EP3862452A1

EP3862452A1 - Austenitic stainless steel sheet and method for producing same

Info

Publication number: EP3862452A1
Application number: EP19868476.3A
Authority: EP
Inventors: Natsuko Sugiura; Hiroshi Kamio
Original assignee: Nippon Steel Corp
Current assignee: Nippon Steel Corp
Priority date: 2018-10-04
Filing date: 2019-10-04
Publication date: 2021-08-11
Also published as: JP7165202B2; KR102550028B1; CN112789362B; JPWO2020071534A1; KR20210052502A; WO2020071534A1; CN112789362A; EP3862452A4

Abstract

An austenitic stainless steel sheet containing, as a chemical composition, by mass%: C: 0.005% to 0.150%; Si: 1.0% or less; Mn: 1.5% or less; P: 0.10% or less; S: 0.010% or less; Al: 0.10% or less; Cr: 15.0% to 20.0%; Ni: 6.0% to 15.0%; N: 0.005% to 0.150%; Mo: 0% to 2.0%; Cu: 0% to 1.5%; Nb: 0% to 0.500%; V: 0% to 0.150%; Ti: 0% to 0.300%; B: 0% to 0.010%; and a remainder: Fe and impurities, in which a Md30 value determined according to Md30 Value = 497 - 462 × (C + N) - 9.2 × Si - 8.1 × Mn - 13.7 × Cr - 20 × (Ni + Cu) - 18.7 × Mo is 60°C or less, and in a surface layer portion, the area ratio of martensite is 5.0% or less, and the area ratio of austenite grains having a {110} plane orientation is 50% or greater.

Description

[Technical Field of the Invention]

The present invention relates to an austenitic stainless steel sheet and a method for producing the austenitic stainless steel sheet.
Priority is claimed on Japanese Patent Application No. 2018-189321, filed October 04, 2018 , the content of which is incorporated herein by reference.

[Related Art]

A member having high surface glossiness is used for a housing of an electronic device which is a precisely worked component, and for example, a member formed of a stainless steel sheet is frequently used. In recent years, in order to stably obtain a member having high surface glossiness, the member has been required to have higher polishability than before.
In view of such a circumstance, for example, in Patent Documents 1 to 4 an improvement in polishability of a stainless steel sheet is examined.
Patent Document 1 discloses a method for producing a mirror-finished stainless steel sheet for curved mirror, which has wrapping-finished surface gloss and excellent image clarity.
Patent Document 2 discloses an austenitic stainless steel for press forming, which has improved polishability for mirror finishing.
Patent Document 3 discloses a method for producing a stainless steel strip and a steel sheet having excellent polishability.
Patent Document 4 discloses a method for producing a steel strip having few micro surface defects in the production of strips of austenitic stainless steel, martensitic stainless steel, or ferrite + austenitic duplex stainless steel.
However, as a result of studies by the inventors, it has been found that sufficient polishability may not be obtained by the related art, and there is still room for further improvement.
In many cases, the precisely worked component is produced by a method in which stainless steel sheets are laminated and subjected to diffusion bonding at a high temperature. For example, a method in which precision processing by photoetching or laser is performed to form micropores or a pattern on a surface, and then the steel sheets are laminated and subjected to diffusion bonding is employed to produce the precisely worked component. Demands for such precisely worked components and products are on the increase, and diffusion bonding is expected to be further applied and expanded.
A steel sheet which is used for the above purpose is required to have good bondability.
For example, in Patent Documents 5 to 9 an improvement in diffusion bondability is examined.
Patent Document 5 proposes a method for producing a diffusion-bonded product which can be processed without the application of special high-temperature heat or high surface pressure by using the growth of crystal grains accompanying the phase transformation during diffusion bonding.
Patent Document 6 discloses a stainless steel diffusion-bonded product which is excellent in reliability of a bonding portion and has a diffusion bonding structure in which there are many places where crystal grains on the steel side grow so as to invade the other side beyond the pre-bonding interface.
Patent Document 7 discloses a steel sheet in which diffusion bondability is increased by controlling austenite fraction during diffusion bonding.
Patent Document 8 discloses, as a stainless steel having excellent diffusion bondability, a stainless steel foil having fine crystal grains with an average crystal grain size of 0.001 to 5 µm in a foil thickness direction and an Al content of 0.5% to 8%.
Patent Document 9 describes that the etching surface is smoothened by grain refining and diffusion bondability is thus improved.
The inventors have conducted studies, and as a result, found that sufficient diffusion bondability may not be obtained by the related art and there is room for further improvement.

[Prior Art Document]

[Patent Document]

[Patent Document 1] Japanese Unexamined Patent Application, First Publication No. H3-169405
[Patent Document 2] Japanese Unexamined Patent Application, First Publication No. H9-3605
[Patent Document 3] Japanese Unexamined Patent Application, First Publication No. S62-253732
[Patent Document 4] Japanese Unexamined Patent Application, First Publication No. 2000-273546
[Patent Document 5] Japanese Unexamined Patent Application, First Publication No. 2013-103271
[Patent Document 6] Japanese Unexamined Patent Application, First Publication No. 2013-173181
[Patent Document 7] Japanese Unexamined Patent Application, First Publication No. 2016-89223
[Patent Document 8] Japanese Unexamined Patent Application, First Publication No. H9-279310
[Patent Document 9] PCT International Publication No. WO2016/043125

[Disclosure of the Invention]

[Problems to be Solved by the Invention]

The invention is contrived to solve the above problems, and an object thereof is to provide an austenitic stainless steel sheet having good polishability. In the invention, the expression "having good polishability" means that smoothing can be easily achieved by mechanical polishing. The austenitic stainless steel sheet has good polishability, and preferably further has good diffusion bondability.

[Means for Solving the Problem]

(1) An austenitic stainless steel sheet according to an aspect of the present invention containing, as a chemical composition, by mass%: C: 0.005% to 0.150%; Si: 1.0% or less; Mn: 1.5% or less; P: 0.10% or less; S: 0.010% or less; Al: 0.10% or less; Cr: 15.0% to 20.0%; Ni: 6.0% to 15.0%; N: 0.005% to 0.150%; Mo: 0% to 2.0%; Cu: 0% to 1.5%; Nb: 0% to 0.500%; V: 0% to 0.150%; Ti: 0% to 0.300%; B: 0% to 0.010%; a total of Ca, Mg, Zr, Sn, Pb, and W: 0% to 0.10%; and a remainder: Fe and impurities, in which a Md30 value determined according to the Expression (i) is 60°C or lower, and in a surface layer portion, the area ratio of martensite is 5.0% or less, and the area ratio of austenite grains having a { 110} plane orientation is 50% or greater. $Md 30 Value = 497 - 462 \times (C + N) - 9.2 \times Si - 8.1 \times Mn - 13.7 \times Cr - 20 \times (Ni + Cu) - 18.7 \times Mo$

In the expression, element symbols represent amounts of respective elements in the steel by mass%, and 0 is substituted for the element in a case where the element is not contained.
(2) The austenitic stainless steel sheet according to (1), in which the chemical composition may contain Nb: 0.010% to 0.500%, the Md30 value may be 20°C to 60°C, and in the surface layer portion, an average grain size of the austenite grains may be 5.0 µm or less, and an X-ray random intensity ratio of a {110}<112> orientation of the austenite grains may be 8.5 or greater.
(3) The austenitic stainless steel sheet according to (1) or (2), in which the chemical composition may contain, by mass%, one or more selected from the group consisting of: Mo: 0.1% to 2.0%; Cu: 0.1% to 1.5%; Nb: 0.010% to 0.500%; V: 0.010% to 0.150%; Ti: 0.010% to 0.300%; and B: 0.001% to 0.010%.
(4) A method for producing an austenitic stainless steel sheet, including: performing temper rolling on the austenitic stainless steel sheet according to any one of (1) to (3) under conditions of a rolling reduction of 50% or less.

[Effects of the Invention]

According to the aspect of the invention, it is possible to industrially stably obtain an austenitic stainless steel sheet having good polishability.
According to a preferable aspect of the invention, it is possible to obtain an austenitic stainless steel sheet which has good diffusion bondability in addition to good polishability.

[Brief Description of the Drawings]

Fig. 1 is a diagram showing an ODF of a cross section with ϕ2 = 45°.

[Embodiments of the Invention]

Hereinafter, requirements of an austenitic stainless steel sheet according to an embodiment of the invention (austenitic stainless steel sheet according to this embodiment) will be described in detail.

1. Chemical Composition

The reasons for limiting elements are as follows. In the following description, "%" for content means "mass%". A numerical range expressed using "to" includes numerical values before and after "to". Numerical values expressed using "less than" or "greater than" are not included in the range.

C: 0.005% to 0.150%

C is a potent solid solution strengthening element that increases the strength of a steel sheet at a low price. However, in a case where the C content is excessive, coarse carbides are formed and random crystal rotation occurs around the carbides during rolling deformation in hot rolling or cold rolling, whereby the crystal orientation is randomized. Therefore, the C content is 0.150% or less. The C content is preferably 0.130% or less, and more preferably 0.120% or less.
In a case where the C content is less than 0.005%, this leads to only an increase in production cost, and a particularly effective effect is not obtained. Therefore, the C content is 0.005% or greater. In addition, C is effective for suppressing recrystallization and grain growth by combining with Nb and precipitating as a fine Nb compound. In obtaining the above effects, the C content is preferably 0.010% or greater.

Si: 1.0% or less

In a case where the Si content is excessive, there is a high possibility that coarse oxides will be formed, and there is a concern that workability may be reduced. Therefore, the Si content is 1.0% or less. The Si content is preferably 0.6% or less.
Si is an element that is used as a deoxidizing material during melting and also contributes to the strengthening of steel. In a case where the above effects are desired, the Si content is preferably 0.1% or greater.

Mn: 1.5% or less

Mn is a potent austenite forming element. Therefore, in a case where the Mn content is excessive, the amount of strain-induced martensite formed during cold rolling is reduced, and thus the accumulation in the { 110} plane orientation after final annealing is reduced. In addition, fine crystal grains cannot be obtained. Therefore, the Mn content is 1.5% or less. The Mn content is preferably 1.2% or less.
Mn is an element that contributes to the prevention of brittle fracture during hot working and the strengthening of steel. In a case where the above effects are desired, the Mn content is preferably 0.1% or greater.

P: 0.10% or less

P is an impurity element. In a case where the P content is greater than 0.10%, workability significantly deteriorates. Therefore, the P content is limited to 0.10% or less. Since the P content is preferably low, it may be 0%. However, it is not preferable the P content is less than 0.005% in view of cost. Therefore, the lower limit of the P content may be 0.005%.

S: 0.010% or less

S is an impurity element. In a case where the S content is greater than 0.010%, melt embrittlement is caused during hot working. Therefore, the S content is limited to 0.010% or less. Since the S content is preferably low, it may be 0%. However, it is not preferable the S content is less than 0.001% in view of cost. Therefore, the lower limit of the S content may be 0.001 %.

Al: 0.10% or less

Al is an impurity element. In a case where the Al content is greater than 0.10%, workability is reduced. In addition, oxides are formed during bonding, and diffusion bondability is reduced. Therefore, the Al content is limited to 0.10% or less. Since the Al content is preferably low, it may be 0%. However, it is not preferable the Al content is less than 0.01% in view of cost. Therefore, the lower limit of the Al content may be 0.01%.

Cr: 15.0% to 20.0%

Cr is a basic element of a stainless steel, and is an element that acts to form an oxide layer on a surface of a steel and to increase corrosion resistance. In order to obtain the above effects, the Cr content is 15.0% or greater. The Cr content is preferably 16.0% or greater.
Cr is a potent ferrite stabilizing element. Therefore, in a case where the Cr content is excessive, δ ferrite is formed. The δ ferrite deteriorates hot workability of the material. Therefore, the Cr content is 20.0% or less. The Cr content is preferably 19.0% or less.

Ni: 6.0% to 15.0%

Ni is an austenite forming element, and is an element that acts to stabilize austenite at room temperature. In order to obtain the above effects, the Ni content is 6.0% or greater. The Ni content is preferably 6.5% or greater.
In a case where the Ni content is excessive, the austenite is excessively stabilized, and thus strain-induced martensitic transformation during cold rolling does not occur. Whereby, the accumulation in the { 110} plane orientation is reduced. In addition, Ni is an expensive element. In a case where the Ni content is excessively increased, the cost is significantly increased. Therefore, the Ni content is 15.0% or less. The Ni content is preferably 11.0% or less, and more preferably 9.0% or less.

N: 0.005% to 0.150%

As in the case of C, N is a solid solution strengthening element, and is an element that contributes to an improvement in strength of a steel. It is not preferable that the N content is less than 0.005% in view of cost. Therefore, the N content is 0.005% or greater.
In addition, N is effective for suppressing recrystallization and grain growth by combining with Nb and precipitating as a fine Nb compound during hot rolling or annealing. In obtaining the above effects, the N content is preferably 0.010% or greater.
In a case where the N content is excessive, a large number of coarse nitrides are formed in the production process of a steel sheet. Since these coarse nitrides are points where fracture starts, and significantly deteriorate hot workability, there are difficulties in production in a case where a large number of coarse nitrides are formed. As in the case of C, N is also a potent austenite stabilizing element. In a case where the N content is excessive, strain-induced transformation required for grain refining does not occur. Therefore, the N content is 0.150% or less. The N content is preferably 0.130% or less, and more preferably 0.120% or less.
Basically, the austenitic stainless steel sheet according to this embodiment has a chemical composition containing the above elements and a remainder consisting of Fe and impurities. However, in order to improve various characteristics, one or more selected from the group consisting of Mo, Cu, Nb, V, Ti, and B may be contained in a range to be described later. Since these elements are not necessarily contained, the lower limit of the amount thereof is 0%.
Here, the "impurities" include components mixed from raw materials such as ore and scrap in the industrial production of a steel, or components mixed due to various factors during the production process, and mean substances allowed within a range not affecting the austenitic stainless steel sheet according to this embodiment.

Mo: 0% to 2.0%

Mo is an element that improves corrosion resistance of a material. Therefore, Mo may be optionally contained. In a case where the above effects are desired, the Mo content is preferably 0.1% or greater.
Mo is an extremely expensive element. In a case where the Mo content is excessively increased, the cost is significantly increased. Therefore, even in a case where Mo is contained, the Mo content is 2.0% or less. The Mo content is preferably 1.0% or less.

Cu: 0% to 1.5%

Cu is an austenite forming element, and is an effective element for adjusting the stability of austenite. Therefore, Cu may be optionally contained. In a case where the above effects are desired, the Cu content is preferably 0.1% or greater.
In a case where the Cu content is excessive, Cu segregates at the grain boundaries during the production process. Since the segregation at the grain boundaries causes a significant deterioration in hot workability, there are difficulties in production in a case where Cu segregates at the grain boundaries. Therefore, even in a case where Cu is contained, the Cu content is 1.5% or less. The Cu content is preferably 1.0% or less.

Nb: 0% to 0.500%

Nb is an element that forms fine carbides or nitrides during annealing. Since these fine carbides or nitrides suppress crystal grain growth by the pinning effect, Nb is an effective element for refining the crystal grains of the material. In addition, Nb is an element that is solid-solubilized or suppresses recrystallization during hot working as a carbonitride, thereby developing the deformation texture of austenite. Therefore, Nb may be contained.
In a case where the average grain size of the austenite grains is 5.0 µm or less and the X-ray random intensity ratio of the austenite grains of the {110}<112> orientation is 8.5 or greater, the Nb content is preferably 0.010% or greater. The Nb content is more preferably 0.030% or greater, and even more preferably 0.040% or greater.
In a case where the Nb content is excessive, recrystallization is suppressed, and a large amount of unrecrystallized portions remains after annealing. Moreover, hot workability deteriorates. In addition, Nb is an extremely expensive element. In a case where the Nb content is excessively increased, the cost is significantly increased.
Therefore, even in a case where Nb is contained, the Nb content is 0.500% or less. The Nb content is preferably 0.300% or less, and more preferably 0.200% or less.

V: 0% to 0.150%

Ti: 0% to 0.300%

Both V and Ti are elements that are effective for suppressing recrystallization, strengthening a desired texture, and refining the crystal grains. Therefore, one or more selected from the group consisting of V and Ti may be optionally contained. In order to obtain the above effects, it is preferable to contain one or more selected from the group consisting of V: 0.010% or greater and Ti: 0.010% or greater.
In a case where the above elements are excessively contained, workability deteriorates. Therefore, even in a case where the above elements are contained, the V content is 0.150% or less and the Ti content is 0.300% or less.

B: 0% to 0.010%

B is an element that strengthens the grain boundaries and contributes to an improvement in hot workability. Therefore, B may be optionally contained. In order to obtain the above effect, the B content is preferably 0.001% or greater.
In a case where the B content is excessive, workability deteriorates. Therefore, even in a case where B is contained, the B content is 0.010% or less.
As described above, the chemical composition of the austenitic stainless steel sheet according to this embodiment contains essential elements and a remainder consisting of Fe and impurities, or contains essential elements, one or more optional elements, and a remainder consisting of Fe and impurities. Examples of the "impurities" include Ca, Mg, Zr, Sn, Pb, and W in addition to the above-described P, S, and Al. The total amount of impurity elements such as Ca, Mg, Zr, Sn, Pb, and W excluding P, S, and Al is preferably 0.10% or less.

Md30 Value: 60°C or less

The Md30 value is an index indicating the stability of austenite in the austenitic stainless steel sheet according to this embodiment or the like, and is a value calculated from the chemical composition, that is thought to correspond to a temperature at which 50 vol% of strain-induced martensite is formed when rolling is performed with a reduction of 30%. In a case where the Md30 value is higher than 60°C, the austenite reverse-transformed during the heat treatment may transform into martensite again during the cooling or temper rolling. In this case, the amount of austenite is reduced, and as a result, the area ratio of the grains having the {110} plane orientation is also reduced.
Therefore, the Md30 value determined according to Expression (i) is 60°C or lower. The Md30 value is preferably 55°C or lower, and more preferably 50°C or lower. $Md 30 Value (° C) = 497 - 462 \times (C + N) - 9.2 \times Si - 8.1 \times Mn - 13.7 \times Cr - 20 \times (Ni + Cu) - 18.7 \times Mo$
In the expression, element symbols represent amounts of respective elements in the steel by mass%, and 0 is substituted for the element in a case where the element is not contained.
In a case where the Md30 value is 20°C or higher, fine crystal grains are obtained by utilizing the transformation from austenite to strain-induced martensite (martensite) during the cold rolling and the reverse transformation from strain-induced martensite to austenite in the subsequent heat treatment. In addition, in this case, it is advantageous for development of the {100} plane orientation, especially the {110 }<112> orientation.
Therefore, in a case where the average grain size of the austenite grains is 5.0 µm or less and the X-ray random intensity ratio of the austenite grains of the {110 }< 112> orientation is 8.5 or greater, the Md30 value is preferably 20°C to 60°C. The Md30 value is more preferably 25°C or higher, and even more preferably 30°C or higher.

2. Metallographic Structure

In order to obtain good polishability, it is important to control the metallographic structure of a surface layer portion of the steel sheet. Specifically, it is necessary to adjust the area ratio of martensite and austenite grains having the {110} plane orientation in the surface layer portion of the steel sheet within the following range. The respective regulations will be described in detail. In this embodiment, the surface layer portion of the steel sheet means a region from the surface to a position at a depth of 1/10 of the sheet thickness in the sheet thickness direction.

Area Ratio of Martensite in Surface Layer Portion: 5.0% or less

Martensite is a hard structure. Therefore, in a case where the amount of martensite is excessive in the surface layer portion of the steel sheet in the producing stage before polishing, polishability deteriorates. In addition, in a case where the area ratio of martensite is increased, the area ratio of austenite grains having the {110} plane orientation is relatively reduced. Therefore, the area ratio of martensite in the surface layer portion of the steel sheet is 5.0% or less. The area ratio is preferably 4.0% or less, and more preferably 3.0% or less.
In addition, in a case where the amount of martensite is large in the surface layer portion of the steel sheet, the martensite is transformed into austenite in a case where heat is applied by diffusion bonding or laser working, and the flatness of the steel sheet is reduced, resulting in reduced diffusion bondability. In addition, in a case where the amount of martensite is large in the surface layer portion of the steel sheet, the area ratio of austenite is reduced, and thus the fraction of the grains having the {1101<112> orientation in the whole structure is also reduced. Therefore, from the viewpoint of diffusion bondability, the area ratio of martensite in the surface layer portion is preferably 5.0% or less.
In the austenitic stainless steel sheet according to this embodiment, the structure other than the martensite is substantially austenite.
The area ratio of martensite in the surface layer portion is determined by the following procedure.
First, regarding a plane which is parallel to a steel sheet surface and has an area of 100 µm × 100 µm or greater where the material is subjected to electrolytic polishing or chemical polishing, a fcc structure and a bcc structure are selected as crystal structures, and the measurement is performed by EBSD. Then, a region that is not discriminated to have an fcc structure, that is, a region having a bcc crystal structure, or a region where the measurement is not possible due to high strain (a linear region such as a grain boundary is not included) is regarded as martensite, and the area ratio thereof is obtained.
In a case where finish polishing with an abrasive such as colloidal silica is performed in the production of a sample, the austenite of the surface layer may undergo strain-induced martensitic transformation. Therefore, it is necessary to produce a sample by electrolytic polishing or chemical polishing. In order to observe the surface layer portion which is a region from the surface to the position at a depth of 1/10 of the sheet thickness in the sheet thickness direction, a polishing amount is limited to 1/10 of the sheet thickness.

Area Ratio of Austenite Grains Having { 110} Plane Orientation in Surface Layer Portion: 50% or greater

The {110} plane orientation is a representative principal orientation of the rolled texture of austenite. Good polishability is secured by setting the area ratio of austenite grains having the above plane orientation in the surface layer portion of the austenitic stainless steel sheet according to this embodiment to 50% or greater. The area ratio of austenite grains having the above plane orientation is preferably 52% or greater, and more preferably 55% or greater. The upper limit is not particularly set. However, since toughness is reduced in a case where the area ratio of austenite grains having the above plane orientation is greater than 85%, the upper limit is desirably 85%.
The area ratio of austenite grains having the {110} plane orientation in the surface layer portion can be determined by the following method.
First, in the surface layer portion of the material produced by the above method, a region having an area of 500 µm × 500 µm or greater is subjected to EBSD measurement. A region having a fcc crystal structure and surrounded by a grain boundary of 15° or greater is regarded as an austenite grain. Strictly speaking, the {110} plane orientation has a crystal orientation in which the <110> axis is parallel to a vector perpendicular to the surface of the steel sheet (= an angle difference from the vector perpendicular to the surface is 0), however, in this embodiment, an angle difference of 0° to 15° is allowed. The total area of austenite grains having the {110} plane orientation is divided by the measurement area and multiplied by 100, and the resulting value is defined as the area ratio (%) of austenite grains having the {110} plane orientation.

Average Grain Size of Austenite Grains In Surface Layer Portion: 5.0 µm or less

It is thought that in a case where the average grain size of the austenite grains in the surface layer portion is 5.0 µm or less, the number of crystal grains per unit area is increased, the existence frequency of grains having the {110}<112> orientation is averaged, and thus diffusion bondability is improved. In addition, in a case where the average grain size of the austenite grains is 5.0 µm or less, when etching or the like is performed, a worked surface is smoothened.
Therefore, in order to improve the diffusion bondability, the average grain size of the austenite grains in the surface layer portion is preferably 5.0 µm or less.
The average grain size of the austenite grains is calculated by the following procedure.
First, in the surface layer portion of the material produced by the above method, an area of 100 µm × 100 µm or greater is subjected to EBSD measurement. Among regions discriminated to have an fcc structure, a region surrounded by a boundary with an orientation difference of 15° or greater is regarded as one crystal grain, and an average area S per crystal grain is calculated from the number of crystal grains included in the predetermined area.
From the average area, an average grain size D of the austenite grains is calculated by Expression (iii). $D = {(2 S / π)}^{0.5}$

X-Ray Random Intensity Ratio of {110}<112> Orientation : 8.5 or greater

The {110}<112> orientation is a representative principal orientation of the rolled texture of austenite. High diffusion bondability is secured by setting the accumulation in the {1101<112> orientation in the surface layer portion (bonding surface) of the steel sheet to 8.5 or greater. Therefore, in order to improve the diffusion bondability, the X-ray random intensity ratio of the {110}<112> orientation is preferably 8.5 or greater. The X-ray random intensity ratio of the { 110}<112> orientation is more preferably 9.0 or greater, and even more preferably 10.0 or greater. The upper limit of the X-ray random intensity ratio of the {110}<112> orientation is not particularly set. However, in a case where the X-ray random intensity ratio is greater than 20.0, the orientation difference of 15° or greater between adjacent crystal grains cannot be satisfied, and the crystal grain boundary does not effectively act. Accordingly, the upper limit is desirably 20.0.
The X-ray random intensity ratio of the {110}<112> orientation may be obtained from a crystal orientation distribution function (orientation distribution function, called ODF) representing a three-dimensional texture, calculated by a series expansion method based on a plurality of pole figures among {200}, {311}, and {220} pole figures measured by X-ray diffraction. In this embodiment, the X-ray random intensity ratio is a numerical value obtained by measuring X-ray intensities of a standard sample with no accumulation in a specific orientation and a test material by an X-ray diffraction method or the like under the same conditions, and by dividing the obtained X-ray intensity of the test material by the X-ray intensity of the standard sample. As the standard sample, a sample with no specific accumulation in any plane measurement of {200}, {311}, and {220} is used. The method for producing a standard sample is not specified, but usually, the standard sample is produced by compressing and sintering a powder of a metal having an fcc crystal structure at room temperature with a Fe group such as Fe-C, Fe-Ni, and Fe-Cr stably.
Fig. 1 shows an ODF of a cross section with ϕ2 = 45° in which the above-described crystal orientation is displayed. Strictly speaking, the {110}<112> orientation refers to an orientation expressed by ϕ1 = 55° and Φ = 90°. However, since measurement errors may occur due to the test piece processing and sample setting, the maximum value in a range of ϕ1 = 50° to 60° and Φ = 85° to 90° is represented as the intensity ratio in the above orientation.
Here, regarding the crystal orientation, an orientation perpendicular to the sheet surface is usually represented by (hkl) or {hkl}, and an orientation parallel to the rolling direction is usually represented by [uvw] or <uvw>. {hkl} and <uvw> are generic names for equivalent planes, and (hkl) and [uvw] refer to individual crystal planes. That is, in this embodiment, since the target structure is an fcc structure, for example, (111), (-111), (1-11), (11-1), (-1-11), (-11-1), (1-1-1), (-1-1-1) planes are equivalent and are not differentiated.
In such a case, the orientations thereof are collectively referred to as {111}.
The ODF is also used to display the orientations of a low-symmetry crystal structure. Accordingly, in general, the orientations are expressed in a range of ϕ1 = 0° to 360°, Φ = 0° to 180°, and ϕ2 = 0° to 360°, and each orientation is displayed by (hkl), [uvw]. However, in the invention, since the target structure is a high-symmetry fcc crystal structure, Φ and ϕ2 are expressed in a range of 0° to 90°. In addition, the range of ϕ1 changes depending on whether the symmetry due to deformation is taken into account in the calculation, and in the invention, ϕ1 is expressed in a range of ϕ1 = 0° to 90° in consideration of symmetry. That is, a method is selected in which the average value in the same orientation with ϕ1 = 0° to 360° is expressed on the ODF of 0° to 90°. In this case, (hkl), [uvw] and {hkl}, <uvw> are synonymous.
Therefore, for example, the X-ray random intensity ratio in (110)[1-12] of the ODF of the cross section with ϕ2 = 45° shown in Fig. 1 is synonymous with the X-ray random intensity ratio of the {110}<112> orientation.
A sample for X-ray diffraction is produced as follows.
In order to improve diffusion bondability, the X-ray random intensity ratio of the surface layer portion to be a bonding surface is important. In order to perform the X-ray measurement, mechanical polishing, chemical polishing, and electrolytic polishing are required for a while or quite a while to obtain the flatness of the measurement plane or to remove strain. Therefore, the surface layer portion from the surface of the steel sheet to the position at a depth of 1/10 of the sheet thickness is adjusted so as to be the measurement plane.
In a case where the measurement by X-ray diffraction is difficult to perform, the measurement may be performed a statistically sufficient number of times by an electron back scattering pattern (EBSD) method or an electron channeling pattern (ECP) method.
The sheet thickness of the austenitic stainless steel sheet according to this embodiment is not limited, and is, for example, 0.5 mm or less.

3. Production Method

Although the method for producing an austenitic stainless steel sheet according to this embodiment is not particularly limited, the austenitic stainless steel sheet can be produced by the following method. In the method for producing an austenitic stainless steel sheet according to this embodiment, the steel is melted and cast in the usual manner to obtain a steel piece to be hot-rolled. The steel piece may be prepared by forging or rolling a steel ingot. From the viewpoint of productivity, the steel piece is preferably produced by continuous casting. The steel piece may be produced using a thin slab caster or the like.
By applying a production method including the following steps to the obtained steel piece, the austenitic stainless steel sheet according to this embodiment can be produced.

(a) Heating Step

Usually, the steel piece is cooled after being cast, and reheated for hot rolling. In the method for producing an austenitic stainless steel sheet according to this embodiment, the heating temperature of the steel piece during hot rolling is 1,150°C or higher. This is because in a case where the heating temperature is lower than 1,150°C, coarse carbonitrides remain unmelted, which may be points where cracking starts during hot working, and promote randomization of the texture during hot rolling (suppress the formation of a desired texture). The heating temperature is desirably 1,170°C or higher. The upper limit of the heating temperature is not particularly specified. However, in a case where the heating is performed at a temperature higher than 1,400°C, this may lead to a reduction in productivity and growth in an orientation that does not develop in usual rolling. Therefore, the upper limit is desirably 1,400°C.
After casting of the melted steel, a process such as continuous casting-direct rolling (CC-DR) in which hot rolling is performed (without reheating) before the temperature drops below 1,150°C may be employed.

(b) Hot Rolling Step

In the method for producing an austenitic stainless steel sheet according to this embodiment, hot rolling is performed on the heated steel piece. In that case, the hot rolling is ended in a temperature range of 880°C to 1,000°C. In a case where the temperature at which the hot rolling is ended is lower than 880°C, deformation resistance increases. Thus, the productivity is significantly impaired, and the development of a shear layer of a surface layer portion of the hot-rolled sheet is promoted. The end temperature is desirably 900°C or higher.
In a case where the temperature at which the hot rolling is ended is higher than 1,000°C, recrystallization occurs in all rolling passes, and thus the development degree of the texture of the hot-rolled steel sheet is reduced (the structure is randomized). Moreover, the area ratio of austenite grains having the { 110} plane orientation in the surface layer portion is reduced. In addition, the X-ray random intensity ratio of the {110}<112> orientation in the surface layer portion is also reduced. Therefore, the temperature at which the hot rolling is ended is 1,000°C or lower. The end temperature is desirably 980°C or lower, and more desirably 950°C or lower.
In the hot rolling step, a shape ratio L determined according to Expression (ii) is 4.5 or less in final two passes respectively. In a case where at least one of the shape ratios in the final two passes is greater than 4.5, a layer called a shear layer having a different crystal orientation from that of the central layer in the sheet thickness direction is formed in the surface layer portion of the hot-rolled sheet due to the friction between the steel sheet and the rolling roll. The shear layer does not include the {110} plane orientation. Accordingly, in a case where the shear layer develops at the stage of hot rolling, the area ratio of austenite grains having the {110} plane orientation is also reduced. Furthermore, since the shear layer does not include the {110}<112> orientation, the {110}<112> of the surface layer portion is also reduced. The shape ratio L is desirably 4.2 or less, and more desirably less than 4.0. The lower limit of the shape ratio L is not particularly set. However, in a case where the lower limit is less than 2.5, the sheet thickness of the hot-rolled sheet is increased, and the load of cold rolling increases. Therefore, the shape ratio is desirably 2.5 or greater in final two passes respectively. The shape ratio L is more desirably 2.8 or greater, and even more desirably 3.0 or greater. $L = (\sqrt (R \times (t_{in} - t_{out}))) / ((2 t_{out} + t_{in}) / 3)$
The meanings of the symbols in the expression are as follows.

L: A shape ratio in the present pass
R: A roll radius (mm) in the present pass
t_in: An entry-side thickness (mm) in the present pass
t_out: An exit-side thickness (mm) in the present pass

(C) Coiling Step

The steel sheet (hot-rolled sheet) hot-rolled under the above conditions is coiled in a temperature range of 900°C or lower. In a case where the coiling temperature is higher than 900°C, recrystallization proceeds during the coiling, and the desired texture is weakened. The coiling temperature is desirably 880°C or lower, and more desirably 850°C or lower.
The lower limit of the coiling temperature is not particularly specified. However, even in a case where the coiling temperature is lower than 550°C, no special effects can be obtained, and there are difficulties in uncoiling due to the increased coil strength. Therefore, the coiling temperature is desirably 550°C or higher.
After completion of the above hot rolling, cold rolling and annealing are repeated once or multiple times in the usual manner to produce a steel sheet. In that case, only the final steps of the cold rolling and the annealing are limited as will be described later. The temperature in the steps other than the final step is not particularly limited, and the temperature of the annealing (intermediate annealing) other than the final step is generally 900°C to 1,100°C.

(D) Final Cold Rolling Step

In a case where a rolling reduction (reduction) of the final cold rolling is less than 40%, the deformation texture is not formed, and the {110} plane orientation does not develop. Therefore, the rolling reduction of the final cold rolling is 40% or greater. In a case where the rolling reduction is less than 40%, martensitic transformation during the cold rolling does not sufficiently occur, and grain refining due to the reverse transformation during the subsequent annealing does not occur. Therefore, from the viewpoint of reducing the austenite grain size, the rolling reduction is 40% or greater. The rolling reduction is desirably 45% or greater, and more desirably 50% or greater.
In a case where the rolling reduction is greater than 90%, an orientation different from that developed by usual rolling, and the area ratio of austenite grains having the { 110} plane orientation is reduced. In addition, the load on the device is extremely increased. Therefore, the rolling reduction is 90% or less. The rolling reduction is desirably 85% or less, and more desirably 80% or less.
In a case where the rolling roll in the final cold rolling step has a small roll diameter, a shear layer is formed in the surface layer portion of the steel sheet due to the friction between the steel sheet and the rolling roll, and an orientation different from the { 110} plane orientation develops. Therefore, the roll diameter of the rolling roll in the final cold rolling step is 80 mm or greater. The roll diameter is desirably 90 mm or greater, and more desirably 100 mm or greater.

(E) Final Annealing Step

In a case where the end-point temperature of the final annealing is lower than 600°C, the worked α-structure remains, and the ratio of austenite grains having the {110} plane orientation is reduced. Therefore, polishability cannot be secured. Furthermore, in a case where the end-point temperature of the final annealing is lower than 600°C, reverse transformation does not occur, and austenite grains have an average grain size greater than 5.0 µm. Therefore, the end-point temperature of the final annealing is 600°C or higher. The end-point temperature of the final annealing is desirably 650°C or higher, and more desirably 700° C or higher.
In a case where the end-point temperature of the final annealing is higher than 1,000°C, grain growth is promoted, the grain size is coarsened, and toughness is reduced. In addition, an orientation other than the { 110} plane orientation develops. In addition, the X-ray random intensity ratio of the {110}<112> orientation is also reduced. Therefore, the end-point temperature of the final annealing is 1,000°C or lower. The end-point temperature of the final annealing is desirably 980°C or lower, and more desirably 970° C or lower.
The holding time at the annealing temperature (end-point temperature) is 60 seconds or shorter. Holding for longer than 60 seconds causes randomization of the texture and coarsening of the grain size. From the above viewpoint, the holding time is preferably 30 seconds or shorter, and more preferably 10 seconds or shorter.
In addition to the above production conditions, the hot-rolled sheet may be annealed (intermediate annealing) before cold rolling. The annealing temperature before cold rolling is desirably 600°C to 1,000°C. The reasons for this are as follows: in a case where the temperature is lower than 600°C, the hot-rolled sheet is not sufficiently softened, and the working load during the cold rolling increases, and in a case where the temperature is higher than 1,000°C, the grain size is coarsened, and static recrystallization proceeds so that the structure is randomized.
After the final annealing, cold rolling (temper rolling) for adjusting the mechanical characteristics of the steel sheet, and a subsequent heat treatment for reducing residual stress (strain relief) that causes a change in the shape of the sheet and for reverse transformation to the γ-primary phase may be performed. By virtue of the above steps, the mechanical properties of the austenitic stainless steel sheet can be adjusted within a preferable range.
In a case where the temper rolling is performed, the rolling reduction is desirably 50% or less. This is because in a case where the rolling reduction is 50% or less, adjustment to the required mechanical properties specified in JIS standards (G4305) and the like is possible. In a case where the heat treatment is performed, the heat treatment temperature is desirably 600°C to 900°C, and more desirably 650°C to 850°C. This is because in a case where the heat treatment temperature is lower than 600°C, the effect of strain relief cannot be obtained, and reverse transformation does not occur. In addition, in a case where the heat treatment temperature is higher than 900°C, the performance adjustment effect in the cold rolling disappears.

[Examples]

Hereinafter, the invention will be described in greater detail with examples, but the invention is not limited thereto.

Steel pieces were produced by melting steels each having a chemical composition shown in Table 1. The steel pieces were heated and roughly hot-rolled, and then subjected to finish rolling under conditions shown in Tables 2-1 and 2-2. In Tables 2-1 and 2-2, SRT (°C) represents a heating temperature of the steel piece, L1 represents a shape ratio in a pass immediately before a final pass, L2 represents a shape ratio in the final pass, and FT (°C) represents a temperature after the final pass of the finish rolling, that is, a temperature on the finishing exit side. CT (°C) represents a coiling temperature.
After hot rolling, pickling was performed. Intermediate cold rolling (intermediate cold rolling) was performed with a reduction of 60%, and intermediate annealing was performed to hold the resulting sheets at 1,050°C for 20 minutes. Then, final cold rolling was performed thereon to obtain steel sheets having a thickness of 0.2 mm. CR (%) represents a rolling reduction of the final cold rolling. Then, annealing in which the temperature is increased to an end-point temperature represented by AT (°C) was performed.
Regarding the obtained austenitic stainless steel sheets, in the surface layer portion, an area ratio of martensite (α'), an average grain size of austenite grains (γ), an area ratio of austenite grains having the {110} plane orientation, and an X-ray random intensity ratio of the {110}<112> orientation were measured.
The average grain size of the austenite grains and the area ratio of the martensite in the surface layer portion were measured by the following methods. First, a plane which was parallel to a steel sheet surface at a position at a depth of 1/10 of the sheet thickness in the sheet thickness direction from the steel sheet surface and had an area of 500 µm × 500 µm was subjected to EBSD measurement. Among regions discriminated to have an fcc structure, a region surrounded by a boundary with an orientation difference of 15° or greater was regarded as one crystal grain, and an average area S per crystal grain was calculated from the number of crystal grains contained in the predetermined area. From the average area, an average grain size D of the austenite grains was calculated by Expression (iii).
A region that was not discriminated to have an fcc structure, that is, a region having a bcc crystal structure, or a region where the measurement was not possible due to high strain (a linear region such as a grain boundary was excluded) was regarded as martensite, and the area ratio thereof was obtained.
The area ratio of the martensite (α'-area ratio) and the average grain size of the austenite grains (γ-grain size) each are represented by an average value after final annealing.
The area ratio (γ-area ratio of {110} plane) of austenite grains having the {110} plane orientation in the surface layer portion was measured as follows.
First, a region having an area of 500 µm × 500 µm in a plane which was parallel to a steel sheet surface as with the above was subjected to EBSD measurement. A region having a fcc crystal structure and surrounded by a grain boundary of 15° or greater was regarded as an austenite grain, and among the grains, grains having a crystal orientation in which the <110> axis had an angle difference of 0° to 15° with respect to a vector perpendicular to the surface of the steel sheet were defined as austenite grains having the {110} plane orientation. The total area of the grains having the {110} plane orientation was divided by the measurement area and multiplied by 100, and the resulting value was defined as the area ratio of austenite grains having the {110} plane orientation.
The X-ray random intensity ratio ({110}<112> X-ray random intensity ratio) of the {110}<112> orientation in the surface layer portion of the steel sheet was measured as follows.
First, using a sample in which the steel sheet was subjected to mechanical polishing and buffing, and then subjected to electrolytic polishing to remove strain, and a plane parallel to a steel sheet surface at a depth of 1/10 of the sheet thickness from the steel sheet surface was adjusted so as to be the measurement plane, X-ray diffraction was performed. The X-ray diffraction of a standard sample without the accumulation in a specific orientation was also performed under the same conditions.
Based on {200}, {311}, and {220} pole figures obtained by the X-ray diffraction, an ODF was obtained by a series expansion method. Then, the X-ray random intensity ratio was determined from the ODF. For the X-ray diffraction of the surface layer portion, the front side of the steel sheet was measured.
The polishability of the austenitic stainless steel sheet was evaluated.
The polishability was evaluated as follows.
A test piece having a length of 100 mm, a width of 150 mm, and a thickness of 0.2 mm was collected from the austenitic stainless steel sheet, and then the collected test piece was polished under conditions of a contact pressure of 8.0 N/cm², #400 alumina abrasive grains, a rotation speed of 300 rpm, and a polishing time of 10 seconds. Then, roughness Ra after polishing was measured according to JIS B 0601: 2013. In this example, the austenitic stainless steel sheet was judged to have good polishability in a case where the roughness Ra after polishing was 0.050 µm or less.
The diffusion bondability of the austenitic stainless steel sheet was evaluated as follows.
Two steel sheets of 50 mm x 50 mm (x thickness) collected from the austenitic stainless steel sheet were stacked. Then, 30 MPa of stress was applied, and the steel sheets were held at 900°C for 30 seconds for diffusion bonding. Then, a cavity in the diffusion bonding portion was evaluated by ultrasonic flaw detection.
The diffusion bonding portion was evaluated by a transmission method. A position where the transmission pulse height was 25% or greater was judged as a diffusion bonding portion, and a position where the transmission pulse height was less than 25% was judged as a cavity portion to calculate the area ratio of the diffusion bonding portion.
In this example, the austenitic stainless steel sheet was judged to have good diffusion bondability in a case where the area ratio of the diffusion bonding portion was 70% or greater.
The transmission method is a method of grasping a size and a degree of a defect inside a measurement target from the degree to which ultrasonic waves are attenuated due to the scattering occurring by the defect in the measurement target in the process in which the ultrasonic waves transmitted from a probe for transmission pass through the measurement target and are received by a probe for reception. The height of the transmitted pulse received after passing through the measurement target is measured as compared to that of the pulse of the transmitted ultrasonic waves. It is evaluated that the closer the height of the transmitted pulse received is to 100%, the fewer defects are in the measurement target and the better the diffusion bonding is achieved, and the lower the height of the transmitted pulse received is, the poorer the bonding is.
In this example, tap water was used as a contact medium. In addition, a 0.4 mm thick austenitic stainless steel sheet, desirably an austenitic stainless steel sheet having a chemical composition range according to the invention was used as a test piece for calibration, and the transmitted pulse was measured at a pitch of 0.2 mm for each of the vertical and horizontal directions of the measurement target after adjustment of the oscillator diameter of the ultrasonic probe to 0.5 mm.
As is obvious from the results shown in Tables 2-1 and 2-2, since the area ratio of martensite was reduced and the { 110} plane orientation developed in the invention examples (Test Nos. 1 to 3, 5, 7, 9, 11, 13, 15, 17, 22, 24, 26, 28, 31, 33, 35, 37, 39, and 44), excellent polishability was obtained.
In addition, in Test Nos. 3, 9, 13, 22, 24, 26, 28, 31, 33, 35, 37, 39, and 44 among the above invention examples, since the average grain size of the austenite grains was small and the X-ray random intensity ratio of the austenite grains of the {110}<112> orientation was high, excellent diffusion bondability was also obtained.
On the other hand, test Nos. 18 to 21, 41, and 43 are comparative examples using a steel whose chemical composition is outside the specified range of the invention. In Test No. 18, since the C content was too large, the texture was randomized, and the {110} plane orientation did not sufficiently develop. In Test No. 19, since the Cr content was too large, cracks occurred during hot rolling, and the test was stopped. In Test Nos. 20, 21, and 43, since the Md30 value was too high and the amount of martensite was excessive, the polishability was reduced.
In Test No. 41, since the Nb content was too large, the hot workability was reduced and an edge of the hot-rolled sheet was cracked, so that the test was stopped.
Test Nos. 4, 6, 8, 10, 12, 14, 16, 23, 25, 27, 29, 30, 32, 34, 36, and 38 are all comparative examples in which although their chemical compositions satisfy the provisions of the invention, the production conditions are outside the preferable range of the invention, and as a result, the desired texture was not obtained.
In Test Nos. 4, 6, 25, and 27, the shape ratio in both or any one of the final two rolling stages of the hot rolling was greater than 4.5. Therefore, a shear texture developed in the surface layer portion of the hot-rolled sheet. As a result, the development of the {110} plane orientation after cold rolling annealing was finally suppressed, and the polishability was reduced. In Test Nos. 8 and 29, the temperature at which the hot rolling was ended was too high. In Test No. 8, the coiling temperature was also high. Therefore, recrystallization proceeded, and the desired texture did not develop.
In Test Nos. 10 and 32, since the rolling reduction in the cold rolling was too low, the texture did not develop. In Test No. 12, since the roll diameter of the rolling roll in the final cold rolling was too small, a shear texture developed on the surface layer portion of the steel sheet. In Test Nos. 14 and 36, since the end-point temperature of the final annealing was too low, reverse transformation did not occur, and the martensite fraction increased. In Test Nos. 16 and 38, since the end-point temperature of the annealing was too high, recrystallization proceeded, and the desired texture did not sufficiently develop. Therefore, the polishability was poor in these examples.
In Test No. 23, the heating temperature before hot rolling was low. Therefore, randomization of the texture during hot rolling was promoted. As a result, the desired texture did not sufficiently develop.
In Test No. 30, the finish rolling completion temperature was low. Therefore, the development of a shear layer in the surface layer portion was promoted. As a result, the desired texture did not sufficiently develop.
In Test No. 34, the coiling temperature was high. Recrystallization proceeded during coiling. As a result, the desired texture did not sufficiently develop.

Steel pieces were produced by melting steels each having a chemical composition (A, I, F2, I2) shown in Table 1. The steel pieces were heated and roughly hot-rolled, and then subjected to finish rolling under conditions shown in Table 3. After hot rolling, pickling was performed. Intermediate cold rolling was performed with a reduction of 55%, and intermediate annealing was performed to hold the resulting sheets at 1,120°C for 20 minutes. Then, final cold rolling was performed thereon. Then, annealing was performed to increase the temperature to an end-point temperature represented by AT (°C). After the annealing, temper rolling was performed with a rolling reduction shown in Table 3, and stress relief annealing was performed.

[Table 3]

Test No.	Steel Type	SRT (°C)	L1	L2	FT (°C)	CT (°C)	Roll Diameter (mm)	CR (%)	AT (°C)	Temper Rolling (%)	Stress Relief Annealing (°C)	Grain Size (µm)	α'-Area Ratio (%)	γ-Area Ratio of {110} Plane	{110}<112> X-Ray Random Intensity Ratio	Roughness After Polishing (µm)	Area Ratio of Diffusion Bonding Portion (%)	Remarks
45	A	1200	3.4	3.3	910	800	100	50	900	10	620	5.2	4.3	65	8.3	0.034	67	Invention Example
46	I	1250	3.5	3.4	900	750	100	70	900	10	700	7.6	4.4	66	7.2	0.036	65	Invention Example
47	I	1300	3.4	3.4	920	800	100	70	900	5	700	6.8	1.2	62	7.0	0.034	65	Invention Example
48	F2	1200	3.5	3.4	950	780	100	50	900	10	600	1.2	3.8	62	8.9	0.036	89	Invention Example
49	12	1200	3.6	3.3	890	550	100	60	900	8	650	1.7	2.1	60	8.6	0.035	78	Invention Example

As can be seen from Table 3, good polishability was obtained even in a case where temper rolling and stress relieving annealing were performed. In addition, all of the examples had the required mechanical properties specified in JIS standards (G4305) and the like.

[Industrial Applicability]

According to the invention, it is possible to industrially stably obtain an austenitic stainless steel sheet having good polishability. Accordingly, an austenitic stainless steel sheet according to the invention is suitable as a material for a member such as a housing of an electronic device which requires high surface glossiness.

Claims

An austenitic stainless steel sheet comprising, as a chemical composition, by mass%:
C: 0.005% to 0.150%;

Si: 1.0% or less;

Mn: 1.5% or less;

P: 0.10% or less;

S: 0.010% or less;

Al: 0.10% or less;

Cr: 15.0% to 20.0%;

Ni: 6.0% to 15.0%;

N: 0.005% to 0.150%;

Mo: 0% to 2.0%;

Cu: 0% to 1.5%;

Nb: 0% to 0.500%;

V: 0% to 0.150%;

Ti: 0% to 0.300%;

B: 0% to 0.010%;

a total of Ca, Mg, Zr, Sn, Pb, and W: 0% to 0.10%; and

a remainder: Fe and impurities,
wherein a Md30 value determined according to Expression (i) is 60°C or lower, and
in a surface layer portion, an area ratio of martensite is 5.0% or less, and an area ratio of austenite grains having a {110} plane orientation is 50% or greater, $Md 30 Value = 497 - 462 \times (C + N) - 9.2 \times Si - 8.1 \times Mn - 13.7 \times Cr - 20 \times (Ni + Cu) - 18.7 \times Mo$
in the expression, element symbols represent amounts of respective elements in the steel by mass%, and 0 is substituted for the element in a case where the element is not contained.
The austenitic stainless steel sheet according to claim 1,
wherein the chemical composition contains Nb: 0.010% to 0.500%,
the Md30 value is 20°C to 60°C, and
in the surface layer portion, an average grain size of the austenite grains is 5.0 µm or less, and an X-ray random intensity ratio of a {110}<112> orientation of the austenite grains is 8.5 or greater.
The austenitic stainless steel sheet according to claim 1 or 2,
wherein the chemical composition contains, by mass%, one or more selected from the group consisting of:
Mo: 0.1% to 2.0%;

Cu: 0.1% to 1.5%;

Nb: 0.010% to 0.500%;

V: 0.010% to 0.150%;

Ti: 0.010% to 0.300%; and

B: 0.001% to 0.010%.
A method for producing an austenitic stainless steel sheet, the method comprising:
performing temper rolling on the austenitic stainless steel sheet according to any one of claims 1 to 3 under a condition of a rolling reduction of 50% or less.