following range.
T2: 1050-1300℃
t2: 1 to 60 minutes Each step will be explained below.

[(Process 1) Preparation process]
In the preparation step, a material having the chemical composition of Feature 1 described above is prepared. Materials may be supplied or manufactured by a third party. The material may be an ingot, a slab, a bloom, or a billet.

When manufacturing the material, use the following method to manufacture the material. Molten steel having the above chemical composition is produced. Using the produced molten steel, an ingot is produced by an ingot-forming method. Slabs, blooms, and billets may be manufactured by continuous casting using the manufactured molten steel. A billet may be manufactured by hot working the manufactured ingot, slab, or bloom. For example, an ingot may be hot forged to produce a cylindrical billet, and this billet may be used as the raw material. In this case, the temperature of the material immediately before the start of hot forging is not particularly limited, but is, for example, 1000 to 1300°C. The method for cooling the material after hot forging is not particularly limited.

[(Step 2) Hot processing step]
In the hot working step, hot working is performed on the material prepared in the preparation step to produce an intermediate alloy material. The intermediate alloy material may be, for example, an alloy tube, an alloy plate, or an alloy bar.

When the intermediate alloy material is an alloy tube, the following processing is performed in the hot processing step. First, prepare the cylinder material. Through machining, a through hole is formed along the central axis of the cylindrical material. A cylindrical material with through holes formed therein is heated. The heated cylindrical material is subjected to hot extrusion, typically the Eugene-Séjournet method, to produce an intermediate alloy material (alloy tube). Instead of the hot extrusion method, a hot extrusion tube manufacturing method may be used.

Furthermore, instead of hot extrusion, the alloy tube may be manufactured by performing piercing rolling using the Mannesmann method. In this case, the cylindrical material is heated. The heated cylindrical material is punched and rolled using a punching machine. In the case of piercing rolling, the piercing ratio is not particularly limited, but is, for example, 1.0 to 4.0. The hole-rolled cylindrical material is further hot-rolled using a mandrel mill, reducer, sizing mill, etc. to form a hollow tube (alloy tube). The cumulative area reduction rate in the hot working process is not particularly limited, but is, for example, 20 to 80%. When manufacturing an alloy tube by hot working, the temperature (finishing temperature) of the hollow tube immediately after hot working is preferably 800° C. or higher.

When the intermediate alloy material is an alloy plate, the hot working step uses, for example, one or more rolling mills equipped with a pair of work rolls. Heating materials such as slabs. The heated material is hot rolled using a rolling mill to produce an alloy plate.

In the hot working process, the above-mentioned condition 1 is satisfied. That is, the heating temperature T1 (° C.) during heating before hot working and the holding time t1 (minutes) at the heating temperature T1 are within the following range.
T1: 1100~1280℃
t1: 3-120 minutes

Preferably, the following condition 3 is satisfied in the hot working step.
(Condition 3)
The heating temperature T1 (° C.) and the holding time t1 (minutes) at the heating temperature T1 are made to satisfy the following formula (A).
800≦T1×LOG(t1)≦2100 (A)

Define FA=T1×LOG(t1). FA influences the amount of TiC in the manufactured alloy material.
If FA is 800 or more, a sufficient amount of TiC will be generated during heating before hot working. Therefore, in the manufactured alloy material, [Ti] _R becomes higher than 0.050.
On the other hand, if FA is 2100 or less, TiC is generated in an appropriate amount during heating before hot working. Therefore, in the manufactured alloy material, [Ti] _R is less than F3 (=0.72Ti-0.01(Ti/Al)-0.11). Therefore, preferably FA is 800-2100.

The lower limit of FA is more preferably 820, still more preferably 840, even more preferably 860, still more preferably 1000, and still more preferably 1200.
A more preferable upper limit of FA is 2,050, still more preferably 2,000, still more preferably 1,950, and still more preferably 1,850.

[(Step 3) Cold working step]
Cold working steps are carried out as necessary. In other words, the cold working step does not have to be performed. When carried out, cold working is carried out after carrying out pickling treatment on the intermediate alloy material. When the intermediate alloy material is an alloy tube or an alloy bar, the cold working is, for example, cold drawing. When the intermediate alloy material is an alloy plate, the cold working is, for example, cold rolling. By performing the cold working step, recrystallization can occur and grain size regulation can be performed. The area reduction rate in the cold working process is not particularly limited, but is, for example, 10 to 90%.

[(Step 4) Heat treatment step]
In the heat treatment step, heat treatment is performed on the intermediate alloy material after the hot working step or the cold working step to adjust the amount of TiC and the size of crystal grains in the alloy material.

In the heat treatment step, the above-mentioned condition 2 is satisfied. That is, the heat treatment temperature T2 (° C.) and the holding time t2 (minutes) at the heat treatment temperature T2 are within the following range.
T2: 1050-1300℃
t2: 1-60 minutes

Preferably, the following condition 4 is satisfied in the heat treatment step.
(Condition 4)
The heat treatment temperature T2 (° C.) and the holding time t2 (minutes) at the heat treatment temperature T2 are made to satisfy the following formula (B).
2600≦T2×(LOG(t2)+2)≦4400 (B)

Define FB=T2×(LOG(t2)+2). Like FA, FB influences the amount of TiC in the manufactured alloy material.
If FB is 2600 or more, a sufficient amount of TiC will be generated in the manufactured alloy material. Therefore, [Ti] _R becomes higher than 0.050.
On the other hand, if FB is 4400 or less, TiC will be produced in an appropriate amount in the manufactured alloy material. Therefore, [Ti] _R is less than 0.72Ti-0.01(Ti/Al)-0.11. Therefore, FB is preferably between 2,600 and 4,400.

A more preferable lower limit of FB is 2,650, more preferably 2,700, still more preferably 2,750.
A more preferable upper limit of FB is 4350, still more preferably 4300, still more preferably 4250, still more preferably 4000, and still more preferably 3800.

After holding at the heat treatment temperature T2 (°C) for a holding time t2 (minutes), the intermediate alloy material is cooled. The preferred cooling method is rapid cooling (water cooling).

Preferably, the following condition 5 is further satisfied in the hot working step and the heat treatment step.
(Condition 5)
0.30≦FA/FB (C)

Define FC=FA/FB. FC, like FA and FB, affects the amount of TiC in the manufactured alloy material. If FC is 0.30 or more, a sufficient amount of TiC can be easily obtained in the manufactured alloy material. Therefore, [Ti] _R becomes higher than 0.050.
Therefore, FC is preferably 0.30 or more.

A more preferable lower limit of FC is 0.33, still more preferably 0.35, and still more preferably 0.38.
The upper limit of FC is not particularly limited. The upper limit of FC is, for example, 0.60.

Through the above steps, the alloy material of this embodiment can be manufactured. The above-mentioned manufacturing method is an example of the manufacturing method of the alloy material of this embodiment. Therefore, the method for manufacturing the alloy material of this embodiment is not limited to the above-described manufacturing method. As long as Features 1 to 3 are satisfied, or Features 1 to 4 are satisfied, the method for manufacturing the alloy material is not limited to the above-described manufacturing method.

[Method for manufacturing welded joints of alloy materials]
The welded joint of the alloy material of this embodiment can be manufactured by the following method.

The alloy material of this embodiment is prepared as a base material. A groove is formed on the prepared base material. Specifically, a groove is formed at the end of the base material by a well-known processing method. The groove shape may be V-shape, U-shape, X-shape, or other shapes other than V-shape, U-shape, and X-shape. .

Welding is performed on the prepared base metal to manufacture a welded joint. Specifically, two base materials in which grooves are formed are prepared. Butt the grooves of the prepared base material together. Then, welding is performed on the pair of butted grooves using a well-known welding material to form a weld metal having the above-mentioned chemical composition. The welding material is, for example, AWS standard name: ER NiCr-3. However, the welding material is not limited to this.

The welding method may be to form one layer of weld metal or may be multilayer welding. Welding methods include, for example, TIG welding (GTAW), shielded arc welding (SMAW), flux-cored wire arc welding (FCAW), gas metal arc welding (GMAW), and submerged arc welding (SAW). Through the above manufacturing process, the welded joint of the alloy material of this embodiment can be manufactured.

The effects of the alloy material of this embodiment will be explained in more detail with reference to Examples. The conditions in the following examples are examples of conditions adopted to confirm the feasibility and effects of the alloy material of this embodiment. Therefore, the alloy material of this embodiment is not limited to this one example condition.

[Manufacture of alloy materials]
Ingots having the chemical compositions shown in Tables 1-1 and 1-2 were produced. The shape of the ingot was a cylinder with an outer diameter of 120 mm, and the mass of the ingot was 30 kg.

"-" in Table 1-2 means that the content of the corresponding element was below the impurity level.

The produced ingot was hot forged to produce a material (alloy plate) with a thickness of 30 mm. The heating temperature of the ingot during hot forging was 1000 to 1300°C.
A hot working process was performed on the manufactured material. Specifically, the material was heated in a heating furnace. The heating temperature T1 in the hot working step was 1100 to 1280°C, and the holding time t1 at the heating temperature T1 was 3 to 120 minutes. The FA values are shown in Table 2. The heated material was hot rolled to produce an intermediate alloy material (alloy plate) with a thickness of 15 mm.

A heat treatment process was performed on the intermediate alloy material. The heat treatment temperature T2 in the heat treatment step was 1050 to 1300°C, and the holding time t2 at the heat treatment temperature T2 was 1 to 60 minutes. Table 2 shows the FB and FC values. After the holding time t2 had elapsed, the intermediate alloy material was water-cooled to room temperature. Through the above steps, alloy materials (alloy plates) of each test number were manufactured.

[Evaluation test]
The following evaluation test was conducted using the manufactured alloy material.
(Test 1) [Ti] _R measurement test (Test 2) Creep strength evaluation test (Test 3) Stress relaxation cracking resistance evaluation test (Test 4) Weld hot cracking resistance evaluation test Each evaluation test will be explained below.

[(Test 1) [Ti] _R measurement test]
A test piece was taken from a position 1 mm or more deep from the surface of the alloy material of each test number. The size of the test piece was 10 mm in diameter x 70 mm in length. Based on the above-mentioned [[Ti] _R measurement method], the Ti content [Ti] _R (mass %) in the residue was determined. The obtained [Ti] _R is shown in the "[Ti] _R (mass %)" column in Table 2.

[(Test 2) Creep strength evaluation test]
The following creep strength evaluation test was conducted on the alloy materials (alloy plates) of each test number.
A creep rupture test piece in accordance with JIS Z2271:2010 was taken from the center position of the plate width and the center position of the plate thickness of the alloy material (alloy plate) of each test number. The cross section of the parallel part of the creep rupture test piece perpendicular to the axial direction was circular. The outer diameter of the parallel portion was 6 mm and the length was 30 mm. The longitudinal direction of the creep rupture test piece was parallel to the rolling direction of the alloy plate.

A creep rupture test in accordance with JIS Z2271:2010 was conducted using the collected creep rupture test piece. Specifically, a creep rupture test piece was heated to 700°C. Thereafter, a creep rupture test was conducted. The test stress was 80 MPa. In the test, creep rupture time (hours) was determined.

The creep strength was evaluated as follows according to the obtained creep rupture time.
Evaluation E (Excellent): Creep rupture time is longer than 4000 hours Evaluation G (Good): Creep rupture time is 2000 to 4000 hours Evaluation B (Bad): Creep rupture time is shorter than 2000 hours Evaluation G or E In this case, it was judged that excellent creep strength was obtained. The evaluation results are shown in the "Creep strength" column in Table 2.

[(Test 3) Stress relaxation cracking resistance evaluation test]
The following stress relaxation cracking resistance evaluation test was conducted on the alloy materials (alloy plates) of each test number.
A square test piece was taken from the center position of the plate width and the center position of the plate thickness of the alloy material (alloy plate) of each test number. The cross section perpendicular to the longitudinal direction of the square test piece was a rectangle of 10 mm x 10 mm. The length of the square test piece was 100 mm. The longitudinal direction of the square test piece was parallel to the rolling direction of the alloy material (alloy plate).

Using a high-frequency thermal cycle device, the following thermal history was given to the collected square specimen. Specifically, the temperature of the square test piece was raised from room temperature to 1300°C at a rate of 70°C/second in the atmosphere. Thereafter, the temperature was maintained at 1300°C for 180 seconds. Thereafter, the square test piece was cooled to room temperature at a cooling rate of 50° C./sec. A welding simulation test piece was prepared by applying the above thermal history to the square test piece.

A stress relaxation test in accordance with ASTM E328-02 was conducted using a welding simulated test piece. Specifically, a test piece for a stress relaxation test was prepared from a welding simulation test piece. The test piece was a brimmed creep test piece with a length of 80 mm and a gage distance GL=30 mm. An initial cold strain of 20% was applied to the test piece using a test jig for deflection displacement loading. The test jig to which the cold strained test piece was attached was placed in a heating furnace and held at 650°C for 300 hours.

The results of the stress relaxation test in accordance with ASTM E328-02 were evaluated as follows.
Evaluation E (Excellent): The test piece did not break after 300 hours. Evaluation G (Good): The test piece broke after 200 to 300 hours. Evaluation B (Bad): The test piece broke after less than 200 hours. In the case of evaluation G or E, it was judged that excellent stress relaxation cracking resistance was obtained. The evaluation results are shown in the "stress relaxation cracking resistance" column in Table 2.

[(Test 4) Welding hot cracking resistance evaluation test]
A test piece with a thickness of 12 mm, a width of 40 mm, and a length of 300 mm was taken from the alloy material (alloy plate) of each test number, centered on the center position of the plate width and the center position of the plate thickness. The following LongiValle restraint test was conducted on the sampled test piece.

Specifically, TIG tan welding was performed in the longitudinal direction of the test piece at the center of the plate width under the conditions of a welding current of 200 A, a voltage of 12 V, and a welding speed of 15 cm/min. During TIG tanning welding, bending stress was momentarily applied in parallel to the welding direction so that 2% strain was applied to the surface layer.

The part including the part where weld cracking occurred due to the application of bending stress was cut out to a size that could be observed with an optical microscope. The size of the cut sample was 40 mm x 40 mm x 12 mm.

The scale on the surface of the welded part of the cut sample was removed by buffing. Thereafter, using a 100x optical microscope, the presence or absence of cracks in the HAZ and, if cracks occurred, the length of the cracks were measured. Specifically, the length of a crack that propagated in a direction perpendicular to the welding direction starting from the boundary between the weld metal and the HAZ (length in the direction perpendicular to the welding direction) was measured. The length of all cracks that occurred in the test piece in the direction perpendicular to the welding direction was determined. The sum of the lengths of those cracks was defined as the total crack length (mm). The total crack length was determined for each of the two test pieces. The arithmetic mean value of the determined total crack lengths was defined as the average total crack length.

Based on the obtained average total crack length, weld hot cracking resistance was evaluated as follows.
Evaluation E (Excellent): Average total crack length is 2.0 mm or less Evaluation G (Good): Average total crack length is more than 2.0 to less than 3.0 mm Evaluation B (Bad): Average total crack length If the length is 3.0 mm or more and the evaluation is G or E, it was determined that excellent welding hot cracking resistance was obtained. The evaluation results are shown in the "welding hot cracking resistance" column in Table 2.

[Test results]
Table 2 shows the test results.

Referring to Tables 1-1, 1-2, and 2, in test numbers 1 to 35, the alloy materials satisfied characteristics 1 to 3. Therefore, sufficient creep strength was obtained in a high-temperature environment. Furthermore, excellent stress relaxation cracking resistance and excellent welding hot cracking resistance were obtained.

Furthermore, in test numbers 1 to 28, the manufacturing conditions FA satisfied formula (A), FB satisfied formula (B), and FC satisfied formula (C). As a result, in test numbers 1 to 28, the alloy material satisfied not only characteristics 1 to 3 but also characteristic 4. Therefore, in test numbers 1 to 28, a rating of E was obtained in the creep strength evaluation test, the stress relaxation cracking resistance evaluation test, and the welding hot cracking resistance evaluation test, and even more excellent creep strength and stress relaxation cracking resistance were obtained. and welding hot cracking resistance were obtained.

On the other hand, in test number 36, the Al content was too high. Therefore, sufficient stress relaxation cracking resistance and weld hot cracking resistance could not be obtained. Furthermore, sufficient creep strength could not be obtained.

In test number 37, although the content of each element in the chemical composition was appropriate, F1 was less than the lower limit of formula (1). Therefore, sufficient creep strength could not be obtained.

In test number 38, although the content of each element in the chemical composition was appropriate, F1 exceeded the upper limit of formula (1). Therefore, sufficient welding hot cracking resistance could not be obtained.

In test number 39, although the content of each element in the chemical composition was appropriate, F2 was less than the lower limit of formula (2). As a result, sufficient stress relaxation cracking resistance could not be obtained.

The embodiments of the present invention have been described above. However, the embodiments described above are merely examples for implementing the present invention. Therefore, the present invention is not limited to the embodiments described above, and can be implemented by appropriately modifying the embodiments described above without departing from the spirit thereof.

Claims (3)

The chemical composition is in mass%,
C: 0.050-0.100%,
Si: 1.00% or less,
Mn: 1.50% or less,
P: 0.035% or less,
S: 0.0015% or less,
Cr: 19.00-23.00%,
Ni: 30.00-35.00%,
N: 0.100% or less,
Al: 0.15-0.70%,
Ti: 0.15-0.70%,
B: 0.0010-0.0050%,
Nb: 0 to 0.30%,
Ta: 0 to 0.50%,
V: 0-1.00%,
Zr: 0 to 0.10%,
Hf: 0-0.10%,
Cu: 0 to 1.00%,
Mo: 0-1.00%,
W: 0-1.00%,
Co: 0-1.00%,
Ca: 0-0.0200%,
Mg: 0 to 0.0200%,
Rare earth elements: 0 to 0.1000%, and
The remainder consists of Fe and impurities,
satisfies formula (1) and formula (2),
Alloy material.
0.60<Al+Ti<1.20 (1)
1.12≦Ti/Al (2)
Here, each element symbol in formulas (1) and (2) is substituted with the content of the corresponding element in the chemical composition of the alloy material in mass %. The alloy material according to claim 1, further comprising:
When the Ti content in mass % in the residue obtained by electrolytic extraction is defined as [Ti] _R , formula (3) is satisfied,
Alloy material.
0.050<[Ti] _R <0.72Ti-0.01(Ti/Al)-0.11 (3)
Here, each element symbol in formula (3) is substituted with the content of the corresponding element in the chemical composition of the alloy material in mass %. The alloy material according to claim 1 or claim 2,
Nb: 0.01-0.30%,
Ta: 0.01 to 0.50%,
V: 0.01-1.00%,
Zr: 0.01~0.10%
Hf: 0.01-0.10%,
Cu: 0.01 to 1.00%,
Mo: 0.01-1.00%,
W: 0.01-1.00%,
Co: 0.01 to 1.00%,
Ca: 0.0001-0.0200%,
Mg: 0.0001 to 0.0200%, and
Rare earth elements: 0.001 to 0.1000%,
Containing one or more elements selected from the group consisting of
Alloy material.

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