Austenitic stainless steel sheet

Abstract

To provide an austenitic stainless steel sheet with low anisotropy having both excellent workability and strength.SOLUTION: There is provided an austenitic stainless steel sheet comprising, by mass%, 0.020 to 0.060% of C, 1.00% or less of Si, 2.0% or less of Mn, 0.040% or less of P, 0.030% or less of S, 17.0 to 20.0% of Cr, 7.0 to 10.5% of Ni, 3.0% or less of Cu, 3.0% or less of Mo, 0.060% or less of N and the balance Fe with impurities, wherein the average crystal grain size is 5 to 25 μm, the cross-sectional hardness is 220 HV or less and the average aspect ratio of crystal grains is 0.50 or more.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an austenitic stainless steel sheet. [Background technology]

[0002] Austenitic stainless steel generally has an excellent balance of strength and workability, making it suitable for a wide range of applications and also being recycled as scrap. Methods for increasing strength include forming strain-induced martensite through plastic processing, which creates strain, and then refining the grain size by reverse transforming the martensite, as well as increasing tensile strength through rolling.

[0003] For example, Patent Document 1 discloses an austenitic stainless steel material that is flat and has high hardness. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2016 / 043125 Summary of the Invention [Problem to be solved by the invention]

[0005] Although recycling of austenitic stainless steels has progressed as mentioned above, the recycling process using scrap as a raw material requires the use of electric furnaces, which places a heavy burden on the environment, and there is a growing demand for reducing the environmental impact of subsequent manufacturing processes. Furthermore, austenitic stainless steel sheets are required to be lightweight through high strength and thin wall thickness for various applications, while also being required to have ductility that can withstand even more severe processing to allow for greater design flexibility. Therefore, there is an increasing demand for austenitic stainless steel sheets with an optimal balance between strength and ductility.

[0006] In order to adjust the balance between strength and ductility, it is effective to grow the refined crystal grains, but in the case of austenitic stainless steel sheets, this requires annealing at high temperatures exceeding 1000°C, which goes against the goal of reducing the environmental impact.In addition, strength can be adjusted by reducing the temper rolling ratio, but this results in uneven strain distribution in the thickness direction and the grains are stretched by rolling, which can lead to anisotropy during subsequent forming into components, etc.

[0007] An object of one aspect of the present invention is to provide an excellent austenitic stainless steel sheet that has small anisotropy and combines excellent workability and strength. [Means for solving the problem]

[0008] In order to solve the above-mentioned problems, an austenitic stainless steel sheet according to one embodiment of the present invention contains, by mass%, C: 0.020% or more and 0.060% or less, Si: 1.00% or less, Mn: 2.0% or less, P: 0.040% or less, S: 0.030% or less, Cr: 17.0% or more and 20.0% or less, Ni: 7.0% or more and 10.5% or less, Cu: 3.0% or less, Mo: 3.0% or less, N: 0.060% or less, with the balance being Fe and impurities, an average crystal grain size of 5 μm or more and 25 μm or less, a cross-sectional hardness of a cross section parallel to the rolling direction and the sheet thickness direction of 220 HV or less, and an average aspect ratio of crystal grains of 0.50 or more. [Effects of the Invention]

[0009] According to one aspect of the present invention, an austenitic stainless steel sheet can be provided that has small anisotropy and combines excellent workability and strength. DETAILED DESCRIPTION OF THE INVENTION

[0010] Preferred embodiments of the present invention will now be described in detail.

[0011] [Austenitic stainless steel plate] (composition) First, the chemical composition of an austenitic stainless steel sheet according to one embodiment of the present invention will be described below. Note that the "%" used to represent the content of each element means "mass %." In this specification, the austenitic stainless steel sheet according to one embodiment of the present invention may also be simply referred to as "the present stainless steel sheet."

[0012] This stainless steel plate contains, by mass%, C: 0.020% or more and 0.060% or less, Si: 1.00% or less, Mn: 2.0% or less, P: 0.040% or less, S: 0.030% or less, Cr: 17.0% or more and 20.0% or less, Ni: 7.0% or more and 10.5% or less, Cu: 3.0% or less, Mo: 3.0% or less, N: 0.060% or less, with the remainder consisting of Fe and impurities.

[0013] (C: 0.020% or more, 0.060% or less) C, together with N (described later), is a strong austenite-stabilizing element and also a solid-solution strengthening element, so a small C content is desirable to ensure ductility. Meanwhile, the inventors have discovered that carbides precipitated in the hot-rolled sheet after hot-rolling and coiling are effective in increasing the aspect ratio (described later in detail) of the grains after the subsequent annealing process after cold rolling (hereinafter sometimes referred to as the cold-rolling annealing process). To achieve this aspect ratio-increasing effect, the lower limit of C is set to 0.020% or more, preferably 0.030% or more. On the other hand, depending on the heat treatment conditions in the cold-rolling annealing process, C can combine with Cr, which is important for corrosion resistance, to cause sensitization, and in a solid-solution state, it can reduce the grain growth rate. Therefore, the upper limit of C is set to 0.060% or less, preferably 0.05% or less.

[0014] (Si:1.00% or less) Si functions as a deoxidizing agent during melting and also as a ferrite stabilizing element. However, excessive addition of Si generates coarse inclusions, degrading workability and destabilizing the austenite phase, so the upper limit is set to 1.00% or less, preferably 0.90% or less. There is no particular lower limit, but to ensure the deoxidizing effect, 0.05% or more is preferred.

[0015] (Mn:2.0% or less) Mn is a relatively inexpensive and effective austenite stabilizing element. However, excessive addition of Mn not only leads to the formation of coarse inclusions, which deteriorates workability, but also reduces the grain growth rate in a solid solution state. Therefore, the upper limit is set to 2.0% or less. It is preferably 1.8% or less, and more preferably 1.6% or less. There is no particular lower limit, but from the viewpoint of reliable stabilization of the austenite phase, a content of 0.1% or more is preferred.

[0016] (P: 0.040% or less, S: 0.030% or less) P and S are elements that are inevitably mixed into this stainless steel sheet, but both reduce hot workability and slow the grain growth rate by segregating at grain boundaries. Therefore, the upper limits for P and S are set at 0.040% and 0.030%, respectively.

[0017] (Cr:17.0% or more, 20.0% or less) Cr is a basic element of stainless steels such as the present stainless steel sheet, and is an element required for obtaining effective corrosion resistance. To obtain effective corrosion resistance, 17.0% or more is added, preferably 17.2% or more. However, since Cr is a ferrite stabilizing element, excessive addition can destabilize the austenite phase, resulting in reduced manufacturability, so the upper limit is set to 20.0% or less, preferably 19.4% or less.

[0018] (Ni: 7.0% or more, 10.5% or less) Ni is a strong austenite-stabilizing element that improves ductility by solution softening. To stabilize the austenite phase down to room temperature and ensure ductility, including the addition of C and N, the upper limit is set to 7.0% or less. It is preferably set to 7.2% or more. However, excessive addition increases alloy costs and reduces the grain growth rate, so the upper limit is set to 10.5% or less. It is preferably set to 10.3% or less, and more preferably set to 10.0% or less.

[0019] (Cu:3.0% or less) Cu, like Ni, is an austenite-forming element. It can adjust the stability of the austenite phase more cheaply than Ni, and is effective in ensuring ductility by softening the steel through solution softening. However, excessive Cu content segregates at grain boundaries during the manufacturing process, significantly degrading hot workability and making manufacturing difficult, as well as slowing the grain growth rate. Therefore, the upper limit of the Cu content is set to 3.0% or less. It is preferably 2.0% or less, and more preferably 1.5% or less. While there is no particular lower limit, a content of 0.1% or more is preferred to ensure the stabilization of the austenite phase.

[0020] (Mo: 3.0% or less) Mo is an element that improves the corrosion resistance of the present stainless steel sheet and also functions as a ferrite stabilizer. However, excessive addition of Mo not only increases the precipitation of an embrittlement phase known as the Laves phase, but also leads to a decrease in the grain growth rate and an increase in alloy costs. Therefore, the upper limit is set to 3.0% or less, preferably 2.0% or less. There is no particular lower limit, but from the viewpoint of obtaining the effect of improving corrosion resistance, 0.1% or more is preferred.

[0021] (N:0.060% or less) N, together with the aforementioned C, is a powerful austenite stabilizing element and solid solution strengthening element. Excessive addition not only causes hardening due to solid solution strengthening, but also generates many coarse nitrides during the steel sheet manufacturing process, which act as fracture initiation sites and significantly deteriorate hot workability. Excessive addition also makes steel sheet manufacturing difficult and reduces the grain growth rate, so the upper limit is set to 0.060% or less, preferably 0.050% or less. There is no particular lower limit, but from the viewpoint of obtaining the austenite stabilizing effect, 0.005% or more is preferred, and 0.010% or more is more preferred.

[0022] (Other ingredients) In addition to the basic composition, the present stainless steel sheet may selectively contain one or more elements selected from the following group: Specifically, the present stainless steel sheet may contain one or more elements selected from the group consisting of V, Nb, Ti, Ta, and Zr in a total content of 0.30% or less. The lower limit of these elements in total is 0% or more.

[0023] V, Nb, Ti, Ta, and Zr are all elements that improve the strength of the present stainless steel sheet and also improve intergranular corrosion resistance by fixing C. At least one of these elements, V, Nb, Ti, Ta, and Zr, can be added as needed. However, adding more than necessary of V, Nb, Ti, Ta, and Zr reduces the grain growth rate due to excess precipitates formed in the present stainless steel sheet, so the upper limit of the total content is set to 0.30% or less. Preferably, it is 0.25% or less.

[0024] The balance of this stainless steel sheet consists of Fe and impurities. Impurities include substances that are mixed in from the various raw materials used in the industrial production of steel, or substances that are mixed in during each production process, such as unavoidable impurities such as inclusions in the steelmaking or refining process. Examples of impurities include O (oxygen).

[0025] O is an unavoidable impurity and an element that impairs the hot workability, toughness, and corrosion resistance of this stainless steel sheet. The upper limit is preferably 0.0090% or less, and it is more desirable to reduce it to 0.0040% or less. O does not need to be contained in this stainless steel sheet, and the lower limit is 0%. However, if O is to be reduced drastically, extremely high refining costs are required. Therefore, from an economical perspective, the lower limit of the O content may be set to 0.0001% or less, or 0.0005% or less.

[0026] (Average grain size) When the average grain size of the crystal grains contained in this stainless steel sheet is reduced, the strength can be increased by making the crystal grains finer, and the amount of strengthening can be expressed as the reciprocal of the 1 / 2 power of the crystal grain size. In this stainless steel sheet, to ensure a balance between excellent formability and strength, fine grains are grown in the cold-rolling annealing process to an average grain size of 5 μm or more. As the grains grow, this stainless steel sheet becomes softer and its strength decreases. Furthermore, when this stainless steel sheet is subjected to plastic processing that imparts strain that produces processing-induced martensite, roughness due to the grain size may occur on the surface, so the upper limit of the average grain size is 25 μm or less, preferably 20 μm or less.

[0027] The average grain size is measured by the following method. The L-section of this stainless steel sheet (a cross section parallel to the rolling direction and the sheet thickness direction) is colloidally polished, and then electrolytically polished to remove polishing distortion. Then, an orientation mismatch map of all austenite grains in a 400 μm x 400 μm area at the center of the sheet thickness is obtained using the electron backscatter diffraction (EBSD) method using a scanning electron microscope. From this orientation mismatch map, boundaries with a crystal orientation mismatch of 5° or more are defined as grain boundaries, and <111> The austenite grains are identified by using a common rotation axis of 0°, excluding the grain boundaries at a rotation angle of 60°. The average grain area of ​​the identified austenite grains is calculated using quadrature, and the diameter of a circle having the same area is expressed as the average grain size. In this way, the average grain size in this stainless steel sheet indicates the average grain size of the austenite grains in a cross section parallel to the rolling direction and the sheet thickness direction.

[0028] (cross-section hardness) The cross-sectional hardness of this stainless steel plate at a cross section parallel to the rolling direction and thickness direction shall be 220 HV or less. This cross-sectional hardness can be calculated by embedding the stainless steel plate in resin so that its L-section (a cross section parallel to the rolling direction and thickness direction) is exposed, mechanically polishing and electrolytically polishing the exposed cross section to a mirror finish, and then measuring the hardness at the center of the plate thickness. Hardness is measured at HV1.0 (9.8 N) in accordance with JIS Z 2244:2009 Vickers hardness measurement. Five points are measured at the center of the plate thickness on the above-mentioned L-section, and the average value of these five points is used as the representative value. The cross-sectional hardness of this stainless steel plate is shown as this representative value.

[0029] If the cross-sectional hardness exceeds 220 HV, ductility decreases, making it difficult to ensure excellent workability and strength, so the upper limit of the cross-sectional hardness is 220 HV or less. It is preferably 215 HV or less, and more preferably 210 HV or less. The lower limit of the cross-sectional hardness is not particularly limited, but may be, for example, 170 HV or more. If the cross-sectional hardness is less than 170 HV, the strength may be insufficient, which may result in an increase in plate thickness or a decrease in the degree of design freedom for ensuring rigidity.

[0030] (average aspect ratio) The average aspect ratio of the crystal grains of this stainless steel sheet is 0.50 or more. If the average aspect ratio is less than 0.50, anisotropy in ductility will occur due to elongated crystal grains. It is preferably 0.51 or more, more preferably 0.52 or more. The upper limit of the average aspect ratio is not particularly limited, as the higher the better, and it can be, for example, 0.70 or less.

[0031] The average aspect ratio is calculated by measuring the length of the longest diameter (long side) of the austenite grains identified by the above-mentioned EBSD method and the length of the largest diameter perpendicular to it (short side), and dividing the short side by the long side. The austenite grains are defined as boundaries with a crystal orientation misorientation of 5° or more from the misorientation map of all austenite grains in the same measurement area as the above-mentioned average grain size measurement. <111> The austenite grains are measured using a common rotation axis of 0°, excluding grain boundaries at a rotation angle of 60°. In the L-section of this stainless steel sheet (a cross section parallel to the rolling direction and thickness direction), the aspect ratios of the austenite grains within a 400 μm x 400 μm range at the center of the sheet thickness, which is the same range as the measurement range for the average grain size, are calculated, and the average of these is taken as the average aspect ratio of the grains. In this way, the average aspect ratio of the grains in this stainless steel sheet represents the average aspect ratio of the austenite grains in a cross section parallel to the rolling direction and thickness direction.

[0032] [Method for manufacturing austenitic stainless steel sheet] Next, an example of a method for manufacturing the present stainless steel sheet will be described. The method for manufacturing the present stainless steel sheet includes a hot rolling process including rough hot rolling and finish hot rolling, a cold rolling process, and a cold rolling annealing process. After the hot rolling process, descaling may be performed by pickling or the like. After the cold rolling annealing process, descaling may be performed by pickling or the like, or skin pass rolling or the like may be performed to adjust the shape, surface roughness, etc. However, an annealing process (hot rolling annealing process) is not performed between the hot rolling process and the cold rolling process.

[0033] The present inventors have conducted extensive research into the balance between lowering the annealing temperature in the cold rolling annealing process and the workability and strength of austenitic stainless steel sheets, and have found the following points 1) to 4): 1) A chemical composition that can reduce grain growth after recrystallization, 2) By increasing the final temperature of the finish hot rolling process and coiling at a high temperature, fine recrystallized grains can be generated in the hot-rolled sheet, and carbides can be precipitated at the grain boundaries. 3) By omitting the annealing of hot-rolled sheets and cold-rolling them while maintaining the carbides precipitated at the grain boundaries, it is possible to disperse the carbides within the elongated base material structure. 4) The amount of dissolved carbon in the base material is reduced by the carbides precipitated during the hot rolling process, lowering the recrystallization start temperature, and therefore cold rolling annealing at low temperatures can promote grain growth.

[0034] As a result, it was discovered that by lowering the annealing temperature according to the manufacturing method described below, it is possible to obtain a stainless steel sheet having the above-mentioned chemical composition, an average grain size of 5 to 25 μm, a cross-sectional hardness of 220 HV or less, and an average grain aspect ratio of 0.50 or more.

[0035] The present stainless steel sheet, which has the above-mentioned average grain size, cross-sectional hardness, and average grain aspect ratio, has little anisotropy due to elongated grains, and combines excellent formability and strength. This stainless steel sheet is suitable for weight reduction through high strength and thinning in various applications, and has ductility that allows it to withstand strong forming, allowing for a high degree of design freedom.

[0036] (hot rolling process) The hot rolling process is a process in which a slab having the above-mentioned composition is roughly hot-rolled and then finish hot-rolled. The slab can be produced by melting steel having the above-mentioned composition and using a conventional method. The slab (for example, about 200 mm thick) is heated and then roughly hot-rolled. The heating temperature of the slab is usually in the range of 1150°C or higher and 1250°C or lower, but is preferably 1150°C or higher and 1200°C or lower.

[0037] Rough hot rolling is performed with a final temperature of 1050°C or higher. If the final temperature of rough hot rolling is less than 1050°C, an unrecrystallized structure will remain. There is no particular upper limit to the final temperature of rough hot rolling, but it is typically 1150°C or lower, preferably 1100°C or lower.

[0038] Furthermore, the total reduction rate of the rough hot rolling is not particularly limited, but is preferably 80% or more. By setting the total reduction rate to 80% or more, the amount of strain required for recrystallization after rough hot rolling can be ensured. The upper limit of the total reduction rate of the rough hot rolling is not particularly limited, but is typically 98% or less. The rough hot rolling may be performed in one pass or multiple passes.

[0039] After rough hot rolling, finish hot rolling is performed. The interpass interval from the completion of rough hot rolling to finish hot rolling is set to 30 seconds or more and 90 seconds or less, the final temperature of finish hot rolling is set to 950°C or more, and the coiling start temperature of the hot-rolled sheet in finish hot rolling is set to 700°C or more.

[0040] By controlling the inter-pass interval from the end of rough hot rolling to the start of finish hot rolling within the above range, it is possible to form fine, granular recrystallized grains in which coarse elongated grains are broken up before finish hot rolling. On the other hand, if the inter-pass interval from the end of rough hot rolling to the start of finish hot rolling is outside the above range, an unrecrystallized structure will result, or excessive grain growth will occur after recrystallization.

[0041] The final temperature of finish hot rolling is 950°C or higher. If the final temperature of finish hot rolling is lower than 950°C, the crystal grains will be elongated and an unrecrystallized structure will result before cold rolling. There is no particular upper limit to the final temperature of finish hot rolling, but it is typically 1050°C or lower.

[0042] The coiling start temperature of the hot-rolled sheet in finish hot rolling is 700°C or higher. If the coiling start temperature is lower than 700°C, carbides will not precipitate around the recrystallized grains after finish hot rolling, and in the stainless steel sheet after the cold rolling annealing process, the aspect ratio of the crystal grains will decrease and grain growth during the cold rolling annealing process will also be suppressed. The upper limit of the coiling start temperature is not particularly limited, but is typically 900°C or lower.

[0043] Furthermore, the finish hot rolling can be performed in multiple passes, but the interval between passes is preferably 5 seconds or less. If the interval between passes exceeds 5 seconds, the processing strain introduced during the finish hot rolling will be recovered, resulting in an unrecrystallized structure with elongated grains after the finish hot rolling.

[0044] (cold rolling process) The cold rolling step is a step of cold rolling the hot-rolled sheet obtained in the hot rolling step. The conditions of the cold rolling are not particularly limited, and the cold rolling can be performed in accordance with a conventional method. Although it is preferable to perform the cold rolling once, from the viewpoint of productivity and surface quality, it may be performed two or more times with a cold rolling annealing step (described later) sandwiched therebetween.

[0045] The total reduction rate of the one or more cold rolling passes is not particularly limited, but is preferably 60% or more, more preferably 70% or more, and the upper limit of the total reduction rate is typically 90% or less.

[0046] (Cold rolling annealing process) The cold rolling annealing process is a process in which the cold-rolled sheet obtained in the cold rolling process is annealed at a temperature of 850°C or higher and 950°C or lower. The cold-rolled sheet obtained in the cold rolling process here refers to a cold-rolled sheet that has been subjected to one or more cold rolling passes. That is, the cold rolling annealing process includes final annealing performed on the cold-rolled sheet after the cold rolling process is completed, and intermediate annealing performed between each cold rolling pass when two or more cold rolling passes are performed in the cold rolling process.

[0047] In the cold rolling annealing process, the annealing temperature of the cold rolled sheet is 850°C or higher. If the annealing temperature is lower than 850°C, the resulting structure will be a mixture of fine recrystallized and unrecrystallized structures, which will harden the sheet and leave elongated grains. On the other hand, in the cold rolling annealing process, the annealing temperature of the cold rolled sheet is 950°C or lower. If the annealing temperature exceeds 950°C, recrystallized grains will be obtained, but the crystal grain size will become coarse and the strength will rapidly decrease. From the viewpoint of stably ensuring a predetermined crystal structure, the annealing temperature is preferably 860°C or higher and 920°C or lower.

[0048] The annealing time is not particularly limited, but is typically 1 minute or more and 10 minutes or less.

[0049] 〔summary〕 An austenitic stainless steel sheet according to a first aspect of the present invention contains, by mass%, C: 0.020% to 0.060%, Si: 1.00% or less, Mn: 2.0% or less, P: 0.040% or less, S: 0.030% or less, Cr: 17.0% to 20.0%, Ni: 7.0% to 10.5%, Cu: 3.0% or less, Mo: 3.0% or less, N: 0.060% or less, with the balance being Fe and unavoidable impurities, an average grain size of 5 μm to 25 μm, a cross-sectional hardness of a cross section parallel to the rolling direction and the sheet thickness direction of 220 HV or less, and an average aspect ratio of grains of 0.50 or more.

[0050] The austenitic stainless steel sheet according to aspect 2 of the present invention may be the same as that of aspect 1, but may contain one or more elements selected from the group consisting of V, Nb, Ti, Ta, and Zr in a total amount of 0.30 mass% or less.

[0051] [Additional Notes] The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention. [Example]

[0052] Next, examples of the present invention will be shown, but the conditions in the examples are merely examples adopted to confirm the feasibility and effects of the present invention, and the present invention is not limited to the conditions used in the following examples. Various conditions can be adopted in the present invention as long as they do not deviate from the gist of the present invention and the object of the present invention is achieved.

[0053] (Manufacturing conditions) Stainless steel having the composition shown in Table 1 (the balance being Fe and unavoidable impurities) was vacuum melted and cast into a 200 mm thick slab. The slab was then heated at 1250°C for 2 hours and then rough hot rolled at the final temperature shown in Table 2 (total reduction of 81%, 8 passes). Next, finish hot rolling (6 passes) was performed with a 50 second inter-pass time between the end of rough hot rolling and the start of finish hot rolling, and the final temperature and coiling start temperature shown in Table 2, to obtain a hot-rolled sheet with a thickness of 4.0 mm. Note that underlined items in Tables 1 and 3 indicate conditions outside the range specified in the present invention. Also, underlined items in Table 2 indicate conditions outside the preferred range for the manufacturing method of this stainless steel sheet. Also, in Table 1, the content of O, an unavoidable impurity, is omitted.

[0054] In the finish hot rolling, the sheet passing speed was adjusted so that the interval between each pass was 3 seconds or less. Next, the hot-rolled sheet was pickled and then cold-rolled at a total reduction of 63% to obtain a cold-rolled sheet having a thickness of 1.5 mm. Next, the cold-rolled sheet was annealed for 2 minutes at the cold-rolling annealing temperature shown in Table 2 to obtain a cold-rolled annealed sheet. In Test Nos. 14 and 18, annealing at 1000°C for 1 minute (hot-rolling annealing step) was performed between the finish hot rolling and the pickling. In Test Nos. 1 to 13 and 15 to 17, the hot-rolling annealing step was not performed.

[0055] [Table 1]

[0056] [Table 2]

[0057] The grain size, aspect ratio, and cross-sectional hardness of the L-section (a cross section parallel to the rolling direction and the sheet thickness direction) of the obtained cold-rolled annealed sheet were measured under the above-mentioned conditions. The cross section was measured using an EBSD device attached to a scanning electron microscope, and the obtained measurement results were analyzed using analysis software (OIM Analysis (registered trademark) software (Ver. 8.1.0) manufactured by TSL Solutions Co., Ltd.) to identify austenite grains.

[0058] The results of these measurements are shown in Table 3. The numerical values ​​of each measurement result in Table 3 have been rounded off. Tests No. 9 and No. 10 satisfied the preferred range for the manufacturing method of this stainless steel sheet, but because the C content was outside the range, the aspect ratio and average grain size were not satisfactory. Furthermore, for Tests No. 11 to No. 18, one of the manufacturing conditions was outside the preferred range for the manufacturing method of this stainless steel sheet, so one of the cross-sectional hardness, average grain size, and average aspect ratio was not satisfactory, resulting in an insufficient balance between workability and strength, or anisotropy during processing.

[0059] [Table 3]

Claims

1. The alloy contains, in mass%, C: 0.020% or more and 0.060% or less, Si: 1.00% or less, Mn: 2.0% or less, P: 0.040% or less, S: 0.030% or less, Cr: 17.0% or more and 20.0% or less, Ni: 7.0% or more and 10.5% or less, Cu: 3.0% or less, Mo: 3.0% or less, N: 0.060% or less, and the balance being Fe and impurities, An austenitic stainless steel sheet having, in a cross section parallel to the rolling direction and the sheet thickness direction, an average crystal grain size of 5 μm or more and 25 μm or less, a cross-sectional hardness of 220 HV or less, and an average aspect ratio of crystal grains of 0.50 or more.

2. 2. The austenitic stainless steel sheet according to claim 1, further comprising one or more elements selected from the group consisting of V, Nb, Ti, Ta and Zr in a total amount of 0.30 mass% or less.

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