KR101620252B1 - Stainless steel sheet and method for producing same - Google Patents

Abstract

Mo: 2.0% or less, Cr: 12.0% or more and 20.0% or less, Ni: 4.5% or more and 9.0% or less, Cu: 1.5% or less, , The balance being Fe and impurities, the Md30 value being 20 占 폚 or more and 60 占 폚 or less, and the Ni equivalent being 9.5% or more; Wherein a ratio of a crystal boundary having an inclination angle of at least 15 degrees to a crystal boundary having an inclination angle of at least 2 degrees is at least 95 percent and an average diameter of crystal grains surrounded by a crystal boundary having an inclination angle of at least 15 degrees is 5 占 퐉 or less, Steel plate.

Description

[0001] STAINLESS STEEL SHEET AND METHOD FOR PRODUCING SAME [0002]

The present invention relates to an austenitic stainless steel sheet suitable for use in etching processing and a method for producing the same. The present application claims priority based on Japanese Patent Application No. 2012-181628 filed on August 20, 2012, the contents of which are incorporated herein by reference.

The etching process is a technique of chemically molding a metal plate by masking a part of the metal plate by a photoresist method and then contacting the metal plate with an etching liquid by spraying or dipping to melt the exposed portion of the metal plate. Etching is used to manufacture precision electronic parts such as shadow masks, encoder slits, and lead frames, and to manufacture precision mechanical parts such as springs and gears.

Etching is a technique for dissolving unnecessary portions of a metal plate and removing the unnecessary portions, thereby molding them into a desired shape. When an etching process is applied to a stainless steel plate, if the etching surface is not smooth, the machining precision is lowered. As a result, there is a problem in that, for example, the slit interval to be processed can not be narrowed sufficiently, a problem occurs in that the printing paper is scratched by the paper feeding gear of the printer or ink adheres to the concave portion of the uneven surface, And the like. In addition, there is a case where an etching material is used for the casing, and if the etching surface is not smooth, color unevenness occurs, and designability is largely lowered. Further, when the etching material is used as the microreactor, there is an effect that when the etching surface is smooth, the liquid flowing inside is hard to be stored.

Patent Literature 1 proposes an austenitic stainless steel in which crystal growth is suppressed and the etching rate is improved and the smoothness of the etched surface is ensured by performing the annealing after the final cold rolling at a temperature lower than the conventional one at 500 to 850 캜 have. However, in the stainless steel of Patent Document 1, a carbide is deposited, whereby a substance called "smut" (carbide remaining at the time of etching) adheres to the etching surface to lower the etching rate, There is a problem that the smoothness of the substrate is deteriorated.

Patent Document 2 proposes a stainless steel sheet for photoetching in which the average crystal grain diameter is 15 占 퐉 or less and the etched surface is smooth by adjusting chemical composition and manufacturing process conditions. In recent years, however, there are many applications in which the fineness and precision of processing are required more than the conventional ones, and the invention of Patent Document 2 can not sufficiently satisfy these requirements.

Patent Document 3 proposes a stainless steel for photoetching in which the average crystal grain size is adjusted to 10 μm or less by adjusting the chemical composition and the manufacturing process conditions. However, in the invention of Patent Document 3, since an expensive V is added, the cost of the material is considerably increased.

In the above prior art, the smoothness of the etched surface has been improved. However, when the etching material is used as a paper feeding gear of a printer, there is a problem that scratches are formed on the printing paper, or ink adheres to the concave portion of the uneven surface, thereby causing the printing paper to be dirty. In addition, there is no problem such as color unevenness on the etching surface in the case material.

Japanese Patent No. 2754225 Japanese Patent No. 3562492 Japanese Patent No. 4324509

An object of the present invention is to industrially and stably provide austenitic stainless steel capable of smoothing a single layer of an etched surface in view of the above-described phenomenon. Specifically, there is provided an austenitic stainless steel sheet excellent in smoothness of an etched surface and a method of manufacturing the same.

As described above, the inventors have focused on the etchability of each crystal grain with respect to a problem that can not be solved by conventional techniques.

The etching process is a method of chemically dissolving or removing the surface of the steel sheet to form it. The rate of dissolution depends on the crystal orientation of the steel sheet in contact with the etchant. In other words, since the dissolution rate differs depending on the crystal grain, the size of the irregularities of the etched surface is the same as the grain size. In order to obtain a smooth etched surface, it is preferable that the etched surface of the steel sheet is a set of fine regions (fine crystal grains) having a random crystal orientation.

Austenitic stainless steels include, strictly speaking, metastable austenite phases. The austenitic stainless steels are microstructured by machining organic martensite transformation by cold rolling and by reverse transformation to austenite by subsequent low temperature annealing. However, when low-temperature annealing is performed at a temperature of, for example, less than 700 ° C, as shown in a region surrounded by a dotted line in FIG. 1 (a), the crystal orientation Area remains. The coarse region in which such a crystal orientation is aligned is preferentially dissolved or, conversely, difficult to dissolve in comparison with other portions at the time of etching. As a result, in this rough region, the concave or convex portion of the etching surface becomes remarkably large. Even if such a remarkably large concave or convex portion is formed, the average roughness Ra indicating the smoothness of the surface may not be largely changed. In the present invention, the average length RSm of the roughness curve elements is used as an evaluation of the coarse region in which the crystal orientation is aligned. This value is the average value of the length of one concave and convex portion of the surface.

On the other hand, as shown in Fig. 1 (b), it has been found that if the structure is a set of fine crystal grains having no coarse region in which the crystal orientation is aligned, the etched surface is smooth (the intervals between the concave and convex portions are small). In this case, " crystal grains " is defined as a region surrounded by a boundary having a crystal orientation difference of 15 degrees or more. Further, in order to obtain such a fine grain texture, it was found that it is effective to generate sufficient processed organic martensite by cold rolling before annealing. The? -Phase region remaining in the cold rolling leads to a structure after annealing as a coarse region in which the crystal orientation is aligned. On the other hand, the processed organic martensite produced by cold rolling contains many deformations, thereby resulting in fine γ grains (recrystallized grains) in the subsequent annealing. Further, in order to produce a large amount of martensite by cold rolling, it has been found effective to optimize the chemical composition of the steel sheet.

Based on the above conception, the inventors have studied in detail the relationship between the chemical composition, the grain size and the formability of the material. As a result, they have found that the object of the present invention is achieved by the following constitution, and the present invention has been completed.

Further, as a result of a detailed examination of the production method, it has been found that a stainless steel sheet achieving the object of the present invention can be industrially and stably provided by the following production method, and the present invention has been completed.

Here, the present invention is as follows.

[One]

In terms of% by mass,

C: 0.03% or less,

Si: 1.0% or less,

Mn: 1.5% or less,

Mo: 2.0% or less,

Cr: 12.0% or more and 20.0% or less,

Ni: not less than 4.5% and not more than 9.0%

Cu: 1.5% or less,

N: not less than 0.03% but not more than 0.15%

Nb: 0.01% or more and 0.50% or less,

The balance being Fe and impurities,

The Md30 value represented by the following formula (1) is 20 占 폚 or more and 60 占 폚 or less, the Ni equivalent represented by the following formula (2) is 9.5%

In the metal structure, a ratio of a crystal boundary having an inclination angle of 15 degrees or more among the crystal boundaries having an inclination angle of 2 degrees or more is 95% or more, and an average diameter of crystal grains surrounded by a crystal boundary having an inclination angle of 15 degrees or more is 5 占 퐉 or less , An austenitic stainless steel sheet.

(% By mass),% Si is the content of Si (% by mass),% Mn is the content of Mn (% by mass) (% By mass),% Cr represents the content of Cr (mass%),% Ni represents the content of Ni (mass%),% Cu represents the content of Cu (mass%) and% Mo represents the content of Mo (mass%).

[2]

Austenitic stainless steel sheet obtained by temper rolling of the stainless steel sheet of [1].

[3]

In terms of% by mass,

C: 0.03% or less,

Si: 1.0% or less,

Mn: 1.5% or less,

Mo: 2.0% or less,

Cr: 12.0% or more and 20.0% or less,

Ni: not less than 4.5% and not more than 9.0%

Cu: 1.5% or less,

N: not less than 0.03% but not more than 0.15%

Nb: 0.01% or more and 0.50% or less,

The balance being Fe and impurities,

A method for producing a steel sheet by subjecting a steel sheet having an Md30 value of 20 deg. C or higher and 60 deg. C or lower and represented by the following formula (1) and having an Ni equivalent of 9.5% or higher as shown in the following formula (2) to hot rolling and cold rolling, ,

The cold rolling is carried out by multipass rolling and each pass is performed at 35 DEG C or less, at a rolling speed of 200 m / min or less, and at a tensile force of 30 kg / mm &

The total plate thickness reduction ratio in the cold rolling is set to 50% or more,

Wherein the annealing is performed at a temperature of 700 ° C or more and 950 ° C or less.

[Equation 1]

&Quot; (2) "

(% By mass),% Si is the content of Si (% by mass),% Mn is the content of Mn (% by mass) (% By mass),% Cr represents the content of Cr (mass%),% Ni represents the content of Ni (mass%),% Cu represents the content of Cu (mass%) and% Mo represents the content of Mo (mass%).

[4]

In the production method of [3], temper rolling is performed after the annealing.

Fig. 1 is a crystal orientation map showing the crystal orientation of the stainless steel after annealing. Fig. 1 (a) shows a case where the amount of the processed organic martensite before annealing is 78%. Fig. 1 (b) shows a case where the amount of the processed organic martensite before annealing is 90%.
2 is a schematic diagram of a processed organic martensite structure produced by cold rolling. Fig. 2 (a) shows lath-shaped martensite. Fig. 2 (b) shows cell-shaped martensite.

The reason for limiting the chemical composition and the production conditions of the steel in the present invention is as follows. Further, regarding the chemical composition of the steel, "%" is "mass%".

C: C is precipitated in the grain boundaries as Cr Cr carbide, which causes coarse Cr carbide to generate smut during etching, so the content is preferably as small as possible. However, since it is an element that increases the strength of the steel sheet inexpensively, it may be contained in a range of 0.03% or less without adverse effects of smut. In applications where the smoothness after etching is strictly required, it is preferably 0.02% or less. Further, C is precipitated at the time of annealing as a fine Nb compound in combination with Nb, and has an effect of suppressing crystal grain growth, so that C is preferably contained in an amount of 0.001% or more.

Si: Si is used as a de-oxidizing material in a solvent, and contributes to strengthening of steel. However, if the Si content is excessively large, the etching rate is adversely affected. Therefore, Si may be contained in a range of 1.0% or less. It is preferably 0.6% or less.

Mn: Mn contributes to prevention of brittle fracture and strengthening of steel during hot working. However, since Mn is a strong austenite generating element, if the content is excessively large, the amount of the processed organic martensite produced during cold rolling is small, and the fine grain can not be obtained in subsequent annealing. Therefore, Mn may be contained in a range of 1.5% or less. It is preferably 1.2% or less. More preferably, it is less than 1.2%.

Cr: Cr is a basic element of stainless steel, and it is an element necessary for forming a metal oxide layer on the surface of steel and enhancing corrosion resistance. However, since Cr is a strong ferrite stabilizing element, if the content is too large,? Ferrite is produced. This? -Ferrite deteriorates the hot workability of the material. Therefore, the Cr content is set to 12.0% or more and 20.0% or less. , Preferably not less than 15.0% and not more than 19.0%.

Ni: Ni is an austenite-generating element and is an element necessary for stably obtaining an austenite phase at room temperature. Therefore, the lower limit value is set to 4.5%. However, when the Ni content is excessively large, the austenite phase is excessively stabilized and the transformation of the processed organic martensite during cold rolling is suppressed. Further, Ni is an expensive element, and an increase in the content causes a significant increase in cost. Therefore, the upper limit value is 9.0%. , Preferably not less than 6.0% and not more than 8.5%.

Mo: Mo improves the corrosion resistance of the material. However, if the Mo content is excessively large, the etching property is deteriorated, leading to an increase in cost. Therefore, Mo may be contained in a range of 2.0% or less. It is preferably 1.0% or less. More preferably, it is 0.50% or less.

Cu: Cu is an austenite-generating element and an element capable of adjusting the stability of the austenite phase. If the Cu content is excessively large, it segregates in the grain boundary during the production process. This intergranular segregation significantly deteriorates hot workability and makes it difficult to manufacture. Therefore, the upper limit value may be contained in the range of 1.5%. It is preferably 1.0% or less.

N: N, like C, is a solid solution strengthening element and contributes to the improvement of steel strength. Further, since it is combined with Nb to form a fine Nb compound, it is precipitated at the time of annealing to suppress the growth of crystal grains, and therefore, it is preferably contained in an amount of 0.03% or more. However, if the N content is excessively large, a large number of coarse nitrides are produced in the course of manufacturing the steel sheet. They become breakage starting points, and remarkably deteriorate the hot workability, making manufacture difficult. Therefore, the N content should be 0.15% or less. , Preferably not less than 0.04% and not more than 0.13%.

Nb: Nb produces fine carbides, or nitrides, and inhibits grain growth of the crystal by the pinning effect. In other words, it is an element effective for miniaturization of crystal grains. Therefore, it contains 0.01% or more of Nb. However, if the Nb content is excessively large, recrystallization is inhibited, and there is an adverse effect that a large amount of the non-recrystallized portion remains after the annealing. Further, the addition of a large amount of Nb directly leads to an increase in cost of the material. Therefore, the upper limit value is 0.50%. , Preferably not less than 0.02% and not more than 0.20%.

The chemical composition of the steel according to the present invention is constituted such that the following Md30 value and Ni equivalent are each contained in a range that satisfies the amounts defined below, and the remaining amount is Fe and impurities.

Md30 value: The Md30 value is an index of easiness of production of the processed organic martensite expressed by the formula (1). Qualitatively, if the value of Md30 is large, the processed organic martensite tends to be generated at the time of cold rolling. As described above, in order to make the metal structure at the time of annealing a fine-grained austenite structure, at least 90% of the metal structure after the cold-rolling before annealing needs to be the processed organic martensite. For this, the value of Md30 is set to 20 DEG C or higher. However, if the Md30 value is excessively large, the amount of the processed organic martensite excessively increases in the production process, and the rolling efficiency is remarkably deteriorated. Therefore, the upper limit value is set to 60 deg. The temperature is preferably 30 ° C or more and 50 ° C or less.

[Equation 1]

Ni equivalent: Ni equivalent is an index indicating the stability of the austenite phase at the time of annealing, expressed by the following formula (2). Qualitatively, when the Ni equivalent is high, the austenite phase is stabilized. In order to transform the processed organic martensite produced by cold rolling into an austenite phase at the time of annealing, it is necessary to set the Ni equivalent to 9.5% or more. Preferably, it is 9.8% or more.

&Quot; (2) "

(% By mass),% Si is the content of Si (% by mass),% Mn is the content of Mn (% by mass) (% By mass),% Cr represents the content of Cr (mass%),% Ni represents the content of Ni (mass%),% Cu represents the content of Cu (mass%) and% Mo represents the content of Mo (mass%).

About the inclination angle (orientation difference) of the crystal boundary

In the present invention, the ratio of crystal boundaries having an inclination angle (azimuth difference) of 15 degrees or more among the crystal boundaries having an inclination angle (azimuth difference) of 2 degrees or more is defined as 95% or more. Hereinafter, even when not specifically defined, the ratio of crystal boundaries is a ratio to a crystal boundary having an inclination angle (azimuth difference) of 2 DEG or more.

Here, the "tilt angle" refers to the difference in the angle of the crystal orientation (axis) of two adjacent crystals in a crystal boundary (that is, a crystal grain boundary). Qualitatively, the smaller the tilt angle, And are directed in the same direction. If the ratio of the small crystal boundaries is large, it is easy to form coarse regions in which the crystal grains in which the crystal orientations are aligned are gathered, as shown in Fig. 1 (a). On the contrary, when the ratio of the crystal boundaries having a large " tilt angle " is large, the crystal orientations of the respective crystal grains are different from each other, and when the etching process is performed, the etched surface is smoothed. 1 (b).

More specifically, the inclination angle is measured by EBSP, the inclination angle is represented by color classification, and this can be obtained by using the line segment method.

As described above, since the coarse region in which the crystal grains having the crystal orientation aligned is gathered, only that portion is not selectively dissolved or dissolved, if there is such a coarse region, the unevenness of the etched surface becomes large. That is, when the ratio of the crystal boundaries in which the azimuth difference of adjacent crystals greatly differs becomes large, the etching surface becomes smooth. Specifically, the ratio of crystal boundaries having an inclination angle of 15 degrees or more among the crystal boundaries having an inclination angle of 2 degrees or more is set to 95% or more.

Average crystal grain diameter: As the average crystal grain diameter becomes smaller, the illuminance of the etching surface becomes smaller. This effect is particularly remarkable when the average grain diameter is 5 占 퐉 or less, and the average grain diameter is 5 占 퐉. In order to further demonstrate the effect, 3 mu m or less is preferable.

The crystal boundary is defined as a boundary with a crystal orientation difference of 15 degrees or more, and an average crystal grain size is defined as an average grain size of crystal grains surrounded by a boundary having a crystal orientation difference of 15 degrees or more. The average grain diameter is calculated by the quadratic method from the EBSP orientation difference map at the center of the plate thickness.

Next, a manufacturing method of the stainless steel sheet for etching according to the present invention will be described. The hot rolling may be performed in the same manner as the conventional method. In the present invention, the annealing as the final finishing treatment and the operating conditions of the cold rolling performed prior to the annealing are specified, thereby exerting desired effects. There are no particular restrictions on cold rolling and subsequent annealing.

In the production method of the present invention, as described above, in order to obtain smoothness of a good etched surface, the ratio of boundaries having an inclination angle of 15 degrees or more is 95% or more, and the average diameter of the crystal grains surrounded by these boundaries It is important that the thickness is 5 mu m or less. If there is a coarse region in which the nuclei of the? Grains are not generated at the time of the final annealing, the region remains as a coarse region where the crystal grains divided by only a small inclination angle after the annealing collect. In other words, since the nuclei of the? Particles are generated by the simultaneous multiple distribution at the time of the final annealing, these particles inhibit ingrown growth of each other, and a tissue excellent in smoothness of the above-mentioned etched surface can be obtained.

In addition, the nuclei of the? Particles generate defects such as grain boundaries and dislocations as sites. Since the processed organic martensite phase contains many dislocations as compared with the austenite phase, it is effective to discharge a large amount of the processed organic martensite at the time of cold rolling.

In addition, the processed organic martensite produced by cold rolling is usually a flat, thin and long lath-shaped martensite as shown in Fig. 2 (a). The boundary of the lath effectively functions as a nucleation site of the? Particle. 2 (b), if the lath is also divided into a plurality of cell-shaped martensite, the boundary of the cell becomes the nucleation site of the? At the time of annealing, nuclei of gamma particles can be generated simultaneously at many more places. In order to make the average diameter of crystal grains (recrystallized grains) surrounded by these boundaries (grain boundaries) to be not larger than 5 탆, the ratio of the boundaries having an inclination angle of 15 ° or more is 95% or more. In this cold- Of martensite is generated.

The amount of alpha '(processed organic martensite) produced in the cold rolling becomes larger as the reduction rate (plate thickness reduction rate) is larger.

For example, in [0024] of the above-mentioned Patent Document 2 (Japanese Patent No. 3562492), "the rolling reduction at the time of cold rolling before the final annealing is not particularly limited, and a reduction ratio of about 40% . However, in the present invention, in order to produce as large a quantity as possible before the final annealing, the reduction rate (plate thickness reduction rate) during cold rolling is preferably 50% or more, and more preferably 70% or more. However, under industrially mass production conditions, it is difficult to sufficiently generate cell-shaped martensite simply by increasing the reduction rate. In order to sufficiently generate martensite in a cell shape, it is necessary to control the temperature and tension of cold rolling.

Concretely, in order to produce the cell-shaped martensite, cold rolling is carried out by multipass rolling and each pass is performed at a temperature of 35 DEG C or less, a rolling speed of 200 m / min or less, and a tensile force of 30 kg / , And the total plate thickness reduction rate in cold rolling is set to 50% or more.

When the cold rolling starting temperature exceeds 35 캜, sufficient cell-shaped martensite is not produced. Therefore, in all passes of cold rolling, the rolling starting temperature is set to 35 캜 or lower. Control of the rolling start temperature is largely accomplished in two ways.

One is to suppress the heat itself by cold rolling. For this purpose, it is effective to make the cold rolling a multiple pass rolling and to reduce the reduction rate per pass. Concretely, it is desirable to set the reduction rate of each pass to 20% or less at the maximum.

The other method is to sufficiently cool the plate after each pass. For this purpose, the rolling speed is preferably 200 m / min or less, more preferably 180 m / min or less. In addition, it is effective to leave a sufficient cooling interval between the passes until the temperature of the plate becomes 35 DEG C or less, and in the case of reverse rolling, it is effective to remove the coil from the rolling mill once and to perform rolling after cooling.

Further, during cold rolling, a tension is applied in the rolling direction by the take-up reel. By setting the tensile strength to 30 kg / mm 2 or more, more preferably 40 kg / mm 2 or more, the compressive stress in the plate thickness direction due to rolling and the tensile stress in the longitudinal direction of the plate due to the tensile force of the reels match, A large deformation is given to the steel sheet, and a large amount of cell-shaped martensite can be generated. In addition, by applying tensile stress, there is an effect that the deformation applied is uniform in the thickness direction. By applying a tensile force, the friction between the plate and the roll at the time of rolling is reduced, thereby suppressing the heat generation at the time of rolling. Conventionally, when the tensile force at the time of cold rolling is too large, there is a problem of cracking of the edge of the end portion of the rolled steel sheet and cracking of the plate, so that it is generally made less than 30 kg / mm < 2 >. However, according to the present invention, when the C content is 0.03% or less, ductility is ensured and rolling can be carried out with a tension of 30 kg / mm 2 or more.

The annealing finally performed after the cold rolling is carried out at an annealing temperature of 950 DEG C or lower in order to suppress grain growth. However, if the annealing temperature is too low, a large amount of unrecrystallized portion remains, so the lower limit value is set at 700 캜. In the case of continuous annealing, the annealing time is 2 to 300 seconds, usually 30 to 120 seconds, as the cracking time (time to maintain the predetermined temperature).

After the final annealing, a fine grain structure is formed with a small amount of non-recrystallized portions, and temper rolling may be performed for performance adjustment such as hardness. Depending on the degree of the temper rolling, the processed organic martensite is produced. However, since this martensite is produced in the form of the original? -Particles or a smaller region, the processed organic martensite produced from the fine? Dispersed. As a result, the surface to be etched is smoothed like before the temper rolling. On the other hand, in the case of a non-recrystallized portion having many unrecrystallized portions or a coarse? -Particle structure at the time of final annealing, martensite regions are not dispersed by temper rolling and martensite having similar orientations are produced as agglomerates. The smoothness of the substrate is lowered.

Example

EXAMPLES Next, the present invention will be described in more detail with reference to Examples.

Table 1 shows the chemical compositions of the steel materials. Among the components, those other than the scope of the present invention are indicated by underlining the numerical value of the content. In Table 1, A to E are chemical compositions that satisfy the requirements of the present invention, and F to L are chemical compositions for comparison that do not satisfy the requirements.

A small ingot having the chemical composition of A to L shown in Table 1 was dissolved and subjected to one to three repetitions of cold rolling and annealing after cutting, hot rolling, annealing and descaling. Thereafter, cold rolling (multi-pass rolling) and final annealing were performed under the conditions shown in Table 2 collectively. Test pieces were taken from the obtained steel sheet having a thickness of 0.4 mm and various characteristics were investigated by the following method. The maximum rolling speed means the maximum speed during a plurality of passes in the cold rolling before the final annealing and the minimum tension means the minimum tensile force during a plurality of passes in the same cold rolling.

Percentage of crystal boundaries having an inclination angle of 15 degrees or more: The cross section perpendicular to the rolling direction was cut out, embedded, polished, and then the orientation difference map of EBSP was measured. A crystal boundary having an inclination angle of less than 2 to 15 DEG and a crystal boundary having an inclination angle of 15 DEG or more were distinguished from each other and a ratio of a crystal boundary having an inclination angle of 15 DEG or more to the length of the entire boundary was calculated.

Average grain diameter: The grain boundaries are defined by the boundaries of the adjacent crystal grains exceeding 15 degrees, and the average grain diameter is calculated by the quadratic method from the EBSP bearing difference map at the center of the plate thickness.

Cr carbide present: The surface of the specimen was cut by 10 탆 by chemical polishing, and the diffraction peak was measured with an X-ray diffractometer. The characteristic X-ray was a Co-K? Line, and the 2? Range was 20 to 100 °. Cr carbide was observed in the presence of diffraction peaks of Cr ₂₃ C ₆ and Cr ₇ C ₃ , and no Cr carbide was observed in which the same peak was not observed.

Etching surface roughness: The specimen cut to a length of 20 mm was immersed in the etching solution for 600 seconds. The etching solution was a ferric chloride solution (specific gravity: 1.41) at a liquid temperature of 40 占 폚. The average roughness Ra of the surface of the specimen after immersion and the average length RSm of the roughness curve elements (interval between concavities and convexities) were measured with a laser microscope. The measurement area of the average roughness Ra was a surface of 100 mu m x 100 mu m, and the average value of the results of the measurement at each of the three positions was used as a measurement value. The measurement area of the average length RSm of the roughness curve elements was a line of 200 mu m, and the average value of the results measured at three positions of each of the test pieces was taken as a measured value. As a criterion required for precision machining, there is no Cr carbide, and Ra ≤ 0.35 mu m and RSm ≤

The steel sheets 1 to 6 in Table 2 satisfy the requirements of the present invention and have excellent etching surface roughness. The steel sheets 7 to 17 are inferior in the illuminance of the etching surface in the comparative steel sheet. The steel sheets 7 to 10 satisfy the composition of the present invention, but the ratio of the boundary with an inclination angle of 15 degrees or less is small, so that the illuminance of the etching surface is poor. The comparative steels 11 to 17 do not satisfy the composition of the present invention, and the etching surface is poor in illuminance.

Claims (4)

In terms of% by mass,
C: not less than 0.001% and not more than 0.03%
Si: more than 0% and not more than 1.0%
Mn: more than 0% to 1.5%
Mo: 2.0% or less,
Cr: 12.0% or more and 20.0% or less,
Ni: not less than 4.5% and not more than 9.0%
Cu: 1.5% or less,
N: not less than 0.03% but not more than 0.15%
Nb: 0.01% or more and 0.50% or less,
The balance being Fe and impurities,
The Md30 value represented by the following formula (1) is 20 占 폚 or more and 60 占 폚 or less, the Ni equivalent represented by the following formula (2) is 9.5%
In the metal structure, a ratio of a crystal boundary having an inclination angle of 15 degrees or more among the crystal boundaries having an inclination angle of 2 degrees or more is 95% or more, and an average diameter of crystal grains surrounded by a crystal boundary having an inclination angle of 15 degrees or more is 5 占 퐉 or less , An austenitic stainless steel sheet.
[Equation 1]

&Quot; (2) "

(% By mass),% Si is the content of Si (% by mass),% Mn is the content of Mn (% by mass) (% By mass),% Cr represents the content of Cr (mass%),% Ni represents the content of Ni (mass%),% Cu represents the content of Cu (mass%) and% Mo represents the content of Mo (mass%). The austenitic stainless steel sheet according to claim 1, wherein the stainless steel sheet is subjected to temper rolling. In terms of% by mass,
C: not less than 0.001% and not more than 0.03%
Si: more than 0% and not more than 1.0%
Mn: more than 0% to 1.5%
Mo: 2.0% or less,
Cr: 12.0% or more and 20.0% or less,
Ni: not less than 4.5% and not more than 9.0%
Cu: 1.5% or less,
N: not less than 0.03% but not more than 0.15%
Nb: 0.01% or more and 0.50% or less,
The balance being Fe and impurities,
A method for producing a steel sheet by subjecting a steel sheet having an Md30 value of 20 deg. C or higher and 60 deg. C or lower and represented by the following formula (1) and having an Ni equivalent of 9.5% or higher as expressed by the following formula (2) to hot rolling and cold rolling, ,
The cold rolling is carried out by multipass rolling and each pass is performed at 35 DEG C or less, at a rolling speed of 200 m / min or less, and at a tensile force of 30 kg / mm &
The total plate thickness reduction ratio in the cold rolling is set to 50% or more,
Wherein the annealing is performed at a temperature of 700 ° C or more and 950 ° C or less.
[Equation 1]

&Quot; (2) "

(% By mass),% Si is the content of Si (% by mass),% Mn is the content of Mn (% by mass) (% By mass),% Cr represents the content of Cr (mass%),% Ni represents the content of Ni (mass%),% Cu represents the content of Cu (mass%) and% Mo represents the content of Mo (mass%). The method of claim 3,
And the temper rolling is performed after the annealing.

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