JPH1129847A - Titanium hardened member and hardening treatment therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a titanium hardened member free from deterioration in the quality of the appearance even after hardening treatment, capable of noncoloring and swiftly forming a hardened layer by allowing the hardened layer to contain oxygen in a specified ratio in a specified depth from the surface. SOLUTION: The hardened layer contains 0.5 to 5 wt.% oxygen in a depth of 10 μm from the surface of a titanium member. The hardening treatment of the titanium member is executed as follows. The titanium member is heated in an inert gas atmosphere such as argon, helium or the like. In this way, the relaxation of a working strain layer generated on the surface of the titanium member at the time of polishing is executed. Then, its heated to a treating temp. of 700 to 800 deg.C in a gaseous mixture atmosphere of an inert gas and vapor (primary hardening treatment). Then, it is heated to a treating temp. of 700 to 800 deg.C in an inert gas atmosphere (secondary hardening treatment). In this way, oxygen in the device and the hydrogen component diffused into the inside of titanium are removed. After that, it is cooled in an inert gas atmosphere.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hardened titanium member whose surface is hardened at an arbitrary depth, and more particularly to a decorative member for a watch exterior such as a watch case, a band, and a bezel.

[0002]

2. Description of the Related Art In recent years, titanium and titanium alloys have been used in various fields by utilizing their characteristics of being light, not rusting, and not causing metal allergy. Above all, the above-mentioned features are very effective as a watch material, and therefore, application development has been conventionally attempted. On the other hand, titanium and titanium alloy have a disadvantage that the surface is easily damaged due to a problem inherent to the material. In particular, when considering a mirror surface or the like, which is a surface with an aesthetic appearance, scratches on the surface are easily noticeable, so that sand blast treatment or the like has been conventionally performed to make the scratches less noticeable. For this reason, ordinary people have been given the impression that decorative members made of titanium or titanium alloy have a dark surface.

[0003] The phenomenon that the member is easily scratched is derived from the low surface hardness of the member, and various hardening treatments have been performed on titanium. The surface hardening treatment of titanium is roughly classified into two types: a method of coating a hard film on the titanium member surface and a method of hardening the titanium member itself. As a method for coating a titanium member surface with a hard film, a wet process typified by electroplating and a dry process typified by vacuum deposition, ion plating, sputtering, plasma CVD, etc. are known.
In any case, the adhesion to the member is difficult, and the problem of film peeling has not yet been completely solved. On the other hand, as a method of curing the metal member itself, gas oxidation, ion implantation, ion nitriding, gas nitriding, gas carburizing, gas nitrocarburizing, and the like are known, but the processing time is long and there is a problem in productivity, and Since the treatment temperature is high, there is a problem that the crystal grains are coarsened, the surface is roughened, and the appearance quality is inferior, and the use range is limited.

[0004] Among the above-mentioned methods, the method of hardening the titanium member itself does not cause a film peeling problem because the diffusion element in the member has a concentration that is inclined from the surface. Therefore, it is considered to be useful as a surface hardening treatment method for titanium members, but there is a problem of deterioration of appearance quality due to surface roughness. In the ion nitriding technology, it has been practiced to reduce the ion sputtering effect in order to reduce the surface roughness, but it is fundamentally due to the surface roughness and oxide formation caused by oxygen entering the member itself. The discoloration problem could not be solved. Therefore, in the method of hardening the titanium member itself such as gas oxidation, in the prior art, an oxidation structure and an oxidation treatment method aiming to simultaneously reduce surface roughness and improve colorlessness are considered. Did not.

[0005] The problem of deterioration of the appearance quality is considered to be caused by bumps at crystal grain boundaries and surface roughness due to compound formation. It is considered that the prominence at the crystal grain boundaries generated during the gas oxidation treatment is caused by a phenomenon such as compound formation at the crystal grain boundaries or stress concentration at the crystal grain boundaries generated from lattice distortion due to solid solution diffusion of oxygen. . When the protuberance at the crystal grain boundary was visually observed, it was felt that the surface was rough. In particular, the conventional gas oxidation treatment of titanium forms a scale, which is a thick oxide layer, on the surface. When this scale was formed, problems such as surface roughness and discoloration occurred, and a mirror surface could not be obtained even if the scale was removed by polishing or the like. As a result, for a surface with a beautiful appearance of a decorative member represented by a watch, eyeglasses, jewelry, and the like, the surface is not roughened, and furthermore, a problem such as discoloration of the surface due to a compound such as surface oxidation does not occur. No hardening treatment could be performed. As the height of the ridge at the crystal grain boundary increases, the maximum height Rmax and the average surface roughness Ra increase, and the appearance quality deteriorates.

[0006] As a result of a detailed study of a titanium hardened member that provides a hardened layer without causing surface roughness, the height of the bump is attributed to the oxygen concentration and the size of crystal grains inside the titanium. It was found that the height increased as the oxygen concentration inside the hardened titanium member increased and as the size of the crystal grains increased. The discoloration of the surface was also caused by the oxygen concentration on the surface of the hardened titanium member, and it was found that when the oxygen concentration was increased and a colored compound was formed, a discoloration problem occurred.

Further, in the conventional gas nitriding and oxidizing methods, since the heating is performed at a temperature near the transformation point (800 ° C. to 870 ° C.) for a long time, a phenomenon that crystal grains become coarse occurs. The bumps and the like at the crystal grain boundaries were further increased.

[0008]

The technique of hardening the titanium member itself, such as gas nitriding or oxidation, solves the above-mentioned problems of surface roughness and discoloration after hardening and shortens the processing time. could not.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems, and to prevent the appearance quality from deteriorating even after the curing treatment, to reduce the surface roughness, to make it possible to obtain a non-colored state, and to quickly form a cured layer. An object of the present invention is to provide a curing member and a curing method thereof.

[0010]

In order to achieve the above object, a titanium cured member and a method for curing the same according to the present invention are provided.
The structure and method described below are adopted.

The present invention relates to a titanium hardened member having a hardened layer at an arbitrary depth from the surface of the titanium member, wherein the hardened layer contains 0.5 to 5% by weight of oxygen at a depth of 10 μm from the surface. By providing a titanium hardened member characterized by the fact that the surface hardness required to form a surface layer with high scratch resistance is imparted, furthermore, there is no deterioration in appearance quality, that is, the surface roughness is small It is possible to do.

A heating step of heating the titanium member in an atmosphere of an inert gas such as argon or helium; and a step of heating at 700 to 800 ° C. in a mixed gas atmosphere of the inert gas and steam.
A first curing treatment step of heating to a treatment temperature of, a second curing treatment step of heating to a treatment temperature of 700 to 800 ° C. in the inert gas atmosphere, and a cooling step of cooling in the inert gas atmosphere. By using a method for curing a titanium cured member, a cured layer free from discoloration due to oxide formation can be quickly obtained.

[0013]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view showing a titanium decorative member according to an embodiment of the present invention; FIG. 1 is a three-dimensionally enlarged view of a titanium hardened member having a hardened layer formed by a hardening process according to an embodiment of the present invention.
FIG. 2 is a conceptual view showing a curing device for curing the surface of a titanium cured member of the present invention. FIG. 3 is a schematic view showing a process for forming a hardened layer on a titanium member according to the embodiment of the present invention.

FIG. 1 is a three-dimensionally enlarged view of the hardened titanium member of the present invention, and shows the surface structure that can be confirmed when observed at a high magnification using an optical microscope. The size of the crystal grains described so far is the size 26 of the crystal grains on the surface in FIG.
And the crystal grain boundary is the crystal grain boundary 22 in FIG. 1 and indicates a boundary between crystal grains.

FIG. 2 shows a hardening apparatus for performing the hardening process of the present invention, which comprises a gas inlet 8 and a sample outlet 18.
The apparatus used was such that the surface of the titanium member 2 placed on the sample stage 4 could be heated by the heating means 12 supplied from the heating power supply 14 into the processing tank 6 provided with the above. Further, a vacuum exhaust device 16 and a gas exhaust port 10 are provided so that the processing tank 6 can be evacuated to a vacuum so that the curing process can be performed in a reduced pressure atmosphere.

FIG. 3 shows a hardening method conceptually showing the processing steps. When the temperature of the titanium member is raised to 700 ° C., the temperature raising step 30 for making the atmosphere inert to titanium is performed during polishing. The purpose is to alleviate the work distortion layer generated on the surface of the titanium member. The processing strain layer is in a state crystallinely close to an amorphous phase in a state where the stress during polishing processing remains as lattice distortion. When an oxidizing gas is directly introduced into the polished titanium member to perform a hardening treatment, an oxide serving as a coloring substance is formed on the surface of the processed strained layer because the processed strained layer has high reactivity with oxygen. When these colored substances are formed, the appearance quality is deteriorated, so that this is not a preferable state as a decorative member. Therefore, in the temperature raising step before the first hardening treatment step in the present invention, the work distortion layer is relaxed by setting the atmosphere to an inert atmosphere.

In the first hardening step 32, after the temperature raising step 30, a mixed gas obtained by adding a small amount of oxygen component to an inert gas is introduced into the processing apparatus, and the processing pressure is set to 0.001 to 10T.
The treatment is performed in a mixed gas atmosphere adjusted to a range of orr.

The second curing step is a step for completely removing the oxygen component gas introduced into the processing apparatus from the apparatus. In other words, when the oxygen component gas during the first curing treatment step remains during the subsequent cooling step 36, diffusion into the titanium member is slow because the ambient temperature is low,
An oxide is formed on the surface of the titanium member. As described above, these compounds cause problems of surface roughness and deterioration of appearance quality, and are not in a preferable state as a titanium decorative member. In addition, this step also has the effect of dehydrogenation for removing hydrogen components diffused inside titanium when cured in a mixed gas atmosphere of an inert gas and water vapor or an inert gas, oxygen and hydrogen. .

The cooling step 36 is a step for rapidly cooling the titanium member to room temperature and taking it out of the processing apparatus. Even in the cooling step, when the same gas atmosphere as in the hardening treatment step is used, the oxygen component gas is supplied while cooling, so that the diffusion of oxygen from the surface of the titanium member is delayed, and the surface is colored. Form an oxide. In order to prevent the formation of these coloring substances, the atmosphere in the cooling step needs to be an inert atmosphere with respect to the titanium member.

[0020]

【Example】

(Embodiment 1) A first embodiment of the present invention will be described with reference to FIG. 25mm × 2 as titanium member
5 mm JIS two kinds of pure titanium were used. The treated surface has been polished, and the surface roughness has a maximum height Rmax value of 50.
nm or less. Untreated grain size is 10-3
This is a polycrystalline structure of 0 μm.

First, in the evacuation step 28, the inside of the processing tank 6 is evacuated by the evacuation device 16 to 1 × 10-5 torr.
r atmosphere or less. A predetermined amount of an inert gas such as argon or helium is introduced from the gas inlet 8 and the amount of the introduced gas and the amount of exhaust gas are adjusted to adjust the inside of the processing tank 6 to 0.1 torr.
An inert gas atmosphere with a pressure of Then, as shown in the heating and heating step 30, the titanium member 2 is heated by the heating means 12 to set the curing temperature to 650 ° C, 700 ° C, 800 ° C.
And 850 ° C. First curing process 32
In the above, pure argon and a mixed gas containing a small amount of water vapor in pure argon gas are introduced from the gas inlet 8,
The atmosphere of pure argon of about 0.1 torr and a small amount of water vapor was adjusted by adjusting the amount of introduced gas and the amount of exhaust gas. Here, for all temperatures, the ratio of water vapor to pure argon was about 8000 ppm. Then, the temperature was held for about 2.5 hours while keeping the curing temperature constant. After that, the inside of the treatment tank was again maintained as an inert gas atmosphere under reduced pressure for about 0.5 hour to perform a second curing treatment step. Then, the sample was cooled in an inert atmosphere. When the temperature reached about 100 ° C. or lower, the treatment was completed and the sample was taken out.

(Embodiment 2) FIG. 3 shows a second embodiment of the present invention.
This will be described with reference to FIG. As in the case of Example 1, two types of pure titanium having a shape of 25 mm × 25 mm were used as the titanium member. The treated surface was polished, and the surface roughness was 50 nm or less in maximum height Rmax value. Untreated crystal grains have a polycrystalline structure of 10 to 30 μm in size.

First, in the evacuation step 28, the inside of the processing tank 6 is evacuated by the evacuation device 16 to 1 × 10-5 torr.
r atmosphere or less. A predetermined amount of an inert gas such as argon or helium is introduced from the gas inlet 8 and the amount of the introduced gas and the amount of exhaust gas are adjusted to adjust the inside of the processing tank 6 to 0.1 torr.
An inert gas atmosphere with a pressure of Then, as shown in the heating and heating step 30, the titanium member 2 is heated by the heating means 12, and the curing temperature is 650 ° C., 700 ° C., 800 ° C.
The temperature was raised to 850 ° C. In the first hardening treatment step 32, pure argon and a mixed gas containing a small amount of oxygen in pure argon are introduced from the gas inlet 8, and the amount of introduced gas and the amount of exhaust gas are adjusted to about 0.1 torr of pure argon. And a slight oxygen atmosphere. Here, the ratio of oxygen to pure argon was about 4000 ppm for all temperatures. Then, the temperature was held for about 2.5 hours while keeping the curing temperature constant. After that, the inside of the treatment tank was again maintained as an inert gas atmosphere under reduced pressure for about 0.5 hour to perform a second curing treatment step. Then, the sample was cooled in an inert atmosphere. When the temperature reached about 100 ° C. or lower, the treatment was completed and the sample was taken out.

(Embodiment 3) FIG. 3 shows a third embodiment of the present invention.
This will be described with reference to FIG. Examples 1 and 2 as titanium members
Similarly to the above, two kinds of pure titanium of JIS having a shape of 25 mm × 25 mm were used. The treated surface was polished, and the surface roughness was 50 nm or less in maximum height Rmax value. Untreated crystal grains have a polycrystalline structure of 10 to 30 μm in size.

First, in the evacuation step 28, the inside of the processing tank 6 is evacuated by the evacuation device 16 to 1 × 10-5 torr.
r atmosphere or less. A predetermined amount of an inert gas such as argon or helium is introduced from the gas inlet 8 and the amount of the introduced gas and the amount of exhaust gas are adjusted to adjust the inside of the processing tank 6 to 0.1 torr.
An inert gas atmosphere with a pressure of Then, as shown in the heating and heating step 30, the titanium member 2 is heated by the heating means 12, and the curing temperature is 650 ° C., 700 ° C., 800 ° C.
The temperature was raised to 850 ° C. In the first hardening step 32, pure argon and a mixed gas containing trace amounts of oxygen and hydrogen in pure argon are introduced from the gas inlet 8 and the amount of introduced gas and the amount of exhaust gas are adjusted to about 0.1 torr. Of pure argon and trace amounts of oxygen and hydrogen. The ratio of oxygen to pure argon was approximately 8000 ppm, and the ratio of hydrogen was approximately 1000 ppm. Then, the temperature was held for about 2.5 hours while keeping the curing temperature constant. Thereafter, the inside of the processing tank is again set to an inert gas atmosphere under reduced pressure, and the
After holding for a time, a second curing treatment step was performed. Then, the sample was cooled in an inert gas atmosphere, and when the temperature reached about 100 ° C. or lower, the treatment was completed and the sample was taken out.

(Embodiment 4) FIG. 3 shows a fourth embodiment of the present invention.
This will be described with reference to FIG. As the titanium member, a watch case made of pure titanium material equivalent to two kinds of JIS was used. The treated surface was subjected to a hairline basis weight polishing process, and the surface roughness was 10 μm or less in maximum height Rmax value. The untreated crystal grains have a structure of about 10 μm to 40 μm.

First, in the evacuation step 28, the inside of the processing tank 6 is evacuated by the evacuation device 16 to 1 × 10 −5 torr.
r atmosphere or less. A predetermined amount of an inert gas such as argon or helium is introduced from the gas inlet 8 and the amount of the introduced gas and the amount of exhaust gas are adjusted to adjust the inside of the processing tank 6 to 0.1 torr.
An inert gas atmosphere with a pressure of Then, as shown in the heating and heating step 30, the titanium member 2 was heated by the heating means 12 and heated at a curing treatment temperature of 700 ° C. In the first hardening step 32, pure argon and a mixed gas containing a small amount of water vapor in pure argon are introduced from the gas inlet 8, and the amount of introduced gas and the amount of exhaust gas are adjusted to about 0.1 torr.
An atmosphere of pure argon and a small amount of water vapor was used. The ratio of water vapor to pure argon was about 8000 ppm.
Then, the temperature was held for about 2.5 hours while keeping the curing temperature constant. After that, the inside of the treatment tank was again maintained as an inert gas atmosphere under reduced pressure for about 0.5 hour to perform a second curing treatment step. Then, the sample was cooled in an inert gas atmosphere, and when the temperature reached about 100 ° C. or lower, the treatment was completed and the sample was taken out.

(Embodiment 5) A fifth embodiment of the present invention will be described with reference to FIG. Shape 2 as titanium member
A high-strength pure titanium wristwatch band of 5 mm × 25 mm with fine crystal grains equivalent to three kinds of JIS was used. The treated surface is polished, and the surface roughness is 50 n in maximum height Rmax value.
m or less. Untreated crystal grains have a fine structure of 5 μm or less.

First, in the evacuation step 28, the inside of the processing tank 6 is evacuated by the evacuation device 16 to 1 × 10-5 torr.
r atmosphere or less. A predetermined amount of an inert gas such as argon or helium is introduced from the gas inlet 8 and the amount of the introduced gas and the amount of exhaust gas are adjusted to adjust the inside of the processing tank 6 to 0.1 torr.
An inert gas atmosphere with a pressure of Then, as shown in the heating and heating step 30, the titanium member 2 was heated by the heating means 12 and heated at a curing treatment temperature of 700 ° C. In the first hardening step 32, pure argon and a mixed gas containing trace amounts of oxygen and hydrogen in pure argon are introduced from the gas inlet 8 and the amount of introduced gas and the amount of exhaust gas are adjusted to about 0.1 t.
An atmosphere of pure argon at orr and trace amounts of oxygen and hydrogen was used. The ratio of oxygen to pure argon is about 8000 ppm
And the proportion of hydrogen was about 1000 ppm. And
The temperature was kept for about 2.5 hours while keeping the curing temperature constant. After that, the inside of the treatment tank was again maintained as an inert gas atmosphere under reduced pressure for about 0.5 hour to perform a second curing treatment step. Then, it is cooled in an inert gas atmosphere, and
When the temperature reached 00 ° C. or lower, the treatment was completed and the sample was taken out.

(Embodiment 6) Next, a comparative example of the present invention in which the gas used in the first curing treatment step is always introduced from the heating and heating steps to the cooling step will be described with reference to FIG. As the titanium member, JIS two kinds of pure titanium having a shape of 25 mm × 25 mm were used. The treated surface was polished, and the surface roughness was 50 nm or less in maximum height Rmax value. Untreated crystal grains have a polycrystalline structure of 10 to 30 μm in size.

First, in a vacuum evacuation step 28, the inside of the processing tank 6 is evacuated by the vacuum evacuation device 16 to 1 × 10 −5 torr.
The following vacuum atmosphere was used. Pure argon and a mixed gas containing a small amount of water vapor in pure argon gas are introduced from the gas inlet 8, and the amount of introduced gas and the amount of exhaust gas are adjusted to about 0.1 t.
An atmosphere of pure orr and a small amount of water vapor was used. Here, the ratio of water vapor to pure argon is about 8000.
ppm. And as shown in the heating and heating step 30,
The titanium member 2 was heated by the heating means 12 to raise the temperature by setting the curing temperature to 700 ° C. Then, after maintaining the curing temperature for 2.5 hours, the process was shifted to a cooling step. When the temperature reached about 100 ° C. or less, the processing was completed and the sample was taken out.

As a result of a detailed study of a titanium hardened member that provides a hardened layer without causing surface roughness, the problem of deterioration in appearance quality is attributed to surface roughness due to bumps at crystal grain boundaries and surface roughness due to compound formation. It became clear that it was. It is considered that the prominence at the crystal grain boundary is caused by a phenomenon such as compound formation at the crystal grain boundary or stress concentration at the crystal grain boundary caused by lattice distortion due to solid solution diffusion of oxygen or the like. When the protuberance at the crystal grain boundary is observed with the naked eye, the surface seems to be rough, and there is a problem that it cannot be applied particularly to a mirror-like decorative member. As the height of the protrusion increases, the maximum height Rmax and the average surface roughness Ra increase, and the appearance quality deteriorates. As a result of a detailed study of a titanium hardened member that provides a hardened layer without causing surface roughness, the height of this protrusion is due to the oxygen concentration and the size of crystal grains of the titanium hardened member,
It has been found that the height of the protrusion increases as the oxygen concentration inside the hardened titanium member increases and as the size of the crystal grain increases. It was also found that the discoloration of the surface was also caused by the oxygen concentration on the surface of the hardened titanium member, and the discoloration problem occurred when the oxygen concentration increased and a colored compound was formed.

Further, if the formation of a compound such as titanium oxide TiO 2 progresses in the crystal grain boundaries and the inside of the grains after the hardening treatment, when this is observed with the naked eye, the surface feels rough and the appearance quality is degraded. I do. There was also a problem that a mirror surface could not be obtained even if these scale layers were removed in a post-process such as polishing, and it was found that the method was not particularly applicable to decorative members having a mirror surface.

Therefore, as a method for evaluating the cured member of the present invention, a scratch resistance test (sand removal test), hardness, crystal grain size, and surface roughness were employed. The scratch resistance test was passed when the degree of occurrence of surface scratches was 50% or less based on the result of observation of the surface at 400 times with an optical microscope after the sand removal test. The Vickers hardness of a Vickers hardness tester at a depth of 10 μm or less from the cured surface was Hv500 by a Vickers hardness tester.
Those that passed above were accepted. Regarding the surface roughness, a surface shape analysis in the range of 500 μm was performed. For a mirror surface having a maximum height Rmax of 1000 nm or less, the maximum height change rate before and after the treatment was within 5% for the hairline basis surface. Passed for some. Regarding the colorimetric test, the spectral reflectance was measured with a colorimeter, and no decrease in the reflectance due to light absorption was confirmed in the wavelength region of light from 400 nm to 500 nm.
In the case of * b * color system, both a * and b * showed a negative value, and the color was acceptable without coloring. The comprehensive evaluation results were acceptable if the scratch resistance test, hardness, surface roughness, and colorimetric test passed.

[0035]

[Table 1]

Table 1 corresponds to the first embodiment of the present invention.
Scratch resistance test, surface hardness, surface after hardening treatment using pure argon and water vapor of the present invention at a processing temperature of 650 ° C. to 850 ° C. and after hardening treatment by a conventional technique using gas oxidation. 3 is a table showing roughness and a colorimetric test.

From Tables 1a and 1f, the gas oxidation treatment of the prior art generates scale on the surface, and the surface roughness is less than 50 nm for untreated JIS Class 2 pure titanium at the maximum height Rmax. On the other hand, it is as large as 1800 nm, and the surface is rough. On the other hand, from a, c, and d in Table 1,
The surface roughness according to the implementation of the present invention is 1000n at the maximum height
m, which is lower than that of the prior art. Further, in the prior art, a compound was formed to cause coloring and surface roughness, whereas in the present invention, no compound was formed up to 800 ° C., and surface roughness and coloring were good. On the other hand, from g and h, no increase in surface hardness was observed when the introduced concentration of water vapor was 300 ppm, and when the introduced concentration was 3%, the concentration was high, and a compound was formed on the surface to cause surface roughness and coloring problems.

Tables 2 and 3 correspond to the second and third embodiments of the present invention.
Before the curing treatment, the scratch resistance after the curing treatment using argon and oxygen or argon, oxygen and hydrogen according to the present invention by changing the treatment temperature from 650 ° C. to 850 ° C. and after the curing treatment according to the prior art It is the table | surface which showed about test, surface hardness, surface roughness, and colorimetric test.

[0039]

[Table 2]

[Table 3]

When k and l in Table 2 show that the ratio of oxygen to pure argon is 4000 ppm, 700 ° C. and 80 ° C.
At 0 ° C., the surface hardness also increased, the surface roughness was small, and no coloration was observed. In addition, when the ratio of hydrogen to argon is set to 1000 ppm and the ratio of oxygen is set to 8000 ppm from Tables s and t, the treatment at 700 ° C. and 800 ° C. increases the surface hardness, reduces the surface roughness, and gives good results without coloring. It became.

Further, in the conventional hardening treatment such as the gas oxidation treatment, a scale which is a thick oxide layer is formed on the surface, so that it takes a long time to obtain an effective hardened layer. As conceptually shown in FIG. 4, according to the curing treatment method of the present invention, the diffusion of the oxygen element alone in a solid solution state allows an effective solid solution hardened layer to be quickly obtained.
According to the curing treatment of the present invention, an effective cured layer can be obtained in about 2.5 hours, and the time can be reduced.

FIGS. 5 to 8 show a titanium hardened member having a hardened layer formed at a temperature of 700 ° C. in the first embodiment of the present invention and a hardened layer formed at a temperature of 650 ° C. in the first embodiment of the present invention. Elemental analysis results in the depth direction by secondary ion mass spectrometry of the titanium hardened member and the untreated titanium member and the titanium hardened member formed with the hardened layer in the sixth embodiment shown as a comparative example are shown by weight concentration. It is a result.

As can be seen from FIG. 5, the titanium hardened member according to the embodiment of the present invention diffuses oxygen to a depth of about 20 μm from the surface, and the oxygen concentration at the surface decreases to increase the oxygen concentration at a depth of 10 μm from the surface. From 0.5 weight percent to 5 weight percent. As can be seen from FIG. 8, the titanium-hardened member according to the prior art diffuses oxygen to a depth of about 20 μm from the surface as in the present invention, but the oxygen concentration on the surface increases, and The oxygen concentration is 5% by weight or more in the depth range of.

As can be seen from FIG. 6, the titanium hardened member treated at a temperature of 650 ° C. has a reduced oxygen concentration on the surface, but the oxygen diffusion depth is lower than that of FIGS. It is shallow, and the oxygen concentration at about 10 μm is 0.5% by weight or less. In the results of Tables 1, 2, and 3, 650
The reason why the scratch resistance and the hardness of the processed article at ° C. are unacceptable is that the above-mentioned reduced oxygen concentration is affected.

The reason why the oxygen concentration of 0.5% by weight is required is as follows. That is, as a result of a detailed study of the hardened titanium member, it was found that the increase in surface hardness was correlated with the oxygen concentration at a depth of about 10 μm. That is, as shown in FIG. 9, the Vickers hardness increases as the oxygen concentration increases. It has been found that in order to impart a hardness of 500 or more at a depth of 10 μm, which is judged to be strong in scratch resistance, it is necessary to contain about 0.5% by weight or more of oxygen.

FIG. 10 is an analysis of the titanium cured member according to the first embodiment of the present invention and the titanium cured member according to the sixth embodiment as a comparative example by thin film X-ray diffraction at an incident angle of 0.5 ° before processing. This is the result of performing. As can be seen from the results, the titanium hardened member according to the sixth embodiment has a clearly different peak from the titanium member before the treatment, which is the titanium oxide which is a coloring compound. On the other hand, all of the peaks of the titanium hardened member of the present invention are found at substantially the same positions as those of the titanium member, and are slightly shifted to a lower angle side. This is because oxygen is in a solid solution state in the titanium member and the lattice is distorted. The absence of any other peaks clearly indicates that no compound was formed.

Therefore, what is important in not increasing the surface roughness and not causing coloring is not forming a coloring compound on the surface. For that purpose, the curing method of the present invention is required. That is, the heating and heating step, the second hardening step, and the cooling step in an inert gas atmosphere for crystallizing a strained layer generated by processing such as polishing work effectively. Further, as described in Tables 1, 2, and 3, the concentration of the introduced minute amount of oxygen component also becomes important.

The titanium decorative members of the first, second, third, fourth, fifth and sixth embodiments have been described by taking pure titanium members equivalent to JIS two or three as examples, but the present invention is also applicable to pure titanium members of JIS one kind. It is possible. Further, the present invention is also applicable to JIS standard titanium alloys 60 and 60E. First, second,
The treated surface of the third, fourth, fifth, and sixth embodiments was described with respect to a polished mirror surface and a hairline surface, but is not particularly limited, and any of a polished surface, a honed surface subjected to a honing treatment, and a surface such as a shot peened surface Is also applicable.

In the embodiments of the present invention, the first, second and third embodiments have been described using a plate-shaped titanium hardened member, and the fourth and fifth embodiments have been described using a watch case and a watch band. Not limited to the members described above, mean all applicable to decorative articles such as titanium bezels, piercings, earrings, rings, and frames for glasses, and titanium members such as golf club heads and shafts, bicycle frames, etc. It can be applied to all products that apply.

In the first, second, third, fourth and fifth embodiments of the present invention, the description will be made assuming that an inert gas atmosphere such as argon or helium is used in the heating step, the second curing step and the cooling step. Performed, but when an oxidizing gas as described above is introduced during this step, a compound is formed on the surface,
Since the surface may be roughened or discolored, any atmosphere may be used as long as these gases do not affect the atmosphere, and a high vacuum atmosphere may be used.

In each of the first, second, third, fourth and fifth embodiments of the present invention, the time for the first curing step is 2.5 hours, but it is not particularly necessary to limit the time. The time and temperature conditions are set so that no compound is formed on the surface and the required hardness and scratch resistance are satisfied. Since a long-time treatment and an increase in the treatment temperature affect the formation of the compound, any treatment may be performed for at most 10 hours. The processing temperature is preferably as low as possible due to the problem of surface roughness, but any temperature may be used as long as the processing temperature is from 700 ° C to 800 ° C.

In the first, fourth and second embodiments of the present invention, the water vapor concentration and the oxygen concentration in the first curing treatment step are such that the water vapor concentration is about 8000 ppm and the oxygen concentration is about 4000 ppm.
However, it is not necessary to particularly limit the concentration to 300 ppm to 30000 ppm if it is steam.
And if it is oxygen, it is 300-1500.
Any concentration within the range of 0 ppm can be applied. The important thing is that if these gases are supplied in too much excess, the surface will be discolored by oxides, and if too little, the hardness will be insufficient. It is possible.

In the first, second, third, fourth, and fifth embodiments of the present invention, the processing pressure in all the steps is set to 0.1 torr, but there is no particular limitation.
It is applicable at any pressure between 001 and 10 torr. What is important is that, similarly to the treatment concentration, if the pressure is too low, the absolute amount of the diffusion element is insufficient, and if the pressure is too high, a compound is formed on the surface.

Further, in the first, second, third, fourth and fifth embodiments of the present invention, the explanation has been made assuming that the time of the second curing step is 0.5 hour, but there is no need to particularly limit the cooling time. Any time is acceptable as long as the atmosphere before entering the process is inert.

[0055]

According to the present invention, there is provided a hardened titanium member having a hardened layer at an arbitrary depth from the surface of the titanium member, wherein the hardened layer contains 0.5 to 5% by weight of oxygen at a depth of 10 μm from the surface. By providing a titanium hardened member characterized by the fact that the surface hardness required to form a surface layer having high scratch resistance is imparted, and furthermore, there is no deterioration in appearance quality, that is, the surface roughness is reduced. Became possible.

A heating step of heating the titanium member in an atmosphere of an inert gas such as argon or helium; and a step of heating said inert gas and steam or an inert gas and oxygen or a mixed gas of an inert gas and oxygen and hydrogen. 700-8 in the atmosphere
A first curing treatment step of heating to a treatment temperature of 00 ° C., a second curing treatment step of heating to a treatment temperature of 700 to 800 ° C. in the inert gas atmosphere, and a cooling step of cooling in the inert gas atmosphere By using a method for curing a titanium cured member comprising the following, a cured layer free from discoloration due to oxide formation can be quickly obtained.

[Brief description of the drawings]

FIG. 1 is a three-dimensional view showing a titanium hardened member after a hardened layer is formed in an embodiment of the present invention.

FIG. 2 is a schematic view showing a processing apparatus for forming a hardened layer on a hardened titanium member according to an embodiment of the present invention.

FIG. 3 is a schematic view showing a process for forming a hardened layer on a hardened titanium member according to the embodiment of the present invention.

FIG. 4 is a view conceptually showing a time reduction by a conventional gas oxidation treatment and a curing treatment method of the present invention.

FIG. 5 is a diagram illustrating the results of elemental analysis in the depth direction by a secondary ion mass spectrometer after forming a hardened layer on a hardened titanium member according to an embodiment of the present invention (700 ° C.) in terms of weight concentration. The result.

FIG. 6 shows the results of elemental analysis in the depth direction by a secondary ion mass spectrometer in terms of weight concentration after forming a hardened layer on a hardened titanium member at a temperature of 650 ° C.

FIG. 7 shows the results of elemental analysis of the JIS two-species titanium member in the depth direction by a secondary ion mass spectrometer in terms of weight concentration before treatment.

FIG. 8 shows the results of elemental analysis in the depth direction of a titanium-cured member having a compound formed on its surface in the depth direction by a secondary ion mass spectrometer in terms of weight concentration according to a sixth example as a comparative example. .

FIG. 9 shows the measurement results of surface hardness with respect to the weight concentration of oxygen having a depth of 10 μm.

FIG. 10 shows the results of analysis by thin-film X-ray diffraction at an incident angle of 0.5 ° for the titanium hardened member of the present invention and the titanium hardened member of the prior art before processing, and of the present invention.

[Explanation of symbols]

 Reference Signs List 2 Titanium hardened member 4 Sample table 6 Processing tank 8 Gas inlet 10 Gas exhaust port 12 Heating means 14 Heating power supply 16 Vacuum exhaust device 18 Sample takeout port 20 Hardened layer 22 Crystal grain boundary 24 Surface crystal grain 26 Surface crystal grain Size 28 Vacuum pumping step 30 Heating / heating step 32 First curing step 34 Second curing step 36 Cooling step

Claims (6)

[Claims] 1. A hardened titanium member having a hardened layer having an arbitrary depth from the surface of the titanium member, wherein the hardened layer contains oxygen in a solid solution state. 2. A titanium hardened member having a hardened layer at an arbitrary depth from the surface of the titanium member, wherein the hardened layer contains 0.5 to 5 weight percent oxygen at a depth of 10 μm from the surface. A hardened titanium member, characterized in that: 3. A hardened titanium member having a hardened layer at an arbitrary depth from the surface of the titanium member, wherein the hardened layer contains 0.5 to 5 weight percent oxygen at a depth of 10 μm from the surface, and A hardened titanium member having a surface having a surface roughness Rmax of 1000 nm or less. 4. A heating step of heating a titanium member in an atmosphere of an inert gas such as argon or helium; and 700 to 800 ° C. in a mixed gas atmosphere of the inert gas and steam.
A first curing treatment step of heating to a treatment temperature of, a second curing treatment step of heating to a treatment temperature of 700 to 800 ° C. in the inert gas atmosphere, and a cooling step of cooling in the inert gas atmosphere. Curing method for a titanium cured member. 5. A heating step of heating a titanium member in an atmosphere of an inert gas such as argon or helium; and 700 to 800 ° C. in a mixed gas atmosphere of the inert gas and oxygen.
A first curing treatment step of heating to a treatment temperature of, a second curing treatment step of heating to a treatment temperature of 700 to 800 ° C. in the inert gas atmosphere, and a cooling step of cooling in the inert gas atmosphere. Curing method for a titanium cured member. 6. A heating step of heating a titanium member in an atmosphere of an inert gas such as argon or helium; and 700 to 8 in a mixed gas atmosphere of said inert gas, oxygen and hydrogen.
A first curing treatment step of heating to a treatment temperature of 00 ° C., a second curing treatment step of heating to a treatment temperature of 700 to 800 ° C. in the inert gas atmosphere, and a cooling step of cooling in the inert gas atmosphere A curing method for a titanium cured member comprising: