Stainless steel, turbine blades using the same, and method for manufacturing stainless steel

Abstract

To provide a stainless steel that has low hydrogen embrittlement sensitivity and high strength.SOLUTION: The inventive method includes the steps of: forming a blade body; conducting first aging treatment to the blade body; and conducting second aging treatment to the blade body subjected to the first aging treatment. The first aging treatment is conducted at temperature and time conditions included in a γ phase formation region and not included in a precipitation formation region, while the second aging treatment is conducted at temperature and time conditions included in the γ phase formation region and not included in the precipitation formation region.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to stainless steel, turbine blades using the same, and methods for manufacturing stainless steel. [Background technology]

[0002] Stainless steel is used in a variety of applications. For example, Patent Document 1 describes stainless steel used for turbine blades. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-93991 Summary of the Invention [Problem to be solved by the invention]

[0004] The stainless steel described in Patent Document 1 is a precipitation-hardened martensitic stainless steel that has a higher level of balance between mechanical strength, toughness, and corrosion resistance than conventional stainless steels, and also has excellent corrosion resistance. However, high-strength stainless steels generally have a high susceptibility to hydrogen embrittlement and therefore cannot be used in corrosive environments such as steam turbines. While hydrogen embrittlement susceptibility can be reduced by replacing it with a lightweight titanium alloy, this increases material costs and limits the materials available.

[0005] The present disclosure is intended to solve the above-mentioned problems, and aims to provide a stainless steel that has low susceptibility to hydrogen embrittlement and high strength, a turbine blade that uses the same, and a method for manufacturing the stainless steel. [Means for solving the problem]

[0006] To achieve the above object, the present disclosure provides a stainless steel in which the ratio of the austenite phase (γ phase) to the whole is 10% or more, and the size of the precipitate phase is 0.5 μm or less.

[0007] To achieve the above object, the present disclosure provides a stainless steel having an austenite phase (γ phase) ratio of 10% or more relative to the entire stainless steel, and a 0.2% yield strength of 1000 MPa or more.

[0008] The present disclosure also provides a turbine blade including a blade body formed from any of the stainless steels described above.

[0009] The present disclosure also provides a method for manufacturing stainless steel, including the steps of forming a blade body, performing a first aging treatment on the blade body, and performing a second aging treatment on the blade body that has been subjected to the first aging treatment. [Effects of the Invention]

[0010] According to the present disclosure, it is possible to increase strength while reducing hydrogen embrittlement susceptibility. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a flowchart showing an example of the manufacturing method of this embodiment. [Figure 2] FIG. 2 is an explanatory diagram showing an example of the manufacturing method of this embodiment. [Figure 3] FIG. 3 is an explanatory diagram showing an example of the stainless steel of this embodiment. [Figure 4] FIG. 4 is a graph showing an example of the relationship between the strength of stainless steel and the amount of γ phase. [Figure 5] FIG. 5 is a graph showing the relationship between the strength of stainless steel and the aging conditions. [Figure 6] FIG. 6 is a graph showing an example of the relationship between the strength of stainless steel and the amount of γ phase. [Figure 7] FIG. 7 is a schematic diagram showing an example of the relationship between the amount of γ phase and the time to fracture. [Figure 8] FIG. 8 is a graph showing the relationship between the aging temperature and the amount of the γ phase. DETAILED DESCRIPTION OF THE INVENTION

[0012] Preferred embodiments of the present disclosure will be described in detail below with reference to the drawings. Note that the present disclosure is not limited to these embodiments, and when there are multiple embodiments, the present disclosure also includes configurations that combine the embodiments. Furthermore, the components in the embodiments include those that can be easily imagined by a person skilled in the art, those that are substantially identical, and those that are within the so-called equivalent range.

[0013] FIG. 1 is a flowchart showing an example of a manufacturing method of this embodiment. FIG. 2 is an explanatory diagram showing an example of a manufacturing method of this embodiment. The present disclosure relates to a method for manufacturing stainless steel. Stainless steel is steel containing 12 mass % or more of Cr (chromium) and 2 mass % or less of C (carbon) in Fe (iron). In this embodiment, the manufacturing of a turbine blade using stainless steel will be described. Note that the use and shape of the stainless steel are not limited to this. Note that the turbine blade can be used, for example, as a moving blade in the final stage of a steam turbine. The turbine blade comprises, for example, a blade body and a connecting portion that connects the blade body to a rotor shaft. It is preferable that both the blade body and the connecting portion of the turbine blade are made of stainless steel, but only the blade body may be made of stainless steel.

[0014] 1, the method for manufacturing stainless steel according to this embodiment includes the steps of forming a blade body of a turbine blade, such as a moving blade or a stationary blade of a steam turbine (step S12), performing a first aging treatment (single-stage aging treatment) on the blade body (step S14), and performing a second aging treatment (two-stage aging treatment) on the blade body that has been subjected to the first aging treatment (step S16). The method for manufacturing stainless steel is not limited to the steps described above, and for example, processing of the blade body may be performed after the treatment of step S12.

[0015] In step S12, the blade body is formed. The blade body is formed of stainless steel. In this embodiment, the stainless steel preferably contains Fe, C 0.1% or less by mass, Ni 2.0% to 12.0% by mass, Cr 10.0% to 18.0% by mass, Mo 3.0% or less by mass, and Cu 6.0% or less by mass. Furthermore, the stainless steel more preferably contains Si 0.15% or less by mass, Mn 0.15% or less by mass, P 0.05% or less by mass, S 0.05% or less by mass, Al 1.5% or less by mass, N 0.05% or less by mass, Ti 2.0% or less by mass, and Nb 1.0% or less by mass. In addition to the above materials, the stainless steel also contains unavoidable impurities.

[0016] The blade body is formed by forging or the like using the above-mentioned material.

[0017] In step S14, the blade body is subjected to a first aging treatment. In the first aging treatment, the blade body is placed in a heating furnace and heated to precipitate the γ phase in the matrix. In the first aging treatment, for example, heat treatment is performed at a first temperature for a predetermined time.

[0018] In step S16, the blade body is subjected to a second aging treatment. The second aging treatment is performed immediately after the first aging treatment. Specifically, the second aging treatment is performed by changing the temperature conditions of the heating furnace in which the first aging treatment was performed. Alternatively, after the first aging treatment, the blade body is cooled to room temperature, and then reheated and subjected to the second aging treatment. The second aging treatment involves heating the blade body to precipitate intragranular precipitates in the matrix. The second aging treatment involves, for example, performing a heat treatment at a second temperature for a predetermined time. The second temperature is lower than the first temperature.

[0019] As shown in Figure 2, the stainless steel that is the blade body (base material) has range 12 where the γ phase precipitates and range 14 where intragranular precipitates precipitate, depending on the time and temperature of the aging treatment. Ranges 12 and 14 vary depending on the type of stainless steel, but range 12 is on the higher temperature side than range 14. Ranges 12 and 14 also partially overlap. For stainless steel, the γ phase is formed under conditions that are included in range 12 but not in range 14. Both the γ phase and intragranular precipitates are formed under conditions that are included in both ranges 12 and 14. For stainless steel, intragranular precipitates are formed under conditions that are not included in range 12 but are included in range 14.

[0020] In the manufacturing method of this embodiment, two aging treatments are performed at the temperatures and times shown in condition line 16. Specifically, the first aging treatment is performed at temperature A1 from time t0 to time t1, and the second aging treatment is performed at temperature A2 from time t1 to time t2. In FIG. 2, the temperature changes from temperature A1 to temperature A2 at time t1, but this is changed by a predetermined amount based on the performance of the heating furnace. Alternatively, the material may be cooled to room temperature once and then heated to temperature A2. Temperature A1 from time t0 to time t1 is a condition that is included in range 12 but not in range 14. Temperature A2 from time t1 to time t2 is a condition that is not included in range 12 but is included in range 14. For comparison, FIG. 2 also shows a comparative condition line 18. Comparative condition line 18 represents the case where the aging treatment is a single-stage aging treatment, where temperature A3 is used for time t o From time t a The graph shows the case where the temperature was heated to 1000K.

[0021] The stainless steel of this embodiment is subjected to two-step aging treatment, as shown in Fig. 1. Furthermore, as shown in Fig. 2, the stainless steel of this embodiment is subjected to a first aging treatment (single-step aging treatment) under conditions that generate a γ phase, and a second aging treatment (two-step aging treatment) under conditions that generate intragranular precipitates.

[0022] FIG. 3 is an explanatory diagram showing an example of a stainless steel according to this embodiment. FIG. 3 shows the results of observation of a stainless steel manufactured by the manufacturing method of this embodiment and having a γ phase content of 15 vol%. The γ phase content (volume fraction of the γ phase) is calculated by measuring the diffraction peak intensities of the matrix and γ phase using X-rays and multiplying the results by a correction factor. FIG. 3 shows a cross section enlarged at 2000x, 7000x, and 30,000x magnifications. As shown in FIG. 3, in the stainless steel having a γ phase content of 15 vol%, a γ phase (austenite phase) 24 and a precipitate phase 26 are precipitated in an α phase (matrix, ferrite phase) 20.

[0023] As shown in Figure 3, the stainless steel of this embodiment is formed by dispersing a gamma phase and a precipitate phase in an alpha phase. Furthermore, the stainless steel of this embodiment preferably has a gamma phase content of 10% or more relative to the entire steel. The precipitate phase is an intermetallic compound phase such as NiAl or NiTi, or a Cu-rich phase, with a grain size of 0.5 µm or less.

[0024] Fig. 4 is a graph showing an example of the relationship between the strength of stainless steel and the amount of γ phase. Fig. 5 is a graph showing the relationship between the strength of stainless steel and aging conditions. Fig. 6 is a graph showing an example of the relationship between the strength of stainless steel and the amount of γ phase. Fig. 7 is a schematic diagram showing an example of the relationship between the amount of γ phase and the fracture time.

[0025] Stainless steel is manufactured by a single-step aging treatment, as shown by the comparative condition line 18 in Figure 2. For example, CUSTOM455 (registered trademark), a maraging steel, is specified to be manufactured by a single-step aging treatment according to standards such as ASM5617. In this case, the amount of γ phase (γ content) can be controlled by controlling the aging conditions during manufacturing. As shown in Figure 4, an increase in the amount of γ phase in stainless steel tends to decrease its strength, for example, its 0.2% proof stress. Here, 0.2% proof stress is the stress at which the permanent strain upon unloading is 0.2%. Furthermore, an increase in the amount of γ phase in stainless steel reduces its sensitivity to hydrogen embrittlement. In other words, it becomes less susceptible to embrittlement by hydrogen.

[0026] 5 to 7 show examples of stainless steel with compositions equivalent to maraging steel CUSTOM455. FIG. 5 shows a comparison of the strength of single-step aged stainless steel and double-step aged stainless steel. As shown in FIG. 5, the stainless steel of this embodiment can be made harder than when produced by single-step aging by performing a second aging treatment at 470°C for 24 hours. Furthermore, the precipitates in CUSTOM455 are carbides, a Cu-rich phase, and an intermetallic compound (NiTi).

[0027] Figure 6 shows the relationship between the hardness and the γ content of single-step aged stainless steel and that of the two-step aged stainless steel of this embodiment. As shown in Figure 6, by performing two-step aging, it is possible to increase the strength even with the same γ content.

[0028] Figure 7 is a graph showing the relationship between the amount of γ phase and the decrease in strength due to hydrogen embrittlement susceptibility. In Figure 7, the vertical axis is logarithmic. Figure 7 shows the relationship between the amount of γ phase and the time to fracture when CUSTOM455 is manufactured using single-stage aging. The time to fracture was determined as the time at which the test piece was visually confirmed. As shown in Figure 7, the greater the amount of γ phase in stainless steel, the longer the time to fracture. In other words, it can be seen that hydrogen embrittlement susceptibility can be reduced by increasing the amount of γ phase, specifically by setting the amount of γ phase to 10% or more.

[0029] Here, Figure 8 is a graph showing the relationship between aging temperature and the amount of γ phase. Figure 8 shows an example of a stainless steel with a composition equivalent to that of maraging steel CUSTOM455. In Figure 8, the horizontal axis represents aging temperature, and the vertical axis represents the amount of γ (amount of γ phase). The aging temperature on the horizontal axis represents the aging temperature for single-step aging. Figure 8 shows a case where single-step aging was performed for one hour, followed by two-step aging at 470°C for four hours. For comparison, Figure 8 also shows a case where single-step aging was performed for one hour.

[0030] As shown in FIG. 8, two-step aging allows more γ phase to be formed during single-step aging. For CUSTOM455, the single-step aging temperature is preferably 625°C or higher and 700°C or lower, more preferably 670°C or higher and 700°C or lower. Setting the temperature to 700°C or lower suppresses the formation of γ phase, while setting the temperature to 625°C or higher suppresses the formation of precipitates. This allows the γ phase to be formed while suppressing the formation of precipitate phases. Furthermore, the single-step aging time is preferably 4 hours or shorter. This prevents the γ phase from becoming coarse. By performing single-step aging under the above conditions, suitable fine precipitates can be formed as precipitate phases during two-step aging, improving strength.

[0031] As described above, by manufacturing the stainless steel of this embodiment using two-step aging that satisfies the above conditions, the amount of γ phase can be increased while improving strength, thereby reducing hydrogen embrittlement susceptibility and increasing strength.

[0032] As mentioned above, the more hydrogen-trapping γ phase and precipitate phases are precipitated, the lower the hydrogen embrittlement susceptibility. Furthermore, the more intragranular precipitates there are, the higher the strength tends to be, while the more γ phase there is, the lower the strength tends to be. When manufacturing with single-step aging, increasing the aging temperature can increase the amount of γ, which is considered effective for trapping hydrogen, but the precipitate phase becomes coarse, resulting in a decrease in strength. In other words, if the amount of γ phase is increased with single-step aging, fine precipitates are not formed, resulting in a decrease in strength.

[0033] The method for manufacturing stainless steel according to the present disclosure includes the steps of forming a blade body, performing a first aging treatment on the blade body, and performing a second aging treatment on the blade body that has been subjected to the first aging treatment, thereby making it possible to manufacture stainless steel with high strength while reducing hydrogen embrittlement susceptibility.

[0034] It is also preferable that the first aging treatment is performed at a temperature and for a time within the γ-phase generation region but not within the precipitation region, and the second aging treatment is performed at a temperature and for a time within the precipitation region but not within the γ-phase generation region, thereby precipitating the γ-phase in the first aging treatment and precipitating fine precipitates in the second aging treatment, and adjusting the hydrogen embrittlement susceptibility and strength performance with each aging treatment.

[0035] The second aging treatment is preferably performed at a temperature at least 100° C. lower than that of the first aging treatment. This allows the first aging treatment to be performed in the γ-phase generation region and the second aging treatment to be performed in the precipitation generation region, thereby preventing aging treatment from being performed in the region where the γ-phase generation region and the precipitation generation region overlap.

[0036] Preferably, the first aging treatment is performed for 0.5 hours or more and 4 hours or less, and the second aging treatment is performed for 5 hours or more and 50 hours or less, which allows the γ phase and fine precipitates to be properly precipitated.

[0037] The first aging treatment is performed at a temperature of 550° C. or higher and 850° C. or lower, and the second aging treatment is performed at a temperature of 400° C. or higher and 600° C. or lower, which allows the γ phase and fine precipitates to be properly precipitated.

[0038] The stainless steel of the present disclosure is manufactured by two-step aging, where a γ phase precipitates during the first aging and fine precipitates precipitate during the second aging. As a result, the stainless steel of the present disclosure has a γ phase ratio of 10% or more relative to the total, and the precipitated phase has a size of 0.5 μm or less, i.e., fine precipitates of 0.5 μm or less. Furthermore, the stainless steel of the present disclosure has a γ phase ratio of 10% or more relative to the total, and a 0.2% yield strength of 1000 MPa or more. This allows for the appropriate formation of γ phase and fine precipitates, increasing the amount of γ phase and improving strength. This allows for increased strength while reducing hydrogen embrittlement susceptibility.

[0039] The stainless steel of this embodiment preferably contains Fe, 0.1 mass% or less of C, 2.0 to 12.0 mass% of Ni, 10.0 to 18.0 mass% of Cr, 3.0 mass% or less of Mo, and 6.0 mass% or less of Cu. Furthermore, the stainless steel more preferably contains 0.15 mass% or less of Si, 0.15 mass% or less of Mn, 0.05 mass% or less of P, 0.05 mass% or less of S, 1.5 mass% or less of Al, 0.05 mass% or less of N, 2.0 mass% or less of Ti, and 1.0 mass% or less of Nb. In addition to the above materials, the stainless steel also contains unavoidable impurities. By using stainless steel with the above-mentioned composition, strength and durability can be maintained within appropriate ranges. Furthermore, even stainless steel with a low Ti content can have low hydrogen embrittlement susceptibility.

[0040] As for stainless steel, it is preferably used for maraging steel, specifically, it is preferable to use a composition corresponding to COSTOM 450 (registered trademark), COSTOM 455 (registered trademark), or COSTOM 465 (registered trademark).

[0041] In the case of COSTOM450 (registered trademark), the stainless steel contains Fe, 0.05 mass% or less of C, 6.00 to 7.00 mass% of Ni, 14.00 to 16.00 mass% of Cr, 0.50 to 1.00 mass% of Mo, and 1.25 to 1.75 mass% of Cu. The stainless steel also contains 1.00 mass% or less of Si, 1.00 mass% or less of Mn, 0.030 mass% or less of P, 0.030 mass% or less of S, 0.055 mass% or less of Al, and 0.01 to 0.75 mass% of Nb.

[0042] In the case of COSTOM455 (registered trademark), the stainless steel contains Fe, 0.03 mass% or less of C, 7.50 to 9.50 mass% of Ni, 11.00 to 12.50 mass% of Cr, 0.5 mass% or less of Mo, and 1.50 to 2.50 mass% of Cu. The stainless steel also contains 0.50 mass% or less of Si, 0.50 mass% or less of Mn, 0.015 mass% or less of P, 0.015 mass% or less of S, 0.90 to 1.40 mass% of Ti, 0.015 mass% or less of N, and 0.50 mass% or less of Nb.

[0043] In the case of COSTOM465 (registered trademark), the stainless steel contains Fe, 0.02 mass% or less of C, 10.75 to 11.25 mass% of Ni, 11.00 to 12.50 mass% of Cr, and 0.75 to 1.25 mass% of Mo. The stainless steel also contains 0.25 mass% or less of Si, 0.25 mass% or less of Mn, 0.015 mass% or less of P, 0.010 mass% or less of S, and 1.50 to 1.80 mass% of Ti.

[0044] As for stainless steel, it is preferable to use precipitation hardening stainless steel, specifically, it is preferable to use components corresponding to 13-8Mo steel and 17-4PH stainless steel.

[0045] In the case of 13-8Mo steel, the stainless steel preferably contains Fe, 0.05 mass% or less of C, 7.50 mass% to 8.50 mass% of Ni, 12.25 mass% to 13.25 mass% of Cr, and 2.00 mass% to 2.50 mass% of Mo. The stainless steel also contains 0.10 mass% or less of Si, 0.10 mass% or less of Mn, 0.010 mass% or less of P, 0.008 mass% or less of S, 0.9 mass% to 1.35 mass% of Al, and 0.010 mass% or less of N.

[0046] 17-4PH stainless steel is a steel containing Fe, 0.07% by mass or less of C, 3.00% to 5.00% by mass of Ni, 15.00% to 17.50% by mass of Cr, 0.50% by mass or less of Mo, and 3.00% to 5.00% by mass of Cu. The stainless steel also contains 1.00% by mass or less of Si, 1.00% by mass or less of Mn, 0.040% by mass or less of P, 0.030% by mass or less of S, 0.05% by mass or less of N, and 0.15% to 0.45% by mass of Nb.

[0047] Any of the stainless steels can be manufactured by the manufacturing method of this embodiment and have a structure that satisfies the phase configuration or conditions of this embodiment, thereby reducing hydrogen embrittlement susceptibility and increasing strength.

[0048] The stainless steel of this embodiment is preferably used for turbine blades, more specifically, for the final stage of turbine blades, and more preferably for the final stage of turbine blades in steam turbines. By using it as a turbine blade, it is less susceptible to hydrogen embrittlement and can satisfy the strength required for a turbine blade, allowing it to be used for long-term turbine operation. [Explanation of symbols]

[0049] 12, 14 areas 16 Condition lines 18 Comparison Condition Line

Claims

1. The volume ratio of the austenite phase (γ phase) to the whole is 10 vol% or more, and the size of the precipitate phase is 0.5 μm or less, A martensitic precipitation stainless steel having a 0.2% yield strength of 1000 MPa or more.

2. C is 0.1 mass% or less, Ni is 2.0 mass% or more and 12.0 mass% or less, Cr is 10.0 mass% or more and 18.0 mass% or less, Mo is 3.0 mass% or less, Cu is 6.0 mass% or less, Si is 1.00 mass% or less, Mn is 1.00% by mass or less, P is 0.05% by mass or less, S is 0.05% by mass or less, Al is 1.5% by mass or less, N is 0.05% by mass or less, Ti is 2.0 mass% or less, Nb is 1.0 mass% or less, 2. The martensitic precipitation stainless steel according to claim 1, wherein the other components are Fe and inevitable impurities.

3. C is 0.03% by mass or less, Ni is 7.50 mass% or more and 9.50 mass% or less, Cr is 11.00 mass% or more and 12.50 mass% or less, Mo is 0.5% by mass or less, The martensitic precipitation stainless steel according to claim 1 or 2, wherein Cu is 1.50 mass % or more and 2.50 mass % or less.

4. Si is 0.50% by mass or less, Mn is 0.50% by mass or less, P is 0.015% by mass or less, S is 0.015% by mass or less, Ti is 0.90 mass% or more and 1.40 mass% or less, 4. The martensitic precipitation stainless steel according to claim 3, wherein N is 0.015 mass % or less and Nb is 0.50 mass % or less.

5. C is 0.07% by mass or less, Ni is 3.00 mass% or more and 5.00 mass% or less, Cr is 15.00 mass% or more and 17.50 mass% or less, Mo is 0.50% by mass or less, The martensitic precipitation stainless steel according to claim 1 or 2, wherein Cu is 3.00 mass % or more and 5.00 mass % or less.

6. Si is 1.00 mass% or less, Mn is 1.00% by mass or less, P is 0.040% by mass or less, S is 0.030% by mass or less, N is 0.05% by mass or less, The martensitic precipitation stainless steel according to claim 5, wherein the Nb content is 0.15 mass % or more and 0.45 mass % or less.

7. C is 0.05% by mass or less, Ni is 6.00 mass% or more and 7.00 mass% or less, Cr is 14.00 mass% or more and 16.00 mass% or less, Mo is 0.50 mass% or more and 1.00 mass% or less, The martensitic precipitation stainless steel according to claim 1 or 2, wherein Cu is 1.25 mass % or more and 1.75 mass % or less.

8. C is 0.02% by mass or less, Ni is 10.75 mass% or more and 11.25 mass% or less, Cr is 11.00 mass% or more and 12.50 mass% or less, 3. The martensitic precipitation stainless steel according to claim 1, wherein the Mo content is 0.75 mass % or more and 1.25 mass % or less.

9. A turbine blade comprising a blade body formed from the martensitic precipitation type stainless steel according to any one of claims 1 to 8.

10. forming an airfoil body from stainless steel; performing a first aging treatment on the blade body; and performing a second aging treatment on the blade body that has been subjected to the first aging treatment to produce stainless steel having an austenite phase (γ phase) volume ratio of 10 vol% or more to the entire blade body, a precipitate phase size of 0.5 μm or less, and a 0.2% yield strength of 1000 MPa or more.

11. The first aging treatment is performed at a temperature and for a time that is included in a γ phase generation region but not included in a precipitation generation region, The method for producing a martensitic precipitation-type stainless steel according to claim 10, wherein the second aging treatment is carried out at a temperature and for a time not included in the γ phase generation region but included in the precipitation generation region.

12. 12. The method for producing a martensitic precipitation stainless steel according to claim 10, wherein the second aging treatment is performed at a temperature that is 100°C or more lower than that of the first aging treatment.

13. The first aging treatment is performed for 0.5 hours or more and 4 hours or less, 13. The method for producing a martensitic precipitation stainless steel according to claim 10, wherein the second aging treatment is performed for 5 hours or more and 50 hours or less.

14. The first aging treatment is performed at a temperature of 550°C or higher and 850°C or lower, 14. The method for producing a martensitic precipitation stainless steel according to claim 10, wherein the second aging treatment is performed at a temperature of 400°C or higher and 600°C or lower.

15. The stainless steel is C is 0.1% by mass or less, Ni is 2.0 mass% or more and 12.0 mass% or less, Cr is 10.0 mass% or more and 18.0 mass% or less, Mo is 3.0 mass% or less, Cu is 6.0 mass% or less, Si is 1.00 mass% or less, Mn is 1.00% by mass or less, P is 0.05% by mass or less, S is 0.05% by mass or less, Al is 1.5% by mass or less, N is 0.05% by mass or less, Ti is 2.0 mass% or less, Nb is 1.0 mass% or less, 15. A method for producing a martensitic precipitation stainless steel according to any one of claims 10 to 14, wherein the other components are Fe and inevitable impurities.

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