JP3376240B2 - High-strength titanium alloy, product thereof, and method of manufacturing the product - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a high-strength titanium alloy which is useful as a material for accessories such as watch cases / bands, bracelets, earrings, pendants, necklaces, and eyeglass frames, and the above-mentioned alloys. It relates to products, as well as useful methods for producing such products.

[0002]

2. Description of the Related Art Titanium is expected to be suitable as a material suitable for wearable products such as jewelry because it has excellent corrosion resistance and does not change with time such as discoloration and has a high (strength / specific gravity) ratio. Particularly in recent years, materials used for jewelry are required to have biocompatibility that does not cause allergies to the human body, and even from this viewpoint, titanium, which is also a typical non-metal allergic material, has been attracting attention as a material for jewelry. As a raw material for the above-mentioned various kinds of accessories, the use of the metal materials such as stainless steel has been widespread.

In view of its character, jewelry requires not only a beautiful surface and a complicated and precise shape, but also a robustness that does not lose beauty when it is used during daily life. In addition, in order to obtain the beauty of the accessory, it is need not only that the mirror surface is good, but also that various surface finishing processability after being mirror-finished (for example, hairline property shown in Examples described below) is required. Is. In addition, from the viewpoint of machinability, it is required that, for example, a large number of precise micro-drilling machinability be good.

However, titanium and titanium alloys used as materials for jewelry, and methods for manufacturing jewelry from these materials have been developed for other industrial applications such as the aerospace field, chemical industry and nuclear field. It is the actual situation that these items are diverted, and it does not mean that the various characteristics required for jewelry are obtained.

[0005] For example, industrial pure titanium such as JIS-1 and JIS-2, which are most often used for jewelry, are scratched by contact and friction in daily life, and various finishes are given to the surface. It wears out and is inferior to stainless steel in terms of the beauty and decoration that are essential for jewelry.

On the other hand, the titanium alloy has a higher strength due to the addition of a large amount of alloying elements. Although it is superior to pure titanium for industrial use in terms of scratch resistance, it is inferior in workability and has a precision and delicate precision required for jewelry. Since it is difficult to machine, it has a drawback that the design design is restricted. In addition, most titanium alloys are added with alloying elements such as Al, Ni, V, and Cr, which have poor biocompatibility. Moreover, since these alloy elements are relatively expensive, there is a drawback that the material cost is high.

Various techniques for improving the wear resistance of industrial pure titanium and the machinability of titanium alloys have been developed for other applications, but these techniques are considered in consideration of application to jewelry. These techniques cannot be used as they are as techniques for improving jewelry because they have not been made. For example, Japanese Examined Patent Publication No. 7-62196 proposes a wear resistant titanium alloy in which titanium carbide is dispersed to improve the wear resistance of titanium. However, even if this titanium alloy is used as a material for an accessory, titanium carbide is There is a problem in machining that the drill life is shortened remarkably when drilling too hard and minute holes. A free-cutting titanium alloy in which inclusions such as sulfides are dispersed in order to improve machinability and free-cutting property is also known (for example, Japanese Patent Publication No. 5-4249).
No. 0), the inclusions are too soft to be useful in improving the scratch resistance, and the presence of coarse inclusions also hinders mirror-finishing.

On the other hand, the improvement of the material by the conventional manufacturing technique does not always lead to the improvement of the performance of the accessory. For example, there has been proposed a technique for improving the scratch resistance by applying a hard coating on the surface of pure titanium (for example, JP-A-3-180478). However, this surface treatment causes loss of the original metallic luster, There is a problem in that the color tone of is dark and there is a problem in terms of decorativeness, which reduces the attractiveness as an accessory. Further, in this technique, since titanium itself used as a base material is easily scratched, it may be damaged during handling during processing before surface treatment, resulting in a decrease in commercial value.

By the way, although there is a method by heat treatment as a manufacturing method for further improving the material strength, the machinability deteriorates because not only the surface but also the hardness of the entire product increases. Further, such heat treatment is effective only for β type or α + β type titanium alloys containing many alloy elements. Further, if cold working is performed, hardness can be increased by work hardening, but cold forging increases the overall hardness, and machinability remains unimproved. From this point, a method such as shot peening can improve the hardness of only the surface by giving distortion only to the surface portion, but has another drawback that it cannot be applied to a molded product having a delicate shape. .

[0010] Therefore, when using pure titanium as a material for jewelry, it is the actual situation that, at present, pure titanium for industrial use, which has low scratch resistance, is used as it is, or surface treatment is performed at the expense of some decorativeness. is there. Ti-3A having properties intermediate between those of pure titanium for industrial use and the above titanium alloys
In some cases, an l-2.5V titanium alloy is used,
This alloy does not satisfy the required properties in terms of scratch resistance, workability and cost, and uses Al or V, which is difficult in terms of biocompatibility. Despite the drawbacks described above, titanium alloys may be used as a material for jewelry, but the examples of their use are extremely limited.

[0011]

As described above, the conventional titanium and titanium alloys and their manufacturing techniques cannot be said to be truly suitable for use as accessories. Satisfying all of decorativeness, robustness, processability, biocompatibility, and cost when titanium with excellent material properties is widely used not only for the above-mentioned accessories but also for decorative purposes and general daily necessities. It is desired to establish a new titanium material that can be produced and a product manufacturing technique using the titanium material.

The present invention has been made under these circumstances, and its purpose is excellent in decorativeness and beauty, less susceptible to flaws and dents, and good in machinability. It is an object of the present invention to provide a high-strength titanium alloy useful as a material for jewelry, a product as described above produced by the alloy, and a useful method for producing such a product.

[0013]

The titanium alloy of the present invention which has achieved the above object is Fe: 0.2 to 1.0%, O:
0.15-0.60% and Si: 0.20-1.0%
Is a high-strength titanium alloy having the gist in that each of them contains Ti and inevitable impurities.

In this alloy, the preferable ranges of Fe, O and Si are Fe: 0.3 to 0.7, respectively.
%, O: 0.20 to 0.40%, Si: 0.40 to 0.
It is 80%, and the alloy design may be performed by appropriately combining the contents according to the required characteristics.

The above titanium alloy is useful as a material for various products requiring strength. In addition, this titanium alloy is also excellent in workability, so the product is especially used in watch cases and
The characteristics are most effectively exhibited when the accessory is a band, a bracelet, an earring, a pendant, a necklace, an eyeglass frame or the like. Further, in order to exert the characteristics of this product more effectively, the surface Vickers hardness is preferably 20 or more higher than the internal Vickers hardness.

In producing the above high-strength titanium product, the material temperature is basically (β transformation point −200 ° C.)
Hot forging in the above state may be carried out including a step of cooling, but as a specific manufacturing method for making the surface Vickers hardness higher than the internal Vickers hardness by 20 or more, the following constitution is used. Can be mentioned. That is, when the material temperature is (β transformation point −200 ° C.) or higher, strain rate: 10
^It suffices to carry out hot forging at ^-1 / sec or more and to operate including a step satisfying at least one of the following (a) and (b). (A) The above-mentioned hot forging is performed using a die of 500 ° C. or lower, and then cooled. (B) Cooling rate: 10 ² within 10 seconds after completion of hot forging
The cooling is started at a rate of not less than 0 ° C./minute and continued until the material temperature becomes 500 ° C. or less. The material temperature during hot forging needs to be (β transformation point −200 ° C.) or higher, but the upper limit is preferably 950 ° C.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION In order to design a material that improves the scratch resistance without impairing the machinability, the inventors of the present invention recognize the condition under which the flaw is generated, especially by the naked eye regarding the beauty of the accessory. The material factors that influence the flaw generation were examined from various angles. First of all, scratches due to scratching in daily life are accompanied by large plastic deformation on the surface of the material and its surrounding area on a microscopic scale.The naked eye not only scratches due to the foreign substance itself, but also the surface caused by the deformation around these flaws. It was found that surface defects including irregularities were recognized.

As a result of a detailed investigation of the relationship between the size of such a flaw (including the irregular surface area of the peripheral surface) and various material factors, the width and depth of the irregularity of the flaw are determined by the hardness of the main phase and the grain size. It was found to depend on the diameter. That is, the higher the hardness and the smaller the crystal grain size, the more suppressed the uneven region of the flaw. It is considered that the reason is that the harder the crystal grains are, the more the deformation resistance increases. Therefore, the deformation of the crystal grains in the plastic deformation process such as indentation becomes small and the flaws are small. Also, when a flaw enters a part of a crystal grain, plastic deformation (slip deformation or twinning deformation) generated from it easily spreads throughout the crystal, but if the crystal grain size is small, the extent of deformation narrows, It is considered that the flaws are small, and from this viewpoint, it has been found that the crystal grain size is preferably 10 μm or less.

Based on these findings, the present inventors first investigated means for strengthening the α phase, which is stable at room temperature and used as the alloy design, as the main phase, in which jewelry is used. Since it is necessary to add a large amount of β-stabilizing element in order to allow the β phase to exist at room temperature, there are disadvantages that the material becomes too hard and too sticky to be processed, and the material becomes expensive. On the other hand, if the α phase is too solid-solution strengthened, it becomes clear that the machinability, especially the drill life when drilling small holes with a diameter of 1 mm or less, which is required for jewelry such as watches, is shortened. It was

On the other hand, the increase in strength due to precipitation strengthening due to the precipitation phase and dispersion strengthening resulted in relatively little reduction in drill life. However, in the case of α phase, there is a limit to the increase in strength obtained by precipitation strengthening.

Therefore, the present inventors considered that the element for solid solution strengthening the α phase should be minimized, and any further strengthening should be supplemented with an element for precipitation strengthening. At the same time, this precipitation phase was also expected to have the effect of suppressing the grain growth of the α phase and refining the grain size. Further, as conditions for the additive element, the study was conducted on the premise that a large effect can be obtained with a small amount of addition, the safety to living body is high, and the cost is low.

As a result, oxygen (O) was first selected as the optimum element for solid-solution strengthening the α phase. O is an element that has a high strengthening ability, can be obtained at a low cost in the form of titanium oxide, and has little fear of segregation. Nitrogen (N) is O
Although it was expected to have an effect similar to, it was inferior to O in terms of easiness of segregation and cost. Further, zirconium (Zr) has a problem in that it has a small solid solution strengthening ability and is extremely expensive.

By the way, the present inventors also tried to add carbon (C) as an element which forms another compound. However, addition of C forms titanium carbide (TiC) which is said to improve wear resistance, but this TiC has a Vickers hardness (Hv) of 1000 or more,
It could not be used because the life of the small diameter drill is significantly impaired. In addition, it is said that addition of sulfur (S) improves free-cutting property,
Although it may be used for titanium alloys, sulfides were too soft to improve the scratch resistance.

On the other hand, the addition of O improves the scratch resistance of the titanium alloy, and when the O content is 0.2% or more, the resistance of the titanium alloy to that of the conventional Ti-3Al-2.5V alloy or more is improved. It was found that flaws could be obtained. However, if only 0.2% or more of O is added, Ti-
It was lower than that of the 3Al-2.5V alloy. Therefore, the addition of O alone did not provide a combination of flaw resistance and workability superior to that of the Ti-3Al-2.5V alloy.

On the other hand, iron (Fe) and silicon (Si) were selected as the optimum elements for precipitation strengthening the α phase. Among them, Fe has a small amount of solid solution in the α phase, has a high ability to form and strengthen the β phase, is excellent in biosafety, and is extremely low in cost. Although Ni, Cr, Cu, etc. were expected to have similar effects, they were inferior to Fe in terms of strengthening ability and biocompatibility. Further, Si has a characteristic that it has a small amount of solid solution in the α phase and easily forms a compound (silicide) with Ti, and an effect of refining α crystal grains can be expected. This Si
Is excellent in biocompatibility, and for example, ferrosilicon (F
It is available in an extremely cheap form such as a compound of e and Si). That is, when Fe and Si are simultaneously added to Ti together with O, high strength can be realized and a fine β-phase dispersed state can be obtained, whereby a good balance between strength and machinability can be obtained at a high level. I was able to achieve it.

The titanium alloy of the present invention is a composite addition of Fe and Si at the same time as O, whereby both the scratch resistance and the puncture property are remarkably improved. That is,
The alloy of the present invention has Fe: 0.2 to 1.0% and O: 0.1.
It is a high strength titanium alloy containing 5 to 0.60% and Si: 0.20 to 1.0%, with the balance being Ti and unavoidable impurities.
It is possible to obtain the excellent scratch resistance and workability as compared with the 1-2.5V alloy. The reasons for limiting the range of the chemical composition in this titanium alloy are as follows.

O: 0.15 to 0.60% If the content of O is less than 0.15%, the flaw resistance is inferior, and 0.6
If added in excess of 0%, the workability will fall below the target value. Further, in the surface hardening treatment by thermomechanical treatment described later, if the O content is less than 0.15%, the surface hardness does not sufficiently increase. The preferred range of O content is 0.20 to 0.40%.
Therefore, the O addition effect is maximized in this range.

Fe: 0.2 to 1.0% If the Fe content is less than 0.2%, the effect of improving the flaw resistance and machinability is poor, and even if added in excess of 1.0%, In addition to saturation of the effect, the corrosion resistance of the titanium alloy decreases due to the excessive Fe content, and when the titanium alloy is subjected to a surface treatment such as gold plating to manufacture an accessory,
The plating solution had the adverse effect of eroding the titanium alloy surface. On the other hand, if the Fe content is less than 0.2%, the deformation resistance in hot working becomes large, and it becomes difficult to perform precise molding required for an accessory. The preferable range of the Fe content is 0.3 to 0.7%, and the Fe addition effect is maximized in this range.

Si: 0.20 to 1.0% Si has the effect of improving the flaw resistance due to precipitation by refining the β phase and improving the strength, and also improving the combination of flaw resistance and workability. . Si content is 0.20
If it is less than%, the effect of improving flaw resistance and machinability is poor,
Even if added in an amount of more than 1.0%, these effects saturate, and the excessive Si content lowers the hot workability, causing adverse effects such as cracking during forging. The preferable range of the Si content is 0.40 to 0.80%, and the Si addition effect is maximized in this range. Further, since Si has improved corrosion resistance and is less likely to diffuse than Fe and is thermally stable, it also has an effect of stabilizing Fe.

In manufacturing products such as jewelry using the titanium alloy material of the present invention as described above, basically, hot forging is performed in a state where the material temperature is (β transformation point −200 ° C.) or higher, It may be operated afterwards, including the step of cooling,
The present inventors, a decorative method, a manufacturing method of increasing only the surface hardness without deteriorating the beauty, more specifically, by curing only the surface layer by thermomechanical treatment, while further improving the scratch resistance, The conditions for preventing deterioration of workability such as drilling of internal material were examined. As a result of detailed investigation of the effect of thermomechanical treatment conditions on the surface hardness, the strain rate of machining is sufficiently fast even during hot working, and if it is rapidly cooled before the strain given by machining is recovered, work hardening occurs. It has been found that the condition can be retained on the surface. For example, if the mold temperature is lower than the recovery temperature, it is considered that the material is cooled at almost the same time as the deformation of the material, the temperature of the material near the surface becomes lower than the recovery temperature, and the work-hardened state is frozen. Alternatively, even if the mold temperature is high and the mold is not cooled at the time of processing, it is considered that the hardness of the surface portion can be substantially increased if the mold can be cooled before the softening due to the recovery sufficiently progresses.

Based on such knowledge, the manufacturing conditions under which surface hardening can be effectively carried out only by hot working are as follows. That is, while the material temperature is (β transformation point −200 ° C.) or more, hot forging with a strain rate of 10 ⁻¹ / sec or more is performed, and at least one of the following (a) and (b) is satisfied. It is sufficient to operate including the process. (A) The above-mentioned hot forging is performed using a die of 500 ° C. or lower, and then cooled. (B) Cooling rate: 10 ² within 10 seconds after completion of hot forging
Start cooling at ℃ / min or more and continue until the material temperature becomes 500 ℃ or less.

Under the above manufacturing conditions, for example, even if the mold temperature is higher than 500 ° C., the strain rate: 10 ^-1 /
If hot forging is performed for more than 10 seconds and cooling is started within 10 seconds after processing, cooling at a cooling rate of 10 ² ° C / minute or more is continued and cooling is continued until the material temperature falls to 500 ° C or less, the mold temperature becomes Although the amount of curing is smaller than that at 500 ° C. or lower, the surface can be cured. Further, the operation of the present invention can be obtained by carrying out the operation including the step satisfying at least one of the above (a) and (b), but the operation is carried out under the manufacturing condition satisfying both (a) and (b). If it does, it will be more effective. By satisfying such manufacturing conditions, the hardness of the region limited to the surface layer can be increased by 20 or more in Vickers hardness as compared with the inside.

The reasons for limiting each requirement in the above manufacturing conditions are as follows. The β transformation point is a transformation temperature of α → β or α + β → β, but the material temperature during hot forging needs to be (β transformation point −200 ° C.) or higher. If the material temperature is less than (β transformation point −200 ° C.), the deformation resistance of the material increases and the deformability decreases, making it difficult to perform precision molding required for jewelry, and during hot working such as hot forging. Defects such as surface cracks occur and the required surface hardness cannot be obtained. When the material temperature rises, the deformation resistance tends to decrease and the formability improves, but the upper limit of the material temperature is 950 ° C.
Is preferred. That is, when the material temperature exceeds 950 ° C., the surface of the material is oxidized so much that the time required for the surface polishing performed at the time of surface finishing after molding becomes long.

Even if the mold temperature exceeds 500 ° C., the effect of increasing the surface hardness can be obtained, and if the other requirements are satisfied, the surface hardness should be increased by 20 or more in Vickers hardness than in the inside. However, when the mold temperature is 500 ° C. or lower, the effect of increasing the surface hardness by the mold can be obtained. When the strain rate during forging is 10 ^-1 / sec or more, the hardness of the surface becomes higher than that of the inside, but at a strain rate of less than 10 ^-1 / sec, the surface hardness becomes the same level as the inside. That is, it is presumed that the work is completed in a short time, but the work hardening generated during the forging is not lost due to the recovery phenomenon during the work by setting the strain rate to 10 ^-1 / sec or more.

When the time from the end of forging to the start of cooling exceeds 10 seconds, the surface hardness becomes the same level as the inside. However, within 10 seconds after completion of forging, cooling rate: 10 ² ° C /
If the cooling is continued for more than a minute and is continued until the material temperature becomes 500 ° C. or less, the hardness of the surface becomes higher than that of the inside. Since a forged product with a small mass may obtain a cooling rate of 10 ² ° C / min or more even in cooling without active cooling, the above-mentioned "cooling" means simply cooling after forging. It also includes the case.

The above manufacturing conditions are basically assumed to be final hot forging conditions, and the effect of the present invention can be obtained as long as the finally hot forging satisfies the above conditions. However, it goes without saying that preliminary hot working (for example, hot rolling or hot forging) may be performed before the hot forging described above. In addition, after forming the shape by the hot forging process described above, it is manufactured including a process of primary machining such as cutting and drilling, and a process of secondary machining such as finishing such as polishing. By doing so, it becomes the final product.

The present invention will be described in more detail with reference to the following examples, but the following examples are not intended to limit the present invention, and any modification of the design of the present invention can be made without departing from the spirit of the preceding and the following. It is included in the technical scope.

[0038]

【Example】

Example 1 From a titanium alloy having the composition shown in Table 1 below, diameter: 10
A mm bar was created. The rod is manufactured by forging an ingot melted by plasma melting in the β temperature range and then α + β
In the temperature range, forged into a rod with a diameter of 10 mm and 700
Annealed at 30 ° C for 30 minutes. The obtained bar material was used as a test piece and subjected to a flaw resistance test and a drilling processing test, and its material (defect resistance and workability) was evaluated. At this time, in the scratch resistance test, a diamond indenter was loaded on the surface of the buffed test piece: 50
~ 200 g, speed: 75 mm / min under the condition of the flaw, the depth of the flaw is Ti-3Al-2.5V alloy (hereinafter,
(Referred to as "conventional material"). In the drilling test, a drilling process was performed with a hole diameter of 1 mm and a depth of 8 mm, and the numbers of holes until the drill was broken and became unworkable were compared.

The results of each test are also shown in Table 1 below. The evaluation of the scratch resistance is expressed by the ratio of the depth of the defects (the depth of the defects of the conventional material / the depth of the defects of the test piece), and the evaluation of the workability is the ratio of the number of perforations (the perforation of the test piece. (Number / number of holes drilled in conventional material). Further, the titanium alloy of the present invention has a scratch resistance of 1.5 of that of the conventional product.
Double the workability, the target value is equal to or higher than the conventional product.

[0040]

[Table 1]

From this result, the following can be considered. First, No. No. 1 is a comparative example in which the O content is too low, and the scratch resistance is inferior to the conventional material. No. No. 2 is a comparative example in which the Fe content is too low, and the workability is poor. No. Three
Is a comparative example in which the O content is excessive, and the workability is poor. No. No. 4 is a comparative example in which the Si content is excessive, and the forgeability is impaired. No. No. 5 is a comparative example in which the Fe content is excessive, and the corrosion resistance is impaired. No. 6
Is a comparative example in which the Si content is too low, and both the flaw resistance and workability are inferior. For these, 7-
No. 20 is an example satisfying the component composition defined in the present invention, and has both scratch resistance and workability that are superior to conventional materials.

Example 2 O: 0.30%, Fe: 0.50% and Si: 0.7
A test piece having a diameter of 20 mm was prepared from a titanium alloy containing 0% of each and the balance of Ti and unavoidable impurities. At this time, the test piece had a diameter in the α + β temperature range after forging an ingot melted by plasma melting in the β temperature range:
A bar material of 22 mm was forged, and this was machined into a test piece having a diameter of 20 mm and a length of 30 mm. After high frequency heating this under the conditions shown in Table 2 below, height: 10
It was press-formed (hot forging) to mm and then cooled.

With respect to the test piece after the heat treatment, the Vickers hardness (Hv) of the cross section was measured by a Vickers hardness tester, and the hardness of the surface portion (a region from just below the surface to a depth of 0.5 mm) and the hardness inside it were measured. In comparison, increase in hardness (surface hardness-
Internal hardness) was evaluated. The results are also shown in Table 2 below together with the cooling conditions. The β transformation point of the titanium alloy was 935 ° C.

[0044]

[Table 2]

From this result, the following can be considered. First, No. In No. 1, since the heating temperature of the material was too low, cracking occurred during press molding. No. In No. 2, the mold temperature was low, but the strain rate of processing was too slow, and the increase in surface hardness was small. No. In No. 3, since the mold temperature is high and the strain rate of processing is too slow, the increase in surface hardness is small. No. In No. 4, since the time from the end of forging to the start of cooling is too long, the increase in surface hardness is small. No. In No. 5, since the cooling rate after completion of forging is slow, the increase in surface hardness is small. No. In No. 6, the cooling was interrupted when the material temperature was high, so that the hardness of the surface is at the same level as the inside.

In contrast to these, 7 to 17 satisfy all of the manufacturing conditions specified in the present invention, and it can be seen that the Vickers hardness of the surface is increased by 20 or more than the internal Vickers hardness. However,
No. For 9 and 10, the upper limit of the material temperature is preferable (95
0 ° C.), no. In No. 9, the surface oxidation was slightly increased, and No. 9 was used. 10, the surface oxidation was remarkably increased.

Example 3 Using a titanium alloy having the composition shown in Table 3 below, a round bar (diameter: 20 mm) was prepared by processing such as rolling from an ingot melted by plasma melting. The obtained titanium alloy round bar was cut into a length of 25 mm.

Then, a watch case molding die was set in a hot forging machine, the die was heated to 150 to 250 ° C., and the die was heated to a predetermined temperature shown in Table 3 below by high frequency heating. Primary forging was performed by placing the material held for 5 to 10 seconds. The forging machine used at this time was a 200-ton friction press.

Next, the primary forged product from which the scale has been removed by chemical polishing is heated to a predetermined temperature shown in Table 3 below by high-frequency heating, and then held for 5 to 10 seconds. I did. The mold used at this time was a mold for forming a finished watch case, heated to 200 ° C., and forged using an 80 ton forging machine. The strain rate of forging time is shown in Table 3.
As shown in. In addition, the cooling after the completion of processing was performed under the conditions shown in Table 3.

Next, the inner diameter of the secondary forged product subjected to the deburring process (by pressing), the barrel process (removal of burrs and scales), and the chemical polishing process (complete removal of scales) (the back side in which the module is stored). Part), parting part (front side where dial plate can be seen), etc. are cut with an NC cutting machine, and a spring rod hole for attaching a band and a core hole for inserting a core are drilled. Primary machining was performed. After performing the perforating process, in order to obtain the desired finishing quality on the surface of the secondary forged product, the secondary machining process is performed in which the finishing process is performed by polishing using a grindstone or feather cloth.
Manufactured watch case.

With respect to the obtained watch case products (inventive example and comparative example), the difference in hardness between the surface and the inside (increased amount of hardness), flaw resistance, drilling workability and specularity were investigated, A comparison was made using a conventional Ti-3Al-2.5V alloy as a reference. The results are also shown in Table 3 below.

At this time, the hardness was measured by a Vickers hardness meter under a load of 100 g. The scratch resistance was evaluated by using a diamond indenter under a load of 200 g and a speed of 75 mm / min. The buffed sample surface was scratched and the scratch widths were compared to determine the ratio of the scratch widths (the scratch width of the conventional material). / Scratch width of the obtained product). Evaluation of drilling workability: Pore diameter: 1.5m
m, rotation speed: 2000 RPM, drill material: SKH-9
The number of holes that could be continuously processed was measured by
Similar comparison with. The specularity was evaluated by a visual sensitivity test on the basis of the standard sample, and the specularity was uniform and smooth without pits, scratches, distortion, and the like.

[0053]

[Table 3]

From this result, the following can be considered. First, No. Samples Nos. 1 to 3 were the examples of the material of the present invention and the processing method of the present invention, and the surface was harder than the inside, and all the material properties were good, which was the most excellent. In addition, No. 4,
No. 5 is an example according to the material of the present invention and a processing method outside the specified conditions of the present invention. Although the surface is not cured from the inside, the material is No. It was excellent next to 1-3.

On the other hand, in No. Nos. 6 to 10 are comparative examples of the conventional material and the processing method of the present invention, and there were problems in the following points. (A) No. No. 6 has too much O content and is inferior in hole drilling workability. (B) No. No. 7 has an excessively low Si content and is inferior in scratch resistance and specularity. (C) No. No. 8 has an excessively low O content and is inferior in scratch resistance and specularity. (D) No. 9 is the standard Ti-3Al-2.5V
It is an example of a system alloy. (E) No. No. 10 is an example of a Nearβ alloy that contains a large amount of alloying elements and can be hardened by heat treatment (treatment for hardening + aging), and has high flaw resistance but poor drilling workability.

These watch cases according to the present invention, in particular, the watch case produced by the material according to the present invention and the processing method according to the present invention are superior to the watch cases according to the prior art in terms of the combination of machinability and flaw resistance and the beauty. Was excellent.

That is, Fe: 0.2 to 1.0%, O: 0.
15 to 0.60%, Si: 0.20 to 1.0%, respectively, and the balance is titanium alloy material consisting essentially of Ti, hot forged using a watch case mold. The watch case completed by shaping, barrel machining, machining such as cutting, and finishing such as polishing has a higher surface hardness than those made of conventional materials, so it is less likely to have flaws or dents. As for the surface quality, a mirror-like surface that could not be obtained in the past was obtained, and a light, very beautiful and elegant texture was obtained.

Example 4 Using a titanium alloy having the composition shown in Table 4 below, a round bar (diameter: 6.5 mm) was produced from an ingot melted by plasma melting by processing such as rolling. The obtained titanium alloy round bar was cut into a length of 47 mm.

Next, a watch band forming die (two-piece taking) is set in the hot forging machine and heated to 150 to 250 ° C.,
After the temperature was raised to a predetermined temperature shown in Table 4 below by high frequency heating in this mold, a material held for 5 to 10 seconds was placed on the mold for primary forging. The forging machine used at this time was a 120-ton friction press.

Next, the forged product from which the scale has been removed by chemical polishing is subjected to deburring (the deburring and the disengagement of two pieces into one piece are simultaneously performed by a press),
Barrel processing (removal of burr and scale) and chemical polishing processing (complete removal of scale) were performed. Then, a primary machining process was performed in which a piece was perforated for connecting with a pin or the like. After that, in order to obtain a desired finish quality, the surface of the perforated piece was subjected to secondary machining such as finish barrel polishing or polishing using a feather cloth. The pieces thus obtained were connected by pins to complete a watch band.

The obtained watch band products (examples of the present invention and comparative examples) were examined for differences in hardness between the surface and inside (increased amount of hardness), flaw resistance, punching processability and hairline property, and The Ti-3Al-2.5V alloy as a material was used as a reference for comparison. The results are also shown in Table 4 below.

At this time, the hardness was measured by a Vickers hardness meter under a load of 100 g. The scratch resistance was evaluated in the same manner as in Example 3 by using a diamond indenter under a load of 200 g and a speed of 75 mm / min to scratch the surface of the buffed sample and compare the widths of the scratches. The evaluation of the drilling workability is performed by the hole diameter: 1.0 mm, the rotation speed: 4000 RP.
M, drill material: The number of holes that could be continuously processed by SKH-9 was measured, and compared with Example 2. With respect to the hairline property, the standard sample was used as a standard, and the uniform glossiness without irregularity, breakage, and roughness of the hairline and the regular hairline property were evaluated by a visual sensitivity test.

[0063]

[Table 4]

From this result, the following can be considered. First, No. Samples Nos. 1 to 3 were the examples of the material of the present invention and the processing method of the present invention, and the surface was harder than the inside, and all the material properties were good, which was the most excellent. In addition, No. 4,
No. 5 is an example according to the material of the present invention and a processing method outside the specified conditions of the present invention. Although the surface is not cured from the inside, the material is No. It was excellent next to 1-3.

On the other hand, in No. Nos. 6 to 10 are comparative examples of the conventional material and the processing method of the present invention, and there were problems in the following points. (A) No. No. 6 has too much O content and is inferior in hole drilling workability. (B) No. No. 7 has an excessively low Si content and is inferior in scratch resistance and hairline property. (C) No. No. 8 has an excessively small O content and is inferior in scratch resistance and hairline property. (D) No. 9 is the standard Ti-3Al-2.5V
It is an example of a system alloy. (E) No. No. 10 is an example of a Nearβ alloy that contains a large amount of alloying elements and can be hardened by heat treatment (solution treatment + aging), and has high flaw resistance but poor drilling workability.

These timepiece bands according to the present invention, in particular, the timepiece band produced by the material of the present invention and the processing method of the present invention are superior to the timepiece bands according to the prior art in the combination of machinability and flaw resistance and beauty. Was excellent.

That is, Fe: 0.2 to 1.0%, O: 0.
15-0.60%, Si: 0.20-1.0%, respectively, the balance is titanium alloy material consisting essentially of Ti is heated and hot forged using a watch band die. The watch band made by connecting the pieces completed by shaping, barrel processing, mechanical processing such as drilling, and finishing processing such as polishing with pins etc. is more surface than that made of conventional materials. Due to its high hardness, it was difficult to get scratches and dents, and the surface quality was fine, which was previously unobtainable, and a light, very beautiful and elegant texture was obtained.

In the above-mentioned Embodiments 3 and 4, the case of manufacturing the watch case and the watch band was shown, but other accessories such as bracelets, earrings, pendants, necklaces, and eyeglass frames, as well as ornaments and general daily necessities. Similar results were obtained even when applied to other products such as.

[0069]

EFFECTS OF THE INVENTION The present invention is constituted as described above, is excellent in decorativeness and beauty, is not easily scratched or dented, and has good machinability, and is particularly useful as a material for the above-mentioned various accessories. It has been possible to realize various high strength titanium alloys, the above-mentioned products manufactured by the alloys, and useful methods for manufacturing such products. Further, the effect of the technique of the present invention is most effectively exerted when applied to accessories, but in addition to ornaments where beauty is important as in accessories, bicycle parts, golf, fishing equipment, etc. It is expected to be applied to a wide range of products such as sports applications such as building materials and home appliances.

Front page continuation (51) Int.Cl. ⁷ Identification code FI C22F 1/00 673 C22F 1/00 673 683 683 683 684 684A 692 692A 692B 694 694B 694Z 1/18 1/18 H (72) Inventor Hashimoto Norio Tokyo 6-12 Hommachi Honcho, Miyakotanashi Citizen Watch Co., Ltd. (72) Inventor Hideo Taguchi 6-12 Hommachi Honmachi, Tokyo Tanashi City Citizen Watch Co., Ltd. (56) Reference JP-A-53- 28509 (JP, A) JP 7-70676 (JP, A) JP 7-43478 (JP, A) JP 4-176832 (JP, A) JP 3-226537 (JP, A) JP-A 1-252747 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) C22F 1/00 630 C22F 1/18 C22C 14/00

Claims (9)

(57) [Claims] 1. Fe: 0.2 to 1.0% (meaning mass%; the same applies hereinafter), O: 0.15 to 0.60% and S
i: 0.20 to 1.0%, respectively, and the balance consisting of Ti and unavoidable impurities, a high strength titanium alloy. 2. Fe: 0.3 to 0.7%, and / or O: 0.20 to 0.40%, and / or Si:
The titanium alloy according to claim 1, which is 0.40 to 0.80%. 3. A high-strength titanium product made of the titanium alloy according to claim 1. 4. The product of claim 3, wherein the product is an accessory. 5. The Vickers hardness of the surface is 20 or more higher than the Vickers hardness of the inside.
High strength titanium products described in. 6. When manufacturing the product according to claim 3 or 4, hot forging is performed in a state where the material temperature is (β transformation point −200 ° C.) or higher, and then the step of cooling is performed. Characteristic is a method for producing a high-strength titanium product. 7. The material temperature is 950 ° C. or lower.
The manufacturing method described in. 8. When manufacturing the product according to claim 5, the material temperature is (β transformation point −200 ° C.) or higher,
Strain rate: 10 ^-1 / sec or more hot forging,
A method for producing a high-strength titanium product, which comprises operating including a step satisfying at least one of the following (a) and (b): (A) The above-mentioned hot forging is performed using a die of 500 ° C. or lower, and then cooled. (B) Cooling rate: 10 ² within 10 seconds after completion of hot forging
The cooling is started at a rate of not less than 0 ° C./minute and continued until the material temperature becomes 500 ° C. or less. 9. The material temperature is 950 ° C. or lower.
The manufacturing method described in.