JP6658693B2 - Stainless steel plate - Google Patents

Description

The present invention relates to a stainless steel sheet, and more particularly to a stainless steel sheet used for kitchen equipment and building materials used in an environment where it comes into contact with moisture, indoor water products, vehicle materials, and the like.
In addition, as kitchen equipment, refrigerators, freezers, ranges, ovens, washing machines, disinfectors, sinks, countertops, cupboards, etc., wall materials and roof materials as building materials, and indoor water products Bathtubs, washing machines, etc., and vehicle materials include exterior materials.

Stainless steel sheets are widely used in various products such as kitchen appliances, building materials, bathtubs, and home appliances because of their beautiful appearance and excellent corrosion resistance.
In recent years, there has been a demand for a product which suppresses slime, mold, and the like due to various germs in consideration of not only corrosion resistance, but also hygiene and the environment, and is hardly stained.

  In response to such demands, development of a stainless steel plate that is hardly stained by hydrophilizing the surface and that is easy to wash and remove even when stains or the like adhere is being promoted.

For example, in Patent Document 1,
"Stainless steel containing 10 to 17% by mass of Cr, having a C content of 0.15% by mass or less, and a Si content of 1.0 to 6.0% by mass, and having a surface of 5 μm or less A high-strength duplex stainless steel strip and steel sheet having excellent hydrophilicity, characterized by having irregularities of 0.5 μm or more at intervals of.
Is disclosed.

Further, in Patent Document 2,
“C: 1.0% by mass or less, Si: 0.20 to 5.0% by mass, Mn: 2.0% by mass or less, Ni: 15.0% by mass or less, Cr: 10.0 to 30.0% by mass %, Al: 0.01% by mass or less, Nb + Ti: Less than 0.10% by mass (including 0), the balance being Fe and unavoidable impurities, and formed on the surface by finish bright annealing A hydrophilic stainless steel sheet, characterized in that the coating has a content of Si: 40 atomic% or more and Al: 10 atomic% or less with respect to the total of the elements of Si, Al, Fe, Cr and Mn constituting the coating. "
Is disclosed.

JP 11-279706 A JP 2007-119856 A

However, the technique disclosed in Patent Literature 1 has a multi-layer structure of a martensite phase and an austenite phase, and then preferentially corrodes the austenite phase by pickling to form fine irregularities, thereby increasing hydrophilicity. Since it is a technique to be obtained, it cannot be applied to a ferrite single phase or austenitic single phase stainless steel sheet.
In addition, since fine irregularities are formed on the surface, the aesthetic appearance after bright annealing finish may be impaired.

  In addition, in the technology disclosed in Patent Document 2, when the surface is contaminated with organic matter in the air, the effect of hydrophilization is easily lost.

  The present invention has been developed in view of the above situation, and does not impair the aesthetic appearance of the surface, and can maintain excellent hydrophilicity even when the surface is contaminated by organic matter in the air. It is an object to provide a stainless steel plate that can be used.

The inventors have conducted intensive studies in order to solve the above problems.
First, the inventors tried to reduce the effect of surface contamination on hydrophilicity by adjusting the composition of an oxide film formed on the surface by bright annealing.
However, simply adjusting the composition of the oxide film cannot reduce the effect of surface contamination on hydrophilicity to a certain level or more.

Next, the inventors tried to improve the hydrophilicity by imparting irregularities to the steel sheet surface.
In this case, although it is possible to reduce the effect of surface contamination on hydrophilicity as compared with the case where the composition of the surface oxide film is adjusted, if the steel sheet surface is roughened by pickling to form irregularities, It was found that the aesthetic appearance such as the surface gloss of the stainless steel plate was impaired.

Therefore, the inventors conducted further studies based on the above findings,
-While properly controlling the component composition, especially the amounts of Cr and Ti,
-Precipitates containing Cr and Ti are precipitated on the steel sheet surface during annealing, and then the steel sheet surface is subjected to etching under appropriate conditions to form projections having a shape as shown in FIG.
(Precipitates containing Cr and Ti remain undissolved by the etching process, while the stainless steel base iron portion immediately below the precipitates is hindered by the precipitates and is not dissolved from the top, but gradually from the surroundings. As a result, the precipitate is placed (supported) on a shaft-like portion made of ground iron of a stainless steel plate as shown in FIG. 1 on the steel plate surface, and at least a part of the precipitate is formed. A projection having a shape projecting in the radial direction from the tip of the shaft-like portion is formed, and the projection having such a shape is hereinafter referred to as a mushroom-shaped projection. In the protrusion, the precipitate is referred to as an umbrella portion, and the shaft-like portion made of ground iron is referred to as a handle portion.)
・ Appropriately control the number and shape of the protrusions on the steel sheet surface,
Thus, it has been found that excellent hydrophilicity can be obtained without impairing the appearance of the surface and reducing the influence of surface contamination on the hydrophilicity.

For this reason, the inventors consider as follows.
That is, by forming the protrusions having the above-mentioned shape finely and densely on the surface of the steel sheet, a unique geometrical structure due to the protrusions is generated on the steel sheet surface, and as a result, without impairing the appearance of the surface, The inventors believe that hydrophilicity can be improved while reducing the effect of surface contamination on hydrophilicity.
The present invention has been completed based on the above findings, and further studied.

That is, the gist configuration of the present invention is as follows.
1. A stainless steel plate having mushroom-shaped protrusions on the surface,
The above stainless steel sheet has a component composition containing Cr: 16.0-32.0% and Ti: 0.05-0.45%,
Further, the protrusion has an umbrella portion made of a precipitate containing Cr and Ti, and a handle portion that protrudes and supports the umbrella portion from the ground steel of the stainless steel plate,
The number of the protrusions is 1 or more per 1 μm ² ;
The average value d1 of the diameter of the umbrella portion is 20 nm or more and 300 nm or less, and
A stainless steel sheet in which a ratio d2 / d1 of an average value d2 of the diameter of the handle portion to d1 satisfies a relationship of the following expression (1).
0.20 <d2 / d1 <0.70 (1)

2. Wherein the component composition further comprises
C: 0.003-0.030%,
Si: 0.01-1.00%,
Mn: 0.01-1.00%,
P: 0.050% or less,
S: 0.030% or less,
Ni: 0.01-1.00%,
2. The stainless steel sheet according to 1 above, containing 0.001 to 0.200% of Al and 0.030% or less of N, and the balance being Fe and unavoidable impurities.

3. Wherein the component composition further comprises
Mo: 0.01-2.50%,
Cu: 0.01-0.80%,
Co: 0.01 to 0.50% and W: 0.01 to 3.00%
3. The stainless steel sheet according to the above 2, comprising one or more selected from the group consisting of:

4. Wherein the component composition further comprises
Nb: 0.01 to 0.60%,
Zr: 0.01-0.30%,
V: 0.01 to 0.30%,
Ca: 0.0003-0.0030%,
Mg: 0.0005-0.0050%,
B: 0.0003-0.0050%,
REM (rare earth metal): 0.001 to 0.100%,
Sn: 0.001 to 0.500% and
Sb: 0.001 to 0.500%
4. The stainless steel sheet according to any one of the above 2 or 3, wherein the stainless steel sheet contains one or more kinds selected from the group consisting of:

5. The stainless steel sheet according to any one of the above items 1 to 4, which is for kitchen equipment or building materials.

  According to the present invention, it is possible to obtain a stainless steel sheet that can maintain excellent hydrophilicity even when the surface is contaminated by organic matter in the air without impairing the appearance of the surface, By applying such stainless steel sheets to kitchen equipment and building materials used in environments that come into contact with moisture, it is possible to obtain products that are not only resistant to corrosion, but also have low hygiene and environmental considerations and are resistant to dirt. Become. Further, even when dirt adheres to the product, the dirt can be removed by simple washing or wiping.

It is an example of the TEM image (bright-field image) obtained by observing the projection formed on the surface of the stainless steel plate according to one embodiment of the present invention with a transmission electron microscope (TEM).

Hereinafter, the stainless steel sheet of the present invention will be described based on embodiments.
(1) Component Composition First, the reason why the component composition of the stainless steel sheet of the present invention is limited to the above range will be described. In addition, the unit of the content of each element in the component composition is “% by mass”, but hereinafter, it is simply indicated by “%” unless otherwise specified.
Cr: 16.0-32.0%
Cr is an important element for ensuring the corrosion resistance of stainless steel. In addition, Cr forms nitrides, carbides, carbonitrides, oxides, or a mixture thereof during annealing so that it precipitates together with Ti on the surface as a precipitate, and the umbrella of the protrusion on the final product plate. Is configured. Here, if the Cr content is less than 16.0%, the corrosion resistance required for stainless steel cannot be obtained. In addition, after appropriately controlling the Ti content as described below, by setting the Cr content to 16.0% or more, a precipitate containing a sufficient amount of Cr and Ti is formed during annealing, and as a result, A sufficient number of protrusions can be obtained on the final product plate. However, when the Cr content exceeds 32.0%, the workability decreases. Therefore, the Cr content is in the range of 16.0 to 32.0%. It is preferably at least 18.0%, more preferably at least 20.0%. Further, it is preferably at most 26.0%, more preferably at most 24.0%.

Ti: 0.05 to 0.45%
Ti forms nitrides, carbides, carbonitrides or oxides, or a mixture of these during annealing, thereby precipitating together with Cr on the surface as precipitates, forming an umbrella of projections on the final product plate. I do. Here, by setting the Ti content to 0.05% or more, a precipitate containing a sufficient amount of Cr and Ti is formed at the time of annealing, and as a result, a sufficient number of protrusions can be obtained in the final product plate. It becomes possible. However, when the Ti content exceeds 0.45%, the workability decreases. Therefore, the Ti content is in the range of 0.05 to 0.45%. It is preferably at least 0.10%, more preferably at least 0.15%, even more preferably at least 0.20%. Further, it is preferably at most 0.40%, more preferably at most 0.35%, further preferably at most 0.30%.

  As long as the stainless steel satisfies the above component ranges of Ti and Cr, other components are not particularly limited, but from the viewpoint of strength and workability, for example, Cr: 16.0 to 32.0% and Ti : 0.05 to 0.45%, C: 0.003 to 0.030%, Si: 0.01 to 1.00%, Mn: 0.01 to 1.00%, P: 0.050% or less, S: 0.030% or less, Ni: 0.01 to 1.00%, It is preferable that the composition contains Al: 0.001 to 0.200% and N: 0.030% or less, with the balance being Fe and unavoidable impurities.

C: 0.003 to 0.030%
When C is increased, the strength is improved, while when C is reduced, workability and corrosion resistance are improved. Here, C is preferably contained in an amount of 0.003% or more in order to obtain sufficient strength. However, when the C content exceeds 0.030%, workability and corrosion resistance tend to decrease. Therefore, the C content is preferably in the range of 0.003 to 0.030%. More preferably, it is 0.005% or more. Further, it is more preferably at most 0.020%, further preferably at most 0.015%, still more preferably at most 0.010%.

Si: 0.01-1.00%
Si is an element useful as a deoxidizing agent. The effect is obtained when the Si content is 0.01% or more. However, when the Si content exceeds 1.00%, workability tends to decrease. Therefore, the Si content is preferably in the range of 0.01 to 1.00%. It is more preferably at least 0.10%. Further, it is more preferably at most 0.50%, further preferably at most 0.20%.

Mn: 0.01-1.00%
Mn has a deoxidizing effect, and its effect is obtained when the Mn content is 0.01% or more. However, when the Mn content exceeds 1.00%, workability and corrosion resistance tend to decrease. Therefore, the Mn content is preferably in the range of 0.01 to 1.00%. It is more preferably at least 0.10%. Further, the content is more preferably 0.25% or less, and further preferably 0.20% or less.

P: 0.050% or less P is an element that reduces corrosion resistance. In addition, segregation at the crystal grain boundaries lowers hot workability. Therefore, the P content is desirably as low as possible, and is preferably 0.050% or less. More preferably, it is 0.040% or less. More preferably, it is 0.030% or less. The lower limit of the P content is not particularly limited. However, excessive removal of P causes an increase in cost, so that it is preferably 0.005% or more.

S: 0.030% or less S promotes precipitation of MnS and lowers corrosion resistance. Therefore, the lower the S content, the better, and preferably 0.030% or less. It is more preferably at most 0.010%. More preferably, it is 0.004% or less. Note that the lower limit of the S content is not particularly limited, but excessive removal of S causes an increase in cost. Therefore, the lower limit is preferably set to 0.001% or more.

Ni: 0.01-1.00%
Ni is an element that effectively contributes to improvement in toughness and corrosion resistance in the gap. The effect is obtained when the Ni content is 0.01% or more. However, when the Ni content exceeds 1.00%, the susceptibility to stress corrosion cracking tends to increase. Furthermore, since Ni is an expensive element, the cost is increased. Therefore, the Ni content is preferably in the range of 0.01 to 1.00%. It is more preferably at least 0.10%. Further, it is more preferably at most 0.50%, further preferably at most 0.30%.

Al: 0.001 to 0.200%
Al is an element useful for deoxidation. The effect is obtained when the Al content is 0.001% or more. However, when the Al content exceeds 0.200%, Al is preferentially oxidized or nitrided during annealing, so that a film mainly composed of Al is easily formed on the surface of the steel. There is a possibility that generation of precipitates may be suppressed. Therefore, the Al content is preferably in the range of 0.001 to 0.200%. It is more preferably at least 0.010%, further preferably at least 0.020%, even more preferably at least 0.030%. Further, the content is more preferably 0.150% or less, further preferably 0.100% or less, and still more preferably 0.050% or less.

N: 0.030% or less If the N content exceeds 0.030%, corrosion resistance and workability may be reduced. Therefore, the N content is preferably set to 0.030% or less. It is more preferably at most 0.020%. More preferably, it is 0.015% or less. The lower limit of the N content is not particularly limited, but is preferably 0.003% or more because excessive denitrification causes an increase in cost.

Further, the elements described below can be appropriately contained in the above-mentioned component composition.
Mo: 0.01-2.50%
Mo stabilizes the passivation film of stainless steel to improve corrosion resistance. This effect is obtained when the Mo content is 0.01% or more. However, when the Mo content exceeds 2.50%, the processability decreases. Therefore, when Mo is contained, the content is in the range of 0.01 to 2.50%. It is preferably at least 0.50%, more preferably at least 1.00%. Further, it is preferably at most 2.00%.

Cu: 0.01 to 0.80%
Cu is an element that enhances corrosion resistance. This effect is obtained when the Cu content is 0.01% or more. However, when the Cu content exceeds 0.80%, the hot workability decreases. Therefore, when Cu is contained, the content is in the range of 0.01 to 0.80%. Preferably it is 0.10% or more. Further, it is preferably 0.60% or less, more preferably 0.45% or less.

Co: 0.01-0.50%
Co is an element that enhances corrosion resistance. This effect is obtained when the Co content is 0.01% or more. However, if the Co content exceeds 0.50%, the processability decreases. Therefore, when Co is contained, the content is in the range of 0.01 to 0.50%. Preferably it is 0.10% or more. Further, it is preferably at most 0.30%.

W: 0.01 to 3.00%
W is an element that enhances corrosion resistance. This effect is obtained when the W content is 0.01% or more. However, when the W content exceeds 3.00%, the workability decreases. Therefore, when W is contained, the content is in the range of 0.01 to 3.00%. Preferably it is 0.10% or more. Further, it is preferably 0.80% or less, more preferably 0.60% or less.

Nb: 0.01 to 0.60%
Nb is an element that, by combining with C and N, prevents excessive precipitation of Cr carbonitride in steel and suppresses deterioration (sensitization) of corrosion resistance. These effects are obtained when the Nb content is 0.01% or more. On the other hand, if the Nb content exceeds 0.60%, the processability decreases. Therefore, when Nb is contained, the content is in the range of 0.01 to 0.60%. Preferably it is 0.40% or less, more preferably less than 0.20%.

Zr: 0.01 to 0.30%
Zr, like Nb, is an element that binds to C and N contained in steel and suppresses sensitization. This effect is obtained when the Zr content is 0.01% or more. On the other hand, when the Zr content exceeds 0.30%, the workability decreases. Therefore, when Zr is contained, the content is in the range of 0.01 to 0.30%. It is preferably at most 0.20%, more preferably at most 0.15%, even more preferably at most 0.10%.

V: 0.01 to 0.30%
V, like Nb and Zr, is an element that binds to C and N contained in steel and suppresses deterioration (sensitization) of corrosion resistance. This effect is obtained when the V content is 0.01% or more. On the other hand, if the V content exceeds 0.30%, the workability decreases. Therefore, when V is contained, the content is in the range of 0.01 to 0.30%. It is preferably at most 0.20%, more preferably at most 0.15%, even more preferably at most 0.10%.

Ca: 0.0003-0.0030%
Ca improves castability and improves manufacturability. The effect is obtained when the Ca content is 0.0003% or more. However, when the Ca content exceeds 0.0030%, it combines with S to generate CaS, and reduces the corrosion resistance. Therefore, when Ca is contained, the content is in the range of 0.0003 to 0.0030%. Preferably it is 0.0005% or more. Further, it is preferably 0.0020% or less.

Mg: 0.0005-0.0050%
Mg acts as a deoxidizer. This effect is obtained when the Mg content is 0.0005% or more. However, if the Mg content exceeds 0.0050%, the toughness of the steel may be reduced and the productivity may be reduced. Therefore, when Mg is contained, the content is in the range of 0.0005 to 0.0050%. Preferably it is 0.0020% or less.

B: 0.0003-0.0050%
B is an element that improves the brittleness of secondary processing. The effect is obtained when the B content is 0.0003% or more. However, when the B content exceeds 0.0050%, a precipitate containing B is formed, and the workability is reduced. Therefore, when B is contained, the content is in the range of 0.0003 to 0.0050%. Preferably it is 0.0005% or more. Further, it is preferably at most 0.0030%.

REM (rare earth metal): 0.001 to 0.100%
REM (rare earth metal: an element having an atomic number of 57 to 71 such as La, Ce, or Nd) is an element effective for deoxidation. The effect is obtained when the REM content is 0.001% or more. However, when the REM content exceeds 0.100%, hot workability decreases. Therefore, when REM is contained, the content is in the range of 0.001 to 0.100%. Preferably it is 0.010% or more. Further, it is preferably 0.050% or less.

Sn: 0.001 to 0.500%
Sn is an element that is effective for suppressing roughening of the processed surface. The effect is obtained when the Sn content is 0.001% or more. However, when the Sn content exceeds 0.500%, hot workability decreases. Therefore, when Sn is contained, the content is in the range of 0.001 to 0.500%. Preferably it is 0.010% or more. Further, it is preferably at most 0.200%.

Sb: 0.001 to 0.500%
Sb, like Sn, is an element that is effective in suppressing roughening of the processed surface. The effect is obtained when the Sb content is 0.001% or more. However, when the Sb content exceeds 0.500%, the processability decreases. Therefore, when Sb is contained, the content is in the range of 0.001 to 0.500%. Preferably it is 0.010% or more. Further, it is preferably at most 0.200%.

Components other than the above are Fe and inevitable impurities.
As described above, the preferred component composition of the stainless steel sheet of the present invention is, by mass%, C: 0.003 to 0.030%, Si: 0.01 to 1.00%, Mn: 0.01 to 1.00%, P: 0.050% or less, and S: 0.050% or less. : 0.030% or less, Cr: 16.0 to 32.0%, Ni: 0.01 to 1.00%, Ti: 0.05 to 0.45%, Al: 0.001 to 0.200% and N: 0.030% or less, if necessary,
Mo: 0.01 to 2.50%, Cu: 0.01 to 0.80%, Co: 0.01 to 0.50%, and W: One or more selected from 0.01 to 3.00%, and if necessary
Nb: 0.01 to 0.60%, Zr: 0.01 to 0.30%, V: 0.01 to 0.30%, Ca: 0.0003 to 0.0030%, Mg: 0.0005 to 0.0050%, B: 0.0003 to 0.0050%, REM (rare earth metal): 0.001 to It is a component composition containing one or more selected from 0.100%, Sn: 0.001 to 0.500% and Sb: 0.001 to 0.500%, with the balance being Fe and unavoidable impurities.

(2) Mushroom-shaped protrusion As described above, in order to obtain excellent hydrophilicity while maintaining the aesthetic appearance of the surface and reducing the influence of surface contamination, a mushroom-shaped protrusion must be provided on the surface of a stainless steel plate. It is important to form and properly control the number and shape of the projections on the steel sheet surface.

As shown in FIG. 1, the above-mentioned mushroom-shaped projections consist of an umbrella portion made of a precipitate containing Cr and Ti, and a handle portion projecting and supporting the umbrella portion from the ground iron of the stainless steel plate. It is configured. Here, as the precipitate constituting the umbrella, nitrides of Cr and Ti, carbides or carbonitrides or oxides, or a mixture thereof, etc., besides Cr and Ti, Fe, Al, Si, Mn or the like may be included.
Here, the constituents of the umbrella part are such that the precipitate (umbrella part) is peeled off from the protrusions on the steel sheet surface, and the separated precipitate is subjected to an energy dispersive X-ray analyzer attached to a transmission electron microscope (TEM). It can be determined from (EDX) analysis and the obtained EDX spectrum.
In addition, the mushroom type referred to here has an umbrella portion and a handle portion supporting the umbrella portion, and at least a part of the umbrella portion means a shape protruding in the radial direction from the tip of the handle portion. The shapes of the part and the handle are not particularly limited. The shape of the umbrella portion may be a substantially spherical shape, a substantially elliptical shape, a substantially hemispherical shape, a substantially semi-elliptical shape, or the like. In addition, examples of the shape of the handle include shapes such as a truncated cone and a truncated cylinder.

Number of protrusions: 1 or more per ² μm ² As described above, in order to obtain desired hydrophilicity, it is necessary that fine and dense protrusions exist on the steel sheet surface. Therefore, the number of protrusions on the surface of the steel sheet is set to 1 or more per 1 μm ² . Preferably, the number is 5 or more per 1 μm ² . More preferably, the number is 10 or more per 1 μm ² . The upper limit is not particularly limited, but is about 100 per 1 μm ² .

The number of protrusions on the surface of the steel sheet is determined as follows.
That is, the surface of a stainless steel plate was observed with a scanning electron microscope (FE-SEM) equipped with a cold-cathode field emission type electron gun at an acceleration voltage of 3 kV and a magnification of 30,000 times for 10 visual fields, and the secondary electron image was obtained. The number of protrusions per 1 μm ² is calculated by counting the number of protrusions observed in the photograph (SEM photograph) for each field of view and averaging them to determine the number of protrusions per 1 μm ^{2 on} the steel sheet surface. .

Average value of diameter of umbrella part d1: 20 nm or more and 300 nm or less As described above, in order to obtain desired hydrophilicity, it is necessary to finely and densely disperse the protrusions on the surface of the steel sheet.
Here, if d1 is less than 20 nm, the umbrella portion (precipitate) becomes excessively fine, and it becomes difficult to form mushroom-shaped projections on the steel sheet surface. On the other hand, if d1 exceeds 300 nm, the projections cannot be finely and densely dispersed on the surface of the steel sheet, and the desired hydrophilicity cannot be obtained. In addition, when processing into a desired shape, the precipitates serve as starting points, and cracks and rough skin are likely to occur. For this reason, the average value d1 of the diameter of the umbrella portion is in the range of 20 nm or more and 300 nm or less. It is preferably at least 30 nm, more preferably at least 40 nm. Further, the thickness is preferably 200 nm or less, more preferably 150 nm or less.

Ratio d2 / d1: 0.20 <d2 / d1 <0.70 of ratio of average diameter d2 of handle portion to average value d1 of umbrella portion diameter
When d2 / d1 is 0.20 or less, the handle becomes relatively small with respect to the umbrella, so that the umbrella is detached from the handle during handling or molding, and as a result, a desired hydrophilic property is obtained. The property cannot be obtained. On the other hand, when d2 / d1 is 0.70 or more, since the size of the umbrella portion and the handle portion are close, the contact angle with water is not effectively reduced, and the desired hydrophilicity cannot be obtained.
Therefore, d2 / d1 is set to 0.20 <d2 / d1 <0.70. d2 / d1 is preferably greater than 0.25. D2 / d1 is preferably less than 0.65.

Note that d1 and d2 and d2 / d1 are obtained as follows.
That is, a thin film sample for section observation is prepared by FIB processing so that a section (C section) perpendicular to the rolling direction of the steel sheet becomes an observation surface, and the sample is arbitrarily observed in five visual fields by a transmission electron microscope (TEM). Then, a TEM image (bright field image) as shown in FIG. 1 is obtained. Then, for each protrusion observed in the TEM image, the maximum length in the radial direction of the umbrella part (rolling perpendicular (plate width) direction) and the minimum length in the radial direction of the handle part (rolling perpendicular (plate width) direction) The average is determined as the diameter of the umbrella and the diameter of the handle, respectively, and these are averaged to determine the average value d1 of the diameter of the umbrella and the average d2 of the diameter of the handle. Also, d2 / d1 is obtained by dividing d2 thus obtained by d1.

  Also, the boundary in the radial direction (rolling right angle (plate width) direction) in the handle portion is defined by the projection area when the umbrella portion is projected in the height direction, and from the viewpoint of obtaining desired hydrophilicity, The average value h of the height of the handle is preferably 10 to 150 nm. Here, similarly to the above, the average value h of the height of the handle is measured by measuring the height (maximum value) of the handle of each protrusion observed in the TEM image as shown in FIG. Ask by doing.

(3) Manufacturing Method Next, a preferable manufacturing method of the above stainless steel sheet will be described.
For example, the above stainless steel plate is
Prepare a material stainless steel sheet having the above component composition (preparation step),
Annealing the material stainless steel plate to obtain an annealed plate (annealing step);
Performing an etching process on the annealed plate (etching process step)
Thus, it can be manufactured.
Hereinafter, each step will be described.

・ Preparation process The preparation process is a process of preparing a material stainless steel plate. The material stainless steel sheet is not particularly limited as long as it is a stainless steel sheet having the above component composition.
For example, a steel slab having the above-described composition is hot-rolled into a hot-rolled sheet, the hot-rolled sheet is subjected to hot-rolling sheet annealing as necessary, and then the hot-rolled sheet is subjected to cold rolling. Thus, a cold-rolled sheet having a desired thickness is formed, and if necessary, the cold-rolled sheet is subjected to intermediate annealing to prepare a material stainless steel sheet having the above-mentioned composition.
The conditions such as hot rolling, cold rolling, hot-rolled sheet annealing, and intermediate annealing are not particularly limited, and may be in accordance with a conventional method.

-Annealing step The annealing step is a step of annealing the stainless steel sheet as a material prepared in the above-described preparation step to form an annealed sheet. In order to form a desired precipitate near the surface of the steel sheet, a dew point:- It is preferable to use a non-oxidizing atmosphere of 30 ° C. or lower.
That is, as the dew point increases, an oxidation reaction of Fe or Cr easily occurs. In particular, when the dew point exceeds -30 ° C, a thick oxide film is easily formed on the surface of the stainless steel sheet, and the formation of precipitates containing Cr and Ti is inhibited, and mushroom-shaped projections are obtained on the final product sheet. It may disappear. Therefore, it is preferable that the dew point in annealing is -30 ° C or less. It is more preferably at most -35 ° C, still more preferably at most -40 ° C.
When forming a precipitate containing Cr and Ti, the annealing atmosphere is, for example, hydrogen gas, nitrogen gas, argon gas, helium gas, carbon monoxide gas, carbon dioxide gas and ammonia gas, and a mixture thereof. It is preferable that the atmosphere be a non-oxidizing atmosphere by using a gas or the like.
In particular, it is preferable to use a mixed gas of nitrogen gas and hydrogen gas, and particularly preferable is an ammonia decomposition gas (hydrogen gas 75 vol% + nitrogen gas 25 vol%).

When the annealing temperature is increased, the number of precipitates containing Cr and Ti can be increased. However, when the annealing temperature is excessively high, the precipitates may be coarsened and a projection having a desired shape may not be obtained. Therefore, the annealing temperature is preferably set to 800 to 1100 ° C. More preferably, it is 850 ° C or higher. Further, the temperature is more preferably 1050 ° C or lower.
The annealing conditions other than those described above may be in accordance with a conventional method.

-Etching process Next, the annealed plate obtained as described above is subjected to an etching process. In this etching process, by appropriately controlling the etching amount, the ground iron portion of the stainless steel plate is melted to form a projection having a desired shape.
That is, the precipitate portion remaining without being dissolved by the etching process becomes an umbrella portion of the protrusion, while the stainless steel base iron portion immediately below the precipitate is not dissolved from the upper portion because it is inhibited by the precipitate. Then, the umbrella portion is gradually etched from the surroundings to become a handle portion projecting and supporting the umbrella portion from the stainless steel base iron, and as a result, a mushroom-shaped projection is formed.

Examples of the etching treatment include an electrolytic treatment in an aqueous sulfuric acid solution (hereinafter, also simply referred to as electrolytic treatment) and an immersion treatment in a hydrofluoric acid aqueous solution (hereinafter, also simply referred to as immersion treatment).
However, in order to form a projection having a desired shape, it is necessary to appropriately control the amount of base iron (base material) dissolved (hereinafter also referred to as an etching amount) during the etching process. In this case, it is conceivable to control the etching amount by adjusting the current density and the electrolysis time. In the case of immersion treatment, it is conceivable to control the amount of etching by controlling the immersion time and the concentration of hydrofluoric acid.

In general, in the case of the electrolytic treatment, the higher the current density and the longer the electrolytic time, the larger the etching amount. In the case of the immersion treatment, the longer the immersion time, the higher the concentration of hydrofluoric acid, and the higher the solution temperature, the larger the etching amount.
However, the amount of etching also changes depending on the amount of Cr contained in a stainless steel plate as a base material. Therefore, in order to form a projection having a desired shape, the relationship between the current density and the electrolytic time in electrolytic treatment and the etching amount in advance for each component composition, or the immersion time in immersion treatment, the concentration of hydrofluoric acid, and the solution temperature It is preferable to determine the relationship with the etching amount, and adjust the processing conditions each time based on this relationship to control the etching amount.

Various stainless steel cold rolled sheets having a thickness of 0.20 mm having the component compositions shown in Table 1 (the balance being Fe and unavoidable impurities) were prepared, and the prepared cold rolled sheets were annealed under the conditions shown in Table 2. did. In addition, the annealing temperature in Table 2 is the temperature measured on the steel plate surface. The annealing time is a residence time in a temperature range from the annealing temperature −10 ° C. to the annealing temperature.
Thereafter, in a 30 g / L sulfuric acid aqueous solution, an etching treatment was performed under the conditions shown in Table 2 at a temperature of 40 ° C. to obtain a stainless steel plate. However, Sample No. 16 was not etched.
Using the thus obtained stainless steel plate, the hydrophilicity was evaluated in the following manner.

-Evaluation of hydrophilicity The hydrophilicity was evaluated by measuring the water contact angle between the surface of the stainless steel plate and water (with ion-exchanged water) under the following two conditions.
(Condition 1)
Equipment: Fully automatic contact angle meter (CA-W, manufactured by Kyowa Interface Science)
Liquid: ion-exchanged water Measurement method: liquid method Water drop volume: 1 μL
Rest time: 1 sec
Temperature: 25 ° C
Humidity: 26%
In addition, 10 points were measured for each steel sheet, and the average value was defined as the water contact angle, and the hydrophilicity was evaluated according to the following criteria. The measurement was performed immediately after the etching process. Table 2 also shows the evaluation results.
○ (pass): less than 60 degrees × (fail): 60 degrees or more

(Condition 2)
In order to evaluate the hydrophilicity when the steel sheet surface was contaminated with organic matter, the stainless steel sheets were exposed to the air for one week after the etching treatment. After exposure to the air, the water contact angle was measured under the same conditions as in Condition 1, and the hydrophilicity when contaminated with organic substances was evaluated according to the following criteria. Table 2 also shows the evaluation results.
○ (pass): less than 60 degrees × (fail): 60 degrees or more In the column of judgment of the hydrophilicity evaluation result in Table 2, “○” indicates that both conditions 1 and 2 were acceptable, and conditions 1 and 2 The case where at least one of the test samples 2 is rejected is described as “x”.

  In addition, the components of the umbrella portion of the protrusion, the number of the protrusions on the steel plate surface, the average value d1 of the diameter of the umbrella portion of the protrusion, the average values d2 and d2 / d1, and the height of the handle portion Was measured by the above-described method. The results are also shown in Table 2.

Table 2 shows that in all of the inventive examples, excellent hydrophilicity was obtained both immediately after the etching treatment and after one week of exposure to the air. In each of the invention examples, sufficient surface gloss was obtained, and the appearance of the surface was excellent.
On the other hand, in the comparative example, the desired hydrophilicity was not obtained.

Claims (5)

A stainless steel plate having mushroom-shaped protrusions on the surface,
The above stainless steel sheet has a component composition containing Cr: 16.0-32.0% and Ti: 0.05-0.45%,
Further, the protrusion has an umbrella portion made of a precipitate containing Cr and Ti, and a handle portion that protrudes and supports the umbrella portion from the ground steel of the stainless steel plate,
The number of the protrusions is 1 or more per 1 μm ² ;
The average value d1 of the diameter of the umbrella portion is 20 nm or more and 300 nm or less, and
A stainless steel sheet in which a ratio d2 / d1 of an average value d2 of the diameter of the handle portion to d1 satisfies a relationship of the following expression (1).
0.20 <d2 / d1 <0.70 (1) Wherein the component composition further comprises
C: 0.003-0.030%,
Si: 0.01-1.00%,
Mn: 0.01-1.00%,
P: 0.050% or less,
S: 0.030% or less,
Ni: 0.01-1.00%,
The stainless steel sheet according to claim 1, which contains 0.001 to 0.200% of Al and 0.030% or less of N, and the balance consists of Fe and unavoidable impurities. Wherein the component composition further comprises
Mo: 0.01-2.50%,
Cu: 0.01-0.80%,
Co: 0.01 to 0.50% and W: 0.01 to 3.00%
The stainless steel sheet according to claim 2, wherein the stainless steel sheet contains one or more kinds selected from the group consisting of: Wherein the component composition further comprises
Nb: 0.01 to 0.60%,
Zr: 0.01-0.30%,
V: 0.01 to 0.30%,
Ca: 0.0003-0.0030%,
Mg: 0.0005-0.0050%,
B: 0.0003-0.0050%,
REM (rare earth metal): 0.001 to 0.100%,
Sn: 0.001 to 0.500% and
Sb: 0.001 to 0.500%
The stainless steel sheet according to claim 2, comprising one or more selected from the group consisting of:   The stainless steel sheet according to any one of claims 1 to 4, which is used for kitchen appliances or building materials.

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