JPH01279A - Coloring method for titanium and titanium alloy materials - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for coloring titanium and titanium alloy materials, in particular a method for coloring titanium and titanium alloy materials, which can be processed continuously with relatively simple operations, and has a stable uniformity that can withstand molding processing after coloring. The present invention relates to a method for coloring titanium and titanium alloy materials that can form a colored surface.

(Prior art) Titanium and titanium alloy materials (hereinafter collectively referred to as "titanium materials") are used as roofing and building materials because they are lightweight, have high specific strength, and have extremely excellent corrosion resistance. However, due to its high price and the lack of a widespread method for easily and robustly coloring plate materials, it has not been used for these mass-consumption applications.
However, if titanium materials come to be used in large quantities, it will be possible to reduce the price and it will be possible to use them as roofing and building materials. development is required.

-a, known methods for coloring metal materials include anodic oxidation, atmospheric oxidation, and nitridation.

However, when these methods are applied to titanium materials, there are problems as described below.

The anodic oxidation method allows coloring in various colors, but it requires electrolysis equipment, which increases equipment costs, and it is technically difficult to continuously color the strip-shaped plate, that is, the strip material. It's difficult.

The atmospheric oxidation method simply oxidizes the material by heating in the air, so it is relatively easy to color the material, but in the case of titanium materials, it has the disadvantage that the coloring tends to be non-uniform.

The nitriding method is a method of coloring by heating in a non-oxidizing nitrogen-containing atmosphere to generate TiN on the surface.
Unlike an oxide film, a nitride film can only be colored golden yellow, and the nitride layer is brittle, so the workability after processing is significantly deteriorated, making processing difficult. Therefore, its use for various purposes is greatly restricted.

(Problems to be Solved by the Invention) An object of the present invention is to develop a method for coloring titanium materials, that is, titanium and titanium alloy materials, which can be relatively easily and continuously processed.

Another object of the present invention is to develop a method for coloring titanium materials that allows stable and uniform coloring of various tones.

Yet another object of the present invention is that even if molded after coloring,
The object of the present invention is to develop a method for coloring titanium materials that does not damage the colored surface.

(Means for Solving the Problems) Among the conventional coloring methods described above, it was determined that the anodic oxidation method and the nitriding method were not suitable for achieving the above object due to their inherent drawbacks. We focused on the atmospheric oxidation method and investigated the reasons why it is difficult to obtain uniform coloring with this method. As a result, as will be explained in detail later, we thought that the cause of the uneven coloring was that the plate material could not be heated uniformly by heating in the atmosphere, so in order to uniformly heat the titanium material, we
As a result of research into an oxidation method using a heat medium with a large heat capacity and good thermal conductivity, we found that by using a molten material containing oxidizing salts such as nitrates as a heat medium and oxidizing agent, titanium materials could be made into gold. It can be colored in various colors such as purple, blue, brown, and black, and even under such harsh corrosive conditions,
They discovered that the corrosion resistance of titanium materials does not deteriorate at all, and completed the present invention.

Here, the present invention is a method for coloring titanium and titanium alloy materials, which is characterized by immersing titanium or titanium alloy materials in an oxidizing melt bath.

(Function) The material to be colored in the present invention is pure titanium material or Ti-
6χ^! It is a titanium alloy material such as -4χV, and its shape is not particularly limited, and may be a plate material, a band material (strip material), a tube material, or a bar material.

The composition of the melt used for coloring the titanium material in the present invention may be any composition containing substances that have strong oxidizing power in the molten state, such as nitrates, dichromates, permanganates, etc. Although not particularly limited, sodium nitrate (
(melting point 308°C), potassium nitrate (melting point 339°C),
The main ingredients are sodium dichromate (melting point 356°C), potassium dichromate (melting point 398°C), potassium permanganate, and sodium permanganate, which have a low melting point and do not corrode titanium materials. It is preferable in terms of strong oxidizing power and heating material cost, and in order to lower the melting point, the main ingredients are sodium hydroxide (melting point 318°C) and potassium hydroxide (melting point 360°C), and oxidized It may be a mixture of an appropriate amount of a strong permanganate or the like. A low melting point is advantageous because it reduces the amount of thermal energy required for operation and reduces the risk of deterioration of the material to be treated.

A single bath of sodium nitrate or potassium nitrate can also be used as the simplest oxidizing molten salt bath, but mixing them lowers the melting point and increases fluidity at the same temperature, causing the material to adhere to the treated material and be removed from the bath. Mixed baths are generally more economically advantageous because less hot material is required. Sodium nitrate and/or potassium nitrate, as well as other nitrates (e.g., ammonium nitrate, calcium nitrate, lithium nitrate, etc.), dichromates (e.g., sodium dichromate,
Oxidizing salts such as potassium dichromate (e.g., potassium dichromate), permanganates (e.g., potassium permanganate), and other alkali metal or alkaline earth metal salts (e.g., sulfates) can be mixed. , carbonates, chlorides, etc.), and even hydroxides (eg, sodium hydroxide, potassium hydroxide, etc.). In addition, since the coloring of the titanium material in the present invention is achieved by surface oxidation,
A substance with oxidizing power is essential as a component of the molten bath, but its content varies depending on the oxidizing power; for example, nitrate requires several tens of percent or more, and permanganate requires several percent or more. .

The temperature of the above-mentioned melt bath may be any temperature at which the substance used is in a suitably fluid molten state, and varies depending on the bath composition. , generally 300-550°C1
Preferably it is within the range of 400 to 500°C. The processing time depends on the type of titanium material, molten salt bath composition and bath temperature,
and varies depending on the desired color, but generally about 30 seconds to 6 seconds.
It is within the range of 0 minutes. For example, sodium nitrate/61
! When a titanium material is immersed in a mixed salt bath of potassium I acid, the color changes from golden yellow to blue to purple as the immersion time increases, as shown in the example. Therefore, the immersion treatment time can be adjusted. The color tone can be changed by changing the color tone. Note that the coloring of titanium materials using a nitrate bath is similar to the anodic oxidation method and the atmospheric oxidation method.
Although the color is due to interference between the two films, the color tone is slightly different from that obtained by the atmospheric oxidation method, and a color unique to the molten salt bath oxidation method is obtained. Further, when permanganate is used, a brown or black coloring is obtained, but this is presumed to be the color of the Ti oxide itself.

By the method of the present invention, when colored by immersion treatment in an oxidizing molten salt bath, the non-uniformity of coloring (color unevenness) at the edges and center of the board, which is observed in the atmospheric oxidation method, is almost eliminated. . This is considered to be due to the following reasons.

When titanium materials, especially titanium plates, are heated and colored in a high-temperature atmosphere, the color tone differs between the edges and the center of the plate, resulting in color unevenness, but this is because the temperature rises faster at the edges than at the center. This is thought to be because it is oxidized much faster and more. That is, the coloring due to atmospheric oxidation is caused by the interference effect of the Ti0z film formed on the surface of the titanium material, but the greater the degree of oxidation, the thicker the 110g film becomes and the color tone changes. The tentative ends come into contact with a larger amount of high-temperature air than the center. Conversely, if a cold titanium plate is introduced into high-temperature air, the same amount of high-temperature air will heat up the titanium plate. is considerably higher in the center than at the edges (because heating the titanium plate removes heat from the atmosphere and cools it down, in the process of heating the titanium plate in the high-temperature atmosphere, the high temperature around the titanium temporarily increases). A temperature gradient occurs in the atmosphere, where the temperature of the atmosphere decreases the closer it is to the titanium plate, but this temperature gradient, that is, the temperature drop of the atmosphere near the titanium plate, is greater at the center of the plate than at the edges. This delays the temperature rise of the plate.

In other words, it is thought that the cause of the uneven color is that the heating temperature is not uniform between the center and edges of the plate, but this is due to the fact that the heat capacity of the atmosphere, which is the heat medium, is too small and the thermal conductivity is poor. As long as the atmosphere is used as a heat medium, it cannot be avoided.

On the other hand, when comparing on a volume basis using known heat capacity data, 1 d of nitrogen gas at 1 atm 6000 K (327°C) is
The amount of heat required to raise or lower the temperature to approximately 0.00°
061 Joules, and for 1 mg of sodium nitrate in the molten state at the same temperature is 3.47 Joules. That is, compared to nitrogen gas, molten sodium nitrate has a heat capacity of about 500 to 6000 times, and the thermal conductivity of a liquid is usually much better than that of a gas. Since we use an oxidizing molten salt, which has a much higher heat capacity and thermal conductivity, as the agent instead of air, the temperature gradient near the surface of the titanium material as mentioned above is almost eliminated, and the temperature is almost uniform over the entire surface of the material to be treated. It is thought that the coloring becomes uniform because it is heated and oxidized.

It has also been found that stirring the molten salt bath to further improve the uniformity of heating is effective in making the coloring more uniform.

Since the method of the present invention can be carried out by simply immersing the material to be treated in a molten salt bath, it can easily be carried out continuously when treating a strip material. Another advantage is that the apparatus can be implemented by reusing an existing strip dipping treatment line, for example, a pickling treatment line.

When strips are continuously treated by the method of the present invention, the high temperature of the bath and its rather high viscosity may cause the titanium plates to become distorted and, in the case of thin plates, to deteriorate the flatness. It was found to be easy to do. In order to prevent the flatness from deteriorating during the continuous processing, it has been found that it is effective to process the titanium strip while applying tension in the longitudinal direction. The method of applying tension is not particularly limited, but for example, as shown in the attached drawings, molten salt is used between the brake-equipped payoff reel 2 that sends out the treated strip 1 and the tensilan reel 3 that winds up the treated strip. By arranging the tank 4 and the washing tank 5 and applying a tension of about 5 to 20 kg/sa" or more to the strip material, a colored titanium material with extremely excellent flatness can be obtained.

In the figure, 6 is a water shower for rinsing, and 7 is an air blower for drying.

Furthermore, as shown in the examples, the corrosion resistance of stainless steel sheets deteriorated considerably due to the coloring treatment of the present invention due to preferential oxidation of chromium in the base metal, whereas the corrosion resistance of titanium materials did not deteriorate at all. There wasn't. Therefore, the method of the present invention is particularly suitable for coloring titanium materials that have extremely good corrosion resistance.

In addition, unlike nitrided coatings, the surface of the coloring material obtained by the method of the present invention is not brittle, so even if it is subjected to processing such as bending after coloring, the colored surface will not be damaged and the workability will be affected. Are better.

The present invention will be further explained below with reference to examples, but the method of the present invention is not limited thereto.

Industrial pure titanium (JIS Class 2) and titanium alloy (T
A thin plate of i-6χA1-4χV) was immersed in various molten baths, such as a mixed molten salt bath of NaNOs (sodium nitrate) and KNOs (potassium nitrate), and colored in various colors by changing the immersion time and temperature. The processing conditions and coloring results are summarized in Table 1 below.

1-4 and 8-20 and 22-24 are 0.4
x 70 x 150 pure titanium cut plate or 0.
This is a test in which a titanium alloy cut plate with a size of 5 x 70 x 150 mm was treated in a laboratory, and specifically, the inner diameter was 1501 mm and the depth was 35 mm.
An amount of the above mixture sufficient for immersing a test piece was placed in a 0.0 mm Ni pot and heated to a predetermined temperature with a nichrome wire electric heater to prepare a molten bath. When stirring the bath, stirring was carried out using a stirrer using an electric motor at a rotational speed of 1100 rpm.

Stones 5 to 7 are tests in which a strip-shaped long pure titanium material was treated using a small-scale continuous coloring device as shown in the attached drawing. This is a comparative test in which an electric furnace was installed and continuous coloring was performed using an atmospheric oxidation method. 10 is a comparative test in which a titanium alloy cut plate with the same dimensions as above was oxidized in the atmosphere in an electric furnace.
．． 25 is a control material of titanium material itself.

As is clear from the results in Table 1, the molten salt bath oxidation method of the present invention has less color unevenness than the comparative atmospheric oxidation method (
Furthermore, when comparing the time required to obtain the same golden color, the treatment time is shorter than that of the atmospheric oxidation method.The 0 color tone is different from the atmospheric oxidation method and produces a color tone unique to a molten salt bath. For example, the gold color obtained by the atmospheric oxidation method in Example 7 is a bright yellow gold color, but
The gold color obtained by the molten salt bath oxidation method is a calm and mysterious gold color with a slightly blackish tinge.

In the Demon 4 test in which the bath was stirred, the color and unevenness were further reduced, and no color unevenness was observed at all. On the other hand, °
Cases 7 and 10 obtained by the atmospheric oxidation method had a golden color in the center, but the oxidation progressed near the edges, giving them a red to purple color.

When the strip material was processed continuously, the flatness of the plate deteriorated slightly in the test in which no tension was applied in the longitudinal direction (lIi[L5), but the flatness deteriorated slightly in the test in which moderate tension was applied (N116). It was very good.

Samples Nos. 11 to 14 are examples of coloring using a bath of dichromate and nitrate, and gold and purple interference colors were obtained.

Samples Nos. 15 to 17 are examples of coloring using a bath in which permanganate was added to nitrate, and it was found that the treatment time was significantly shorter than when using only nitrate.

This is presumably due to the strong oxidizing power of permanganate. Nos. 18 to 20 are examples of coloring using a bath in which permanganate is added to hydroxide (alkali), and in this case, it is possible to color gray, brown, or black. In addition, none of the coloring materials cracked during the bending test, and the original material (
It had the same workability as untreated material).

In order to investigate the deterioration of titanium material due to oxidation treatment in a molten salt bath, the corrosion resistance of the colored test piece of Example 1 with a test distance of 1 was measured by CASS.
Evaluated by test (JIS 00201-1964),
For comparison, stainless steel 5US304 (1
8χCr-8XNi) and SUS 430 (16,5
χCr) BA material (bright annealing material, plate thickness 0.4aa),
Table 2 also shows the results of coloring under the treatment conditions of test Nα1 in Example 1 (however, the treatment time was 1 minute) and evaluating the corrosion resistance in the same manner as with the untreated test materials.

Table 2 As shown in Table 2, when stainless steel is colored using the method of the present invention, its corrosion resistance deteriorates considerably due to the harsh conditions, whereas titanium, which has extremely excellent corrosion resistance, does not deteriorate at all. Shows the same corrosion resistance as untreated material.

(Effects of the Invention) - Titanium materials can be colored stably and uniformly in a short period of time, and various color tones can be obtained by changing the processing temperature and especially the processing time. Uniform coloring reduces loss, and stirring of the molten salt bath is effective for further improving coloring uniformity, which is particularly advantageous in continuous processing of strips.

■Since the treatment can be carried out by simply immersing the material to be treated in a molten salt bath, the equipment and operation are simple, and the strip material can be easily and continuously processed. Additionally, existing processing lines can be repurposed for implementation. In the case of continuous processing, good flatness can be maintained by applying appropriate tension to the strip material.

(2) Despite the harsh processing conditions, the colored surface is not brittle, so moldability is good, and the colored surface is not damaged even during molding. In addition, no deterioration in corrosion resistance is observed after treatment, so it can be molded and used for various purposes.

[Brief explanation of the drawing]

The accompanying drawing schematically shows an example of a continuous processing line that can be employed when coloring a strip according to the method of the present invention. 1. Band-shaped titanium material 2. Pay-off reel 3. Tension reel 4. Molten salt tank 5. Washing tank Applicant: Japan Stainless Co., Ltd. Agent Patent attorney Akira Hirose - To Δ

Claims (4)

[Claims] (1) A method for coloring titanium and titanium alloy materials, which comprises immersing titanium or titanium alloy materials in an oxidizing melt bath. (2) the melt is one or a mixture of two or more of nitrates, dichromates, permanganates, and hydroxides;
A method according to claim 1. (3) The method according to claim 1 or 2, wherein the immersion is performed while stirring the melt bath. (4) The titanium or titanium alloy material is a strip material, and the strip material is continuously immersed in the melt bath while applying tension in the longitudinal direction. Any method described.