WO2016043125A1

WO2016043125A1 - Austenitic stainless steel plate

Info

Publication number: WO2016043125A1
Application number: PCT/JP2015/075765
Authority: WO
Inventors: 正美澤田; 善久白井; 渋谷　将行; 勇人喜多; 孝一武内
Original assignee: 新日鐵住金株式会社
Priority date: 2014-09-17
Filing date: 2015-09-10
Publication date: 2016-03-24
Also published as: KR20170056007A; CN107075651B; JPWO2016043125A1; JP5939370B1; SG11201701799RA; CN107075651A; KR101939926B1

Abstract

　An austenitic stainless steel sheet having a chemical composition that contains no more than 0.03% of C, no more than 1.0% of Si, no more than 1.5% of Mn, 15.0-20.0% of Cr, 6.0-9.0% of Ni, and 0.03-0.15% of N, the remainder being Fe and inevitable impurities; the Md30 value as computed from 497‒462(C+N)‒9.2(Si)‒8.1(Mn)‒13.7(Cr)‒20(Ni+Cu)‒18.7(Mo) being 30-50°C; the average amount of deformation-induced martensite being no more than 5.0% by volume; the average austenite grain diameter being no more than 5.0 μm; and the X-ray diffraction half width of the γ(220) phase at both the sheet surface and the sheet center being 0.50° or greater, the difference between these not exceeding 0.10°. This steel plate is suitable, e.g., as a laser metal mask.

Description

Austenitic stainless steel sheet

The present invention relates to an austenitic stainless steel sheet.

An austenitic stainless steel sheet is used for precision processing, particularly photoetching processing, and processing for which heat is subsequently applied by diffusion bonding or the like. Photo-etching is a method that forms a pattern by the photoresist method on the surface of the metal plate that is the material, then melts the metal plate by etching by spraying or dipping, and processes the metal plate into almost the same shape as the photoresist pattern It is. Laser processing is a processing method in which holes or predetermined patterns are formed by melting the surface of a metal plate with a laser based on CAD data or the like.

Since the metal plate thus processed is used for a metal mask or the like, the material of the metal plate is required to have excellent flatness and high hardness. In particular, in the case of photoetching processing, a smut is used. In order to suppress it, it is required that it has a low carbon content, that the etching surface is smooth, and that the warpage is small even after half-etching.

In addition, recently, the number of cases where heat exchangers and complicated flow path parts are manufactured by laminating stainless steel plates that have been subjected to photo-etching processing or laser processing and performing diffusion bonding processing at about 700 ° C. or higher is increasing. Yes. For such applications, in addition to the above-described characteristics, good bondability and small volume change and shrinkage after heating are also required.

For example, Patent Document 1 discloses that a material for photo-etching is flattened and stress-relieved by a method (tension annealing method) in which heat treatment is performed while applying tension after adjusting the hardness of a stainless steel foil by temper rolling. A method for achieving this is disclosed.

In Patent Document 2, after adjusting the hardness of the austenitic stainless steel strip by temper rolling, correction is performed with a tension leveler, and then a tension corresponding to 0.7 to 1.0 times the 0.2% proof stress. And a method of manufacturing a stainless steel plate having excellent flatness after etching by performing an annealing treatment at 700 to 800 ° C. is disclosed.

The stainless steel plate manufactured by the method disclosed in Patent Document 2 is internally annealed at 700 to 800 ° C. to eliminate the processing strain applied to the material by temper rolling and tension leveler correction. Residual stress is reduced, and warpage after half etching is suppressed. In addition, this stainless steel sheet is characterized in that, when annealed at 700 to 800 ° C., martensite reversely transforms into austenite, so that volume change and ripening shrinkage are small even when heat is applied during subsequent diffusion bonding.

Further, in Patent Document 3, as stainless steel having excellent diffusion bonding properties, the average crystal grain size in the foil thickness direction is 0.001 to 5 μm, and the Al content having fine crystal grains is 0.5 to 8% ( In this specification, “%” relating to chemical composition means “mass%” unless otherwise specified).

Japanese Examined Patent Publication No. 4-69229 Japanese Patent No. 3573447 Japanese Patent No. 3300285

The method disclosed in Patent Document 1 requires special annealing equipment that can apply tension to the stainless steel foil in the furnace, or in order to sufficiently relieve stress, the plate is passed at a low temperature of about 400 ° C. at a low speed. Therefore, there is a problem in that the productivity is lowered and the manufacturing cost of the photoetching processing material is increased.

In addition, some stainless steel foils manufactured by the method disclosed in Patent Document 1 satisfy the required characteristics during photoetching, but the volume change and thermal shrinkage during diffusion bonding after photoetching are large. There is also the problem that there are things. This problem is the same when heat is applied by laser processing. According to the examination results of the present inventors, this problem is that the work-induced martensite generated by temper rolling remains after the tension annealing, and therefore, when heat is applied during subsequent diffusion bonding, This is thought to be due to the reverse transformation to austenite.

The stainless steel sheet manufactured by the method disclosed in Patent Document 2 has a problem that sufficient hardness cannot be obtained with a low carbon content material due to the disappearance of processing strain.

Furthermore, although the invention disclosed in Patent Document 3 is directed to ferritic stainless steel, it is considered that diffusion bonding properties may be improved by making crystal grains fine even in austenitic stainless steel.

The object of the present invention is not obtained by the inventions disclosed in Patent Documents 1 and 2, but includes the required characteristics (characteristic I) at the time of two photoetching and laser processing listed below, diffusion bonding, laser processing, and the like. To provide an austenitic stainless steel sheet suitable for materials used for precision processing, such as for laser metal masks, and a method for producing the same, which can satisfy required characteristics (characteristic II) when used in applications where heat is applied. It is.

(Characteristic I) As required characteristics at the time of photoetching or laser processing, the material is flat, has high hardness, and further has a low carbon content in order to suppress smut at the time of photoetching, half The warpage is small after the etching process, and the etched surface and laser processed surface are smooth.

(Characteristic II) As a required characteristic when used in applications where heat is applied by diffusion bonding or laser processing, volume change and shrinkage due to heating are small.

FIG. 1 (a) to FIG. 1 (c) are explanatory views conceptually showing the distribution of processing strain inside and on the plate surface.

As shown in FIG. 1A, the processing strain distribution of the plate after correction by conventional temper rolling and tension leveler becomes a distribution that increases on the plate surface and decreases on the inside of the plate. When half-etching is performed in this state, the compressive stress in the vicinity of the plate surface is released, and the half-etched surface is warped.

On the other hand, as disclosed in Patent Document 2, annealing is performed at 700 to 800 ° C. for about 30 seconds to 10 minutes (SR treatment: an abbreviation for stress relief, heat treatment mainly for removing residual stress). Thus, as shown in FIG. 1B, it is possible to eliminate the processing strain of the entire plate including the plate surface and the inside of the plate, and the occurrence of warpage after half etching is surely suppressed. However, as described above, since the processing strain disappears, the hardness of the plate is lowered, and the characteristics recently required as an etching material may not be satisfied.

As a result of intensive studies in order to solve these problems, the present inventors, as shown in FIG. 1 (c), do not eliminate the processing strain of the entire plate by SR processing, but provide a constant processing strain. It has been found that the hardness required as an etching material can be satisfied while suppressing the occurrence of warpage after half-etching by remaining uniformly in the plate thickness direction.

However, by simply lowering the temperature of the conventional SR treatment, processing-induced martensite (α ′) generated by temper rolling and tension leveler correction remains, and the volume change during diffusion bonding becomes large. Further, if the SR treatment is simply shortened, the processing-induced martensite (α ′) disappears, but the processing strain does not disappear, and the warpage after half etching increases.

FIG. 2A to FIG. 2C are explanatory diagrams showing various SR processing conditions.
Therefore, as a result of further studies, the present inventors have found that in order to have a uniform processing strain in the plate thickness direction as shown in FIG. 1C and to reduce the amount of processing-induced martensite, FIG. As in the conventional SR treatment conditions shown in FIG. 5), the reverse transformation of work-induced martensite to austenite and the disappearance of work strain are not simultaneously performed by high-temperature and long-time heat treatment, but by temper rolling and a tension leveler. After the correction, as shown in FIG. 2 (b) and FIG. 2 (c), the plate thickness is heated to 700 to 800 ° C. at a temperature rising rate of 10 ° C./second or more at this temperature range for 10 seconds or less. Heat treatment X that reversely transforms the processing-induced martensite to austenite by applying a heat treatment that cools at a cooling rate of 10 ° C./second or more on the plate surface after holding, and 1 in a temperature range of 600 ° C. or more and less than 700 ° C. Was found that by heat treatment of holding sec is possible to adopt a SR process condition with the heat treatment Y step of adjusting the working strain are effective.

The order of the heat treatment X process and the heat treatment Y process is not limited, and the heat treatment Y process may be performed after the heat treatment X process is performed, or the heat treatment Y process may be performed after the heat treatment Y process is performed. Good. In either case, the characteristics required by the present invention can be satisfied. In addition, it is possible to satisfy the characteristics required in the present invention even if the heat treatment Y process is continuously performed following the heat treatment X process, or the heat treatment X process is continuously performed subsequent to the heat treatment Y process. is there.

In the chemical composition targeted by the present invention, work-induced martensite generated by cold rolling or further tension leveling is transformed back to austenite in a shear type (non-diffusion), and thus disappears even in the short holding time as described above. .

Since the austenitic stainless steel sheet provided by the present invention is reduced in work-induced martensite (α ′) in this way, the volume change due to reverse transformation of work-induced martensite to austenite during heating of diffusion bonding, etc. Is suppressed. Similarly, when heat is applied by laser processing or the like, the shape change due to the reverse transformation of processing-induced martensite to austenite on the processed surface is suppressed.

On the other hand, almost all of the processing strain remains when the SR treatment at 700 ° C. or higher is performed in a short time, so that a constant processing strain remains uniformly in the thickness direction as shown in FIG. I can't let you. However, by performing the SR treatment for an appropriate time in a lower temperature region, diffusion near the surface with a large amount of processing strain proceeds with priority, and a constant processing strain is applied in the plate thickness direction as shown in FIG. It becomes possible to remain uniformly.

In addition, in order to quantitatively evaluate the processing strain, the half width of the peak obtained by X-ray diffraction measurement can be used. If the amount of strain is large, the distance between crystal lattices expands and contracts from the original length, and the behavior appears in the half width of the peak obtained by X-ray diffraction measurement. That is, as the amount of strain increases, the distance between crystal lattices increases from the original length to a longer or shorter distance, and the peak half-value width increases.

The present invention is listed below.
% By mass
C: 0.03% or less,
Si: 1.0% or less,
Mn: 1.5% or less,
Cr: 15.0-20.0%,
Ni: 6.0 to 9.0%,
N: 0.03-0.15%,
Nb: 0 to 0.50%,
V: 0 to 0.50%,
Ti: 0 to 0.20%,
Cu: 0 to 1.5%,
Mo: 0 to 2.0%,
The balance is Fe and inevitable impurities,
The Md30 value calculated by the following formula (1) has a chemical composition of 30.0 to 50.0 ° C.,
The average value of the processing induced martensite amount is 5.0% or less in volume ratio,
The average value of the austenite particle size is 5.0 μm or less,
An austenitic stainless steel sheet having a metal structure in which the X-ray diffraction half-value width of the γ (220) phase at each of the plate surface and the plate center is 0.50 ° or more and the difference between them is 0.10 ° or less. .
Md30 value (℃) = 497-462 (C + N) -9.2 (Si) -8.1 (Mn) -13.7 (Cr) -20 (Ni + Cu) -18.7 (Mo) (1)
However, the element symbol in the formula (1) indicates the content of each element.

The austenitic stainless steel sheet according to the present invention is, for example, subjected to temper rolling at a rolling reduction of 30% or more on an austenitic stainless cold-rolled steel strip to adjust the hardness, and then according to a tension leveler as necessary. It can manufacture by performing the heat processing provided with the following heat processing X and the heat processing Y after performing correction.
Heat treatment X: a heat treatment in which heating is performed at a temperature increase rate of 10 ° C./second or more on the plate surface to 700 to 800 ° C. and maintained in the temperature range for 10 seconds or less, and then cooled at a cooling rate of 10 ° C./second or more on the plate surface;
Heat treatment Y: heat treatment for holding in a temperature range of 600 ° C. or higher and lower than 700 ° C. for 10 seconds or longer.

According to the present invention, the required characteristics during photoetching and laser processing (the material is flat, has high hardness, low carbon content to suppress smut during photoetching, and even after half-etching treatment) Small warpage, smooth etching surface and laser processing surface), and required characteristics when used in applications where heat is applied in diffusion bonding, laser processing, etc. (volume change and shrinkage due to heating are small) Thus, an austenitic stainless steel sheet having both of the above can be obtained. The austenitic stainless steel sheet of the present invention is suitable for materials used for precision processing such as for laser metal masks.

FIG. 1A to FIG. 1C are explanatory views conceptually showing the distribution of processing strain inside and on the plate surface. FIGS. 2A to 2C are explanatory diagrams showing various SR processing conditions.

A mode for carrying out the present invention will be described.
1. The austenitic stainless steel sheet according to the present invention is intended for metastable austenitic stainless steel, but from the viewpoint of the smoothness of the etched surface, the average crystal grain size is small, and there is no smut during etching. Desirably, the chemical composition is defined as follows.

(1-1) Chemical composition [C: 0.03% or less]
If the C content exceeds 0.03%, coarse Cr carbide precipitates at the crystal grain boundaries during production and causes smut generation during etching. Therefore, the C content is preferably small. However, since C is an element that can increase the strength of the steel sheet at a low cost, it may be contained in a range of 0.03% or less that does not adversely affect the smut. For this reason, C content is made into 0.03% or less. For applications in which smoothness after etching is strictly required, the C content is preferably 0.02% or less. The C content is preferably 0.012% or less.

[Si: 1.0% or less]
Si is used as a deoxidizing material during melting and contributes to strengthening of steel. However, if the Si content exceeds 1.0%, the etching rate is reduced. Therefore, the Si content is 1.0% or less. Desirably, it is 0.8% or less, More desirably, it is 0.6% or less. The Si content is more preferably 0.3% or less.

[Mn: 1.5% or less]
Mn contributes to prevention of brittle fracture during hot working and strengthening of steel. However, since Mn is a strong austenite-forming element, if the Mn content exceeds 1.5%, work-induced martensite generated during cold rolling decreases, and fine crystal grains can be obtained by subsequent annealing. Can not be. Therefore, the Mn content is 1.5% or less. Desirably, it is 1.2% or less.

[Cr: 15.0-20.0%]
Cr is a basic element of stainless steel. By containing 15.0% or more, Cr has an effect of forming a metal oxide layer on the surface of the steel material and improving corrosion resistance. However, since Cr is a strong ferrite stabilizing element, when the Cr content exceeds 20.0%, soot ferrite is generated, and this soot ferrite deteriorates the hot workability of the material. Therefore, the Cr content is 15.0% or more and 20.0% or less.

[Ni: 6.0 to 9.0%]
Ni is an austenite generating element and is an element for stably obtaining an austenite phase at room temperature. Therefore, the lower limit of the Ni content is 6.0%. A preferred lower limit is 6.1%. However, if the Ni content exceeds 9.0%, the austenite phase is excessively stabilized, and the work-induced martensitic transformation during cold rolling is suppressed. Furthermore, Ni is an expensive element, and an increase in the Ni content causes a significant increase in cost. Therefore, the upper limit of the Ni content is 9.0%. A preferable upper limit is 8.9%.

[N: 0.03-0.15%]
N, like C, is a solid solution strengthening element and contributes to improving the strength of steel. Further, N combines with Nb and precipitates as a fine Nb compound during annealing, and has the effect of suppressing crystal grain growth. For this reason, N content shall be 0.03% or more. However, if the N content exceeds 0.15%, a large number of coarse nitrides are generated in the manufacturing process of the steel sheet, and these coarse nitrides become the starting point of fracture, which significantly deteriorates hot workability. Make manufacturing difficult. Therefore, the N content is 0.15% or less. A preferable upper limit is 0.13%.

[Md30 value obtained by the above formula (1): 30.0 ° C. or higher and 50.0 ° C. or lower]
The metastable austenitic stainless steel targeted by the present invention utilizes the austenite ⇒ work-induced martensite (martensite) transformation during cold rolling and the work-induced martensite ⇒ austenite reverse transformation in the subsequent heat treatment, Fine crystal grains are obtained. The Md30 value is less than 30.0 ° C., the austenite stability is high, and sufficient work-induced martensite is hardly generated during cold rolling. On the other hand, if the Md30 value exceeds 50.0 ° C., the austenite stability is low, so the cold rolling load increases. Therefore, Md30 value shall be 30.0 degreeC or more and 50.0 degrees C or less. A preferred lower limit is 36.0 ° C and a preferred upper limit is 48.0 ° C.

[Nb: 0 to 0.50%]
[V: 0 to 0.50%]
[Ti: 0 to 0.20%]
Nb, V, and Ti are elements that generate fine carbides or nitrides, suppress the crystal grain growth by the pinning effect, and are effective in making the crystal grains of the material finer. The refinement of crystal grains contributes to an improvement in the smoothness of the etched surface. For this reason, you may contain these elements. However, if the content of Nb, V, Ti is too large, recrystallization is suppressed and there is an adverse effect that a large amount of unrecrystallized portions remain after annealing. In addition, the addition of a large amount of these elements directly increases the cost of the material. Therefore, the upper limit when these elements are contained is 0.50% for Nb and V, and 0.20% for Ti. The preferable lower limit of the content of these elements is 0.001% for Nb, 0.001% for V, and 0.001% for Ti.

[Mo: 0 to 2.0%]
Mo may be added as appropriate in order to improve the corrosion resistance of the material. However, if the Mo content exceeds 2.0%, etching is hindered, leading to an increase in cost. Therefore, when it contains Mo, the content shall be 2.0% or less. Desirably, it is 1.8% or less, more desirably 1.0% or less. A preferable lower limit of the Mo content is 0.001%.

[Cu: 0 to 1.5%]
Cu is an austenite-forming element and is an element capable of adjusting the stability of the austenite phase, so it may be added as appropriate. However, if the Cu content exceeds 1.5%, segregation occurs at the grain boundaries in the production process, and this grain boundary segregation significantly deteriorates hot workability and makes production difficult. Therefore, when Cu is contained, the upper limit of the content is set to 1.5%. Desirably, it is 1.4% or less. A preferable lower limit of the Cu content is 0.001%.

(1-2) Metallographic structure [Average value of processing-induced martensite amount: 5.0% or less by volume ratio]
When the amount of work-induced martensite is large, when heat is applied by diffusion bonding or laser processing, it transforms into an austenite phase, which causes a volume change. Therefore, the average value of the processing-induced martensite amount is set to 5.0% or less in volume ratio. The average value of the processing-induced martensite amount is calculated from the integrated intensity of the peak obtained by X-ray diffraction measurement (BDCullity, Element Of X-Ray Diffraction. Addison-Wesley, 1978). Specifically, the average value of the processing induced martensite amount is obtained by the following formulas (2) and (3). Here, C _γ and C _α are the volume fractions of the austenite phase and the martensite phase, respectively, I _γ and I _α are the integrated intensities of the X-ray diffraction peaks from the austenite phase and the martensite phase, and R _γ and R _α are It is a coefficient calculated | required by Formula (4). Where v is the unit cell volume, F is the structure factor, p is the multiplicity factor, Θ is the angle of incidence, and e ^−2M is the temperature factor.
C _γ + C _α = 1 (2)
I _γ / I _α = R _γ C _γ / R _α C _α (3)
^{R = (1 / v 2)} [F 2 p (1 + cos 2 2Θ) / (sin 2 ΘcosΘ)] (e -2M) ···· (4)

[Average value of austenite grain size: 5.0 μm or less]
By making the average value of the austenite grain size as small as 5.0 μm or less, the etched surface becomes smooth and the diffusion bonding property is further improved. Therefore, in the present invention, the upper limit of the average value of the austenite grain size is 5.0 μm.

The average value of the austenite particle size is calculated as follows. First, the vertical cross section in the rolling direction of the material is measured by EBSD, and a region surrounded by a boundary having an orientation difference of 15 ° or more is regarded as one crystal grain, and one crystal grain is determined from the number of crystal grains contained in a predetermined area. The average area S per unit is calculated, and from the average area S, the austenite particle size D obtained by the following formula (5) is calculated.
D = (2S / π) ^0.5 (5)

[X-ray diffraction half-value width of austenite γ (220) phase measured at each of the plate surface and the plate center: both 0.50 ° or more, the difference between these: 0.10 ° or less]
As described above, one of the basic ideas of the present invention is to control the distribution of strain in the thickness direction. In the present invention, in order to maintain the hardness of the material, it is necessary that the amount of strain on each of the plate surface and the plate center be a certain level or more, which is defined as a half width of 0.5 ° or more.

In addition, in order to suppress warpage and deformation of the plate during half-etching, etc., the difference in strain between the plate surface and the center of the plate must be small. The difference is defined as 0.1 ° or less.

In the X-ray diffraction measurement, Co—Kα ray is used for the characteristic X-ray, and the half width of γ (220) is used. The center of the plate thickness is measured on a polished surface that is masked on one side and chemically polished until the plate thickness is halved.

2. Production method (2-1) Temper rolling and straightening of tension leveler The austenitic stainless steel sheet according to the present invention is obtained by subjecting an austenitic stainless cold-rolled steel strip having the above-mentioned chemical composition to temper rolling at a reduction rate of 30% or more. Go and adjust the hardness. That is, the hardness is adjusted by temper rolling after finish annealing. More specifically, temper rolling is performed at a rolling reduction of 30% or more in order to ensure a hardness of about 304-H or higher, which is defined as HV370.

Since the austenitic stainless steel plate after temper rolling may be corrugated, it is desirable to correct the shape by applying a tension leveling treatment with a tension leveler in order to ensure flatness of the plate.

The temper rolling and the tension leveler correction may be performed by means commonly known as this type, and are not limited to specific means.

(2-2) SR treatment In the conventional SR treatment, as shown in FIG. 2 (a), the processing strain of the entire plate is eliminated as shown in FIG. It was.

On the other hand, the method of the present invention adjusts the processing strain by performing a heat treatment including the following heat treatment X and heat treatment Y.
Heat treatment X: Heat treatment X which is heated to 700 to 800 ° C. at a temperature rise rate of 10 ° C./second or more on the plate surface and kept in the temperature range for 10 seconds or less and then cooled at a cooling rate of 10 ° C./second or more on the plate surface ,
Heat treatment Y: heat treatment for holding in a temperature range of 600 ° C. or higher and lower than 700 ° C. for 10 seconds or longer.

The heat treatment in the method of the present invention may be any heat treatment including heat treatment X and heat treatment Y. For example, heat treatment Y may be performed after heat treatment X as shown in FIG. Alternatively, the heat treatment Y may be performed after the heat treatment Y. As a result, as shown in FIG. 1 (c), a constant processing strain can remain uniformly in the thickness direction, and the hardness required as an etching material is satisfied while suppressing the occurrence of warpage after half etching. Can be made.

In heat treatment X, when the rate of temperature rise is less than 10 ° C./second, the heat treatment temperature exceeds 800 ° C., the heat treatment time exceeds 10 seconds, or the cooling rate is less than 10 ° C./second, austenite Not only is the reverse transformation to excessive, but the processing strain is excessively relaxed, making it difficult to obtain the required strength. On the other hand, when the heat treatment temperature is as low as less than 700 ° C., the reverse transformation to austenite becomes insufficient. Therefore, after heating to 700 to 800 ° C. at a temperature increase rate of 10 ° C./second or more on the plate surface and holding in this temperature range for 10 seconds or less, cooling is performed at a cooling rate of 10 ° C./second or more on the plate surface. . The rate of temperature rise depends on the equipment performance to be used, but is preferably 50 ° C./second or less from the viewpoint of heating uniformly and suppressing shape defects due to thermal strain. The cooling rate is desirably 20 ° C./second or less. The heat treatment Y is held for 10 seconds or more in a temperature range of 600 ° C. or more and less than 700 ° C. from the viewpoint of eliminating only the processing strain in the vicinity of the steel sheet surface. The heat treatment time is desirably 180 seconds or less.

Further, as shown in FIG. 2B, when cooling in the heat treatment X, the heat treatment Y may be subsequently transferred, or as shown in FIG. It may be cooled to a lower temperature (for example, room temperature) and then reheated to perform the heat treatment Y.

By the above manufacturing method, the austenitic stainless steel sheet according to the present invention described above can be manufactured.

Table 1 shows the chemical compositions of steel types A to K used in this example. Steel types A to H satisfy the chemical composition defined in the present invention, and steel types I, J, and K do not satisfy the chemical composition defined in the present invention.

A small ingot having a chemical composition of steel types A to K was melted, and after cutting, hot rolling, annealing, and descaling were sequentially performed, cold rolling and annealing were repeated three times to obtain a sheet thickness of 0. A 2 mm stainless steel plate was used. The average crystal grain size of each stainless steel plate at this time is about 2 μm except for steel types I and J. Steel types I and J, which do not satisfy the chemical composition defined in the present invention, could not obtain a fine grain structure in the above process.

Then, after temper rolling at the temper rolling rate shown in Table 2, tension leveler correction was performed, and SR treatment was further performed under the conditions shown in Table 2. Then, the processing induction martensite ((alpha) ') amount measurement of the stainless steel plate which completed SR processing, the average value of an austenite particle size, X-ray-diffraction measurement, and cross-sectional hardness measurement were performed using the above-mentioned measuring method.

Furthermore, the average roughness of the etched surface after half etching, warpage, and the deformation rate after the heating test were measured.

Specifically, the roughness of the half-etched surface is obtained by masking one side of a 10 mm × 100 mm strip test piece and then chemically dissolving it from one side with a ferric chloride solution until the plate thickness is halved. The arithmetic average roughness measured with a contact-type roughness meter. The measurement direction was perpendicular to the rolling direction, the measurement length was 4 mm, and the average of the arithmetic average roughness measured five times was taken. The warpage after half-etching was measured for the subsequent curvature in the longitudinal direction. Furthermore, the deformation rate after the heating test was calculated from the ratio of the hole sizes before and after heating after making a hole with a diameter of 10 mm by photoetching in advance and heating at 1000 ° C. for 5 minutes.

Laminate bondability is obtained by stacking stainless steel plates as disk-shaped test pieces with a diameter of 8 mm, holding at 750 ° C. for 30 seconds while applying a load of 60 MPa, and holding the two test pieces after holding. Was marked with ◯, and unbonded was marked with ×.

In Table 2, the holding temperature of heat treatment Y means the ultimate temperature, and the holding time means the time during which the steel plate is heat-treated in the temperature range of 600 ° C. or higher and lower than 700 ° C.

The test results are summarized in Table 2.

Steel plates 1 to 11 in Table 2 are all examples of the present invention that satisfy the present invention. On the other hand, the steel plates 12 to 25 are comparative steels that do not satisfy the present invention.

Steel sheets 1 to 11 have a cross-sectional hardness of 392 to 415 Hv, an average roughness after half etching of 0.13 to 0.18 μm, a curvature of 0.0005 to 0.0020 mm ⁻¹ , and a deformation rate of 0 after a heating test. .015 to 0.020. The steel plates 1 to 11 have the above-mentioned features I and II, and it can be seen that they are precision working austenitic stainless steel plates suitable for laser metal masks, for example.

On the other hand, since the steel plate 12 has a C content outside the range of the present invention, the average value of the austenite grain size is not 7 μm and fine crystal grains, and as a result, the half-etched surface is inferior in smoothness. Lamination bondability was also unsatisfactory.

Since the steel plate 13 has an Md30 value smaller than the range of the present invention, the average value of the austenite grain size is not 8 μm and does not become fine crystal grains. As a result, the smoothness of the half-etched surface is inferior, and the lamination bondability is poor. there were.

Since the steel plate 14 had an Md30 value larger than the range of the present invention, a large amount of work-induced martensite (α ′) remained, and the deformation after the heating test was large.

Since the temper rolling rate of the steel sheet 15 was below the lower limit of the range of the present invention, the X-ray half width at each of the plate surface and the plate center was small, and the cross-sectional hardness was also small.

Since the steel plate 16 was subjected to SR treatment under conventional general conditions, almost no processing strain remained, so the X-ray half width was small and the cross-sectional hardness was also small.

Since the steel plate 17 is obtained by shortening the conventional general SR processing conditions for a short time, the processing induced martensite (α ′) amount is reduced, but the processing strain hardly disappears, and the plate surface and the plate center respectively. The difference in processing strain was almost unchanged, and the warpage after half-etching was large.

Since the steel plate 18 was obtained by lowering the temperature of conventional general SR processing conditions, a large amount of work-induced martensite (α ′) remained, and the deformation after the heating test was large.

The steel plate 19 is subjected to two stages of SR treatment. However, since the temperature increase rate of the first stage SR treatment is lower than the range defined in the present invention, a large amount of processing strain disappears and sufficient hardness is obtained. Was not obtained.

The steel plate 20 is subjected to two stages of SR treatment, but since the holding temperature of the first stage SR treatment is below the range defined in the present invention, a large amount of processing-induced martensite (α ′) remains. did.

The steel plate 21 is subjected to two stages of SR treatment. However, since the cooling rate of the first stage SR treatment is lower than the range defined in the present invention, a large amount of processing distortion disappears and sufficient hardness is obtained. It was not obtained.

The steel plate 22 is subjected to two stages of SR treatment, but since the second stage SR treatment temperature exceeds the range specified in the present invention, a large amount of processing distortion disappears and sufficient hardness is obtained. There wasn't.

The steel plate 23 is subjected to a two-stage SR treatment, and is performed in the order of a first-stage heat treatment for adjusting and eliminating processing strain and a second-stage heat treatment for performing reverse transformation of work-induced martensite to austenite. Carried out. Since the SR treatment holding time of the second stage heat treatment exceeds the range defined in the present invention, a large amount of processing strain disappears and sufficient hardness cannot be obtained.

The steel plate 24 is subjected to a two-stage SR treatment, and is performed in the order of a first-stage heat treatment for adjusting and eliminating work strain and a second-stage heat treatment for performing reverse transformation of work-induced martensite to austenite. Carried out. Since the SR treatment temperature of the second stage heat treatment was below the range specified in the present invention, a large amount of work-induced martensite remained, and the curvature after half etching and deformation after the heating test were large.

Further, since the steel plate 25 has not been subjected to SR treatment itself, in addition to a large amount of processing-induced martensite (α ′) remaining, the X-ray half width at the plate surface and the plate center increases, Both the warp after etching and the deformation rate after the heating test were unsatisfactory.

In this example, five types of steels A to H have been described as examples. However, the present invention is similarly applied to a metastable austenitic stainless steel having a chemical composition that does not depart from the scope of the present invention. Needless to say.

Claims

% By mass
C: 0.03% or less,
Si: 1.0% or less,
Mn: 1.5% or less,
Cr: 15.0-20.0%,
Ni: 6.0 to 9.0%,
N: 0.03-0.15%,
Nb: 0 to 0.50%,
V: 0 to 0.50%,
Ti: 0 to 0.20%,
Cu: 0 to 1.5%,
Mo: 0 to 2.0%,
The balance is Fe and inevitable impurities,
The Md30 value calculated by the following formula (1) has a chemical composition of 30.0 to 50.0 ° C.,
The average value of the processing induced martensite amount is 5.0% or less in volume ratio,
The average value of the austenite particle size is 5.0 μm or less,
An austenitic stainless steel sheet having a metal structure in which the X-ray diffraction half-value width of the γ (220) phase at each of the plate surface and the plate center is 0.50 ° or more and the difference between them is 0.10 ° or less. .
Md30 value (℃) = 497-462 (C + N) -9.2 (Si) -8.1 (Mn) -13.7 (Cr) -20 (Ni + Cu) -18.7 (Mo) (1)
However, the element symbol in the formula (1) indicates the content of each element.
The chemical composition contains, in mass%, one or more selected from Nb: 0.001 to 0.50%, V: 0.001 to 0.50%, and Ti: 0.001 to 0.20%. The austenitic stainless steel sheet according to claim 1.
The austenitic stainless steel sheet according to claim 1 or 2, wherein the chemical composition contains Cu: 0.001 to 1.5% and / or Mo: 0.001 to 2.0% by mass%. .