CN120936737A

CN120936737A - Alloy material

Info

Publication number: CN120936737A
Application number: CN202480021785.2A
Authority: CN
Inventors: 小薄孝裕; 净德佳奈; 山田健太; 青田翔伍; 井泽贵央
Original assignee: Nippon Steel and Sumitomo Metal Corp
Current assignee: Nippon Steel Corp
Priority date: 2023-03-28
Filing date: 2024-03-28
Publication date: 2025-11-11
Also published as: JPWO2024204622A1; KR20250164823A; WO2024204622A1

Abstract

Provided is an alloy material which has high creep strength and excellent weld cracking resistance and hot workability. The alloy material of the present disclosure contains, in mass%, C:0.050 to 0.100%, si: less than 1.00%, mn: less than 1.50%, cr: 19.00-23.00%, ni: 30.00-35.00%, N: less than 0.010%, al:0.15 to 0.70 percent of Ti:0.15 to 0.70 percent, B: 0.0001-0.0030%, nb:0.0010 to 0.5000 percent, mo:0.01 to 1.00 percent of Ca:0.0001 to 0.0200 percent, and the balance of Fe and impurities, wherein the alloy material satisfies the formulas (1) and (2), and the alloy material also satisfies the formula (3) when B is less than or equal to 0.0010 percent. 0.60< Al+Ti <1.20 (1), 3.3-41C-Si+2Mo+3Ti+245B-12 Nb is less than or equal to 2.00 (2), 0.4+67C+1.3Si+5.5Mo+5.2Ti+13.4Nb is less than or equal to 8.25 (3).

Description

Alloy material

Technical Field

The present disclosure relates to alloy materials, and more particularly, to alloy materials that can be utilized in a high temperature environment.

Background

Alloy materials used in a steam reforming apparatus, an ethylene decomposing furnace, a heating furnace tube for petroleum refining and petrochemical equipment, a polysilicon manufacturing apparatus, and the like are used in a high-temperature environment of 500 to 1000 ℃. Therefore, an alloy material used in such a high-temperature environment is required to have excellent corrosion resistance and high creep strength in the high-temperature environment. As alloy materials used in such a high-temperature environment, alloy 800H, and alloy 800HT are known.

Alloy 800, alloy 800H and alloy 800HT contain Cr and Ni in large amounts. Therefore, these alloy materials are excellent in corrosion resistance at high temperatures. These alloys also contain Al and Ti. Therefore, in these alloy materials, a γ' (GAMMA PRIME) phase (Ni ₃ (Al, ti)) is generated in use under a high temperature environment. By precipitation strengthening based on the γ' phase, a high creep strength is obtained in these alloy materials.

However, in the alloy 800, the alloy 800H, and the alloy 800HT containing Al and Ti, welding hot cracks are likely to occur in a welding Heat-Affected Zone (HAZ) during welding work. Further, these alloy materials are produced by hot working in a temperature range of about 900 ℃, but cracks are likely to occur due to embrittlement during hot working. Therefore, these alloy materials are required to have excellent weld heat crack resistance and excellent hot workability.

Techniques for improving the solder heat cracking resistance of an alloy material containing Al and Ti are disclosed in Japanese patent application laid-open Nos. 2022-163425 (patent document 1), 2022-163585 (patent document 2) and 2022-163586 (patent document 3).

The alloy disclosed in patent document 1 has a chemical composition containing, by mass%, 0.15% or less of C, 0.05 to 2.0% of Si, 0.05 to 2.0% of Mn, 0.035% or less of P, 0.0015% or less of S, 16 to 30% of Cr, 18 to 50% of Ni, 0.01 to 1.0% of Al, 0.01 to 1.5% of Ti, 0.35% or less of N, 0.003% or less of O, 8% or less of Mo, 4% or less of Cu, 3% or less of Co, 0.0003 to 0.0050% of Ca, and 0.0045% or less of Mg, with the balance being Fe and impurities. The mass ratio of CaO, mgO, and Al ₂O₃ in the inclusions calculated from the average Ca concentration, the average Mg concentration, and the average Al concentration of the inclusions detected as O or S satisfies [ CaO-0.6xMgO ]/[ CaO+MgO+Al ₂O₃ ]. Gtoreq.0.20. In patent document 1, the mass ratio of oxide inclusions (CaO, mgO, and Al ₂O₃) in the alloy material is appropriately controlled. Thus, the formation of coarse TiC is suppressed, and the weld cracking resistance of the alloy material is improved.

The alloy disclosed in patent document 2 has a chemical composition containing, by mass%, 0.15% or less of C, 0.05 to 2.0% of Si, 0.05 to 2.0% of Mn, 0.035% or less of P, 0.0015% or less of S, 16 to 30% of Cr, 18 to 50% of Ni, 0.01 to 1.0% of Al, 0.01 to 1.5% of Ti, 0.35% or less of N, 0.003% or less of O, 8% or less of Mo, 4% or less of Cu, 3% or less of Co, 0.0003 to 0.0050% of Ca, and 0.0060% or less of Mg, with the balance being Fe and impurities. The number density of TiC-based precipitates having an equivalent circle diameter of 1.0 [ mu ] m or more and the Mg content in steel satisfy the number density (number/mm ²) of TiC and the Mg concentration (mass ppm) in steel is not more than 463 and 9.5 x. In patent document 2, the amount of coarse TiC deposition is appropriately controlled according to the Mg concentration in the alloy material. Thereby, the weld hot cracking resistance of the alloy material is improved.

The alloy disclosed in patent document 3 has a chemical composition containing, by mass%, 0.15% or less of C, 0.05 to 2.0% of Si, 0.05 to 2.0% of Mn, 0.035% or less of P, 0.0015% or less of S, 0.0020% or less of O, 0.0020% or less of the sum of O and S, 16 to 30% of Cr, 18 to 50% of Ni, 0.01 to 1.0% of Al, 0.01 to 1.5% of Ti, 0.02% or less of N, 8% or less of Mo, 4% or less of Cu, 3% or less of Co, 0.0010 to 0.0050% of Ca and 0.0010 to 0.0050% of Mg, and the balance Fe and impurities. The average concentration of S in the oxide inclusions and the sulfide inclusions is 0.70% or more by mass%. In patent document 3, S, which decreases the grain boundary strength and the melting point of the grain boundary, is fixed in the inclusion. Thereby, the weld hot cracking resistance of the alloy material is improved.

Further, japanese patent application laid-open No. 2021-070838 (patent document 4) discloses a technique for improving hot workability of an alloy material containing Al and Ti.

The alloy disclosed in patent document 4 has a chemical composition containing, by mass%, 0.10% or less of C, 0.05 to 1.0% of Si, 0.05 to 2.0% of Mn, 0.035% or less of P, 0.0015% or less of S, 18 to 25% of Cr, 18 to 50% of Ni, 0.05 to 1.0% of Al, 0.15 to 1.5% of Ti, 0.02% or less of N, 0.003% or less of O, 5% or less of Mo, 2% or less of W, 3% or less of Cu, 2.0% or less of Co, 0.0003 to 0.005% of Ca and 0.006% or less of Mg, and the balance Fe and unavoidable impurities. The Ca/Al mass ratio in the oxide inclusion is 1.0-15. Further, the excess Ca (DeltaCa) calculated by DeltaCa=Ca-1.25xS-K (Ca/O). Times.O is 0.0003 to 0.0030%. In patent document 4, Δca in the alloy material is appropriately controlled. This improves the hot workability of the alloy material.

Prior art literature

Patent literature

Patent document 1 Japanese patent application laid-open No. 2022-163425

Patent document 2 Japanese patent application laid-open No. 2022-163585

Patent document 3 Japanese patent laid-open No. 2022-163586

Patent document 4 Japanese patent laid-open No. 2021-070838

Disclosure of Invention

Problems to be solved by the invention

Although the alloy materials described in patent documents 1 to 3 can obtain excellent weld cracking resistance, the hot workability of the alloy materials is not examined in these documents. Although the alloy material described in patent document 4 can obtain excellent hot workability, no study has been made on weld hot cracking resistance.

An object of the present disclosure is to provide an alloy material that can obtain high creep strength, and that can obtain excellent weld hot cracking resistance and excellent hot workability.

Solution for solving the problem

The chemical composition of the alloy material of the present disclosure is in mass percent

C:0.050~0.100%、

Si is less than 1.00%,

Mn 1.50% or less,

P is less than 0.035%,

S is less than 0.0015%,

Cr:19.00~23.00%、

Ni:30.00~35.00%、

N is less than 0.010%,

Al:0.15~0.70%、

Ti:0.15~0.70%、

B:0.0001~0.0030%、

Nb:0.0010~0.5000%、

Mo:0.01~1.00%、

Ca:0.0001~0.0200%、

Ta:0~0.50%、

V:0~1.00%、

Zr:0~0.100%、

Hf:0~0.10%、

Cu:0~1.00%、

W:0~1.00%、

Co:0~1.00%、

0 To 0.1000% of rare earth element,

0 To 0.0200% of Mg, and

The balance of Fe and impurities,

The alloy material satisfies the formulas (1) and (2),

When the B content in the chemical composition is 0.0010% or less, the formula (3) is also satisfied.

0.60<Al+Ti<1.20(1)

3.3-41C-Si+2Mo+3Ti+245B-12Nb≤2.00(2)

0.4+67C+1.3Si+5.5Mo+5.2Ti+13.4Nb≤8.25(3)

Wherein the content of the corresponding element in the chemical composition is substituted in mass% at each element symbol in the formulas (1) to (3).

Effects of the invention

In the alloy material of the present disclosure, high creep strength can be obtained, and excellent weld hot cracking resistance and excellent hot workability can be obtained.

Detailed Description

The inventors of the present invention studied, first, from the viewpoint of chemical composition, an alloy material that can obtain high creep strength and also can obtain excellent weld hot cracking resistance and excellent hot workability. As a result, the inventors have found that an alloy material having a chemical composition of 0.050 to 0.100% by mass 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 to 23.00% of Cr, 30.00 to 35.00% of Ni, 0.010% or less of 、Al：0.15～0.70％、Ti：0.15～0.70％、B：0.0001～0.0030％、Nb：0.0010～0.5000％、Mo：0.01～1.00％、Ca：0.0001～0.0200％、Ta：0～0.50％、V：0～1.00％、Zr：0～0.100％、Hf：0～0.10％、Cu：0～1.00％、W：0～1.00％、Co：0～1.00％、 rare earth elements, 0 to 0.1000% of Mg,0 to 0.0200% by mass of Mg, and the balance Fe and impurities can be used in a high-temperature environment, and that excellent weld cracking resistance and excellent hot workability can be obtained.

Accordingly, the inventors of the present invention have further studied on the creep strength, weld hot cracking resistance and hot workability of an alloy material satisfying the above chemical composition. As a result, the present inventors have found the following.

[ Concerning creep Strength ]

The present inventors have studied a method for improving creep strength in a high-temperature environment for an alloy material satisfying the above chemical composition. As described above, al and Ti form a γ' (GAMMA PRIME) phase (Ni ₃ (Al, ti)) in the alloy material in use under a high temperature environment. The gamma prime phase increases creep strength. Thus, the total content of Al and Ti has an influence on creep strength. Specifically, in the alloy material having the chemical composition described above, if the following formula (1) is satisfied, sufficient creep strength can be obtained.

0.60<Al+Ti<1.20(1)

Wherein the content of the corresponding element in the chemical composition of the alloy material is substituted in mass% at each element symbol in the formula (1).

[ Concerning weld thermal cracking resistance and Hot workability ]

Of the elements in the chemical composition, P, S and Mg are likely to segregate at grain boundaries. If these elements segregate, the grain boundaries embrittle, and the hot workability at around 900 ℃ is reduced. B suppresses a decrease in hot workability caused by segregation of these elements to grain boundaries. Specifically, B segregates at the grain boundaries, and other elements than B are inhibited from segregating at the grain boundaries. Therefore, the grain boundary is reinforced by the segregation of B. As a result, the hot workability of the alloy material is improved.

However, if B is contained, the solidification temperature of the HAZ grain boundary of the alloy material melted during the temperature increase at the time of welding is lowered. Therefore, B improves hot workability, but reduces weld cracking resistance.

Accordingly, the present inventors have studied a method capable of improving the hot workability by containing B and improving the weld cracking resistance. As a result, the inventors of the present invention have found that (a) the melting temperature and solidification temperature of Ti-based precipitates deposited at grain boundaries are increased and (B) the solidification temperature of grain boundaries melted by the liquefaction phenomenon of composition during the temperature increase at the time of welding are effective in order to further improve weld hot cracking resistance while containing B.

[ Concerning (A) increasing the melting temperature and solidification temperature of Ti-based precipitates deposited at grain boundaries ]

In the present specification, the Ti-based precipitate means a precipitate containing Ti. The Ti-based precipitates are mainly Ti-containing carbides. The Ti-based precipitate may contain an element other than Ti (for example, si, nb, etc.).

C. si and Nb raise the melting temperature and solidification temperature of Ti-based precipitates. Specifically, C and Si improve the stability of Ti-based precipitates at high temperatures. Therefore, the melting temperature and solidification temperature of the Ti-based precipitate are increased. Nb is contained in the Ti-based precipitate to raise the melting temperature and solidification temperature of the Ti-based precipitate. Therefore, C, si and Nb are elements that raise the melting temperature and solidification temperature of Ti-based precipitates deposited at grain boundaries.

[ Concerning (B) increasing the solidification temperature of grain boundaries which are melted according to the liquefaction phenomenon of the composition during the temperature increase at the time of welding ]

Even when the melting temperature and solidification temperature of the Ti-based precipitate are high, if the liquefaction phenomenon of the composition occurs, the weld hot cracking resistance is reduced. Specifically, the alloy material is locally and rapidly heated at the time of welding heating. In this case, eutectic melting reaction occurs in the heated portion (HAZ) of the alloy material in the Ti precipitates and the grain boundary region of the grain boundary, and the Ti precipitates and the grain boundary liquefy at a temperature lower than the melting points thereof. Such a phenomenon is called a liquefaction phenomenon of composition.

Grain boundaries where the liquefaction of the composition occurs become the starting points of cracks. Therefore, in order to improve the weld hot cracking resistance, it is effective to raise not only the melting temperature and solidification temperature of the Ti-based precipitate but also the solidification temperature of the grain boundary in which the liquefaction phenomenon of the composition occurs. Then, the present inventors have studied a method of increasing the solidification temperature of grain boundaries in which a liquefaction phenomenon of composition occurs. As a result, it was found that Mo, ti and B promoted liquefaction of the composition of grain boundaries. When Mo, ti, or B is contained at the grain boundary where the liquefaction of the composition occurs, the solidification temperature of the grain boundary where the liquefaction of the composition occurs decreases. If the solidification temperature of the grain boundary in which the liquefaction phenomenon of the composition occurs becomes low, weld hot cracks are liable to occur.

Based on the above findings, the inventors considered that weld cracking resistance was improved by increasing the C content, si content, and Nb content to increase the melting temperature and solidification temperature of Ti-based precipitates in the alloy material, and by suppressing the Mo content, ti content, and B content to increase the solidification temperature of grain boundaries where the liquefaction phenomenon of the composition occurred. Then, the relationship between these elements and weld hot cracking resistance was further studied. As a result, it was found that when the above-mentioned alloy material having the chemical composition further satisfies the following formula (2), excellent weld hot cracking resistance and excellent hot workability can be obtained.

3.3-41C-Si+2Mo+3Ti+245B-12Nb≤2.00(2)

Wherein the content of the corresponding element in the chemical composition of the alloy material is substituted in mass% at each element symbol in the formula (2).

[ Case where the B content was 0.0010% or less ]

However, even in the case of an alloy material satisfying the chemical composition and satisfying the formulas (1) and (2), if the B content is 0.0010% or less, even if excellent weld hot cracking resistance is obtained, sufficient hot workability may not be obtained. Accordingly, the present inventors have further studied a method that can achieve both excellent hot workability and excellent weld cracking resistance when the B content is low. As a result, the present inventors have obtained the following findings.

In the alloy material having the chemical composition, ti-based precipitates may be present in the crystal grains during hot working at about 900 ℃. The alloy material is hardened by the Ti-based precipitates. As a result, the hot workability of the alloy material is reduced. Therefore, in order to improve hot workability at about 900 ℃, it is effective to suppress hardening of the alloy material due to Ti-based precipitates.

Then, the present inventors have studied a method of sufficiently suppressing hardening of an alloy material due to Ti-based precipitates during hot working when the B content is 0.0010% or less. As a result, the present inventors have found the following.

In the above hot working temperature range, C, ti, si, and Nb promote the formation of Ti-based precipitates. C and Ti directly contribute to the formation of Ti-based precipitates. Si enhances the diffusion rate of C and Ti, contributing to the formation of Ti-based precipitates. Nb replaces Ti sites of Ti-based precipitates (that is, lattice points occupied by Ti atoms in Ti-based precipitates), and promotes the formation of Nb-containing Ti-based precipitates (composite precipitates). In the chemical composition described above, mo is solid-solution strengthened in the crystal grains, and the alloy material is hardened even in the hot working temperature range.

Based on the above findings, the inventors considered that when the B content is 0.0010% or less, the hot workability at about 900 ℃ is improved by appropriately controlling the C content, ti content, si content, nb content, and Mo content.

Then, based on the findings described above, the relationship between the contents of the above elements (C, si, mo, ti and Nb) and the hot workability in the case where the B content is 0.0010% or less was further studied. As a result, it was found that, in the alloy material satisfying the chemical composition and satisfying the formulas (1) and (2), when the B content is 0.0010% or less, the alloy material further satisfies the formula (3), and thus both excellent weld hot cracking resistance and excellent hot workability can be achieved.

0.4+67C+1.3Si+5.5Mo+5.2Ti+13.4Nb≤8.25(3)

Wherein the content of the corresponding element in the chemical composition is substituted in mass% at each element symbol in the formula (3).

The alloy material of the present embodiment is completed based on the above findings, and has the following configuration.

The alloy material of the 1 st component has a chemical composition in mass percent

C:0.050~0.100%、

Si is less than 1.00%,

Mn 1.50% or less,

P is less than 0.035%,

S is less than 0.0015%,

Cr:19.00~23.00%、

Ni:30.00~35.00%、

N is less than 0.010%,

Al:0.15~0.70%、

Ti:0.15~0.70%、

B:0.0001~0.0030%、

Nb:0.0010~0.5000%、

Mo:0.01~1.00%、

Ca:0.0001~0.0200%、

Ta:0~0.50%、

V:0~1.00%、

Zr:0~0.100%、

Hf:0~0.10%

Cu:0~1.00%、

W:0~1.00%、

Co:0~1.00%、

0 To 0.1000% of rare earth element,

0 To 0.0200% of Mg, and

The balance of Fe and impurities,

The alloy material satisfies the formulas (1) and (2),

The formula (3) is also satisfied when the B content in the chemical composition is 0.0010% or less.

0.60<Al+Ti<1.20(1)

3.3-41C-Si+2Mo+3Ti+245B-12Nb≤2.00(2)

0.4+67C+1.3Si+5.5Mo+5.2Ti+13.4Nb≤8.25(3)

According to the alloy material of the 1 st constitution, the chemical composition of the alloy material of the 2 nd constitution contains a composition selected from the group consisting of, in mass%

Ta:0.01~0.50%、

V:0.01~1.00%、

Zr:0.001~0.100%、

Hf:0.01~0.10%、

Cu:0.01~1.00%、

W:0.01~1.00%、

Co:0.01~1.00%、

0.0001-0.1000% Of rare earth element, and

0.0001-0.0200% Of Mg.

According to the alloy material of the 1 st or 2 nd, the chemical composition of the alloy material of the 3 rd contains B in mass% of more than 0.0010% and not more than 0.0030%,

The Ti content [ Ti ] in the residue obtained by the extraction residue method is less than 0.020% by mass, or

The [ Ti ] is 0.020% or more, and the Nb content [ Nb ] in mass% in the residue is 0.015% or more, and the [ Ti ] and the [ Nb ] satisfy the formula (4).

[Ti]+[Nb]≥0.050(4)

According to the alloy material of the 1 st or 2 nd, the chemical composition of the alloy material of the 4 th contains B0.0001 to 0.0010% by mass,

The Ti content [ Ti ] in the residue obtained by the extraction residue method is 0.031% or less by mass%, or

The [ Ti ] is more than 0.031%, and the Nb content [ Nb ] in mass% in the residue is 0.3 x [ Ti ]% or more.

The alloy material according to the present embodiment will be described in detail below. In addition, "%" related to elements means mass% unless otherwise specified.

[ Characteristics of alloy Material of the embodiment ]

The alloy material according to the present embodiment satisfies the following features 1 to 4.

(Feature 1)

The chemical composition comprises, by 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, 0.010% or less of N 、Al：0.15～0.70％、Ti：0.15～0.70％、B：0.0001～0.0030％、Nb：0.0010～0.5000％、Mo：0.01～1.00％、Ca：0.0001～0.0200％、Ta：0～0.50％、V：0～1.00％、Zr：0～0.100％、Hf：0～0.10％、Cu：0～1.00％、W：0～1.00％、Co：0～1.00％、 rare earth elements, 0-0.1000% of Mg, 0-0.0200% of Mg, and the balance of Fe and impurities.

(Feature 2)

The chemical composition of feature 1 also satisfies formula (1).

0.60<Al+Ti<1.20(1)

(Feature 3)

The chemical composition of feature 1 also satisfies formula (2).

3.3-41C-Si+2Mo+3Ti+245B-12Nb≤2.00(2)

(Feature 4)

The formula (3) is also satisfied when the B content in the chemical composition of feature 1 is 0.0010% or less.

0.4+67C+1.3Si+5.5Mo+5.2Ti+13.4Nb≤8.25(3)

Wherein the content of the corresponding element in the chemical composition of the alloy material is substituted in mass% at each element symbol in the formula (3).

The alloy material according to the present embodiment satisfies the above-described features 1 to 4. Therefore, the alloy material according to the present embodiment can obtain high creep strength, and can obtain excellent weld hot cracking resistance and excellent hot workability. Hereinafter, features 1 to 4 will be described.

[ Concerning (feature 1) chemical composition ]

The alloy material of the present embodiment has the following chemical composition.

C:0.050~0.100%

Carbon (C) improves creep strength of the alloy material in a high temperature environment. If the C content is less than 0.050%, the above-described effects cannot be sufficiently obtained even if the other element content is within the range of the present embodiment.

On the other hand, if the C content is more than 0.100%, M ₂₃C₆ type Cr carbide is formed at the grain boundary. In this case, cr-depleted regions are generated at the grain boundaries. Therefore, even if the content of other elements is within the range of the present embodiment, the stress relaxation crack resistance of the alloy material is reduced.

Thus, the C content is 0.050 to 0.100%.

The preferable lower limit of the C content is 0.055%, more preferably 0.060%, still more preferably 0.065%, still more preferably 0.070%.

The upper limit of the C content is preferably 0.097%, more preferably 0.095%, more preferably 0.093%, more preferably 0.090%, more preferably 0.085%, more preferably 0.080%.

Si of 1.00% or less

Silicon (Si) deoxidizes the alloy in the steel making process. Si also improves the oxidation resistance of the alloy material in a high temperature environment. If Si is contained in a small amount, the above-described effects can be obtained to some extent even if the content of other elements is within the range of the present embodiment.

However, if the Si content is more than 1.00%, the weld hot cracking resistance and hot workability are reduced even if the content of other elements falls within the range of the present embodiment.

Thus, the Si content is 1.00% or less.

The preferable lower limit of the Si content is more than 0%, more preferably 0.01%, still more preferably 0.05%, still more preferably 0.10%, still more preferably 0.15%, still more preferably 0.20%.

The preferable upper limit of the Si content is 0.90%, more preferably 0.80%, more preferably 0.70%, more preferably 0.65%, more preferably 0.60%, more preferably 0.55%, more preferably 0.50%.

Mn 1.50% or less

Manganese (Mn) deoxidizes the welded portion of the alloy material at the time of welding. Mn also stabilizes austenite. The above-described effects can be obtained to some extent by only containing Mn in a small amount. However, if the Mn content is more than 1.50%, sigma phase (sigma phase) tends to be generated when used in a high temperature environment. The sigma phase reduces the toughness and creep ductility of the alloy in high temperature environments. Thus, the Mn content is 1.50% or less.

The preferable lower limit of the Mn content is more than 0%, more preferably 0.01%, more preferably 0.05%, more preferably 0.10%, more preferably 0.40%, more preferably 0.50%, more preferably 0.60%.

The preferable upper limit of the Mn content is 1.45%, more preferably 1.40%, more preferably 1.35%, more preferably 1.30%, more preferably 1.25%, more preferably 1.20%.

P is less than 0.035%

Phosphorus (P) is an impurity inevitably contained. That is, the P content is greater than 0%. P segregates at grain boundaries of the alloy material during welding to reduce stress relaxation crack resistance. P segregates at grain boundaries also reduces hot workability.

Thus, the P content is 0.035% or less.

The P content is preferably as low as possible. However, excessive reduction in the P content greatly increases the manufacturing cost. Therefore, in consideration of industrial production, the lower limit of the P content is preferably 0.001%, more preferably 0.002%, and still more preferably 0.005%.

The upper limit of the P content is preferably 0.030%, more preferably 0.025%, more preferably 0.020%, and even more preferably 0.015%.

S is less than 0.0015%

Sulfur (S) is an impurity inevitably contained. That is, the S content is greater than 0%. S segregates at grain boundaries of the alloy material during welding and hot working, and the weld hot cracking resistance and hot workability are lowered.

Thus, the S content is 0.0015% or less.

The S content is preferably as low as possible. However, excessive reduction in the S content greatly increases the manufacturing cost. Thus, in consideration of industrial production, the preferable lower limit of the S content is more than 0%, more preferably 0.0001%, still more preferably 0.0002%.

The preferable upper limit of the S content is 0.0012%, more preferably 0.0010%, still more preferably 0.0008%, still more preferably 0.0006%.

Cr:19.00~23.00%

Chromium (Cr) improves corrosion resistance of alloy materials in high temperature environments. If the Cr content is less than 19.00%, the above-described effects cannot be sufficiently obtained even if the other element content is within the range of the present embodiment.

On the other hand, if the Cr content is more than 23.00%, the stability of austenite is lowered in a high-temperature environment. In this case, even if the content of other elements falls within the range of the present embodiment, the creep strength of the alloy material decreases.

Thus, the Cr content is 19.00 to 23.00%.

The preferable lower limit of the Cr content is 19.20%, more preferably 19.40%, still more preferably 19.60%.

The preferable upper limit of the Cr content is 22.50%, more preferably 22.00%, more preferably 21.50%, more preferably 21.00%, more preferably 20.50%, more preferably 20.00%.

Ni:30.00~35.00%

Nickel (Ni) stabilizes austenite and improves creep strength of an alloy material in a high-temperature environment. If the Ni content is less than 30.00%, the above-described effects cannot be sufficiently obtained even if the other element content is within the range of the present embodiment.

On the other hand, if the Ni content is more than 35.00%, the above effect is saturated. Further, the cost of raw materials increases.

Thus, the Ni content is 30.00 to 35.00%.

The preferable lower limit of the Ni content is 30.20%, more preferably 30.40%, still more preferably 30.60%, still more preferably 30.80%.

The upper limit of the Ni content is preferably 34.70%, more preferably 34.50%, more preferably 34.00%, more preferably 33.50%, more preferably 33.00%, more preferably 32.50%, more preferably 32.00%, more preferably 31.50%, more preferably 31.00%.

N is less than 0.010%

Nitrogen (N) is an impurity. N is solid-dissolved in the matrix (parent phase) to stabilize austenite. Solid-solution N also forms fine nitrides in the alloy material during use in a high-temperature environment. Since the fine nitride strengthens the Cr-depleted region, the stress relaxation crack resistance of the alloy material is improved. The fine nitrides generated during use in a high-temperature environment also increase creep strength by precipitation strengthening. The above-described effects can be obtained to some extent by only containing N in a small amount. However, if the N content exceeds 0.010%, ti nitride is excessively formed and coarsened. In this case, the weld heat crack resistance of the alloy material is lowered, and the toughness and hot workability are also lowered. Thus, the N content is 0.010% or less.

The preferable lower limit of the N content is 0.001%.

The preferable upper limit of the N content is 0.007%, more preferably 0.006%, still more preferably 0.005%.

Al:0.15~0.70%

Aluminum (Al) deoxidizes the alloy in the steel making process. Al also improves the oxidation resistance of the alloy material in a high temperature environment. Al also generates gamma' phase in high temperature environment, and improves creep strength of alloy material in high temperature environment. If the Al content is less than 0.15%, the above-described effects cannot be sufficiently obtained even if the content of other elements is within the range of the present embodiment.

On the other hand, if the Al content is more than 0.70%, a large amount of γ' phase is generated in the production process of the alloy material. In this case, even if the content of other elements is within the range of the present embodiment, the hot workability in the manufacturing process of the alloy material is lowered.

Thus, the Al content is 0.15 to 0.70%.

The lower limit of the Al content is preferably 0.17%, more preferably 0.19%, more preferably 0.21%, more preferably 0.23%, more preferably 0.30%.

The preferable upper limit of the Al content is 0.65%, more preferably 0.60%, more preferably 0.57%, more preferably 0.55%, more preferably 0.53%, more preferably 0.51%, more preferably 0.45%, more preferably 0.40%.

Further, the Al content is the so-called total Al (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, and improves creep strength of an alloy material in a high temperature environment. If the Ti content is less than 0.15%, the above-described effects cannot be sufficiently obtained even if the other element content is within the range of the present embodiment.

On the other hand, if the Ti content is more than 0.70%, the Ti-based precipitates coarsen or a large amount of γ' phase is generated in the production process of the alloy material. In this case, even if the content of other elements falls within the range of the present embodiment, the weld hot cracking resistance or the hot workability is lowered.

Thus, the Ti content is 0.15 to 0.70%.

The lower limit of the Ti content is preferably 0.16%, more preferably 0.17%, still more preferably 0.18%, and still more preferably 0.20%.

The preferable upper limit of the Ti content is 0.65%, more preferably 0.60%, more preferably 0.57%, more preferably 0.55%, more preferably 0.50%, more preferably 0.45%.

B:0.0001~0.0030%

Boron (B) segregates at grain boundaries under a high temperature environment of about 900 ℃, improving grain boundary strength. Therefore, the hot workability of the alloy material is improved. If the B content is less than 0.0001%, the above-described effects cannot be sufficiently obtained even if the other element content is within the range of the present embodiment.

On the other hand, if the B content is more than 0.0030%, B lowers the solidification temperature of the grain boundary melted at the time of welding heating. In this case, even if the content of other elements is within the range of the present embodiment, the weld hot cracking resistance is lowered.

Thus, the B content is 0.0001 to 0.0030%.

The preferable lower limit of the B content is 0.0003%, more preferably 0.0005%, still more preferably 0.0010%.

The upper limit of the B content is preferably 0.0028%, more preferably 0.0025%, further preferably 0.0023%, further preferably 0.0020%.

Nb:0.0010~0.5000%

When niobium (Nb) is contained in the Ti-based precipitate, the melting temperature and solidification temperature of the Ti-based precipitate are increased. As a result, the weld hot cracking resistance of the alloy material is improved. Nb also forms fine precipitates in the alloy material in a high-temperature environment, and improves the creep strength of the alloy material. If the Nb content is less than 0.0010%, the above-described effects cannot be sufficiently obtained even if the other element content is within the range of the present embodiment.

On the other hand, if the Nb content is more than 0.5000%, the hot workability of the alloy material is lowered even if the other element content is within the range of the present embodiment.

Thus, the Nb content is 0.0010 to 0.5000%.

The lower limit of the Nb content is preferably 0.0020%, more preferably 0.0050%, further preferably 0.0080%, further preferably 0.0100%.

The preferable upper limit of the Nb content is 0.4500%, more preferably 0.4000%, still more preferably 0.3000%, still more preferably 0.2500%, still more preferably 0.2400%.

Mo:0.01~1.00%

Since molybdenum (Mo) is contained together with B, grain boundaries are reinforced by co-segregation, and hot workability of the alloy material is improved. Even if the B content is more than 0.0010%, the above-mentioned effects cannot be sufficiently obtained if the Mo content is less than 0.01%.

On the other hand, if the Mo content is more than 1.00%, LAVES equivalent intermetallic compounds are generated in the grains. In this case, the strength difference between the inside of the crystal grain and the grain boundary becomes large. Therefore, hot workability is degraded. When the B content is 0.0010% or less, not only the above-described effect of Mo becomes small, but also the hardness in the crystal grains becomes high due to solid solution strengthening of Mo. Therefore, hot workability around 900 ℃ is degraded.

Thus, the Mo content is 0.01 to 1.00%.

The lower limit of the Mo content is preferably 0.02%, more preferably 0.03%, even more preferably 0.04%, and even more preferably 0.05%.

The upper limit of the Mo content is preferably 0.90%, more preferably 0.80%, more preferably 0.70%, more preferably 0.60%, more preferably 0.50%.

Ca:0.0001~0.0200%

Calcium (Ca) fixes S (sulfur) as an inclusion, and improves hot workability of the alloy material. Ca also fixes S and suppresses grain boundary segregation of S. In this case, the weld hot cracking resistance is improved. If the Ca content is less than 0.0001%, the above-described effects cannot be sufficiently obtained even if the content of other elements is within the range of the present embodiment.

On the other hand, if the Ca content is more than 0.0200%, the cleanliness of the alloy material is reduced. In this case, even if the content of other elements falls within the range of the present embodiment, the hot workability of the alloy material is rather deteriorated.

Thus, the Ca content is 0.0001 to 0.0200%.

The preferable lower limit of the Ca content is 0.0002%, more preferably 0.0005%, still more preferably 0.0010%.

The upper limit of the Ca content is preferably 0.0150%, more preferably 0.0100%, more preferably 0.0080%, more preferably 0.0050%, more preferably 0.0040%, more preferably 0.0030%.

The balance of the chemical composition of the alloy material of the present embodiment is Fe and impurities. Here, the impurities having chemical composition are substances which are mixed from ores, scraps, manufacturing environments, or the like as raw materials and allowed to be contained in the range that does not adversely affect the alloy material of the present embodiment when the alloy material is industrially manufactured. Typical examples of impurities are Sn, as, zn, pb, sb, bi and O (oxygen). The total content of these impurities is 0.10% or less.

[ Arbitrary element (Optional Elements) ]

The alloy material of the present embodiment may further comprise a chemical composition selected from the group consisting of

Ta:0~0.50%、

V:0~1.00%、

Zr:0~0.100%、

Hf:0~0.10%、

Cu:0~1.00%、

W:0~1.00%、

Co:0~1.00%、

0 To 0.1000% of rare earth element, and

0-0.0200% Of Mg to replace part of Fe. These arbitrary elements are described below.

[ Group 1: ta, V, zr, hf ]

The alloy material of the present embodiment may further contain one or more selected from the group consisting of Ta, V, zr, and Hf described above in place of part of Fe. These elements are arbitrary elements. These elements all raise the melting temperature of the Ti carbide to stabilize the Ti carbide and improve the weld cracking resistance.

Ta:0~0.50%

Tantalum (Ta) is an arbitrary element, and may not be contained. That is, the Ta content may also be 0%.

In the case of containing Ta, that is, in the case where the Ta content is more than 0%, ta is incorporated with Ti and C and contained in the Ti-based precipitate. The melting temperature and solidification temperature of the Ta-containing Ti-based precipitates become high. Therefore, the solidification temperature of the melted grain boundary at the time of welding becomes high. As a result, weld hot cracking resistance is improved. The above-described effects can be obtained to some extent by only a small amount of Ta.

However, if the Ta content is more than 0.50%, the weld hot crack resistance is lowered in the weld heat affected zone of the alloy material during the welding process of the alloy material. If the Ta content is more than 0.50%, the hot workability further decreases.

Thus, the Ta content is 0 to 0.50%.

The preferable lower limit of the Ta content is 0.01%, more preferably 0.02%, still more preferably 0.05%, still more preferably 0.08%.

The upper limit of the Ta content is preferably 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 arbitrary element, and may not be contained. That is, the V content may be 0%.

In the case of containing V, that is, in the case where the V content is more than 0%, V is incorporated with Ti and C to be contained in Ti carbide. The melting temperature and solidification temperature of the V-containing Ti-based precipitate become high. Therefore, the solidification temperature of the melted grain boundary at the time of welding becomes high. As a result, weld hot cracking resistance is improved. The above-described effects can be obtained to some extent by only containing V in a small amount.

However, if the V content is greater than 1.00%, the weld hot crack resistance is lowered in the weld heat affected zone of the alloy material during the welding process of the alloy material.

Thus, the V content is 0 to 1.00%.

The preferable lower limit of the V content is 0.01%, more preferably 0.02%, still more preferably 0.04%, still more preferably 0.06%.

The preferable upper limit of the V content is 0.80%, more preferably 0.50%, still more preferably 0.40%, still more preferably 0.35%, still more preferably 0.30%.

Zr:0~0.100%

Zirconium (Zr) is an arbitrary element, and may be not contained. That is, the Zr content may be 0%.

In the case of Zr content, that is, in the case of Zr content of more than 0%, zr is incorporated in Ti carbide by being combined with Ti and C. The melting temperature and solidification temperature of the Zr-containing Ti-based precipitates become high. Therefore, the solidification temperature of the melted grain boundary at the time of welding becomes high. As a result, weld hot cracking resistance is improved. The above-described effects can be obtained to some extent by only containing a small amount of Zr.

However, if the Zr content is more than 0.100%, the weld hot crack resistance is rather lowered in the weld heat affected zone of the alloy material during the welding process of the alloy material.

Thus, the Zr content is 0 to 0.100%.

The lower limit of the Zr content is preferably 0.001%, more preferably 0.002%.

The preferable upper limit of the Zr content is 0.090%, more preferably 0.080%, still more preferably 0.050%, still more preferably 0.030%, still more preferably 0.010%.

Hf:0~0.10%

Hafnium (Hf) may be any element, or may not be contained. That is, the Hf content may also be 0%. In the case of containing Hf, that is, in the case where the Hf content is more than 0%, hf is incorporated with Ti and C to be contained in the Ti based precipitate. The melting temperature and solidification temperature of the Ti-based precipitates containing Hf become high. Therefore, the solidification temperature of the melted grain boundary at the time of welding becomes high. As a result, weld hot cracking resistance is improved. The above-mentioned effects can be obtained to some extent by only a small amount of Hf.

However, if the Hf content is more than 0.10%, the weld hot crack resistance will be rather lowered in the weld heat affected zone of the alloy material during the welding process of the alloy material.

Thus, the Hf content is 0 to 0.10%.

The preferable lower limit of the Hf content is 0.01%, and more preferably 0.02%.

The upper limit of the Hf content is preferably 0.09%, more preferably 0.08%, still more preferably 0.07%, still more preferably 0.06%.

[ Group 2: cu, W and Co ]

The alloy material of the present embodiment may further contain one or more selected from the group consisting of Cu, W, and Co in place of part of Fe. These elements are arbitrary elements, and all improve creep strength of the alloy material.

Cu:0~1.00%

Copper (Cu) is an arbitrary element, and may not be contained. 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 in the crystal grains during use of the alloy material in a high-temperature environment. By this precipitation strengthening, the creep strength of the alloy material is improved. The above effects can be obtained to some extent by only a small amount of Cu.

However, if the Cu content is more than 1.00%, excessive precipitation of Cu phase occurs in the crystal grains. At this time, the difference in strength between the inside of the crystal grains and the grain boundaries becomes large. Therefore, stress relaxation crack resistance is reduced.

Thus, the Cu content is 0 to 1.00%.

The lower limit of the Cu content is preferably 0.01%, more preferably 0.02%, more preferably 0.05%, more preferably 0.10%, more preferably 0.15%, more preferably 0.20%.

The upper limit of the Cu content is preferably 0.90%, more preferably 0.80%, more preferably 0.70%, more preferably 0.60%, more preferably 0.55%, more preferably 0.50%.

W:0~1.00%

Tungsten (W) is an arbitrary element, and may be absent. That is, the W content may be 0%.

When W is contained, that is, when the W content is greater than 0%, the creep strength of the alloy material is improved by solid solution strengthening in the use of the alloy material in a high-temperature environment. The above-described effects can be obtained to some extent by only containing W in a small amount.

However, if the W content is more than 1.00%, LAVES equivalent intermetallic compounds are generated in the grains. In this case, the secondary induction precipitation hardening increases, and the strength difference between the inside of the crystal grains and the grain boundaries increases. Therefore, stress relaxation crack resistance is reduced.

Thus, the W content is 0 to 1.00%.

The preferable lower limit of the W content is 0.01%, more preferably 0.02%, still more preferably 0.03%, still more preferably 0.04%, still more preferably 0.05%, still more preferably 0.10%.

The preferable upper limit of the W content is 0.90%, more preferably 0.80%, more preferably 0.70%, more preferably 0.65%, more preferably 0.60%, more preferably 0.50%.

Co:0~1.00%

Cobalt (Co) is an arbitrary element, and may not be contained. That is, the Co content may be 0%.

In the case of Co, that is, in the case where the Co content is more than 0%, co stabilizes austenite and improves creep strength of the alloy material in a high-temperature environment. The above-described effects can be obtained to some extent by only containing Co in a small amount.

However, if the Co content is more than 1.00%, the raw material cost increases.

Thus, the Co content is 0 to 1.00%.

The lower limit of the Co content is preferably 0.01%, more preferably 0.02%, more preferably 0.03%, more preferably 0.05%, more preferably 0.10%.

The upper limit of the Co content is preferably 0.90%, more preferably 0.80%, more preferably 0.70%, more preferably 0.60%, more preferably 0.50%.

[ Group 3: rare earth element (REM) ]

The alloy material of the present embodiment may further contain a rare earth element (REM) in place of a part of Fe.

0 To 0.1000 percent of rare earth element

The rare earth element (REM) may be any element, or may not be contained. That is, the REM content may be 0%.

When REM is contained, that is, when the REM content is more than 0%, REM fixes S (sulfur) as an inclusion, and improves hot workability of the alloy material. REM also fixes S, suppressing grain boundary segregation of S. In this case, the weld hot cracking resistance is improved. The above-described effects can be obtained to some extent by only containing a small amount of REM.

However, if the REM content is more than 0.1000%, the cleanliness of the alloy material is lowered. In this case, the hot workability of the alloy material is rather lowered.

Thus, REM content is 0 to 0.1000%.

The preferable lower limit of the REM content is 0.0001%, more preferably 0.0005%, still more preferably 0.0010%, still more preferably 0.0020%.

The upper limit of the REM content is preferably 0.0800%, more preferably 0.0600%, and still more preferably 0.0400%.

In the present specification, REM contains at least one or more elements selected from Sc, Y and lanthanoid (La to Lu of atomic number 57), and the REM content means the total content of these elements.

[ Regarding group 4: mg ]

The alloy material of the present embodiment may contain Mg instead of part of Fe.

Mg is 0 to 0.0200%

Magnesium (Mg) is an impurity, and may not be contained. That is, the Mg content may be 0%.

If Mg is greater than 0.0200%, mg segregates at grain boundaries in a high temperature environment of about 900 ℃ to embrittle the grain boundaries. In this case, the hot workability of the alloy material is degraded.

Thus, the Mg content is 0 to 0.0200%.

The Mg content is preferably as low as possible. However, excessive reduction in Mg content greatly increases manufacturing costs. Accordingly, in consideration of general industrial production, the preferable lower limit of Mg content is more than 0%, more preferably 0.0001%, still more preferably 0.0002%.

The lower limit of the Mg content is preferably 0.0150%, more preferably 0.0100%, more preferably 0.0080%, more preferably 0.0050%, more preferably 0.0040%.

[ About (feature 2) formula (1) ]

The chemical composition of the alloy material of the present embodiment also satisfies the formula (1).

0.60<Al+Ti<1.20(1)

Wherein the content of the corresponding element of the chemical composition of the alloy material is substituted in mass% at each element symbol in the formula (1).

Defined as F1 =al+ti. F1 is an index of the amount of gamma' -phase produced in use of the alloy material of the present embodiment in a high-temperature environment. In the alloy material of the present embodiment, a γ' phase is generated during use in a high-temperature environment. According to the gamma' -phase, the creep strength of the alloy material in a high-temperature environment is improved.

Even when the alloy material satisfies the characteristics 1, 3, and 4, if F1 is 0.60 or less, a sufficient amount of γ' phase is not generated in the alloy material in a high-temperature environment. In this case, the creep strength of the alloy material in the high-temperature environment is reduced.

On the other hand, even when the alloy material satisfies the characteristics 1, 3, and 4, if F1 is 1.20 or more, excessive γ' phase is generated in the alloy material. In this case, the weld hot cracking resistance is lowered.

Thus, F1 is greater than 0.60 and less than 1.20.

The preferable lower limit of F1 is 0.61, more preferably 0.62, more preferably 0.64, more preferably 0.66, more preferably 0.68, more preferably 0.70.

The upper limit of F1 is preferably 1.15, more preferably 1.10, more preferably 1.05, more preferably 1.00, more preferably 0.95.

The value of F1 is set to be a value obtained by rounding the third digit after the decimal point and remaining the second digit after the decimal point.

[ About (feature 3) formula (2) ]

The chemical composition of the alloy material of the present embodiment also satisfies the formula (2).

3.3-41C-Si+2Mo+3Ti+245B-12Nb≤2.00(2)

Wherein the content of the corresponding element of the chemical composition of the alloy material is substituted in mass% at each element symbol in the formula (2).

Defined as f2=3.3-41C-si+2mo+3ti+245 b-12Nb. F2 is an index of weld hot cracking resistance. In order to improve hot workability when hot working at about 900 ℃, B is contained in the alloy material of the present embodiment. However, in an alloy material having a chemical composition satisfying feature 1, the solidification temperature of the grain boundaries of the alloy material is lowered due to the segregation of B to the grain boundaries. Therefore, weld hot cracking resistance tends to be lowered. Therefore, in the alloy material of the present embodiment, as described above, (a) the melting temperature and solidification temperature of the Ti-based precipitates precipitated at the grain boundaries are increased, and (B) the solidification temperature of the grain boundaries melted by the liquefaction phenomenon of the composition during the temperature rising at the time of welding is increased. As a result, weld hot cracking resistance is improved.

Specifically, C, si and Nb increase the solidification temperature of the Ti-based precipitate after melting in the chemical composition satisfying feature 1. On the other hand, mo, ti and B promote the liquefaction phenomenon of the composition, and lower the solidification temperature after the grain boundary melting. Accordingly, by properly controlling the C content, si content, nb content, mo content, ti content, and B content, the above (a) and (B) are simultaneously realized, and the solidification temperature of the grain boundary after melting at the time of welding is increased, as a result, the weld hot cracking resistance is improved. Even when the alloy material satisfies the characteristics 1,2, and 4, if F2 is greater than 2.00, the above-described effects cannot be sufficiently obtained. Thus, F2 is 2.00 or less.

The upper limit of F2 is preferably 1.97, more preferably 1.95, still more preferably 1.93, and still more preferably 1.90.

The lower limit of F2 is not particularly limited, but is preferably-7.00, more preferably-6.00, still more preferably-5.00, and still more preferably-4.00.

The value of F2 is set to be a value obtained by rounding the third digit after the decimal point and remaining the second digit after the decimal point.

[ About (feature 4) formula (3) ]

When the B content in the chemical composition satisfying feature 1 is 0.0010% or less, the chemical composition of the alloy material of the present embodiment also satisfies formula (3).

0.4+67C+1.3Si+5.5Mo+5.2Ti+13.4Nb≤8.25(3)

Wherein the content of the corresponding element of the chemical composition of the alloy material is substituted in mass% at each element symbol in the formula (3).

Defined as f3=0.4+67c+1.3si+5.5mo+5.2ti+13.4nb. F3 is an index of hot workability in the case of performing hot working at about 900 ℃.

As described above, B segregates at the grain boundaries of the alloy material, and the solidification temperature of the grain boundaries decreases. Therefore, in the alloy material satisfying feature 1 and containing B, the weld cracking resistance tends to be lowered. Therefore, in the present embodiment, the chemical composition of the alloy material satisfies the formula (2), thereby increasing the solidification temperature of the melted grain boundaries during welding and improving the weld hot cracking resistance.

However, when welding is performed on an extremely thick wall material or when welding is performed with high heat input, an alloy material having high resistance to welding heat cracking is used. In this case, the B content in the alloy material may be adjusted to 0.0010% or less.

When the B content is 0.0010% or less, the weld hot cracking resistance is improved by the decrease in the B content. However, the hot workability tends to be lowered due to the decrease in the B content. Therefore, when the B content in the chemical composition is 0.0010% or less, the alloy material of the present embodiment is improved in hot workability by suppressing hardening of the alloy material due to Ti-based precipitates.

C. Si, mo, ti and Nb promote the formation of Ti-based precipitates. Therefore, when the B content in the chemical composition is 0.0010% or less, the value of F3 composed of C content, si content, mo content, ti content, and Nb content is appropriately adjusted, and the formation of Ti-based precipitates is suppressed. This improves the hot workability at around 900 ℃.

Even when the alloy material satisfies the characteristics 1 to 3, if F3 is greater than 8.25, the above-described effects cannot be sufficiently obtained. Thus, F3 is 8.25 or less.

The preferable upper limit of F3 is 8.20, more preferably 8.15, still more preferably 8.13, still more preferably 8.10.

The lower limit of F3 is not particularly limited, but is preferably 4.60, more preferably 4.80, still more preferably 5.00, and still more preferably 5.50.

The value of F3 is set to be a value obtained by rounding the third digit after the decimal point and remaining the second digit after the decimal point.

[ Effect of alloy Material ]

The alloy material according to the present embodiment satisfies the above-described features 1 to 4. As a result, the alloy material of the present embodiment has sufficient creep strength in a high-temperature environment, and can achieve both excellent weld hot cracking resistance and excellent hot workability.

[ Microstructure and shape of alloy Material ]

The microstructure of the alloy material according to the present embodiment is composed of austenite. The shape of the alloy material according to the present embodiment is not particularly limited. The alloy material may be an alloy pipe or an alloy plate. The alloy material may be rod-shaped. Preferably, the alloy material of the present embodiment is an alloy pipe or an alloy plate.

[ Preferable embodiment of the alloy material of the present embodiment when the B content is more than 0.0010% ]

In the case where the B content is more than 0.0010% and not more than 0.0030% in the chemical composition satisfying the characteristics 1 to 3, the alloy material of the present embodiment preferably satisfies the following characteristic 5.

(Feature 5)

The Ti content [ Ti ] in the residue obtained by the extraction residue method is less than 0.020% by mass, or [ Ti ] is 0.020% or more, and the Nb content [ Nb ] in the residue is 0.015% or more by mass, and [ Ti ] and [ Nb ] satisfy the formula (4).

[Ti]+[Nb]≥0.050(4)

Hereinafter, feature 5 will be described.

[ (Feature 5) relation (one) between Ti content [ Ti ] and Nb content [ Nb ] in the residue ]

In the alloy material of the present embodiment, when the B content in the chemical composition is greater than 0.0010% and equal to or less than 0.0030%, the alloy material satisfies the characteristics 1 to 3, and thus has sufficient creep strength in a high-temperature environment, and can achieve both excellent weld cracking resistance and excellent hot workability.

However, in the alloy material of the present embodiment, a certain amount of Ti-based precipitates are contained in the alloy material before welding. Therefore, the Ti-based precipitates trapped in the grain boundaries are eutectic melted during the temperature increase in welding the alloy material. Since the alloy material of the present embodiment contains B, B segregates at grain boundaries. Therefore, the solidification temperature of the grain boundary after melting is lowered by B. As a result, weld hot cracking resistance is reduced.

Therefore, in the alloy material of the present embodiment, when the B content is greater than 0.0010% and not more than 0.0030%, either one of the following two countermeasures I and II is preferably adopted.

(Countermeasure I)

Ti-based precipitates pre-existing in the alloy material are reduced as much as possible. This suppresses eutectic melting at a low temperature of the grain boundary, and the solidification temperature of the grain boundary is increased.

(Countermeasure II)

Nb is contained in the Ti based precipitate, and the Ti based precipitate is stabilized up to a high temperature. In this case, the eutectic melting temperature of the grain boundaries including the Ti-based precipitates is increased, and the solidification temperature of the grain boundaries is also increased.

Therefore, when the B content is more than 0.0010% and not more than 0.0030%, it is preferable that any one of the following conditions I and II is satisfied in the alloy material of the present embodiment.

(Condition I)

The Ti content [ Ti ] in the residue is less than 0.020%.

(Condition II)

The [ Ti ] in the residue obtained by the residue extraction method is 0.020% or more, and the Nb content [ Nb ] in the residue is 0.015% or more, and the [ Ti ] and [ Nb ] satisfy the formula (4).

[Ti]+[Nb]≥0.050(4)

[ Concerning condition I ]

When the B content is more than 0.0010% and not more than 0.0030%, it is difficult to generate weld hot cracks due to eutectic melting of the Ti-based precipitates and grain boundaries even if the amount of Ti-based precipitates generated is small.

In condition I, the Ti content [ Ti ] in the residue is less than 0.020%. In this case, the amount of Ti-based precipitates in the alloy material can be sufficiently suppressed. Thus, more excellent weld thermal cracking resistance can be obtained.

The upper limit of the Ti content [ Ti ] in the residue in the case of the condition I is preferably 0.019%, more preferably 0.017%.

[ Concerning condition II ]

When the B content is more than 0.0010% and not more than 0.0030%, if the Ti-based precipitates are formed in a certain amount, the solidification temperature after eutectic melting of the Ti-based precipitates and grain boundaries is preferably increased. If the Ti-based precipitates in the alloy material contain Nb, the Ti-based precipitates are stabilized at high temperatures. Therefore, the solidification temperature of the grain boundary after eutectic melting of the Ti-based precipitate and the grain boundary can be increased.

In condition II, the [ Ti ] in the residue is 0.020% or more, and the Nb content [ Nb ] in the residue is 0.015% or more, and the [ Ti ] and [ Nb ] satisfy the formula (4).

[Ti]+[Nb]≥0.050(4)

In this case, the proportion of Ti-based precipitates containing Nb among Ti-based precipitates present in the alloy material is high. Therefore, the solidification temperature of the grain boundary after the eutectic melting of the Ti-based precipitate and the grain boundary is sufficiently high. As a result, more excellent weld cracking resistance can be obtained.

The lower limit of [ Ti ] + [ Nb ] in the residue in the case of condition II is preferably 0.052%, more preferably 0.060%, still more preferably 0.070%, still more preferably 0.080%, still more preferably 0.090%.

[ Preferable embodiment of the alloy material of the present embodiment when the B content is 0.0010% or less ]

In the chemical composition satisfying the characteristics 1 to 4, the alloy material of the present embodiment also satisfies the following characteristic 6 when the B content is 0.0001 to 0.0010%.

(Feature 6)

The Ti content [ Ti ] in the residue obtained by the residue extraction method is 0.031% or less by mass, or [ Ti ] is more than 0.031%, and the Nb content [ Nb ] in the residue is 0.3 x [ Ti ]% or more by mass.

Hereinafter, feature 6 will be described.

[ (Feature 6) [ relation (two) between Ti and Nb ] in the residue ]

When the B content is 0.0001 to 0.0010%, either one of the following conditions III and IV is preferably satisfied.

(Condition III)

The Ti content [ Ti ] in the residue is 0.031% or less.

(Condition IV)

The [ Ti ] in the residue is more than 0.031%, and the Nb content in the residue is more than 0.3 xTi%.

[ Concerning condition III ]

When the B content is 0.0010% or less, the decrease in weld hot cracking resistance due to the B content can be suppressed as compared with the condition (I). Therefore, if [ Ti ] in the residue is 0.031% or less, the formation of Ti precipitates in the alloy material is sufficiently suppressed, and further excellent weld cracking resistance can be obtained.

[ Concerning condition (IV) ]

Even when the B content is 0.0010% or less, if the Ti-based precipitate is formed in a certain amount, the high-temperature stability of the Ti-based precipitate is improved, and the solidification temperature of the grain boundary after eutectic melting of the Ti-based precipitate and the grain boundary is improved. Specifically, the ratio of the Ti-based precipitates containing Nb in the alloy material is increased.

If [ Ti ] in the residue is more than 0.031% and the Nb content in the residue is 0.3 xTi%, the proportion of the Ti-based precipitate containing Nb is sufficiently high. As a result, more excellent weld cracking resistance can be obtained.

[ Method for measuring Ti content [ Ti ] and Nb content [ Nb ] in residue ]

The [ Ti ] and [ Nb ] in the residue of the alloy material were obtained by the following extraction residue method.

Test pieces were collected from the alloy material. The cross section of the test piece perpendicular to the longitudinal direction may be circular or rectangular.

When the alloy material is an alloy tube, the test piece is collected such that the center of the cross section of the test piece perpendicular to the longitudinal direction is the center position of the wall thickness of the alloy tube and the longitudinal direction of the test piece is the tube axis direction of the alloy tube.

When the alloy material is an alloy plate, the test piece is collected such that the center of the cross section of the test piece perpendicular to the longitudinal direction is the center position of the plate width of the alloy plate, the center position of the plate thickness, and the longitudinal direction of the test piece is the longitudinal direction of the alloy plate.

When the alloy material is a round bar, the test piece is collected such that the center of the cross section of the test piece perpendicular to the longitudinal direction is the R/2 position of the round bar (the center position of the radius in the cross section of the round bar perpendicular to the longitudinal direction), and the longitudinal direction of the test piece is the longitudinal direction of the round bar.

The surface of the test piece thus collected was polished to about 50 μm by preliminary electrolytic polishing to obtain a fresh surface. The test piece after electrolytic polishing was subjected to electrolysis (main electrolysis) with an electrolyte (10% acetylacetone+1% tetra ammonium+methanol). The electrolyte after the main electrolysis was passed through a 0.2 μm filter to trap the residue. The obtained residue was subjected to acid decomposition, and the Ti mass in the residue and the Nb mass in the residue were obtained by ICP (inductively coupled plasma) emission analysis.

Then, the mass of the alloy material after the main electrolysis was obtained. Specifically, the mass of the test piece before the main electrolysis and the mass of the test piece after the main electrolysis were measured. Then, a value obtained by subtracting the mass of the test piece after the main electrolysis from the mass of the test piece before the main electrolysis is defined as the mass of the alloy material after the main electrolysis.

The Ti content [ Ti ] (mass%) in the residue was obtained by dividing the Ti mass in the residue by the mass of the alloy material after the main electrolysis. Then, the mass of Nb in the residue was divided by the mass of the alloy material after the main electrolysis to obtain the Nb content [ Nb ] (mass%) in the residue.

[ Method for producing alloy Material ]

A method for manufacturing an alloy material according to this embodiment will be described. The manufacturing method described below is an example of the manufacturing method of the alloy material of the present embodiment. Therefore, the alloy material of the present embodiment may be manufactured by a manufacturing method other than the manufacturing method described below. However, the manufacturing method described below is a preferred example of the manufacturing method of the alloy material of the present embodiment.

The method for producing an alloy material according to the present embodiment includes the following steps.

(Step 1) preparation step

(Step 2) Hot working step

(Step 3) Cold working step

(Step 4) Heat treatment step

The step 3 (cold working step) is optional, and may not be performed. Hereinafter, each step will be described.

[ (Process 1) preparation Process ]

In the preparation step, a material having a chemical composition satisfying the above-described characteristics 1 to 4 is prepared. The blank may be supplied by a third party or may be manufactured. The blank can be a steel ingot, a plate blank, a bloom and a billet.

In the case of manufacturing a blank, the blank is manufactured by the following method. A molten alloy having the chemical composition described above was produced. A steel ingot is manufactured using the manufactured molten alloy and by an ingot casting method. The slab, bloom, or billet may be produced by continuous casting using the produced molten alloy. The steel slab may be produced by hot working the produced steel slab, slab or bloom. For example, a columnar billet may be manufactured by hot forging a steel ingot, and the billet may be used as a billet. In this case, the temperature of the blank immediately before the start of hot forging is not particularly limited, and is, for example, 1100 to 1300 ℃. The method of cooling the blank after hot forging is not particularly limited.

[ (Process 2) Hot working Process ]

In the hot working step, the billet prepared in the preparation step is subjected to hot working to produce a master alloy material. The intermediate alloy material may be, for example, an alloy pipe, an alloy plate, or an alloy round bar.

When the intermediate alloy material is an alloy pipe, the following processing is performed in the hot working step. First, a cylindrical blank is prepared. A through hole along the central axis of the cylindrical blank is formed by machining. The cylindrical material having the through-hole formed therein is heated. The heated cylindrical material is subjected to hot extrusion typified by a glass lubricant high-speed extrusion method to produce a master alloy material (alloy pipe).

Instead of hot extrusion, an alloy tube may be produced by piercing-rolling by the mannessman method. In this case, the cylindrical blank is heated. The heating temperature is not particularly limited, and is, for example, 1100 to 1300 ℃. And piercing and rolling the heated cylindrical billet by a piercing machine. In the case of piercing-rolling, the piercing ratio is not particularly limited, and is, for example, 1.0 to 4.0. Further, the piercing-rolled cylindrical billet is hot-rolled by a continuous tube mill, a reducing mill, a sizing mill, or the like to produce a hollow shell (alloy tube). The cumulative reduction of area in the hot working step is not particularly limited, and is, for example, 20 to 80%. In the case of producing an alloy pipe by hot working, the temperature (finishing temperature) of the hollow shell immediately after the completion of hot working is preferably 800 ℃ or higher. The hot working step includes hot working at about 900 ℃.

In the case where the intermediate alloy material is an alloy sheet, for example, 1 or more rolling mills having a pair of work rolls are used for the hot working process. The blank such as a slab is heated. The heated material is hot-rolled by using a rolling mill to produce an alloy sheet. The heating temperature of the slab before hot rolling is not particularly limited, and is, for example, 1100 to 1300 ℃. The hot working step includes hot working at about 900 ℃.

In the case where the master alloy material is a round bar, for example, 1 or more rolling mills having a pair of work rolls are used for the hot working process. A pair of work rolls are formed with a hole pattern. The billets and the like are heated. The heated material was hot-rolled by using a rolling mill to produce a round bar. The heating temperature of the slab before hot rolling is not particularly limited, and is, for example, 1100 to 1300 ℃. The hot working step includes hot working at about 900 ℃.

[ (Process 3) Cold working Process ]

The cold working process is performed as needed. That is, the cold working process may not be performed. In the case of implementation, cold working is performed after the intermediate alloy material is subjected to acid washing treatment. In the case where the intermediate alloy material is an alloy pipe or an alloy bar, cold working is, for example, cold drawing. In the case where the intermediate alloy material is an alloy sheet, cold working is, for example, cold rolling. By performing the cold working step, the recrystallization can be developed and granulated. The reduction of area in the cold working step is not particularly limited, and is, for example, 10% to 90%.

[ (Process 4) Heat treatment Process ]

In the heat treatment step, the intermediate alloy material after the heat treatment step or after the cold treatment step is subjected to heat treatment to adjust the amount of solid-solution Ti and the grain size in the alloy material. The heat treatment temperature T1 is 1170-1300 ℃. The holding time at the heat treatment temperature T1 is not particularly limited, and is, for example, 5 to 30 minutes. The master alloy material is quenched after the holding time has elapsed.

Through the above steps, the alloy material of the present embodiment can be manufactured. The above-described manufacturing method is an example of the manufacturing method of the alloy material of the present embodiment. Therefore, the method of manufacturing the alloy material according to the present embodiment is not limited to the above-described manufacturing method. If the characteristics 1 to 4 are satisfied, the method for producing the alloy material is not limited to the above-described production method.

[ Preferable conditions in the heat treatment step ]

Preferably, the heat treatment temperature T1 in the heat treatment step satisfies the following formula (X).

T1≤1600+33011×(Nb)²-6995×(Nb)(X)

Wherein the Nb content in the chemical composition of the alloy material is substituted in mass% at (Nb) in the formula (X).

FA is defined as follows.

FA=1600+33011×(Nb)²-6995×(Nb)

FA is an index that affects the composition of the precipitate of the alloy, and more specifically, affects the Ti content [ Ti ] and Nb content [ Nb ] in the residue.

When the heat treatment temperature T1 is FA or less, the characteristic 5 (condition (I) or condition (II)) is easily satisfied when the B content in the alloy material is more than 0.0010 and 0.0030% or less. When the B content in the alloy material is 0.0001 to 0.0010%, characteristic 6 (condition (III) or condition (IV)) is easily satisfied.

[ Method for producing welded Joint of alloy Material ]

The welded joint of the alloy material according to the present embodiment can be manufactured by the following method.

As a base material, an alloy material of the present embodiment is prepared. A groove is formed in the prepared base material. Specifically, a groove is formed in the end of the base material by a well-known machining method. The groove shape may be a letter V shape, a letter U shape, a letter X shape, or other shapes other than the letter V shape, the letter U shape, and the letter X shape.

The prepared base material is welded to manufacture a welded joint. Specifically, two base materials having grooves formed therein are prepared. The grooves of the prepared base material are butted against each other. Then, the butted pair of groove portions are welded using a known welding material, thereby forming a weld metal having the chemical composition described above. The welding material is for example the AWS standard name ER NiCr-3. However, the welding material is not limited thereto.

The welding method can form 1 layer of welding metal, and can also be multi-layer overlaying welding. Welding methods are, for example, TIG welding (GTAW), coated arc welding (SMAW), flux-cored arc welding (FCAW), gas Metal Arc Welding (GMAW), submerged Arc Welding (SAW). Through the above manufacturing steps, the welded joint of the alloy material according to the present embodiment can be manufactured.

Examples (example)

The effects of the alloy material of the present embodiment will be described more specifically with reference to examples. The conditions in the following examples are examples of conditions used for confirming the workability and effect of the alloy material according to the present embodiment. Therefore, the alloy material of the present embodiment is not limited to the one example of the conditions.

[ Production of alloy Material ]

Steel ingots having the chemical compositions shown in tables 1A and 1B were produced. The shape of the ingot was a cylinder with an outer diameter of 120mm, and the mass of the ingot was 30kg.

[ Table 1A ]

TABLE 1A

[ Table 1B ]

TABLE 1B

The "-" in table 1B means that the content of the corresponding element is at or below the impurity level.

Gleeble test pieces described later were collected from the produced steel ingots. The steel ingot from which the Gleeble test piece was collected was hot forged to prepare a billet (alloy plate) having a thickness of 30 mm. The heating temperature of the steel ingot in hot forging is 1100-1300 ℃. And performing a hot working procedure on the manufactured blank. Specifically, the billet is heated by a heating furnace. The heating temperature in the hot working process was 1200 ℃. The heated material was hot-rolled to produce a master alloy material (alloy sheet) having a thickness of 15 mm.

And performing a heat treatment process on the intermediate alloy material. The heat treatment temperature T1 (°C) in the heat treatment step is shown in the column "T1 (°C)" in Table 2. The holding time at the heat treatment temperature was 30 minutes. And cooling the intermediate alloy material after the retention time to normal temperature. Through the above steps, alloy materials (alloy plates) of each test number were produced.

TABLE 2

In the column "B amount type" in table 2, "H" indicates that the B content of the alloy material is greater than 0.0010% and 0.0030% or less. "L" represents that the B content of the alloy material is 0.0001 to 0.0010%. The "F1" column, the "F2" column, and the "F3" column show the F1 value, the F2 value, and the F3 value of each test number. The FA value of each test number is shown in the "FA" column. In the column "T1. Ltoreq. FA", T (Yes) is shown when T1 satisfies the formula (X), and F (No) is shown when T1 does not satisfy the formula (X).

[ Evaluation test ]

The following evaluation tests were carried out using the produced alloy materials.

(Test 1) test for measuring Ti content [ Ti ] and Nb content [ Nb ] in residue of alloy material

(Test 2) Gleeble test (evaluation of hot workability)

(Test 3) weld hot cracking resistance evaluation test

(Test 4) creep strength evaluation test

Hereinafter, each test will be described.

[ (Test 1) measurement test of Ti content [ Ti ] and Nb content [ Nb ] in the residue of alloy material ]

The Ti content [ Ti ] (mass%) and the Nb content [ Nb ] (mass%) in the residue were obtained based on the method described in the above [ method for measuring Ti content [ Ti ] and Nb content [ Nb ] in the residue ]. The test piece was collected so that the center of the cross section of the test piece perpendicular to the longitudinal direction became the center position of the plate width of the alloy material (alloy plate) and the center position of the plate thickness, and the longitudinal direction of the test piece became the longitudinal direction of the alloy material (alloy plate). The dimensions of the test piece were 10mm×30mm×plate thickness (15 mm). The obtained Ti content [ Ti ] (mass%) and Nb content [ Nb ] (mass%) are shown in "[ Ti ] (mass%) columns and" [ Nb ] (mass%) columns in table 3. In addition, the values of 0.3× [ Ti ] and [ Ti ] + [ Nb ] are shown in the columns "0.3× [ Ti ]" and "[ Ti ] + [ Nb ]" in Table 3.

TABLE 3

TABLE 3 Table 3

In the column "B amount type" in table 3, "H" indicates that the B content of the alloy material is greater than 0.0010% and 0.0030% or less. "L" represents that the B content of the alloy material is 0.0001 to 0.0010%. In the column "condition I", the "T (yes)" is shown when the B content of the alloy material is more than 0.0010% and 0.0030% or less and the condition I is satisfied. In the column "condition II", the "T (yes)" is shown when the B content of the alloy material is more than 0.0010% and 0.0030% or less and the condition II is satisfied. In the "condition III" column, "T (yes)" is shown when the B content of the alloy material is 0.0001 to 0.0010% and the condition III is satisfied. In the column "condition IV", when the B content of the alloy material is 0.0001 to 0.0010% and the condition IV is satisfied, "T (yes)".

[ (Test 2) Gleeble test (Hot workability evaluation) ]

To evaluate the hot workability of each test-numbered alloy, the necking rate at 900 ℃ was measured by a Gleeble tester.

Gleeble test pieces were collected from the R/2 position of each test-numbered steel ingot (cylinder with an outer diameter of 120 mm). Here, the R/2 position refers to a central position of a radius in a section perpendicular to the axial direction of the ingot. The Gleeble test piece was a cylindrical test piece having a radius of 10mm and a length of 120mm. The central axis of the Gleeble test piece is parallel to the axial direction of the steel ingot. Using a Gleeble test apparatus, after the Gleeble test piece was warmed from room temperature to 1200 ℃ within 60 seconds, it was held at 1200 ℃ for 300 seconds. Thereafter, he gas was used to cool to 900 ℃ at a cooling rate of 100 ℃ per minute, and was kept at 900 ℃ for 10 seconds. After the lapse of the holding time, the Gleeble test piece was subjected to a tensile test at a displacement speed of 10 mm/sec, and the Gleeble test piece was broken. The cross-sectional dimensions of the Gleeble test piece after fracture were measured to determine the necking value (%).

When the necking value was 60% or more, it was evaluated as excellent in hot workability (indicated by "E (excellent)" in the column of "Gleeble test" in table 3). On the other hand, when the necking value is less than 60%, the hot workability is evaluated to be low (indicated by "B (poor)" in the column of "Gleeble test" in table 3).

[ (Test 3) weld hot cracking resistance evaluation test ]

Two test pieces of 12mm, 40mm in width and 300mm in length were collected at the center of the plate width of each test number of the alloy material (alloy plate) and centered at the center of the plate thickness. The following longitudinal strain test was performed on the two test pieces collected.

Specifically, TIG co-welding (bead welding) was performed under welding conditions of a welding current of 200A, a voltage of 12V, and a speed of 15 cm/min in the longitudinal direction of the plate width center portion of each test piece. In the middle of TIG welding, a bending stress is instantaneously applied parallel to the welding direction to apply a 2% strain to the surface layer.

The portion including the portion where the weld crack is generated by imparting the bending stress is cut into a size that can be observed by an optical microscope. The dimensions of the cut sample were 12mm in plate thickness, 30mm in plate width and 30mm in length.

The scale on the surface of the welded portion of the cut sample was removed by polishing. Thereafter, the presence or absence of a crack at the HAZ and the length of the crack when the crack was generated were measured using a 100-fold optical microscope. Specifically, the length of a crack propagating in a direction perpendicular to the welding direction (length in a direction perpendicular to the welding direction) was measured with the boundary between the weld metal and the HAZ as a starting point. The length of all cracks generated in the test piece in the direction perpendicular to the welding direction was determined. The sum of the lengths of these cracks is defined as the total crack length (mm). The total crack length was determined in each of the two test piece clocks. The arithmetic average of the total crack lengths obtained is defined as the average total crack length.

The average total crack length was evaluated as follows.

The average total crack length was 1.5mm or less.

The average total crack length is more than 1.5mm and less than 2.0 mm.

And (3) evaluating that the average total crack length is more than 2.0mm.

In the case of evaluation G or evaluation E, it was evaluated that the weld cracking resistance was excellent (indicated by "G" or "E" in the column of "weld cracking resistance" in table 3). On the other hand, in the case of evaluation B, it was evaluated that sufficient solder heat crack resistance (indicated by "B" in the column of "solder heat crack resistance" in table 3) could not be obtained.

[ (Test 4) creep strength evaluation test ]

The following creep evaluation test was performed on each test-numbered alloy material (alloy plate).

Creep rupture test pieces according to jis z 2271:2019 were collected from the center positions of the widths of the alloy materials (alloy plates) of the respective test numbers and the center positions of the plates. The parallel portion of the creep rupture test piece has a circular cross section perpendicular to the axial direction. The parallel portion had an outer diameter of 6mm and a length of 30mm. The length direction of the creep rupture test piece is parallel to the rolling direction of the alloy plate.

Creep rupture test according to JIS Z2271:2019 was carried out using the collected creep rupture test pieces. Specifically, the creep rupture test piece was heated to 700 ℃. Thereafter, a creep rupture test was performed. The test stress was set at 80MPa. In the test, creep rupture time (hours) was determined.

When the creep rupture time was 2000 hours or longer, it was evaluated that the creep strength was excellent (indicated by "E" in the column of "creep strength" in table 3). On the other hand, in the case where the creep rupture time is less than 2000 hours, the creep strength is evaluated to be low (indicated by "B" in the column of "creep strength" in table 3).

[ Test results ]

Referring to tables 1A, 1B, 2 and 3, in test numbers 1 to 30, the alloy material satisfied characteristics 1 to 3 when the B content was greater than 0.0010% and equal to or less than 0.0030%, and satisfied characteristics 1 to 4 when the B content was 0.0001 to 0.0010%. Thus, sufficient creep strength is obtained in a high temperature environment. Further, excellent weld hot cracking resistance and excellent hot workability are obtained.

Among test numbers 1 to 13, in which the content of B is greater than 0.0010% and not more than 0.0030%, test numbers 2 and 3 also satisfy the condition I of the feature 5, and test numbers 4 to 13 satisfy the condition II of the feature 5. Therefore, the weld hot crack resistance was more excellent than that of test No. 1 which did not satisfy feature 5.

The test numbers 15 to 29 of the test numbers 14 to 30 having a B content of 0.0001 to 0.0010% satisfy the condition III of the feature 6, and the test number 30 satisfies the condition IV of the feature 6. Therefore, the weld hot crack resistance was more excellent than test No. 14, which did not satisfy feature 6.

On the other hand, in test numbers 31 to 34, the content of each element in the chemical composition was adequate, but F1 was too low. Therefore, sufficient creep strength cannot be obtained.

In test numbers 35 to 38, the content of each element in the chemical composition was appropriate, but F1 was too high. Therefore, sufficient weld hot cracking resistance cannot be obtained.

In test numbers 39 to 43, the content of each element in the chemical composition was adequate, but F2 was too high. Therefore, sufficient weld hot cracking resistance cannot be obtained.

In test numbers 44 and 45, the content of each element in the chemical composition was appropriate, but the content of B was 0.0010% or less, and F3 was too high. Therefore, sufficient hot workability cannot be obtained.

The embodiments of the present invention have been described above. However, the above embodiments are merely examples for implementing the present invention. Accordingly, the present invention is not limited to the above-described embodiments, and can be implemented by appropriately changing the above-described embodiments within a range not departing from the gist thereof.

Claims

1. An alloy material, the chemical composition of which, by mass%, is C: 0.050–0.100%.

Si: below 1.00%

Mn: below 1.50%

P: below 0.035%

S: less than 0.0015%

Cr: 19.00～23.00%

Ni: 30.00～35.00%

N: less than 0.010%

Al: 0.15–0.70%

Ti: 0.15–0.70%

B: 0.0001～0.0030%

Nb: 0.0010～0.5000%

Mo: 0.01～1.00%

Ca: 0.0001～0.0200%

Ta: 0-0.50%

V: 0～1.00%

Zr: 0～0.100%

Hf: 0～0.10%

Cu: 0–1.00%

W: 0～1.00%

Co: 0-1.00%

Rare earth elements: 0～0.1000%

Mg: 0–0.0200%, and

The balance consists of Fe and impurities.

The alloy material satisfies equations (1) and (2).

When the B content in the chemical composition is less than 0.0010%, the alloy material also satisfies formula (3).

0.60 < Al + Ti < 1.20 (1),

3.3-41C-Si+2Mo+3Ti+245B-12Nb≤2.00 (2),

0.4+67C+1.3Si+5.5Mo+5.2Ti+13.4Nb≤8.25 (3),

In formulas (1) to (3), the content of the corresponding element in the chemical composition is substituted into the element symbol in formula (1) to (3) by mass%.

2. The alloy material according to claim 1, wherein,

The chemical composition contains, by mass%, selected from [amount].

Ta: 0.01～0.50%

V: 0.01～1.00%

Zr: 0.001～0.100%

Hf: 0.01～0.10%

Cu: 0.01～1.00%

W: 0.01～1.00%

Co: 0.01～1.00%

Rare earth elements: 0.0001～0.1000%, and

Mg: 0.0001 to 0.0200% of one or more of the group.

3. The alloy material according to claim 1 or claim 2, wherein,

The chemical composition, expressed as a percentage by mass, contains B: greater than 0.0010% and less than 0.0030%.

The Ti content [Ti] in the residue obtained by the extraction method, expressed as a percentage by mass, is less than 0.020%, or...

The [Ti] content is 0.020% or more, and the Nb content [Nb] in the residue, expressed as a mass percentage, is 0.015% or more, wherein the [Ti] and the [Nb] satisfy equation (4).

[Ti]+[Nb]≥0.050 (4).

4. The alloy material according to claim 1 or claim 2, wherein,

The chemical composition contains B: 0.0001–0.0010% by mass.

The Ti content [Ti] in the residue obtained by the residue extraction method, expressed as a percentage by mass, is less than 0.031%, or...

The [Ti] content is greater than 0.031%, and the Nb content [Nb] in the residue, expressed as a percentage by mass, is 0.3 × [Ti]% or more.