JPH108234A - Outdoor titanium or titanium alloy material excellent in discoloration resistance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain outdoor titanium in which the generation of discoloration is prevented over a long period and free from the need of maintenance by imparting surface roughness in which the center line average roughness is prescribed and oxidized coating on the surface in which thickness is specified to outdoor titanium or the like. SOLUTION: The surface roughness of an outdoor titanium or titanium allay material is regulated to <=3μm, preferably to <=1.5μm by the center line average roughness Ra, and the thickness of oxidized coating on the surface is regulated to >=20Å preferably, to >=40Å. Furthermore, the regulation of the surface roughness is executed by regulating the surface roughness of rolling rolls, rolling loads and the velocity thereof, and for the regulation of the thickness of the oxidized coating, an oxidation treating method by heat treatment and an anodic oxidation treating method of forming oxidized coating by flowing electric current to titanium in a soln. are adopted. In this way, the outdoor titanium or titanium allay material excellent in discoloration resistance can be obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to titanium or a titanium alloy used for outdoor applications such as building exterior materials and monument materials (for example, monuments). In particular, when used in these applications, it is possible to minimize the occurrence of dirt over time and to exhibit an excellent effect of discoloration resistance. Lumber "
In some cases).

[0002]

2. Description of the Related Art In recent years, due to the occurrence of acid rain due to air pollution and the progress of waterfront development, the use environment of building exterior materials such as roofing materials and outer wall materials and monument materials has become severer, and these materials have been used for outdoor applications. Metal materials to be used are required to have excellent corrosion resistance. As a metal material used for such outdoor use, a material having relatively good corrosion resistance, such as aluminum, stainless steel and copper, has been used.

[0003] However, under the circumstance where the use environment is becoming severe, it cannot be said that such a metal material can sufficiently cope with such a situation, and in recent years, it is much better than the above-mentioned metal material against acid rain and seawater. Corrosion-resistant titanium materials are increasing in use as alternatives to the above-mentioned metal materials.

[0004] It has been more than ten years since titanium materials began to be used for the above applications, but there has been no report that corrosion has occurred. However, as the use period becomes longer, a slightly brownish discoloration may occur as in the case of conventionally used metal materials such as aluminum, stainless steel, and copper. The cause of such discoloration has not been fully elucidated so far, but if such discoloration occurs, the appearance will be impaired depending on the discolored portion and its degree.

At present, the technology for preventing the above-mentioned discoloration has not been established because the cause of the aging dirt has not been elucidated at present. Actually, discoloration is removed by wiping the surface with an acid such as nitric hydrofluoric acid or lightly polishing the surface with an abrasive paper. However, such a countermeasure has a problem of poor maintainability.
Under such circumstances, there is a demand for the development of an outdoor titanium material that does not cause such discoloration over a long period of time, that is, has excellent discoloration resistance so that maintenance-free operation can be achieved.

[0006]

DISCLOSURE OF THE INVENTION The present invention has been made under such a circumstance, and an object of the present invention is to provide a discoloration-resistant color that does not cause discoloration over a long period of time and is maintenance-free. An object of the present invention is to provide an excellent outdoor titanium or titanium alloy material.

[0007]

The outdoor titanium or titanium alloy material of the present invention, which has achieved the above object, has a surface roughness of 3 μm or less in center line average roughness Ra and an oxidation of the surface. The point is that the film thickness is 20 ° or more.

In the outdoor titanium or titanium alloy material, the surface roughness is 1.5 μm in center line average roughness Ra.
The following is preferred. Alternatively, the thickness of the oxide film is preferably 40 ° or more.

The above-mentioned oxide film can be formed by various means described later, and examples of the effective method include an oxidation treatment by heating or an anodic oxidation treatment.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Under the above-mentioned background, the present inventors have studied from various angles with the aim of developing a titanium material with less aging stain. First, the cause of the contamination with time of the titanium material could be clarified. That is, according to the study by the present inventors, the stain with time is at least the following (a),
It was clarified that the two factors (b) are involved. (A) Fe, C, NaCl, SiO ₂ present in the atmosphere
(B) Growth of oxide film on titanium material surface (increase in film thickness) due to adhesion of gas components such as SOx and NOx and moisture etc. existing in the atmosphere

That is, Fe in the above (a) is fine powder of rust generated from iron sand or steel structures, C is a component contained in exhaust gas from factories, etc., and NaCl is sand containing seawater droplets or seawater components. And SiO ₂ are considered to be derived from sand, respectively, and they fly to the surface of the titanium material and are physically attached to cause discoloration.

On the other hand, the gas components such as SOx and NOx in the above (b) are components in flue gas from automobiles and factories,
The moisture is atmospheric moisture, rain, and the like. When these are present on the surface of the titanium alloy material, SOx and NOx are dissolved in moisture, and extremely low concentrations of sulfuric acid and nitric acid are formed. With such an acid, titanium does not corrode at all macroscopically, but titanium is eluted as an ion although it is microscopically very small. The eluted titanium ions react with oxygen and moisture in the air to form an oxide film. Then, the oxide film is in a state in which the above-mentioned gas components are involved, and when the oxide film has a thickness of a certain degree or more, the oxide film looks colored due to the interference effect of light. In the process of forming the oxide film, if a floating component such as Fe, C, NaCl, or SiO _{2 of} (a) is involved in the oxide film, even a thinner oxide film looks colored (that is, discoloration is accelerated). Will be).

Accordingly, the present inventors have proposed that, if (a) the physical adhesion of airborne components and (b) the formation of an oxide film on the titanium surface can be effectively prevented, the titanium alloy material can be prevented from being stained with time. We thought that it could be reduced, and conducted intensive research on the specific means.

As a result, first, since the above (a) is the physical attachment of the suspended component particles, it was considered that the surface of the titanium material should be formed in a state in which the particles are hardly attached. Then, the relationship between the surface roughness of the titanium material and the particle adhesion was investigated.

FIG. 1 is a graph showing the relationship between the surface roughness (center line average roughness Ra) of titanium material and the adhesion of particles (the number of fine powders attached). In this experiment, a titanium material adjusted to various surface roughness and Fe, C, NaCl, SiO
_Put the mixed powder of _{2 in} the chamber and pulverize the fine powder by air pressure.
After stirring for 0 minutes, the surface of the sample was scanned with a scanning microscope (SEM).
And the number of adhered fine powders per unit area (mm ² ) was measured.

As is clear from FIG. 1, when the surface roughness is 3 μm or less in center line average roughness Ra, the adhesion of fine powder can be reduced, and especially when the surface roughness is 1.5 μm or less, the effect is remarkable. I understand. This is presumably because, when the surface roughness is reduced, the surface of the titanium material becomes substantially smooth, the particles are hardly caught physically, and the adhesion of the particles is reduced.

On the other hand, the excellent corrosion resistance of the titanium material is due to the fact that the oxide film (formed in the form of TiO, Ti ₂ O ₃ , TiO ₂ ) present on the surface exhibits excellent underlayer protection in various environments. It is due to. It is considered that the greater the thickness of the oxide film, the better the protection of the underlayer by the oxide film of the titanium material. Therefore, with respect to the above factor (b), it was thought that if the thickness of the oxide film existing on the surface of the titanium material was set to a certain value or more, the elution of trace amounts of titanium could be suppressed.

The present inventors have investigated the relationship between the thickness of the oxide film and the degree of discoloration. The relationship between the thickness of the oxide film and the degree of discoloration when a titanium material having variously changed oxide film thickness on the surface is put in a chamber and sprayed with water in which about 100 ppm of SOx and NOx are respectively dissolved in these surfaces for 48 hours. It is shown in FIG. At this time, the thickness of the oxide film was adjusted by a storage time when the titanium material was stored indoors after the pickling or by an air oxidation treatment. The evaluation of discoloration is performed visually, and the degree of discoloration is divided into 11 groups.
Those with the most intense discoloration were evaluated as rank “0”, and those with the least discoloration were evaluated as rank “10”.
As is evident from the results, the discoloration is reduced when the thickness of the oxide film is 20 ° or more.
分 か る It can be seen that the discoloration reduction effect is large with the above.

If the thickness of the oxide film is set to a certain value or more, the surface of the titanium material will be colored, and this cannot be applied to a titanium material that does not require such coloring. If it does, it does not become a colored film, so such inconvenience does not occur. However, in the case of a titanium material that is not inconvenient even if colored, it is needless to say that these points need not be considered. In the above investigation, the thickness of the oxide film can be adjusted by the storage time of the titanium material because the surface of the titanium material activated by pickling reacts with oxygen and moisture in the air to form an oxide film. is there. At this time, depending on the environment, the oxide film may grow up to several tens to hundreds of square meters.However, in the case of indoor storage, there is no entrapment of fine powder in the film formation process and there is no adhesion of sulfuric acid, nitric acid, etc. Unlike the above, discoloration due to film growth is unlikely to occur (however, coloring occurs when the thickness exceeds 100 °).

Based on the above-mentioned examination results, it has been found that if the surface roughness and the thickness of the oxide film are controlled so as to have appropriate values, a synergistic effect of these can further improve the effect of preventing contamination with time. The present invention has been completed. That is, the surface roughness of titanium is set to an appropriate value, and the above-mentioned floating components are less likely to adhere to the oxide film surface, and, further, in a clean atmosphere, an oxide film having an appropriate surface roughness is formed in advance. This prevents the oxide film from functioning as a barrier layer and subsequently forming an oxide film involving a gas component causing discoloration.

The method for producing the titanium material of the present invention is not particularly limited. For example, the titanium material can be produced by adjusting the surface roughness and the thickness of the oxide film by the following method.

The surface roughness of the titanium material can be adjusted by adjusting the surface roughness, rolling load, and speed of the rolling roll, as long as it is used as it is as the rolled surface. After the rolling, the surface of the titanium material can be adjusted by adjusting the components, composition, temperature, time, and the like of the pickling solution, if the material is a titanium material that is pickled and used as it is after pickling. The surface roughness can also be adjusted by skin pass rolling or dull roll rolling after pickling or rolling. That is, the order of the roughness of the substrate is several μm, and the order of the thickness of the oxide film is several tens.
Since it is several hundred degrees, the roughness does not change depending on the thickness of the oxide film. Therefore, if the surface roughness of the base titanium material is adjusted, the surface roughness is reflected and becomes the surface roughness after the oxide film is formed.

On the other hand, the thickness of the oxide film is adjusted so that the titanium material after pickling is not exposed to direct wind and rain such as indoors, or to polluted air such as an industrial zone, if the oxide film is used for pickling skin. If stored in an environment (essentially, it should be stored in an environment other than the environment that causes discoloration described above), there is a difference depending on the storage location and time, but it will react with oxygen and moisture in the atmosphere. Then, the oxide film grows spontaneously from several tens of degrees to about 100 degrees (the thickness of the oxide film immediately after pickling is considered to be close to 0). When used on a rolled surface, vacuum annealing is usually performed after rolling. However, even after vacuum annealing, an oxide film of about several to ten degrees usually exists. And the amount of this oxide film depends on the vacuum annealing conditions (degree of vacuum, temperature,
Therefore, the thickness of the oxide film may be adjusted under these conditions, or the film may be stored indoors for a certain period of time after the vacuum annealing similarly to the pickling material to grow the oxide film.

As methods for forcibly and efficiently forming an oxide film on the surface of the titanium material, there are an oxidation treatment method by heat treatment and an anodic oxidation treatment method in which electricity is passed through titanium in a solution to form an oxide film. These treatments are usually used for coloring the titanium surface, but these treatments make it easy to control the thickness of the oxide film. In addition, the thickness of the oxide film can be controlled. For example, when the titanium material is used as it is without coloring, if the oxide film thickness is 1 as described above.
If the temperature is less than 00 °, a colored film is not formed. Therefore, the processing conditions may be controlled to form an oxide film of 100 ° or less.

On the other hand, a coloring material is required in some applications. In this case, the surface roughness is the center line average roughness R
When a titanium material having a thickness of 3 μm or less or 1.5 μm or less is used, oxidation treatment or anodic oxidation treatment is performed by heat treatment, and an oxide film thickness is grown until a required color tone is obtained. Material can be obtained.

Although the thickness of the oxide film is specified in the present invention, this value can be determined by a composition analysis in the depth direction of the titanium oxide film by Auger electron spectroscopy (AES method). That is, it can be obtained by multiplying the sputtering time required until the oxygen concentration decreases to an intermediate concentration between the maximum concentration and the base concentration by the sputtering speed. The sputtering speed at this time is the speed at which SiO ₂ was sputtered under the sputtering conditions at the time of measurement. FIG. 3 schematically shows a method of obtaining the oxide film thickness from the results of the composition analysis of the titanium oxide film in the depth direction by the AES method.

Hereinafter, the present invention will be described in more detail with reference to examples. However, the following examples do not limit the present invention. It is included in the technical scope.

[0028]

EXAMPLE A pure titanium material adjusted to various surface roughnesses (surface roughness after oxide film formation) and various oxide film thicknesses was placed in a chamber, and Fe, C, N
aCl, microscopic powder of SiO _2, and SOx and NOx the respectively about 100ppm crowded dissolved water 1 month to month spraying,
The surface discoloration situation was investigated. The atmosphere at this time is 70
The environment was very susceptible to discoloration at a high temperature of ８０80 ° C. and a high humidity of 99% humidity. In other words, this test is a kind of accelerated discoloration test, which is an extremely severe environment as compared with an outdoor use environment, and can generate a degree of discoloration that cannot be caused by ordinary use.

As a sample, one of (1) air-annealed → salt-immersed → pickled or (2) vacuum-annealed JIS Class 1 industrial pure titanium cold rolled material is used.
The surface roughness was adjusted by controlling the pickling conditions (adjusting the composition, time and temperature) and by rolling using rolling rolls having different surface roughness. The thickness of the oxide film can be adjusted by pickling the sample after pickling or vacuum annealing in various environments (temperature,
(Humidity varies) indoors for one week to one year,
This was performed by an air oxidation treatment or an anodic oxidation treatment. About the obtained titanium material, the degree of discoloration (hereinafter, referred to as
"Stain resistance") was evaluated. The results are shown in Table 1 below together with the production history and surface properties (surface roughness, oxide film thickness, presence or absence of coloring) of the titanium material. The evaluation criteria for stain resistance are as follows.

[Evaluation Criteria for Stain Resistance] A: Very little discoloration occurred compared to the sample before the test. ：: slightly discolored as compared to the sample before the test, but the degree is still small. Δ: Average discoloration level of a titanium material used outdoors. Although discoloration occurs more than those of ◎ and ○, it is not enough to impair the aesthetic appearance. ×: The color is remarkably discolored, and the appearance may be impaired.

[0031]

[Table 1]

From Table 1, the following can be considered. First, the sample No. Nos. 1 to 14 each had an oxide film formed after being pickled or vacuum-annealed and stored indoors, and each had a surface roughness of 3 μm or less in center line average roughness Ra, and a thickness of the oxide film. Is 20 ° or more, which means that the film has excellent stain resistance. Among them, Sample No. 6-8,1
Samples Nos. 3 and 14 exhibit particularly excellent stain resistance because the surface roughness is 1.5 μm or less in center line average roughness Ra and the oxide film thickness is 40 ° or more.

Sample No. Nos. 15 to 25 were prepared by forcibly forming an oxide film by pickling and then subjecting them to atmospheric oxidation or anodic oxidation treatment.
Since a is 3 μm or less and the thickness of the oxide film is 20 ° or more, it can be seen that the stain resistance is excellent. Among them, Sample No. 15, 16, 19, 21, 22, 2
4 had a surface roughness of 1.5 μm in center line average roughness Ra.
m or less and an oxide film thickness of 40 ° or more, showing particularly excellent stain resistance.

Sample No. 20 and 25 are 40
Although thick oxide films of 0 ° and 600 ° were formed, the surface roughness was 3 μm, which is the upper limit of the center line average roughness Ra, and was not evaluated as ◎. From this, it can be determined that it is important to control both the surface roughness and the oxide film thickness within a predetermined range in order to improve the stain resistance.

On the other hand, the sample No. 26 to 28 and 31, 32 were discolored because either the surface roughness or the oxide film thickness was out of the range specified in the present invention, and was evaluated as Δ. Sample No. 2
Samples 9 and 30 were markedly discolored because both the surface roughness and the thickness of the oxide film were out of the ranges specified in the present invention, and were evaluated as x.

Sample No. 15-18 and 21-23
The non-colored film was formed because the thickness of the formed oxide film was 100 ° or less, and when it exceeds this value, the film becomes a colored film due to the interference of light. Further, in the above embodiment, only pure titanium material is used, but this does not indicate that the present invention is applicable only to pure titanium. That is, since the effects of the present invention can be obtained by controlling the surface roughness and the thickness of the surface oxide film within an appropriate range, the present invention can of course be applied to the case where a titanium alloy material is used. .

[0037]

As described above, according to the present invention, it is possible to obtain a titanium or titanium alloy material which can prevent or reduce aging stains due to outdoor use or the like and does not cause discoloration for a long period of time. When the titanium or titanium alloy material thus obtained is used as a material such as a roof material, a wall material, and a monument material, maintenance-free operation can be achieved, which is extremely useful.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the surface roughness of a titanium material and the adhesion of particles.

FIG. 2 is a graph showing the relationship between the thickness of an oxide film and the degree of discoloration (stain resistance).

FIG. 3 is a graph schematically showing a method for obtaining an oxide film thickness from a result of a composition analysis of a titanium oxide film in a depth direction by an AES method.

Claims (4)

[Claims] The surface roughness is 3 μm in center line average roughness Ra.
An outdoor titanium or titanium alloy material having excellent discoloration resistance, wherein the thickness is not more than 20 mm. 2. The outdoor titanium or titanium alloy material according to claim 1, wherein the surface roughness is 1.5 μm or less in center line average roughness Ra. 3. The outdoor titanium or titanium alloy material according to claim 1, wherein the thickness of the oxide film is 40 ° or more. 4. The outdoor titanium or titanium alloy material according to claim 1, wherein the oxide film is formed by oxidation treatment by heating or anodic oxidation treatment.