JP2000087259A - Stainless steel sheet and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a stainless steel sheet excellent in glare preventability, stain resistance and fingerprint resistance and to provide a method for producing it. SOLUTION: This stainless steel sheet is the one that the surface of a base material having a compsn. contg., by weight, 7 to 35% Cr, 0 to 11% Ni, 0 to 4% Mo, 0.01 to 0.2% N, 0.05 to 2.0% Si, in which index M value expressed by Cr+3Mo+15N} is 10.5 to 50 and having 0.6 to 10 μm surface roughness Ra is provided with an oxidized film contg. 0.3 to 20% SiO2 and having 0.01 to 0.2 μm thickness and a photocatalystic layer contg. 10 to 90% photocatalystic grains and having 0.1 to 10 μm thickness. In the case, as the photocatalystic grains, a mixture of a bonded material of titanium oxide and zirconium titanate is used, its photocatalystic activity is made better. In the case the space between the oxidized film and the photocatalystic layer is provided with a chromate film of 5 to 50 mg/m2 coating weight contg. 50 to 80% silica, its adhesion is made better. More preferably, degreasing with an alkali soln. and bright annealing at 800 to 1200 deg.C in an atmosphere of hydrogen >=8 vol.% and dew point <=-20 deg.C are executed, and, after chromate treatment, the photocatalystic layer is applied.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stainless steel sheet provided with a photocatalytic layer having good adhesion and suitable for a processing material such as a building material or a vehicle part, which emphasizes anti-glare properties and aesthetics, and a method for producing the same.

[0002]

2. Description of the Related Art Stainless steel sheets have excellent corrosion resistance and beautiful metallic luster, and are rich in design, so that they have been widely used in building materials and vehicle materials. Recently, glare has been suppressed (it has anti-glare properties) to prevent reflected light from vehicles, building roofs, exterior materials, etc. from becoming a factor in traffic obstruction.
There is a need for stainless steel plates.

As a method of improving the anti-glare property, there is a method of dulling the surface. In an area where the amount of dust and floating dust is large, floating dust and dirt adhere to the surface of the dull steel plate having fine irregularities. Since the steel sheet is easily removed and hardly removed, the appearance of the steel sheet dulled to improve the antiglare property is impaired.

[0004] Further, it is considered that a steel sheet used for applications that emphasize design such as a vehicle has a characteristic (fingerprint resistance) that makes it difficult for fingerprints to adhere in order to maintain aesthetic appearance. As described above, stainless steel sheets are required to have excellent stain resistance and fingerprint resistance.

In order to solve such a problem, various methods have been disclosed. Tokuhei 7-9024
No. 7, in the final pass of cold rolling, after rolling at a rolling reduction of 3 to 30% using a roll dulled so that the 10-point average roughness (Rz) becomes 10 to 30 μm, and then bright annealing. A method for producing a cold-rolled stainless steel sheet having excellent anti-glare properties, gloss, and cleanability (cleanliness) by eliminating the need for pickling after annealing is disclosed. Pickling after dull rolling and annealing causes fine cracks on the surface, dirt may enter the cracks and impair the appearance, but in order to avoid this, pickling after annealing is unnecessary. Things.

However, in the method disclosed in the above-mentioned publication, dull is transferred to a steel sheet which has already been cold-rolled and hardened, so that the dull of the rolling roll is severely worn.
For this reason, in order to uniformly transfer dull to a steel plate, it is necessary to frequently change the roll, and there is a problem that productivity is not good.

Japanese Patent Application Laid-Open No. 6-182401 discloses an antiglare property in which cold rolling is annealed in the air, pickled, dulled, annealed in the air or bright annealing, and further pickled. A method for producing a dull-finished stainless steel sheet having excellent color tone uniformity and corrosion resistance is disclosed. This method
Although pickling is performed for the purpose of removing fine fogging (fine fogging of steel) which may occur during dull rolling, the problem is that the number of steps increases and the production cost increases.

The methods disclosed so far are not sufficient methods for inexpensively producing a stainless steel sheet satisfying both stain resistance and anti-glare properties. In addition, there is a problem that it is difficult to remove dirt when contaminants adhere.

Attempts have been made to apply the photocatalysis of metal compound semiconductors such as titanium oxide, zinc oxide and iron oxide to environmental purification by decomposing and removing pollutants. This is because when these substances are irradiated with light having a wavelength having energy equal to or greater than the band gap, electrons having strong reducing action and holes having strong oxidizing action are generated on the irradiated surface, and contact with the surface of the metal compound semiconductor is caused. This is a method that utilizes the phenomenon in which the organic substance is decomposed by the redox action.

When a photocatalyst is used, a method has been considered in which the photocatalyst is used by fixing it to the surface of a substrate in order to facilitate its handling. In that case, there is a problem that it is difficult to secure the adhesion between the photocatalyst particles and the substrate and maintain the photocatalytic activity.

In Japanese Patent Application Laid-Open No. 9-173865, a support layer made of oxide particles is provided on the surface of a substrate, and on the surface,
A photocatalyst in which titanium oxide particles having an average particle size smaller than the particle size of the oxide particles in the support layer is disclosed. This is because the size of the oxide particles constituting the support layer is reduced on the substrate side to increase the adhesion between the substrate and the support layer, and the diameter on the photocatalyst side is increased to strongly adhere the titanium oxide particles. An example in which the present invention is applied to a light reflecting surface of a lighting fixture or the like is disclosed.

In Japanese Patent Application Laid-Open No. 9-310185, an underlayer made of SiO ₂ is provided on the surface of a metal plate, and a Ti layer is formed thereon.
A photocatalyst-coated metal plate provided with an O ₂ layer is disclosed. When a TiO ₂ layer is directly applied to a metal plate and heated and dried,
The metal atoms of the substrate may diffuse into the photocatalyst layer and impair the photocatalytic activity. The above technique suppresses metal diffusion from a substrate by providing an SiO ₂ layer on the surface of a metal plate,
It is intended to prevent a decrease in iO ₂ catalyst activity.

[0013]

The surface of a stainless steel plate or a steel strip (hereinafter simply referred to as "stainless steel plate") used for building materials and vehicles has a photocatalytic function and is used for building materials and vehicle members. If a photocatalytic layer having strong adhesion that can withstand processing can be provided, by using this as a material, it is possible to extremely efficiently manufacture building materials and vehicle parts having excellent stain resistance.

However, the method of fixing a photocatalyst to the surface of a base material disclosed so far requires additional manufacturing steps such as application and drying of a chemical agent in order to provide an underlayer or a support layer. not good. Furthermore, the adhesion of the photocatalyst layer is not sufficient, and if the photocatalyst body is subjected to severe processing, the photocatalyst layer may be peeled off, resulting in poor product quality and poor photocatalytic performance. For this reason, a method of fixing a photocatalyst to the surface of a molded article has conventionally been adopted, and a stainless steel sheet having a photocatalyst layer having excellent adhesion that can withstand press working has been demanded.

An object of the present invention is to provide a photocatalytic layer having good adhesion, which solves these problems and is suitable as a processing material for building materials and vehicle parts, which emphasizes antiglare and stain resistance. It is an object of the present invention to provide a stainless steel plate and an efficient manufacturing method thereof.

[0016]

Means for Solving the Problems The present inventors have intensively studied a method for efficiently improving the adhesion of the photocatalyst layer when a stainless steel plate is used as a base material, and as a result, the following new method has been proposed. Knowledge was obtained.

A. The adhesion of the photocatalyst layer has a correlation with the surface roughness of the stainless steel plate, and good adhesion can be secured if the surface roughness Ra of the base material is 0.6 μm or more. This roughness range matches the range in which the antiglare property can be ensured, and is a range in which both can coexist.

B. When a dense oxide film containing SiO ₂ is provided on the surface, the adhesion between the steel sheet and the photocatalyst layer is further improved. It is presumed that SiO ₂ in the oxide film had a strong binding action to both the steel sheet surface and the photocatalyst layer.

The above-mentioned oxide film is provided with a silica-containing chromate film (hereinafter, also simply referred to as “silica-containing chromate film”) formed by applying and drying a silica-containing coating type chromate treatment solution. By doing so, the adhesion of the photocatalyst layer can be further improved. It is presumed that by interposing a relatively soft chromate film between the hard steel plate and the photocatalyst layer, there is an effect of reducing the impact on the photocatalyst layer.

C. The photocatalytic sol contained in the coating composition for forming the photocatalyst layer (hereinafter simply referred to as “photocatalytic layer coating”) is stabilized using a nitric acid solution. Therefore, if this paint is applied directly to the surface of the stainless steel plate, the stainless steel plate may be corroded.

However, ΔCr (%) + 3Mo
(%) + Indicator M for pitting corrosion expressed as 15N (%)}
Using a steel sheet having a value of 10.5 or more, a strong oxide film is formed on the surface by bright annealing, and SiO ₂ in the oxide film is used.
By increasing the content, it resists corrosion by nitric acid solution,
The corrosion resistance of the stainless steel plate can be maintained even when the coating for the photocatalyst layer is directly applied.

D. As the photocatalyst particles, titanium oxide particles are preferable, but a combination of titanium oxide and crystalline zirconium titanate (hereinafter simply referred to as a “titanium oxide-zirconium titanate combination” or “TZ combination”) )
The use of a compound containing the compound can further improve the photocatalytic performance.

Since the oxide film and the chromate-treated layer are thin, compared to the conventional case where a supporting layer or an underlayer is provided, the photocatalyst layer is less likely to peel off during processing and has a photocatalyst layer. A steel sheet with excellent workability can be obtained.

The present invention has been completed on the basis of the newly obtained knowledge as described above, and the gist of the present invention is to provide the anti-glare property and stain resistance described in any of the following (1) to (4). A stainless steel sheet having excellent properties and a method for producing the same according to (5) or (6).

(1) Cr: 7 to 35% by weight, N
i: 0-11%, Mo: 0-4%, N: 0.01-0.
2%, Si: 0.05 to 2.0%
(%) + 3Mo (%) + 15N (%)}, the surface of the base steel sheet having an index M value of 10.5 to 50
₂ containing 0.3 to 20% by weight and having a thickness of 0.01 to 0.2
A stainless steel sheet excellent in stain resistance and fingerprint resistance, comprising an oxide film having a thickness of μm and a photocatalyst layer containing photocatalyst particles.

(2) The surface roughness of the base material is 0.6 to 1 in Ra.
0 μm, and the photocatalyst layer contains 10 to 90% by weight of photocatalyst particles and has a thickness of 0.1 to 10 μm, and is excellent in antiglare property, stain resistance and fingerprint resistance. The stainless steel sheet according to the above (1).

(3) The stainless steel sheet according to the above (1) or (2), wherein the photocatalyst particles contain a titanium oxide-zirconium titanate conjugate.

(4) Cr between the oxide film and the photocatalyst layer
The stainless steel sheet according to any one of the above (1) to (3), further comprising 5 to 50 mg / m ^{2 of} a chromate film containing 20 to 50% by weight of silica and 50 to 80% by weight of silica.

(5) The base steel sheet having the chemical composition and surface roughness described in (1) is subjected to a series of processes described in (a) to (c) below. A) producing a stainless steel sheet; The base steel sheet contains 8% by volume or more of hydrogen, and the remainder is substantially composed of nitrogen in an atmosphere having a dew point of -20 ° C or less.
Performing bright annealing at 00 to 1200 ° C., b. Subjecting the bright annealed base steel sheet to degreasing with an alkaline solution; c. 5 to 20% by weight of ethanol or butyl alcohol and a solid content weight ratio of 1
A coating composition containing photocatalyst particles in an amount of 0 to 90% by weight is applied so as to have a dry film thickness of 0.1 to 10 μm, and dried at 100 to 500 ° C. for 1 minute or more in the atmosphere.

(6) The base steel sheet having the chemical composition and surface roughness described in (1) is subjected to a series of processes described in (a) to (d) below, wherein Method for producing stainless steel sheet; a. The base steel sheet contains 8% by volume or more of hydrogen, and the remainder is substantially composed of nitrogen in an atmosphere having a dew point of -20 ° C or less.
Performing bright annealing at 00 to 1200 ° C., b. Subjecting the bright annealed base steel sheet to degreasing with an alkaline solution; c. Cr is added to the degreased base steel sheet at a dry solid content weight ratio of 2%.
An amount of chromium phosphate necessary for containing 0 to 50% by weight, and a silica-containing chromate treatment solution containing silica in an amount of 50 to 80% by weight on a dry solids basis, have an adhesion amount of 5 to 50% after drying. Coating in an amount of 50 mg / m ² and drying, d. A coating composition containing 5 to 20% by weight of ethanol or butyl alcohol and an amount of photocatalyst particles having a solid content weight ratio after drying of 10 to 90% by weight has a dry film thickness of 0.1 to 10 μm. And apply to 100-500
Dry in air at ℃ for 1 minute or more.

[0031]

Embodiments of the present invention will be described below in detail. The percentages of the chemical compositions described below represent% by weight.

Chemical composition of base stainless steel sheet: Cr is set to 7% or more in order to ensure corrosion resistance. In order to strengthen the formation of a passive film on the surface of the steel sheet, preferably 13
% Or more. If the Cr content exceeds 35%, the ductility and toughness of the steel sheet deteriorate and rolling becomes difficult, so the upper limit of the Cr content is 35%.

Although Ni is not an essential element, it has an effect of stabilizing the austenite structure of the steel. Therefore, when the base material is an austenitic stainless steel sheet, it is preferable to contain 8.5% or more. Since Ni is expensive, the upper limit is 11% even when Ni is contained.

Mo is not an essential element, but may be contained because it has an effect of improving the pitting corrosion resistance of the steel sheet. If Mo is contained excessively, the hot workability is significantly reduced. Therefore, even when Mo is contained, the content is 4%.
The following is assumed.

N has an effect of improving the pitting corrosion resistance, so that it is contained in an amount of 0.01% or more. However, if N is excessively contained, the hot workability is significantly reduced, so the content is set to 0.2% or less.

Si is contained in an amount of 0.05% or more in order to secure the Si content in the oxide film generated by bright annealing. If the Si content is less than 0.05%, the adhesion of the photocatalyst layer may not be favorable. Preferably, the content is 0.1% or more. On the other hand, if the Si content is excessively contained, the formability as a stainless steel plate is impaired, so the upper limit is set to 2%. Preferably, it is 1.5% or less.

The source of the corrosion resistance is a passive film formed of Cr. When Mo or N is added to Cr-containing steel, the passive film is further strengthened and the corrosion resistance is further improved. You. It is convenient to determine the coefficient of each element in consideration of these effects on corrosion resistance, and to evaluate the corrosion resistance of steel using the sum of these as an index.

In the present invention, as such an index, ΔC
r (%) + 3Mo (%) + 15N (%)} is used as the index M value. In the present invention, the M value of the steel sheet is set to 10.5 or more in order to secure corrosion resistance under a normal environment.
Preferably it is 15 or more. If the M value is excessively high, the hardening of the steel becomes remarkable, and the rollability and workability are impaired. In addition, when an oxide film is provided, the adhesion may be impaired. To avoid these, the M value is set to 50 or less. Preferably it is 45 or less.

The content of elements other than those described above is not particularly limited, but may contain 0.1 to 0.5% of Nb or Ti, respectively, for the purpose of improving the food quality of the base material.
In order to obtain austenitic stainless steel, Ni is used.
May be contained at 8.5 to 11%. The balance is Fe and inevitable impurities. In addition, C as an inevitable impurity may impair the corrosion resistance, so is preferably set to 0.09% or less.

The surface roughness of the base stainless steel sheet: The surface roughness of the base stainless steel sheet is determined by
The arithmetic average roughness Ra specified in JIS-B-0601 is preferably 0.6 μm or more. When Ra is 0.6 μm or more, irregular reflection upon irradiation with light is remarkable, so that interference color due to having the photocatalyst layer on the outermost layer hardly causes a problem and does not impair the appearance. More preferably, it is 1 μm or more.

If the surface roughness is excessively high, the corrosion resistance is impaired. Therefore, the upper limit is preferably set to 10 μm or less in Ra. More preferably, it is 6 μm or less.

Oxide film: 0.3% of SiO ₂ is applied to the surface of the stainless steel sheet in order to secure the adhesion of the photocatalyst layer.
An oxide film containing the above is provided. SiO _{2 in} oxide film
Is preferably 0.5% or more for better adhesion. If SiO ₂ is excessively contained, a dense oxide film will not be formed, secondary adhesion will be impaired, and formability of the steel sheet will be impaired. Therefore, the upper limit is set to 20%. Preferably it is 5% or less.

The oxide film having a high SiO ₂ content of the present invention can be formed by, for example, performing bright annealing on a stainless steel plate having the above-mentioned chemical composition, whereby Si in the steel is concentrated and oxidized in the surface layer portion. . Do not perform bright annealing
In a stainless steel plate manufactured by pickling and temper rolling, SiO ₂ contained in a passivation film formed on the surface thereof is used.
The content is usually about 0.001 to 0.2%. In the case of the present invention, a larger amount of SiO ₂ is contained.

If the thickness of the oxide film is less than 0.01 μm, the effect of improving the adhesion by concentrating Si is not sufficient. Therefore, the thickness of the oxide film is 0.01
μm or more. Preferably it is 0.03 μm or more.
If the thickness of the oxide film exceeds 0.2 μm, the oxide film becomes brittle, the adhesion to the base material is impaired, and the photocatalyst layer is easily peeled off. Therefore, the upper limit is set to 0.2 μm. More preferably, it is 0.1 μm or less.

In the oxide film, in addition to the above SiO ₂ ,
To improve the corrosion resistance of the oxide film, a Cr oxide such as Cr ₂ O ₃ it is preferable to contain 20 to 80 wt%.
Others include alloy elements contained in the base material such as Mo and Si and oxides of Fe.

Chromate film: When a chromate film containing SiO ₂ (silica-containing chromate film) is provided between the oxide film on the steel sheet surface and the photocatalyst layer described later, the adhesion of the photocatalyst layer is further improved. It is presumed that the effect of improving the adhesion by incorporating silica in the film is due to the fact that silica has a strong binding action to both the steel sheet surface and the photocatalytic layer.

To obtain the effect of improving the adhesion, 20 to 50% by weight of Cr and 5 to 50% by weight of
A silica-containing chromate film containing 0 to 80% by weight is preferred. If the Cr content is less than 20%, the finish of the chromate film is not good, and if it exceeds 50%, the effect of improving the adhesion cannot be obtained because the content of silica becomes too small. If the content of silica is less than 50%, the effect of improving the adhesion cannot be obtained, and if it exceeds 80%, the effect of improving the adhesion due to the inclusion of silica is saturated, and film formation is poor.

The adhesion amount of the chromate film is 5 to 50 mg /
m ² is good. When the amount is less than 5 mg / m ² , the effect of improving the adhesion to the photocatalyst layer is insufficient. More preferably, it is 10 mg / m ² or more. 50mg attached amount
/ M ² , the adhesion of the chromate film itself is impaired. More preferably, it is 30 mg / m ² or less. As the type of the chromate film, a coating type is preferable because of excellent handleability.

Photocatalyst layer: The photocatalyst layer preferably contains 10 to 90% of photocatalyst particles based on the weight of the photocatalyst layer. If the content is less than 10% by weight, the photocatalytic function is not sufficient. As the content of the photocatalyst particles increases, the effect of the photocatalyst increases. However, when the content exceeds 90% by weight, cracks and cracks on the film surface increase, which is not good because the adhesion is impaired. Since handling is easy, 50% or less is more preferable.

The thickness of the photocatalyst layer is preferably at least 0.1 μm in order to obtain a sufficient photocatalytic effect. Its thickness is 1
If the thickness exceeds 0 μm, the photocatalytic effect is saturated and the workability of the photocatalyst layer deteriorates. Therefore, the thickness is set to 10 μm or less. In the case where it is used for an application in which processing is severe, the thickness is more preferably 5 μm or less.

Photocatalyst particles: As the photocatalyst particles, known photocatalysts such as titanium oxide, iron oxide, zinc oxide, cadmium oxide, and cadmium selenide can be used. Among them, titanium oxide particles provide a good photocatalytic effect. can get. Furthermore, when a TZ bond (titanium oxide-zirconium titanate bond) is used, the photocatalytic function can be further improved as compared with the case where titanium oxide alone photocatalyst particles are used. 5 to 20% by weight of the photocatalyst particles
Is preferably used as a mixture with titanium oxide so that is a TZ bond.

Here, the TZ bonded body is not simply a mixture of titanium oxide and crystalline zirconium titanate.
It is obtained by integrating titanium oxide and zirconium titanate through a Ti—O—Zr bond. By arranging titanium oxide and zirconium titanate in such a manner, the photocatalytic function is significantly improved as compared with the case where the photocatalyst particles of titanium oxide alone are used.

This TZ bonded body is prepared by mixing crystalline zirconium titanate and titanium oxide, firing in the air, pulverizing and dispersing in water to form a slurry, adjusting the pH, and performing heat treatment. Obtainable.

The size of the photocatalyst particles is desirably in the range of 0.05 to 1 μm in terms of the average particle size observed with a transmission electron microscope. The smaller the photocatalyst particles are, the better the catalytic activity is. Therefore, when the particle size exceeds 1 μm, the photocatalytic activity is reduced. Particles having a particle size of less than 0.05 μm are difficult to classify by ordinary means and are difficult to obtain.

The size of the crystallite constituting the photocatalyst particles is preferably from 5 to 50 nm. The crystallite size is calculated from the diffraction peak on the (101) plane of the anatase crystal obtained by X-ray diffraction. If the crystallite size exceeds 50 nm, the photocatalytic activity is undesirably reduced. The smaller the crystallite size is, the better the photocatalytic activity is. Therefore, the crystallite size may be reduced as much as possible.

Manufacturing method: The steel sheet of the present invention can be easily manufactured by the following method. The base steel sheet is preferably a cold-rolled steel sheet, but may be a hot-rolled steel sheet. The surface roughness of the base material is, for example, hot-rolled steel sheet, after pickling, or cold-rolled steel sheet, during the final rolling pass of cold rolling or after annealing, rolling using a dulled roll, etc. Can be adjusted by a known method.

The base steel sheet is preferably subjected to bright annealing, and an oxide film is preferably provided on the surface. Bright annealing is preferably performed in an atmosphere containing 8% by volume or more of hydrogen and the balance substantially consisting of nitrogen. All or part of nitrogen may be used as argon gas. If the hydrogen concentration in the atmosphere is less than 8% by volume, it is not preferable because a bright surface cannot be obtained after annealing. It is even better to use a 100% hydrogen atmosphere.

The dew point of the bright annealing atmosphere is determined by the S in the oxide film.
In order to make the content of iO ₂ within a desired range, the content is preferably -20 ° C or lower. It is more preferably -35 ° C or lower.

The annealing temperature is preferably set to 800 ° C. or more in order to obtain an oxide film in a short time while avoiding the sensitization phenomenon of the base steel sheet. It is more preferably at least 900 ° C. If the annealing temperature is too high, the steel becomes too soft, so the annealing temperature is preferably 1200 ° C. or less. More preferably 11
It is below 00 ° C.

The annealing time may be appropriately determined according to the above temperature so that the oxide film has a predetermined thickness. The annealing method is optional, but the continuous annealing method is preferable because it is easy to control.

After the bright annealing treatment and before applying the coating for the photocatalytic layer, it is preferable to carry out alkali degreasing with a known chemical such as sodium silicate or sodium hydroxide in order to remove organic stains on the surface of the steel sheet. Thereby, the wettability of the steel sheet surface is improved, and the effect of improving the adhesion of the photocatalyst layer is obtained.

In order to further improve the adhesion of the photocatalyst layer, it is preferable to interpose a chromate film containing silica between the oxide film and the photocatalyst layer. In order to perform the chromate treatment, it is preferable to apply and dry a chromate treatment liquid mixed with an amount of silica necessary to make the weight ratio of the dry solid content to a desired value.

The type of the chromate treatment solution may be a known one, but a known coating type chromate is preferred because it is easy to handle. When a chromate treatment solution containing a water-soluble chromium compound containing at least one kind of α or β-ethylenically unsaturated simple substance and containing an oligomer having a hydrophilic group is used, a long-term stable solution can be obtained. This is preferable because the work becomes easier. The method of chromate treatment is arbitrary, and may be applied by a known method such as a spray method or an immersion method, and dried by a known method such as drying at about 120 ° C.

The coating for the photocatalyst layer preferably contains photocatalyst particles in an amount of 10 to 90% based on the weight of the dried photocatalyst layer. The coating for the photocatalyst layer preferably contains at least a surfactant and one or more alcohols in addition to the photocatalyst particles. Known surfactants may be used. Alcohol is contained to improve the wettability of the surface of the steel sheet, and its type is preferably, for example, 5 to 20% by weight of ethanol, butyl alcohol and the like. The coating material for the photocatalyst layer may further contain silica, alumina or the like for the purpose of improving the film-forming properties.

The method of applying the coating for the photocatalyst layer is optional.
Known methods such as roll coating, spray coating, and spin coating can be applied. Painted steel sheet is 15
It is preferable to dry in the air in a temperature range of 0 to 500 ° C. for 1 minute or more. If the drying temperature is lower than 150 ° C., the drying becomes insufficient and good adhesion cannot be obtained. Drying temperature is 50
If the temperature exceeds 0 ° C., the surface of the substrate may be oxidized and colored, or the film may be peeled off. Further, the corrosion resistance of stainless steel may be impaired. More preferably 4
It is below 00 ° C.

The cooling rate after drying the photocatalyst layer is 5 to 2
The range of 00 ° C./sec is good. If the temperature is lower than 5 ° C./sec, it takes a long time for cooling, which is not economical. If the speed is higher than 200 ° C./sec, the film may be cracked or peeled off.

Processing conditions other than those described above may be generally known conditions. A series of treatments such as application and drying of chemicals may be performed in a batch manner using a cutting plate, but using a coil-shaped base material using a continuous coil coating equipment of a two-coat two-bake method. Processing is preferred because of its excellent quality and economy.

[0068]

EXAMPLES (Example 1) Table 1 is a table showing the chemical composition of the base material used in the test.

[0069]

[Table 1]

As shown in Table 1, six types of steel satisfying the conditions specified in the present invention and three types of steels out of the range specified in the present invention were cold-rolled to a thickness of 0.4 mm. Cold-rolled stainless steel sheets having various surface roughnesses Ra, dew point: −55 ° C., hydrogen: 75% by volume, nitrogen: 25
Bright annealing was performed by heating to 1020 ° C. in an atmosphere consisting of volume%.

For comparison, some steel sheets were annealed in air without annealing in a hydrogen-containing atmosphere, and the
A steel sheet with a higher O ₂ content (Test No. 19) was also prepared.
Some steel sheets were annealed in an air atmosphere for comparison to produce steel sheets in which a thick oxide film was formed (Test No. 20).

After the above steel sheet was degreased and washed with water, sol-like silica was mixed in a coating type chromate solution at a weight ratio of 4 parts of silica to 1 part of chromium phosphate at 25 ° C.
Was immersed in a silica-containing chromate solution, heated at 150 ° C. for 1 minute, and subjected to a chromate treatment with an adhesion amount of 15 mg / m ² after drying. As a result of analyzing the composition of the obtained chromate film, the content of chromium phosphate was 70%, and the content of silica was 3%.
It was 0%.

Crystalline zirconium titanate and titanium oxide were mixed at a weight ratio of 1: 9, and were mixed at 500 ° C. in air.
And then crushed and dispersed in water to obtain a solid content of 1
A slurry of 0% by weight was prepared. Sodium hydroxide was added to the mixture to adjust the pH to 10, the mixture was heat-treated in an autoclave at 150 ° C. for 3 hours, and nitric acid having a concentration of 60% by weight was added.
7, and filtered to obtain a titanium oxide-zirconium titanate conjugate (TZ bond).

The TZ bonded body and titanium oxide were mixed at various ratios to obtain a photocatalyst particle raw material, and silica was added at various ratios for the purpose of adjusting the film-forming property to a sol,
10% by weight of ethanol and several drops of a surfactant were mixed to prepare a coating for a photocatalytic layer. The steel plate subjected to the above-mentioned chromate treatment is immersed in the above-mentioned paint, the amount of adhesion is adjusted, and after it is pulled up, it is heated at 350 ° C. for 1 minute so that the thickness of the photocatalytic layer is
A stainless steel plate of 0.7 μm was obtained. The following investigation was performed on the obtained steel sheet.

Thickness of oxide film: The thickness of the oxide film was measured by observing the cross section of the steel sheet of the sample using a scanning electron microscope. The chemical composition of the oxide film was measured using EPMA (electron beam microanalyzer). The test pieces cut out from these steel sheets were evaluated for adhesion and photocatalytic activity of the photocatalyst layer and corrosion resistance of the steel sheets by the following methods.

Primary adhesion: A 10 mm square portion of the test piece was cross-cut in a grid pattern from above the photocatalyst layer at 1 mm intervals, and an adhesive tape was stuck thereon and peeled off. Was measured and the primary adhesion was evaluated according to the following criteria.

Less than 5%: （(extremely good), 5% or more, less than 15%: （(good), 15% or more: × (poor).

Secondary adhesion: After cross-cutting the film in a grid pattern in the same manner as described above, the film was immersed in ion-exchanged water for 1 hour.
The test piece that was boiled for a period of time and pulled up was subjected to a peeling test using an adhesive tape in the same manner as in the evaluation of the primary adhesion, and the secondary adhesion was evaluated based on the same criteria as in the primary test.

Anti-glare properties: The angle of incidence was set to 60 degrees using a gloss meter, and the case where the reflected light receiving intensity was less than 80 was extremely good (◎), and the case where 80 or more and less than 100 was good (○), 10
0 or more was evaluated as defective (x).

Photocatalytic activity: Evaluated by an artificial fingerprint removal test and color difference (yellowness). The artificial fingerprint removal test is based on JIS-
Using an artificial fingerprint liquid described in K-2246, a fingerprint was transferred to a test piece, and the time required for the artificial fingerprint to disappear by irradiation with black light was measured. The case where the fingerprint disappearance time was less than 5 hours was evaluated as very good (◎), the case of 5 hours or more and less than 24 hours was evaluated as good (○), and the case where the fingerprint did not disappear after 24 hours was evaluated as poor (×).

Color difference: After attaching a test piece to a vehicle and running for three months, the color difference was measured according to the method specified in JIS-Z-8730, and the yellowness b ^{* of the} L ^* a ^* b ^* color system was measured ^.
The value was measured. When the stain is small, that is, when the discoloration is small, the yellowness b ^* value is measured to be small. In the present invention, the stain resistance was evaluated as extremely good (◎) when the b ^* value was less than 3, good (）) when it was 3 or more and less than 10, and poor (x) when it was 10 or more.

Corrosion resistance: Evaluated by a salt spray test in which an aqueous solution containing 5% of NaCl at 30 ° C. was sprayed for 72 hours. Good when no rust was observed (O), and poor when rust was observed (×) ). Table 2 shows the results obtained.

[0083]

[Table 2]

As shown in Table 2, Test Nos. 1 to 25, which are within the condition range specified by the present invention, have excellent antiglare properties, have good adhesion and photocatalytic activity, and have good corrosion resistance of stainless steel sheets. there were.

On the other hand, in test No. 26 using steel G whose chemical composition was out of the range specified by the present invention, steel H and steel I having poor corrosion resistance and excessively large M values were used. In Test Nos. 27 and 28, the adhesion of the oxide film was poor. In Test Nos. 29 and 30, in which Ra of the steel sheet was out of the range specified by the present invention, the antiglare property and the secondary adhesion were not good. In Test Nos. 31 and 32 in which the SiO ₂ content of the oxide film was out of the conditions prescribed by the present invention, and in Test Nos. 33 and 34 in which the thickness of the oxide film was not preferable, the non-adhesion of the oxide film was good. Did not.

Test Nos. 35 and 36 in which the content of the photocatalyst particles was small showed poor photocatalytic activity. In Test No. 37 in which the content of the photocatalyst particles was too large, the adhesion was not good. In Test No. 38 in which the thickness of the photocatalyst layer was insufficient, the photocatalytic effect was not sufficient.

(Example 2) A steel having the same chemical composition as steel A shown in Table 1 having a thickness of 0.4 mm and a surface roughness Ra of 0.6 μm.
m cold rolled stainless steel sheet, 75% by volume of hydrogen, 25% of nitrogen
Volume%, dew point -55 ° C, atmosphere temperature 900
Bright annealing was performed at ℃ for 1 hour. After that, alkali degreased in the same manner as described in Example 1, washed with water, and then immersed in a treatment liquid whose composition was adjusted so that the weight ratio of chromium phosphate and silica in the dry film thickness became various values. Then, the amount of adhesion is changed so that the weight after drying becomes various values, and 1
A chromate treatment of heating at 50 ° C. for 1 minute was performed. On top of that, 2.5% by weight of the TZ conjugate and 1% by weight of titanium oxide prepared in the same manner as described in Example 1 on a dry solid content weight ratio.
A stainless steel sheet having a photocatalyst layer provided by applying a photocatalyst layer paint adjusted to contain 2.5% and silica at 30% so as to have a dry film thickness of 0.7 μm and heating at 300 ° C. for 1 minute. I got The performance of the obtained steel sheet was evaluated by the same method as described in Example 1. Table 3 summarizes these manufacturing conditions and the obtained performance evaluation results.

[0088]

[Table 3]

As shown in Table 3, Test Nos. 41 to 44 in which the composition of the chromate film was in a more preferable range showed particularly excellent adhesion.

[0090]

The stainless steel having the photocatalyst layer of the present invention on the surface of a steel sheet has excellent antiglare properties and also has an excellent photocatalytic function, so that it has excellent stain resistance and adhesion of the photocatalyst layer. Is also excellent. Therefore, it is suitable as a material for processed parts, such as building materials and vehicles, where importance is placed on metallic luster. The stainless steel excellent in stain resistance of the present invention is excellent in economical efficiency because it can be efficiently produced by using a commonly used continuous coating equipment.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C21D 1/76 C21D 1/76 F 9/46 9/46 Q C22C 38/00 302 C22C 38/00 302Z 38 / 44 38/44 C23C 24/08 C23C 24/08 C 28/00 28/00 C (72) Inventor Katsu Takahashi 4-33 Kitahama, Chuo-ku, Osaka-shi Sumitomo Metal Industries Co., Ltd. (72) Invention Person Yasuhiro Masaki 4-5-33 Kitahama, Chuo-ku, Osaka-shi F-term in Sumitomo Metal Industries, Ltd. (reference) 4G069 AA02 AA03 BA48A BB06A BB06B BC50A BC50B BC51A BC51B BD02A BD02B BD05A BD05B CD10 4K037 EA12 EA20 EA17 EA17 EA17 EA17 EA17 EA17 EB14 HA05 4K044 AA03 AB02 BA12 BA14 BB04 BB11 BC00 BC04 BC05 CA02 CA04 CA27 CA53

Claims (6)

[Claims] (1) Cr: 7 to 35%, Ni: 0% by weight
１１11%, Mo: 0 to 4%, N: 0.01 to 0.2%,
Si: containing 0.05 to 2.0%, ΔCr (%) + 3
The index M value represented by Mo (%) + 15N (%)｝ is 1
On the surface of the base material steel plate is 0.5 to 50, the SiO ₂ 0.
A stainless steel sheet excellent in stain resistance and fingerprint resistance, comprising: an oxide film containing 3 to 20% by weight and having a thickness of 0.01 to 0.2 μm; and a photocatalyst layer containing photocatalyst particles. 2. The base material has a surface roughness Ra of 0.6 to 10 μm.
m, and the photocatalyst layer contains 10 to 90% by weight of the photocatalyst particles.
The stainless steel sheet according to claim 1, wherein the stainless steel sheet has excellent anti-glare properties, stain resistance, and fingerprint resistance, containing 0.1 to 10 µm in thickness. 3. The stainless steel sheet according to claim 1, wherein the photocatalyst particles contain a titanium oxide-zirconium titanate conjugate. 4. The method according to claim 1, wherein Cr is added between the oxide film and the photocatalyst layer.
0-50 wt%, stainless steel sheet according to claim 1, the chromate film containing 50 to 80 wt% of silica, characterized in that it comprises 5 to 50 mg / m ^2. 5. The base steel sheet having the chemical composition and the surface roughness described in claim 1 is subjected to a series of processes described in the following a to c. A process for producing the stainless steel sheet described above; a. The base steel sheet contains 8% by volume or more of hydrogen, and the remainder is substantially composed of nitrogen in an atmosphere having a dew point of -20 ° C or less.
Performing bright annealing at 00 to 1200 ° C., b. Subjecting the bright annealed base steel sheet to degreasing with an alkaline solution; c. 5 to 20% by weight of ethanol or butyl alcohol and a solid content weight ratio of 1
A coating composition containing photocatalyst particles in an amount of 0 to 90% by weight is applied so as to have a dry film thickness of 0.1 to 10 μm, and dried at 100 to 500 ° C. for 1 minute or more in the atmosphere. 6. The stainless steel sheet according to claim 4, wherein the base steel sheet having the chemical composition and the surface roughness according to claim 1 is subjected to a series of processes described in the following a to d. Manufacturing method: a. The base steel sheet contains 8% by volume or more of hydrogen, and the remainder is substantially composed of nitrogen in an atmosphere having a dew point of -20 ° C or less.
Performing bright annealing at 00 to 1200 ° C., b. Subjecting the bright annealed base steel sheet to degreasing with an alkaline solution; c. Cr is added to the degreased base steel sheet at a dry solid content weight ratio of 2%.
An amount of chromium phosphate necessary for containing 0 to 50% by weight and a silica-containing chromate treatment solution containing silica in an amount of 50 to 80% by weight in terms of a dry solid content are 5 to 50% by weight. Coating in an amount of 50 mg / m ² and drying, d. A coating composition containing 5 to 20% by weight of ethanol or butyl alcohol and an amount of photocatalyst particles having a solid content weight ratio after drying of 10 to 90% by weight has a dry film thickness of 0.1 to 10 μm. And apply to 100-500
Dry in air at ℃ for 1 minute or more.