JP2006063427A - Stainless steel excellent in temper coloring resistance - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide stainless steel excellent in temper coloring resistance which can suppress or inhibit temper coloring without deteriorating metallic appearance of its surface and bending workability. <P>SOLUTION: The surface of the stainless steel is coated with an oxide layer which comprises a silica compound and has a thickness of ≤1 μm. In the oxide layer, at least one chosen from a ceramic powder, a metal powder and a mineral powder is dispersed in a volume ratio of ≤10% to impart the temper coloring resistance as well as scratch resistance and antibacterial property and to enable surface coloring. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

The present invention relates to a stainless steel excellent in temper color resistance while leaving a metallic texture and having very little discoloration due to temper color at high temperatures.
Stainless steel is used in many devices and equipment because of its excellent corrosion resistance. Especially, it is used also for the apparatus exposed to the temperature (about 200-400 degreeC) higher than room temperature although it is not the temperature where high temperature intensity | strength and heat resistance are requested | required like a cooking appliance. When used in such a temperature range, the surface of the stainless steel may be discolored and colored. The present invention relates to stainless steel suitable for such applications.

Stainless steel has corrosion resistance that does not generate rust in daily use environments, so it is not only used for hygienic cleanliness such as kitchen equipment and medical equipment, but also for building materials, electrical equipment, railway vehicles, automobile decorative parts, Widely used in daily necessities. Among these uses, for example, kitchen appliances and cooking appliances, temperatures that are not high temperature strength and heat resistance are required but higher than room temperature (about 200 to 400 ° C.)
There are a lot of things that are exposed to. In general, it has been experienced that the surface of stainless steel exceeding 200 ° C. is discolored and colored in the atmosphere. This discoloration coloring
This is called temper color or bluing. The temper color is caused by an oxide layer having a thickness of less than 1 μm. When the thickness matches the wavelength of light, reflected light interferes and is recognized. Therefore, it seems that various colors such as blue, yellow, pink, and gold are generated depending on the thickness.

The oxide layer that causes the temper color has relatively good adhesion to the stainless steel, and since it is merely colored, there is also an application that does not recognize that it is directly damaged. However, it is often understood that the design as a device is damaged only by the color change. Furthermore, since bacteria easily adhere to the oxide layer, it becomes a sanitary problem in the case of cooking appliances. In addition, since the temper color is a Cr-based oxide, the amount of Cr at the interface between the stainless steel coated with the oxide layer and the oxide is reduced, resulting in deterioration of corrosion resistance. large.

Conventionally, in order to prevent discoloration due to temper color, the use of stainless steel with excellent high-temperature oxidation resistance, the use of stainless steel rods, the prevention of temperature rise due to the device structure, and the high temperature due to the device structure It has been done to prevent atmospheric contact.

The oxide film that is the cause of discoloration due to the temper color is generally the same as a high-temperature oxide film (generally referred to as scale) that appears black when exposed to a high temperature of 800 ° C. or higher. Therefore, it is presumed that the stainless steel excellent in high temperature oxidation resistance has a slight occurrence of temper color. In fact, it has been recognized that high-Cr steels with high high-temperature oxidation resistance are less likely to cause temper color than low-Cr steels. Based on this idea, for example, high Al-containing stainless steel or high Si-containing stainless steel described in Patent Document 1, Patent Document 2, or Patent Document 3 may be used. However, it has been experienced that the temper color of stainless steel excellent in high-temperature oxidation resistance with a large amount of Al or Si added is not much different from SUS304 steel, which is widely used.

JP-A-57-39159 JP-A-50-93220 Japanese Patent Laid-Open No. 2-115348

High-temperature oxidation of stainless steel generally proceeds by first forming a Cr-based oxide and then forming a Fe-based oxide. Since the oxide mainly composed of Cr is formed at an early stage, it is called a protective oxide layer because it is thin, has few cracks, is nonporous, and has a slow diffusion of oxygen. On the other hand, the oxide layer mainly composed of Fe is generally called a non-protective oxide because it is thick and porous with many cracks and oxygen diffuses quickly into the metal. . Moreover, it is also called a nodule-like oxide or a Woltz-like oxide because of its generation form. High temperature oxidation resistant stainless steel is a stainless steel that is alloy-designed to prevent or retard the transition from a Cr-based protective oxide layer to a non-protective nodular oxide. The tendency of temper color generation is related to the formation and growth of protective oxides composed mainly of thin Cr at the very beginning.
Therefore, high temperature oxidation resistant stainless steel, which does not take into consideration the generation and growth of protective oxides or the relationship between them and temperature, cannot be said to be a material excellent in temper color.

The use of stainless steel having excellent resistance to high-temperature oxidation as described above is not necessarily suitable as a means for preventing discoloration due to temper color, but the effect may be recognized mainly with high Cr steel. However, even if there is an effect, high C
rStainless steel with excellent high-temperature oxidation resistance, including steel, is not only expensive,
Hard, low ductility, deep drawability greatly deteriorates, making it difficult to process and toughness.

Since the stainless steel plate is stainless steel coated with glassy ceramics on the surface, temper colors and scales are not generated up to high temperatures. However, since the surface is coated with a glassy ceramic that is overwhelmingly less ductile than metal, even extremely light metal processing such as slight bending with a large R is impossible. In addition, since the baking temperature of the frit, which is the raw material for soot, coincides with the temperature range of the sensitization treatment of stainless steel, stainless steel is sensitized. There was a drawback of progressing. In addition, the ceramic layer of straw is usually 100
Since the thickness is more than μm, there is a drawback that the texture and cleanliness of stainless steel are completely hindered.

Since the temper color is a kind of high-temperature oxidation, it is natural that it is effective to modify the structure of the device so as not to raise the temperature or to reduce the oxygen partial pressure of the atmosphere. However, this method not only hinders the degree of freedom with respect to the original purpose of the device, but also has a drawback of increasing the cost of the device because the structure must be complicated.

The present invention provides a stainless steel with excellent temper color resistance that suppresses or prevents the occurrence of temper color without impairing the metallic texture of the surface and without deteriorating material properties such as workability. is there.

According to the present invention, stainless steel having a metallic texture and excellent temper color resistance, characterized in that the surface of stainless steel is coated with an oxide layer made of a silica-based compound at a thickness of 1 μm or less. Steel is provided (claim 1).
According to the present invention, the surface of the stainless steel is coated with an oxide layer mainly composed of a silica-based compound with a thickness of 1 μm or less, and the oxide layer has a ceramic ratio of 10% or less by volume. There is provided a stainless steel having a metallic texture and excellent in temper color resistance, characterized in that one or more of powder, metal powder and mineral powder are dispersed and contained.
Preferably, the ceramic powder is one or more of TiN, BN, and alumina powder having a volume ratio of 0.1% or more (Claim 3). Preferably, the metal powder is one or two of 0.001% or more of Ag and Cu by volume ratio (Claim 4). The ceramic powder may be TiO ₂ having a volume ratio of 0.1% or more. The ceramic powder may be an inorganic pigment having a volume ratio of 0.1% or more.

The temper color is generated on the outermost surface of the stainless steel and is not affected by the composition of the central portion of the material. Accordingly, the present inventors have aimed to change the component composition or characteristics of the outermost surface in a direction that suppresses or prevents the progress of oxidation.
On the surface of stainless steel, a passive film, which is a source of corrosion resistance, that is, an amorphous oxide mainly composed of Cr with a thickness of several nanometers is formed to cover the surface. It is considered that this oxide grows and thickens when oxygen diffusion in the oxide is promoted, and further crystallizes into a temper color. Therefore, it was thought that the generation of temper color could be suppressed or prevented by compounding an oxide that suppresses the diffusion of oxygen.

Silica compounds are known as oxides with slow oxygen diffusion. Therefore, it was considered to coat silica on a passive film mainly composed of Cr oxide. However, since silica is the same as glass and metal processing is impossible, there is a concern that the same defects as in the case of soot may occur. However, when the thickness is extremely reduced, the ductility increases and processing becomes possible. Furthermore, there is no coating feeling like wrinkles and it has a metallic texture.
Therefore, the surface of the passive film was coated with a very thin silica compound film.

According to the first and second aspects of the invention, since the surface of the stainless steel is coated with the oxide layer containing the silica-based compound, the stainless steel having excellent temper color resistance is provided. Become.
For example, food ovens are required to be clean, so the use of stainless steel is desired. However, since the internal temperature may exceed 200 ° C., normal stainless steel is usually colored by a temper color, and the internal beauty is usually impaired. Furthermore, since there is a concern that food droplets may adhere to the oxide that produces the temper color, which may cause sanitary problems, a slight but slight polishing may be performed to remove the temper color. It was. When the stainless steel having excellent temper color resistance according to the present invention is used, since such temper color does not occur up to approximately 400 ° C., such a concern is completely eliminated. Such applications include cooking equipment such as a range, toaster and stove, and heating equipment such as a stove.
Stainless steel itself is used in a wide range of applications because it has excellent corrosion resistance and can retain its aesthetic appearance for a long time. However, it may be several hundred degrees Celsius like a muffler of a motorcycle, and the occurrence of temper color is inevitable. When the stainless steel excellent in temper color resistance according to the present invention is used, it can be kept beautiful without discoloration. Such applications include interior materials for commercial drying equipment, interior materials for heating furnaces and chemical equipment, and peripheral parts.

In addition, according to the invention of claim 1 and claim 2, since the thickness of the coating is 1 μm or less, the coating does not crack, and stainless steel having workability such as bending is provided. Furthermore, since the thickness of the coating is 1 μm or less, the metallic texture of stainless steel is not impaired.

According to the invention of claim 2, the oxide layer mainly composed of the silica-based compound has a specific dispersed substance (one or more of ceramic powder, metal powder and mineral powder).
Therefore, it is possible to provide a film having the characteristics of the dispersed material. Further, since these dispersed substances are dispersed by 10% or less by volume with respect to the oxide constituting the film, the metallic texture of stainless steel is not impaired.

According to the invention of claim 3, the dispersed material is made of fine TiN, BN having an effect on scratch resistance.
Since the alumina powder is one type or two or more types in addition to the above effects, the coating has scratch resistance. In addition, since these dispersed substances are dispersed by 0.1% or more by volume with respect to the oxide constituting the film, they can effectively withstand brazing.
According to the inventions of claim 4 and claim 5, since the dispersive substance is a substance having antibacterial and / or antifungal properties (one or two of Ag and Cu, TiO ₂ ), the above effect is achieved. In addition, the film has antibacterial and / or anti-wrinkle properties. Further, in these dispersed substances, the metal powder is 0.001% or more by volume ratio with respect to the oxide constituting the film, Ti
Since O ₂ is dispersed at a volume ratio of 0.1% or more with respect to the oxide constituting the film, it effectively has antibacterial properties and / or antifungal properties.
According to invention of Claim 6, since the ceramic powder which is a dispersal substance is an inorganic pigment, in addition to the said effect, a desired color can be attached | subjected to a membrane | film | coat. In addition, since the inorganic pigment is dispersed in a volume ratio of 0.1% or more with respect to the oxide constituting the film,
Color can be applied effectively.

According to the first embodiment of the present invention, an oxide layer made of a silica-based compound is coated on the surface of stainless steel. “Silica-based compound” means a compound having a bond of Si and O, and examples thereof include those obtained by dehydration condensation of silicon tetraethoxide, but the present invention is not limited thereto.
As will be described later, the coating of the silica-based compound on the stainless steel surface is performed by dehydration condensation of the silica-based compound with the passive film on the stainless steel surface. Therefore, depending on the reaction, an unavoidable compound such as a hydroxyl group remaining may be contained. In the first embodiment of the present invention, the “oxide layer made of a silica-based compound” includes such inevitable compounds.

In the present invention, the film thickness of the oxide layer is 1 μm or less.
One of the features of metal is that it can be easily plastically processed. If plastic processing is not performed, for example, no temper color is generated in a glazed product or even glass. The stainless steel of the present invention imparts plastic workability as a metal. Therefore, the thickness of the film is set to 1 μm or less. Since the film thickness was 1 μm or less,
Even if the bending process is performed, the film does not crack. Also, the film thickness is 1μm
By making the following, you can not feel the feeling of coating (clear painting),
It was possible to maintain a metallic texture, and it was also possible to give it a feature that was indistinguishable from bare stainless steel.
The present invention has been completed based on the above findings. That is,
“Stainless steel with a metallic texture and excellent temper color resistance, characterized by covering the surface of stainless steel with an oxide layer made of a silica-based compound with a thickness of 1 μm or less”
Was invented.

Since it is a silica-type compound which coat | covered the surface of stainless steel that has the function to suppress thru | or prevent generation | occurrence | production of a temper color, the kind of stainless steel itself is not ask | required. Furthermore, if the silica-based compound is reliably coated, it is not necessary to use stainless steel. However, since carbon steel does not require a metallic texture for use, the present invention is limited to stainless steel. The stainless steel can be applied to a so-called Cr-based stainless steel containing no Ni or a so-called Ni-based stainless steel containing 6% or more of Ni. That is, the effect of the present invention can be expected if the steel contains at least 12% to 35% Cr, or at least 12% to 35% Cr and 6% to 30% Ni.

According to the second embodiment of the present invention, the surface of stainless steel is coated with an oxide layer mainly composed of a silica-based compound containing a dispersed material.
The silica-based compound which is the main component of the coating film can be dispersed if it easily dissolves an oxide or the like or is a fine powder. By selecting the type of the dispersed material, it is possible to impart various functions, so the second embodiment has been invented.
Also in the second embodiment, the film thickness of the oxide layer is 1 μm or less, and the reason is the same as that of the first embodiment. Moreover, the stainless steel which can coat | cover the film | membrane by 2nd embodiment is the same as the thing of 1st embodiment.

The substance to be dispersed must be a substance that can easily wet and adhere to the silica-based compound. In consideration of the properties and the function to be imparted, examples of the dispersed material include one or more of ceramic powder, metal powder, and mineral powder.
Also, if dispersed in a large amount, the temper color resistance ensured by the silica-based compound is inhibited, or the texture of the dispersed material becomes obvious and inhibits the metallic texture, so the dispersed material constitutes a film. It was determined that the content was 10% or less (dispersed) by volume with respect to the oxide.
Based on the above knowledge, “the surface of stainless steel is coated with an oxide layer mainly composed of a silica-based compound with a thickness of 1 μm or less, and the oxide layer contains ceramic powder having a volume ratio of 10% or less, 1 type or 2 types or more are disperse | distributed and contained among metal powder and mineral powder,
Stainless steel that maintains a metallic texture and has excellent temper color resistance
Was invented.

One example of the dispersed material is ceramic powder as described above. Specifically, it is TiN, BN, or alumina powder, and two or more of these may be used. Furthermore, as described later, the ceramic powder may be an inorganic pigment.
One of the uses in which the occurrence of temper color is a concern is home cooking equipment as described above. In such an application, other cooking utensils often slip, and a decrease in aesthetics due to the tack is regarded as a problem. For example, on a table inside an oven, a cooking dish is often slid in and out, and the anti-sticking property is indispensable. Therefore, one or more of fine TiN, BN, and alumina powders that are effective in scratch resistance are dispersed and mixed in the coating film.
The TiN or / and BN powder to be dispersed and mixed has a lower limit of 0.1% because a large effect is not recognized when the volume ratio is less than 0.1% with respect to the oxide constituting the film.

Moreover, as mentioned above, metal powder is mentioned as one of the dispersed substances, specifically, silver (Ag) powder or copper (Cu) powder, and these two types may be used. .
Furthermore, mineral powder is mentioned as one of the dispersoids as described above. Examples of mineral powder include TiO ₂ rutile ore, which is known as a photocatalyst.
As described above, there are cooking appliances in which the occurrence of temper color is a concern. Since such a use requires special hygiene, the use of the material further expands if the material used in the device has antibacterial and anti-rust properties. Therefore, fine Ag or / and Cu having antibacterial and / or anti-wrinkle effects are dispersed and mixed in the coating film, and a photocatalyst mainly composed of TiO2 having antibacterial and / or anti-wrinkle properties is dispersed in the coating film. It was decided to mix.

The Ag / and / or Cu powder to be dispersed and mixed is effective by dispersing 0.001% or more by volume, and in the case of a photocatalyst, 0.1% or more by volume.

As described above, the ceramic powder that is one of the dispersed substances may be an inorganic pigment.
One of the objects of the present invention is to maintain the metallic texture of stainless steel. However, stainless steel has an achromatic color. Therefore, the use is expanded by making chromatic colors while taking advantage of the metallic texture. There is a need for a so-called clear color surface that does not have a coating feeling. Therefore, a fine pigment is dispersed and mixed in the coating film. In this case, since the present invention is an application in which the generation of temper color is a concern, it does not include organic pigments that can decompose in such a temperature range or cause a chemical reaction.

For the inorganic pigment, the type of pigment and the amount of added dispersion can be selected according to the desired color type level. For example, cobalt blue, cobalt green, titanium yellow,
There are tail belt, titanium white, antimony white, chrome black, gold pink, yellow iron oxide, black iron oxide, bengara and so on.

In this invention, the coating method of a silica type compound is not specifically limited, It is possible to use a well-known coating method. For example, it is possible to coat a silica-based compound by hydrolyzing silicon alkoxide with an acid or the like, applying the sol solution, and dehydrating and condensing with a passive film on the surface of stainless steel. It is also possible to coat the silica compound by applying a silane coupling agent and oxidizing it at the same time as decomposition at high temperature.
Similarly to the soot, it is also possible to apply a desired silica-based compound powder on the surface and melt it at a high temperature to coat the surface of the stainless steel. However, this method is easy, but it is difficult to reduce the film thickness, and the melting temperature is higher than the dehydration condensation temperature of the silicon alkoxide and the oxidation temperature of the silane coupling agent described above. It is not optimal from the viewpoint of manufacturing cost and quality because it corresponds to the sensitizing temperature range of stainless steel.

First, when a stainless steel surface is coated with a film made of a silica-based compound,
Temper color resistance was examined.
Figure 1 shows SUS304-BA steel coated with about 120 nm of a silica-based compound film (a stainless steel plate is immersed in an ethanol solution of silicon tetraethoxide and hydrolyzed by adding a dilute hydrochloric acid aqueous solution, and dried at 150 ° C after simple drying. It is the figure which showed the change of the color difference after 10-minute heating in air | atmosphere with the SUS304-BA steel which carried out dehydration condensation for 10 minutes and SUS304-BA steel which was not coat | covered.
The film thickness was defined as the average depth until the Fe spectrum was detected by Auger electron spectroscopy and reached the same level as the central part.
The uncoated SUS304-BA steel used for comparison starts discoloration at 300 ° C or higher, and can be clearly seen with the naked eye at 350 ° C or higher, whereas SUS304-BA steel coated with a silica-based compound. There was almost no discoloration up to 400 ° C, and discoloration was first observed at 450 ° C. Thus, it was confirmed that the temper color resistance was clearly improved by coating the silica-based compound.

Next, the thickness of the film made of the silica-based compound and the workability (whether or not the film cracks when bent) were examined.
Fig. 2 shows a SUS304-BA steel coated with a silica-based compound film (a stainless steel plate is immersed in a sol-like solution hydrolyzed by adding a dilute hydrochloric acid aqueous solution to an ethanol solution of silicon tetraethoxide, dried at 10 Coating by dehydration condensation for a minute.The film thickness was changed by the difference in immersion time.For the film thickness of 1650 mm, the coating thickness was 1650 m by performing the coating operation in addition to the above immersion.
m. Is a diagram showing the influence of the film thickness on the bending workability of t / 2.
The film thickness was defined as the average depth until the Fe spectrum was detected by Auger electron spectroscopy and reached the same level as the central part.
Evaluation of the bending workability was carried out by the presence or absence of discoloration with the naked eye after heating in the atmosphere at 400 ° C. for 10 minutes after processing. In the figure, ◯ indicates that no crack was generated and no temper color was generated, that is, the film was satisfactorily processed, and × indicates that the temper color was generated in the film, that is, the film was cracked.
When the film thickness was thin, cracking did not occur even when bending was performed, and temper color did not occur due to heating in the atmosphere. When the thickness was 1 μm (1000 nm) or less, no cracks were generated even when 90 ° bending was performed, and when the thickness was 300 nm or less, bending was possible without causing cracks to 180 °.
Conversely, when the film thickness exceeded 1 μm (1000 nm), the workability deteriorated, cracking occurred even at 60 ° bending, and discoloration due to temper color was observed by atmospheric heating. 3μ more
Beyond m, cracks occurred even when bent at 30 °, and discoloration due to temper color was observed. When bending at 180 °, the film peeled off, and it was confirmed that the flakes were peeled off simply by touching.

From the above results, by limiting the coating thickness of the silica-based compound film to 1 μm (1000 nm) or less, it is possible to provide stainless steel that can maintain the workability as a metal without generating a temper color by heating in the atmosphere. There was found.

Examples 3-7, Comparative Example 1:
A stainless steel plate was immersed in a sol-like solution hydrolyzed by adding a dilute hydrochloric acid aqueous solution to an ethanol solution of silicon tetraethoxide. After simple drying, dehydration condensation was caused in air at 150 ° C. for 10 minutes to coat a silica compound film. The film thickness was controlled by changing the pulling rate from the sol solution. In the case of a film thickness of 1650 mm, the film thickness was set to 1650 mm by performing a coating operation in addition to the above immersion. Table 1 shows the thickness of the film, the temper color generation tendency, the bending workability, and the presence or absence of a metallic texture.

The film thickness was defined as the intermediate depth from the depth at which the Fe spectrum was detected by Auger electron spectroscopy to the same level as the central part.
The temper color generation tendency was evaluated by the presence or absence of temper color generation by heating in the atmosphere at 400 ° C. for 10 min.
Bending workability was evaluated by the presence or absence of the occurrence of temper color with the naked eye after heating in the atmosphere at 400 ° C. for 10 minutes after processing, and the maximum bending angle at which no temper color was produced was shown. However, since this method cannot be applied to Comparative Example 3 (without coating), the bending surface was observed and evaluated with an optical microscope.
The metallic texture is sensuously evaluated for the presence or absence of surface coating, and ○ is the one that can be felt as an untreated metal surface that has not been treated by the naked eye, and the one that is felt to have been painted is ×. evaluated.

As shown in Table 1, the coating materials (Examples 3 to 7) having a film thickness of 1000 nm (= 1 μm) or less, regardless of the base steel type, have good temper color resistance and practical limits on bendability. It was possible to bend at 90 °, and it also had a metallic texture. In particular, the coating materials of Examples 3 to 5 having a thin film thickness could be bent by 180 °.
The coating material of Comparative Example 1 had good temper color resistance, but the film thickness was 100
Since it exceeded 0 nm, bending was possible only up to 30 °, and the surface texture was similar to that of clear paint. Further, the coating material of Comparative Example 2 having a thick film thickness was almost impossible to bend. Since the sample of Comparative Example 3 was not coated, it had a texture without a feeling of coating, and there was no problem with 180 bending in processing, but naturally the temper color resistance was poor.

Examples 8-17, Comparative Examples 5-6:
In the same manner as in Example 1, the surface of a SUS304-BA stainless steel plate was coated with a silica compound film of 70 to 140 nm. At this time, various amounts of ceramic powder and metal powder were dispersed and added to the sol-like solution and dispersed in the silica-based compound film. Tables 2 to 4 show the film thickness, temper color generation tendency, bending workability, presence of metallic texture, scratch resistance, and / or antibacterial properties against Escherichia coli.
The film thickness measurement method, evaluation of temper color generation, evaluation of bending workability, and evaluation of metallic texture are the same as described above.

Scratch resistance was evaluated by rubbing the coated surface with a commercially available sand eraser and observing the presence or absence of wrinkles with the naked eye.
Antibacterial activity against E. coli, NBRC3301 E. coli was placed on the sample surface simultaneously with the culture solution containing polypeptone and yeast extract, and cultured for 24 hours at 35 ° C. The case where the colony was not observed but white turbidity was observed was evaluated as ◯, the case where the colony was generated was evaluated as Δ, and the case where the colony was propagated to the full scab was determined as X. However, the dispersions of the TiO ₂ photocatalysts of Examples 14 and 15 were irradiated with black light for the initial 2 hours out of the test time of 24 hours.
The color was evaluated with the naked eye.

As shown in Table 2, the coating materials (Examples 6 to 8 and Comparative Example 4) in which TiN, BN, and alumina are dispersed alone or in combination are at a level where there is no coating feeling and bending workability is practically acceptable. In addition, the scratch resistance was also good. However, the coating material of Comparative Example 4 is TiN
10% or more is dispersed to give a slightly golden color, no metallic texture, and bendability is 9
Cracks occurred when it exceeded 0 °.

The coating materials of Examples 9 to 11 in which Ag and Cu were dispersed exhibited antibacterial properties in addition to other properties. In particular, in the coating materials of Examples 10 and 11 added in a large amount, no growth of Escherichia coli was observed on the naked eye. The coating materials of Examples 12 and 13 in which the TiO2 photocatalyst was dispersed also exhibited antibacterial properties in addition to other properties.

The coating material of Example 14, in which the inorganic pigment cobalt blue was dispersed, had a blue transparent surface and could be colored without a coating feeling. However, the coating material of Comparative Example 5 in which the pigment dispersion amount exceeded 10% was inferior in the transparency of the coating layer and felt a coating feeling.
In Example 15 and Comparative Example 6, the color in the case of containing no dispersive material was observed. Since the coating material of Example 15 is related to claim 1 of the present invention and does not disperse a special substance, it was silver-colored with no scratch resistance and antibacterial properties and an achromatic surface color. However, the temper color resistance has been greatly improved without deteriorating the metallic texture that is the object of the present invention and without degrading the bending workability. The comparative material of Comparative Example 6 is a SUS304-BA material that is not covered. Naturally, the metallic texture was sufficient and the bending workability was good, but the color was achromatic silver and there was no anti-bacterial and anti-bacterial property, and the liver-and-kidney temper color resistance was poor.

It is the figure which showed the change of the color difference after 10-minute heating in air | atmosphere. It is a figure showing the bending workability of t / 2.

Claims (6)

Stainless steel with an excellent temper color resistance and a metallic texture, characterized in that an oxide layer made of a silica-based compound is coated on the surface of stainless steel with a thickness of 1 μm or less. The surface of stainless steel is coated with an oxide layer mainly composed of a silica-based compound with a thickness of 1 μm or less, and the oxide layer contains ceramic powder, metal powder and mineral powder of 10% or less by volume. Of these, one or more types are dispersed and included,
Stainless steel that maintains a metallic texture and has excellent temper color resistance. The ceramic powder is 0.1% or more of TiN, BN and alumina powder by volume ratio.
Stainless steel excellent in temper color resistance and maintaining a metallic texture according to claim 2, characterized in that it is a seed or two or more kinds The metal powder is one or two of Ag and Cu having a volume ratio of 0.001% or more, and maintains the metallic texture according to claim 2 and has excellent temper color resistance. Stainless steel The ceramic powder is TiO ₂ having a volume ratio of 0.1% or more,
A stainless steel which maintains the metallic texture according to claim 2 and has excellent temper color resistance 3. The stainless steel excellent in temper color resistance and having a metallic texture according to claim 2, wherein the ceramic powder is an inorganic pigment having a volume ratio of 0.1% or more.

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