JP3323909B2 - Method of coloring titanium alloy by thermal oxidation - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for coloring titanium by heating and oxidizing, and the coloring of interior products, Western tableware, decorations, crafts, arts, etc., using the coloring, or a specific method. It is used for temperature sensors that use color development at temperature.

[0002]

2. Description of the Related Art An oxide film is naturally formed on the surface of Ti in air, and its thickness is said to be 0.5 to 7 nm. When Ti is heated in an oxygen-containing atmosphere or subjected to anodic oxidation, the thickness of the oxide film is on the order of several tens of nanometers, and exhibits various colors due to light interference. Although some metal-based alloys other than Ti show oxidative coloring, such as the temper color of steel, Ti provides more various colors and more beautiful coloring than other metal-based alloys.

[0003] Regarding the oxidation coloring method of Ti, titanium / zirconium, Vol. 23, no. 2, p. 75-
78 (1975). According to the report, to form a colored oxide film on the metal Ti surface, (1) a heating oxidation method in air or oxygen,
There are three methods: (2) a chemical oxidation method of boiling with an inorganic acid, and (3) an anodization method, which is an electrochemical treatment. In the case of thermal oxidation, the heating temperature and heating time are controlled, in the case of chemical oxidation, the strength and treatment time of the acid are controlled, and in the case of anodic oxidation, the type of electrolyte and the treatment voltage are controlled. By controlling, it is possible to change the composition and thickness of the film, and accordingly, various colors can be obtained. Hereinafter, these three oxidation coloring methods of Ti will be described in detail.

(1) Thermal oxidation method When a Ti oxide film is formed by thermal oxidation in air, the composition of the film (TiOx, 0
<X ≦ 2), and the color tone changes accordingly. An example of short-time heat oxidation of pure Ti bulk material in air will be described below. At a temperature of 300 ° C. or lower, no oxide film is formed, and the metal α-Ti phase has a silvery white color. 300-400
At ℃, golden to yellow with TiO, brown to dark blue at 400 to 480 ° C, blue with Ti ₂ O ₃ at 480 to 570 ° C, 5
Purple at 70-700 ° C, TiO at 700-800 ° C
_{At 1.9} to 900 ° C., it becomes gray with gloss, and at 900 ° C. or higher, it becomes TiO ₂ (rutile) and has an off-white color. However, this coloring method has poor reproducibility,
There is a difference in coloration between reports. Further, since the color tone changes continuously depending on the heat treatment time, color unevenness is likely to occur.

[0005] As an application example of conventional coloring by thermal oxidation of Ti, there is an α phase and a residual β phase in the microstructure of a Ti alloy based on a difference in coloration due to a difference in oxidation rate of each phase constituting the microstructure. In some cases, carbides are identified by heat oxidation, but it is reported that color uniformity is poor. In addition, there is an example in which the type of Ti alloy scrap is discriminated by utilizing the difference in coloration of Ti and various Ti alloys due to thermal oxidation, but it is described that color reproduction is poor. This is because the thermal oxidation has a complicated oxidation reaction and a complicated oxide film structure. As described above, the thermal oxidation method is not suitable as a coloring method for decorative articles and the like because of poor color uniformity and reproducibility. However, the heat oxidation method is attractive in that it can form an oxide film with a simpler and cheaper device, simple operation and lower cost than other methods, and is suitable for mass production and processing of large products. . It can be used as a temperature sensor that uses the color change due to heating temperature, but it is difficult to judge the color because the reproducibility of the relationship between color and temperature is poor, and the color uniformity is poor and color unevenness tends to occur. There is such a problem.

Although it is not a method of forming an oxide film, there is a nitriding method as the same heating coloring method. When Ti is heated to 750 ° C. or more in a nitrogen gas atmosphere, a thin film of TiN is formed on the surface and has a golden color. Unlike the oxidation method, which exhibits a variety of colors, the nitridation method only colors the golden system. The nitriding method was originally used as one of the surface hardening methods to improve the abrasion resistance.However, when viewed as a coloring method, the formation of a surface nitride layer resulted in rough skin and gloss. When the surface is polished in an attempt to obtain a nitride layer, the colored nitride layer is thin, so that the golden color is reduced. When the treatment is performed at a high temperature for a long time to increase the thickness of the nitride layer, the surface has wrinkles.

(2) Chemical oxidation method Ti is colored when boiled in an inorganic acid. For example, 0.1
When boiled in sulfuric acid of less than wt% for 24 hours, it becomes bluish purple,
It is colored golden when boiled in hydrochloric acid of 0.2 wt% or less for 24 hours, and pale golden when boiled in 30 wt% nitric acid for 24 hours. It is said that the film formed by chemical oxidation is inferior in film quality, and is also inferior to thermal oxidation in terms of corrosion resistance. Further, there is a problem that it takes a long time to form a film and there are few kinds of colors, and it is said that this is not a practically appropriate coloring method. In addition, there is a problem in workability because a strong acid is used.

(3) Anodizing method When a direct current is passed in a suitable electrolyte solution using Ti as an anode and Pt, Ti, stainless steel or the like as a cathode, an oxide film on the titanium surface of the anode grows, so-called anodic oxidation. A film is formed. When anodic oxidation is performed at a constant voltage, the current gradually decreases with time, and only a very small current flows in about 2 to 3 minutes. That is, when anodic oxidation is performed at a constant voltage, an oxide film having a withstand voltage corresponding to the voltage is formed, and the growth of the oxide film stops. Therefore, since an oxide film having a thickness specific to the anodizing voltage is formed, the color tone of the interference color can be controlled. For example, 1%
When anodized in phosphoric acid aqueous solution, 10V dull gold, 20V purple, 30V blue, 40V light blue,
Light yellow at 50V, bright gold at 60V, salmon pink at 70V, light purple at 80V, bluish green at 90V, 100V
Develops a bright green color. As described above, since the color development of the anodizing method is easy, the anodizing method is mainly used for coloring interior products (lighting fixtures, wall materials), western tableware, decorative articles, and the like.

Regarding the formation of a colored oxide film on Ti powder,
Methods involving wet processing such as chemical oxidation and anodic oxidation are practically difficult, and are limited to thermal oxidation. However, even when the Ti powder is heated and oxidized, the color of the oxide film formed is limited to a brownish color, and a variety of colors such as a blue color as in the above-described bulk material cannot be obtained. For these reasons, there has been no research example or application example regarding coloring by forming an oxide film on Ti powder.

[0010]

When a colored oxide film is formed on Ti, the heat oxidation method can form an oxide film with a simple and inexpensive apparatus and at low cost, and is suitable for mass production and processing of large products. However, the oxidation reaction in the air is complicated, and the structure of the oxide film is also complicated, so that it is difficult to control the coloring. Therefore, there has been a problem that it is difficult to form a color with good reproducibility under a certain condition and to form a film having a uniform color without color unevenness. Further, there is a problem that even if the powdered Ti is heated and oxidized, it is not possible to obtain various kinds of colors such as a bulk material.

[0011]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides at least 5 atomic% of at least one of Ti and at least one metal element which is less likely to be thermally oxidized than Ti.
By using an alloy material composed of less than atomic% and having a fine crystalline phase or amorphous phase precipitated on the surface by mechanical alloying, it is easy to control the coloring of the colored oxide film of Ti by thermal oxidation, and it is constant This is a method of coloring a titanium-based alloy by thermal oxidation, which enables the color to be formed with good reproducibility under the above conditions and to form a film having a uniform color without color unevenness.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below using a Ti-Fe alloy as an example. When the Ti—Fe alloy is heated and oxidized, Ti and Fe exposed on the surface are oxidized at the very beginning of the oxidation. It is considered that an alloy such as Ti—Fe has more crystal structure distortion than pure Ti metal, so that the reaction with oxygen proceeds easily at the time of initial oxidation and a uniform film is easily formed. When the surface is covered with an oxide film having a certain thickness, the oxygen potential at the oxide film / alloy interface becomes significantly lower than that of the atmosphere. In that case, immediately below the Fe oxide, Ti, which forms an oxide more stable than Fe,
Is present, Ti becomes F by the following reaction.
eO can be reduced to TiOx by itself. xFeO + Ti = xFe + TiOx

By this reaction, TiOx gradually increases at the oxide film / alloy interface, and eventually TiOx covers the alloy surface. In this way, it is possible to form an oxide film more uniformly by alloying a metal element, for example, Fe, which is less susceptible to thermal oxidation than Ti, with Ti.

However, by alloying, α phase, β
Various types of crystal phases, such as a phase and an intermetallic compound phase, are precipitated. When such an alloy is heated and oxidized, color unevenness occurs due to a difference in color development due to a difference in the oxidation rate of each phase constituting the structure. In order to solve this problem, in the present invention, the occurrence of color unevenness can be suppressed by using an alloy material in which a fine crystalline phase or an amorphous phase is precipitated on the surface or the whole.

As a method for precipitating a fine crystalline phase and / or an amorphous phase on the surface or the whole of the alloy,
There is a mechanical alloying method. Generally, a powder can be produced by a mechanical alloying method.

When a metal element that is more easily oxidized by heating than Ti is alloyed, the alloying element forms an oxide film.
A colored film of Ti oxide cannot be obtained. Therefore, an element which is less likely to be oxidized by heating than Ti is effective as a metal element to be alloyed with Ti. The effect of the present invention is exhibited by alloying with an element that is less likely to be thermally oxidized than Ti. However, a better effect can be obtained by alloying with a Va, VIa, VIIa, VIII, or Ib group metal element.

The alloy is not limited to a binary system,
It is also effective for multi-element alloys with a plurality of elements that are less likely to be thermally oxidized than Ti. The element contained in the alloy is Ti
It is not limited to elements that are less likely to be oxidized by heating than
If the amount does not hinder the effects of the present invention, for example, an amount of an impurity, it may contain an element which is more easily oxidized by heating than Ti.

When the ratio of the alloying element to Ti increases, the surface cannot be sufficiently covered with Ti oxide, which is the element for coloring. If the amount is too small, the above-mentioned reaction hardly occurs. Therefore, the ratio of the metal element alloyed with Ti is 5 to 95 atomic%, preferably 1 to 95 atomic%.
It is at least 0 atomic% and at most 90 atomic%.

The temperature range in which the film is formed depends on the alloy composition, but is preferably 300 ° C. or higher. The atmosphere in which the film is formed may be the most general air, but is not particularly limited as long as it is an atmosphere containing oxygen.

Even if the Ti powder is heated and oxidized, it is not possible to obtain a variety of colors as in the case of a bulk material. However, by applying the method of the present invention, a variety of colors can be formed by changing the temperature conditions. In the case of a powder, it is desirable because it shows the brightest color with a particle size of about 5 to 100 μm, but is not particularly limited.

A sintered compact is produced using the Ti-based alloy powder according to the present invention, and is subjected to thermal oxidation, whereby
The surface of the molded article can be colored. The surface of the cast product can be colored and decorated by fixing the Ti-based alloy powder in the present invention to the surface of the cast product and subjecting it to thermal oxidation.

The thermal oxidation of pure Ti has problems such as poor reproducibility of the relationship of color development with temperature, poor color uniformity, and easy color unevenness, making precise determination of color development difficult. These problems can be solved by using a Ti-based alloy according to the present invention, so that it can be used as a temperature sensor.

[0023]

EXAMPLES The present invention will be further described below with reference to examples.

[0024]

[0025]

Example 1 A heat-treated alloy powder was produced by a mechanical alloying method. Using Ti powder having a particle size of about 40 μm and Fe powder having a particle size of about 5 μm as starting materials, milling was performed for 200 hours in a reduced-pressure argon gas atmosphere using a vibrating ball mill. This allows Fe to be 10, 20, 30, 40, 50, 60, 70, 8
A Ti—Fe alloy powder having a composition containing 0 and 90 atomic% was prepared. The alloy powder was in an amorphous phase or a fine crystalline phase. As a comparative example, a pure Ti powder (purity: 99.5%) was also prepared. These powders were heated in a resistance heating furnace in air to form an oxide film.

Heat oxidation of commercially available pure Ti powder at 400.degree. C. for 30 minutes produces a yellow-brown oxide film.
A brown oxide film was formed by heat oxidation for one minute. 700
Above ° C, the surface became gray and no blue powder was obtained. On the other hand, Ti-Fe containing 10 to 90 atomic% of Fe
By heating and oxidizing the alloy powder sample at 400 ° C. for 30 minutes,
An opaque dark blue oxide film formed.

Example 2 As in Example 1, V is less oxidized than Ti.
V of group a, Cr of group VIa, Mn of group VIIa, C of group VIII
A Ti-based alloy powder in which o, Ni, and Cu of the group Ib are alloyed is produced by a mechanical alloying method.
When heat oxidation was performed for a minute, an opaque dark blue oxide film was formed as in the case of the Ti—Fe alloy. In a similar manner, a Ti-based alloy was prepared by alloying Al, which is more susceptible to thermal oxidation than Ti, and subjected to thermal oxidation at 400 ° C. for 30 minutes. was.

Example 3 A Ti ₅₀ Fe ₅₀ alloy powder was produced by the mechanical alloying method shown in Example 1. Using this powder as a raw material, a sintered compact having a diameter of 15 mm and a thickness of 5 mm was produced by a discharge plasma sintering method in a vacuum. When this sintered compact was heated and oxidized in air at 450 ° C. for 30 minutes, the entire surface of the molded body could be uniformly colored blue without color unevenness.

Example 4 FIG. 1 shows a process relating to a method for decorating a surface of a cast product in which a titanium-based alloy powder is applied to the inner wall of a mold and cast, and then the surface of the cast product is colored by heating and oxidation. Here, Ti ₅₀ Fe ₅₀ alloy powder 1 was produced by the mechanical alloying method shown in Example 1. This alloy powder was suspended in ethanol and applied to the inner wall of a cylindrical mold 2 having an inner diameter of 20 mm. Al molten metal 3 at about 700 ° C. was poured into this mold. The alloy powder was fixed uniformly on the casting surface without any gap. When the casting was heated and oxidized at 450 ° C. for 30 minutes in air, the alloy powder fixed on the surface of the casting developed a uniform blue color.

Example 5 Ti ₅₀ produced by the mechanical alloying method shown in Example 1
The Fe ₅₀ alloy powder was heated and oxidized at various temperatures in the air to confirm color development. As a result, there was no change in color at 300 ° C or lower, gray, brown at 300 ° C to 400 ° C, 400 ° C to 5 ° C.
It showed a vivid blue color at 00 ° C, and became gray at 500 ° C or higher. The reproducibility of the relationship between the temperature and the color development was good, and there was no color unevenness, so it was easy to determine the color development.

On the other hand, commercially available pure Ti powder did not change color at 300 ° C. or lower and became gray, yellowish brown to brown at 300 ° C. to 600 ° C., and gray at 600 ° C. or higher. The color change was dull and dull, without the vivid blue coloration seen in the alloys according to the invention. Thus, it was confirmed that the alloy produced according to the present invention can be used as a temperature sensor.

[0033]

According to the conventional heat oxidation method, the oxidation reaction in air is complicated, and the structure of the oxide film is also complicated, so that it is difficult to control the color development, and color unevenness is likely to occur, ie, uniform color. Although it was difficult to form a film with good reproducibility, the present invention made it possible to generate a vivid color oxide film with good color development without color unevenness with good reproducibility. Further, according to the present invention, it becomes possible to form a high-level oxide film at a much simpler and cheaper device and at a lower cost than the anodic oxidation method which has been mainly used in the past, so that mass production and processing of large products can be performed. became. further,
Even if pure Ti powder is heated and oxidized, it is not possible to obtain many kinds of colors as in the case of bulk material, but by applying the method of the present invention, it becomes possible to form many kinds of colors by changing the temperature conditions. Alloys made according to the invention can be used as temperature sensors.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating one embodiment of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 Ti-based alloy powder 2 mold 3 molten aluminum 4 colored Ti-based alloy powder

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI C23C 26/00 C23C 26/00 E (72) Inventor Teruo Haihara 1618 Ida, Nakahara-ku, Kawasaki Nippon Steel Corporation Technology Kyoko Arita, Examiner in the Development Division (56) References JP-A-1-136958 (JP, A) JP-A-1-123042 (JP, A) JP-A-59-43882 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) C23C 8 / 12,8 / 16 C22C 14 / 00,38 / 00,45 / 10 C22F 1/18 C23C 26/00

Claims (5)

(57) [Claims] (1) containing at least 5 atomic% and at most 95 atomic% of Ti;
The remainder is composed of one or more elements that are less susceptible to thermal oxidation than Ti, and is thermally oxidized to a titanium-based alloy material having a fine crystalline phase and / or an amorphous phase precipitated on the surface by mechanical alloying. A method for coloring a titanium-based alloy by thermal oxidation, wherein a colored oxide film having a uniform color is formed. 2. The method for coloring a titanium-based alloy by thermal oxidation according to claim 1, wherein the element that is less susceptible to thermal oxidation than Ti is Fe. 3. A powder-sintered molded body containing a powdery material among the titanium-based alloy materials according to claim 1 as a raw material, and the Ti-based alloy powder portion fixed on the surface of the molded body. A method for decorating the surface of a sintered molded product, wherein the color is developed by thermal oxidation. 4. A powdery titanium alloy material according to claim 1 or 2, which is applied to the inner wall of a mold and cast.
A method for decorating a surface of a casting, wherein the portion of the Ti-based alloy powder fixed to the surface of the casting is colored by heat oxidation. 5. A temperature sensor using the titanium-based alloy according to claim 1 to form a colored oxide film in a specific temperature range.