JP2019178388A - Ti-BASED ALLOY, MANUFACTURING METHOD THEREFOR, COMPONENT FOR WATCH - Google Patents

Abstract

To provide a Ti-based alloy of which a material itself is hard at a level not requiring a hardening treatment of a surface, which has Vickers hardness of HV580 or more, and Charpy impact value of unnotched test piece at room temperature of 6.0 J/cmor more.SOLUTION: The Ti-based alloy contains at least one of Fe, Mo, W with Fe of 3.0 atom% to 8.0 atom%, Mo of 4.0 atom% to 9.0 atom%, and W of 0 atom% to 3.0 atom%, further containing Al of 6.0 atom% to 12.0 atom%, Zr of 0 atom% to 2.0 atom%, Si of 0 atom% to 1.5 atom%, and N of 0.4 atom% to 1.5 atom%, and the balance Ti with inevitable impurities, and having alloy index represented by Al+0.5Si+2.5 N+0.5Fe+0.3Mo+0.3 W+0.3Zr of 10.5 to 17.0.SELECTED DRAWING: None

Description

  The present invention relates to a Ti-based alloy suitable for use in watch exterior parts, excellent in toughness such as high hardness and impact characteristics, and extremely low in the occurrence of skin allergies, a manufacturing method thereof, and a watch part.

  In recent years, Ti-based alloys (titanium alloys) are frequently used as materials for watch exterior parts. Ti-based alloys are significantly lighter than conventionally used stainless steel and have extremely good corrosion resistance against seawater and the like. Further, compared to stainless steel containing as a main element elements that may cause skin allergies such as Ni and Cr, Ti-based alloys can be configured without these elements. The possibility of causing allergies can be significantly reduced.

  However, since a conventional Ti-based alloy is soft, a surface hardening treatment is indispensable for preventing scratches and improving aesthetics by mirror polishing of the surface. However, there is a problem that the surface roughness is deteriorated by this curing treatment, the surface state becomes a rough gray color, the design is single, and the sense of quality is remarkably impaired. Therefore, there is a need for a Ti-based alloy that does not require surface treatment, the material itself is hard, and can be mirror-polished. Specifically, a Ti-based alloy having HV580 or higher as Vickers hardness which is a unit indicating this hardness is required.

  Many proposals have been made so far to improve the composition of the additive element in order to improve the hardness of the Ti-based alloy, but sufficient hardness has not been obtained in any of the proposals. Patent Document 1 discloses a decorative titanium alloy containing 0.5% or more Fe by weight with respect to Ti. However, the maximum value of the disclosed Vickers hardness is about HV400, and scratches are found. This is insufficient from the viewpoint of preventing or enhancing the mirror polishing property.

  Patent Document 2 proposes a Ti-based alloy containing Al 4.5% (wt%, hereinafter the same), V 3%, Fe 2%, Mo 2%, and O 0.1%. The Ti-based alloy has a Vickers hardness of HV440, which is insufficient from the standpoint of preventing scratches and improving the mirror polishability.

  In Patent Document 3, 4.0 to 5.0% aluminum by weight, 2.5 to 3.5% vanadium, 1.5 to 2.5% molybdenum, and 1.5 to 2.5% iron are included. A titanium alloy containing the balance of titanium and the inevitable component is disclosed. Although the Vickers hardness of this titanium alloy is not explicitly described in the specification, its composition is not much different from that of Patent Document 2, and thus the hardness is considered to be low compared to the target.

  In Patent Document 4, Nb is contained in a proportion of 20% to 40% by mass, Ge is contained in a proportion of 0.2% to 4.0%, and Ta, W, V, Cr, Ni, A germanium-containing high-strength titanium alloy containing one or more of Mn, Co, Fe, Cu, Si in a proportion of 15% or less in total, the balance being made of Ti and inevitable impurities, and excellent in cold workability is disclosed. Yes. Although there is no explicit description of the Vickers hardness, it is unlikely that the hardness will increase significantly compared to the various titanium alloys described above.

  As described above, in order to improve the hardness of the Ti-based alloy, various devices relating to the additive element have been devised, but since any improvement in hardness is slight, at least the surface must be hardened. ing. For this reason, there is a problem that the design becomes single and the sense of quality is remarkably impaired.

JP-A-7-62466 JP-A-7-150274 JP-A-9-145855 JP 2008-127667 A

As described above, it is strongly desired that a Ti-based alloy for a watch exterior part hardens the material itself more significantly than a conventional Ti-based alloy. However, since hard materials generally become brittle, there are problems such as difficulty in processing watch exterior parts and fragility when dropped, and it is necessary to solve these problems. That is, it is necessary to secure toughness typified by an impact value to some extent. The guideline is to secure an impact value that is equal to or higher than the cemented carbide (typically KV30) having the lowest toughness among the watch exterior materials currently in practical use. Specifically, it has an impact value exceeding the Charpy impact value of 6.0 J / cm ² with a KV30 room temperature notched test piece.

The present invention has been made in view of the above circumstances, and the material itself is so hard that surface curing treatment is unnecessary, the Vickers hardness is HV580 or more, and the Charpy impact value of a notched test piece at room temperature is 6 and to provide a .0J / cm ² or more at a Ti-based alloy.

  The basic idea of solving the problem according to the present invention is to obtain a Ti-based alloy in which the toughness of the alloy is improved after making the β-type alloy having high toughness. Al, Zr, Si, and N are used as elements for improving the hardness. However, the addition of these elements facilitates the formation of an α phase that reduces toughness, and therefore a β-stabilizing element is added to prevent this. This β-stabilizing element also improves the hardness of the Ti-based alloy depending on the amount added.

  In addition, in the manufacturing process of Ti-based alloys, an alloy synthesized at a predetermined element ratio is subjected to a high-temperature heat treatment, a solution treatment that is rapidly cooled from a high temperature, and then an aging treatment at a low temperature, thereby age-hardening. Is realized.

  In general, there are many β-stabilizing elements in Ti-based or Ti—Al-based alloys such as Cr, Mo, V, Mn, Fe, W, Nb, Ni, and Co. As industrial parts, Ti alloys having various properties have been developed by freely selecting them. However, it is not appropriate to use an additive element that may cause skin allergy in the watch exterior part that is the subject of the present invention. Therefore, from this viewpoint, in the present invention, Fe, Mo, and W are used as β stabilizing elements. In addition, the β stabilization effect per unit addition amount of each element is different, and if the β phase is extremely stabilized by addition of a large amount, there is a problem that toughness is lowered. Therefore, it is necessary to find an appropriate addition amount for the β-stabilizing element.

  Next, the additive elements Al, Zr, Si, and N act in a complex manner to achieve solution hardening and higher hardness of the alloy obtained by the effect of subsequent aging treatment. When the addition amount is small, there is no effect of improving the hardness, and when the addition amount is too large, there is a problem that the toughness is lowered. Therefore, it is necessary to find an appropriate addition amount for these elements. From these viewpoints, the present inventors have conducted many experiments for selecting an appropriate amount of each additive element. The present invention has been made on the basis of such an experiment, and is characterized by the following configuration.

[1] The Ti-based alloy according to one embodiment of the present invention includes at least one of Fe, Mo, and W, Fe is 3.0 atomic% or more and 8.0 atomic% or less, and Mo is 4.0. 1. Atomic% to 9.0 atomic%, W is 0 atomic% to 3.0 atomic%, Al is 6.0 atomic% to 12.0 atomic%, and Zr is 0 atomic% to 2. 0 atom% or less, Si is contained in an amount of 0 atom% or more and 1.5 atom% or less, N is contained in a ratio of 0.4 atom% or more and 1.5 atom% or less, and Ti and inevitable impurities are contained as the balance, Al + 0.5Si + 2 The alloy index represented by .5N + 0.5Fe + 0.3Mo + 0.3W + 0.3Zr is 10.5 or more and 17.0 or less.

[2] A Ti-based alloy manufacturing method according to an aspect of the present invention is the Ti-based alloy manufacturing method according to [1], in which a heat treatment is performed at a temperature of 900 degrees to 1200 degrees. And a solution treatment process by water cooling or oil cooling, and a second heat treatment process in which heat treatment is performed at a temperature of 400 to 600 degrees.

  [3] A timepiece part according to an aspect of the present invention is made of the Ti-based alloy according to [1].

The Ti-based alloy of the present invention is composed of elements that do not cause skin allergy, and the amount of added elements of Fe, Mo, W, Al, Si, N, and Zr is optimized. Therefore, the Ti-based alloy of the present invention has excellent hardness (Vickers hardness of HV580 or more) and excellent impact characteristics (room temperature) by performing high-temperature heat treatment, solution treatment rapidly quenched from high temperature, and aging treatment. The Charpy impact value of the non-notched test piece is 6.0 J / cm ² or more. In other words, by using the Ti-based alloy of the present invention, the mirror polishability and scratch resistance, which were the problems of the conventional Ti-based alloy, are remarkably improved, and further, toughness such as impact characteristics required at the time of manufacture and use It is possible to provide a material for a watch exterior part in which is secured.

It is an external appearance photograph of the ingot which consists of Ti system alloy of Example 1 of this invention. It is an external appearance photograph after the forge test of the ingot of FIG.

  Hereinafter, a Ti-based alloy which is an embodiment to which the present invention is applied will be described in detail with reference to the drawings. In addition, in the drawings used in the following description, in order to make the features easy to understand, there are cases where the portions that become the features are enlarged for the sake of convenience, and the dimensional ratios of the respective components are not always the same as the actual ones. Absent. In addition, the materials, dimensions, and the like exemplified in the following description are examples, and the present invention is not limited to them, and can be appropriately changed and implemented without changing the gist thereof.

(Configuration of Ti alloy)
The structure of the Ti-based alloy according to one embodiment of the present invention will be described. The Ti-based alloy contains at least one of iron (Fe), molybdenum (Mo), and tungsten (W) in the following ratio, and further includes aluminum (Al), zirconium (Zr), silicon (Si), and nitrogen. (N) is included in the following ratio.
Fe: 3.0 atomic% or more and 8.0 atomic% or less Mo: 4.0 atomic% or more and 9.0 atomic% or less W: 0 atomic% or more and 3.0 atomic% or less Al: 6.0 atomic% or more 12. 0 atom% or less Zr: 0 atom% or more and 2.0 atom% or less Si: 0 atom% or more and 1.5 atom% or less N: 0.4 atom% or more and 1.5 atom% or less Further, the Ti system of this embodiment The alloy contains titanium (Ti) and inevitable impurities as the balance.

Further, in the Ti-based alloy of the present embodiment, an alloy index represented by Al + 0.5Si + 2.5N + 0.5Fe + 0.3Mo + 0.3W + 0.3Zr is obtained as an amount obtained by multiplying each weight of the contained elements by a predetermined coefficient. 10.5 or more and 17.0 or less. When the alloy index is within this range, by performing solution treatment that rapidly cools from high temperature and aging treatment, excellent hardness (Vickers hardness is HV580 or more) and excellent impact properties (no notch at room temperature) An alloy having a Charpy impact value of 6.0 J / cm ² or more in the test piece is obtained.

(Method for producing Ti-based alloy)
The main procedure for manufacturing the Ti-based alloy described above will be described. First, Ti, Fe, Mo, W, Al, Si, N, and Zr raw materials are melted in a melting furnace, and the molten metal is placed in a mold and solidified to obtain a Ti-based alloy (alloy forming step).

  Next, this Ti-based alloy is put in a heat treatment furnace and heated at a temperature of 1100 ° C. or higher and 1250 ° C. or lower for 30 minutes to 120 minutes. Thereafter, the Ti-based alloy is taken out from the heat treatment furnace and hot forged in the atmosphere at room temperature (hot forging step). As a method of hot forging, for example, upsetting (a method of compressing a material in a length direction) or stretching (a method of compressing a material in a radial direction) can be used. In addition to forging, other hot working methods such as rolling and extrusion may be used.

  Next, the hot-forged Ti-based alloy is placed in a heat treatment furnace and heated at a temperature of 900 ° C. to 1200 ° C. (preferably 1100 ° C.) for 30 minutes to 120 minutes (preferably 1 hour). Hold in a state (first heat treatment step).

  Subsequently, the Ti-based alloy after heating is taken out from the heat treatment furnace, water-cooled or oil-cooled, and cooled to a temperature of about room temperature (solution treatment). The cooling rate needs to be high, and is preferably higher than air cooling. The higher the cooling rate, the harder the Ti-based alloy obtained after the aging treatment described below.

  Next, the cooled Ti-based alloy is placed in a heat treatment furnace and heated at a temperature of 400 ° C. to 600 ° C. (preferably 500 ° C.) for 10 hours to 200 hours (preferably 100 hours). By holding (second heat treatment step (aging treatment step)), the Ti-based alloy of the present embodiment is obtained.

As described above, the Ti-based alloy according to this embodiment is composed of elements that do not cause skin allergy, and the amount of added elements of Fe, Mo, W, Al, Zr, Si, and N is optimized. Has been. Therefore, the Ti-based alloy according to the present embodiment has excellent hardness (Vickers hardness of HV580 or more) and excellent impact characteristics by performing high-temperature heat treatment, solution treatment that is rapidly cooled from high temperature, and aging treatment. (Charpy impact value of a notched test piece at room temperature is 6.0 J / cm ² or more). In other words, by using the Ti-based alloy according to the present embodiment, the specular polishing property and the scratch-preventing property, which were problems of the conventional Ti-based alloy, are remarkably improved. It is possible to provide a watch exterior component material in which the toughness is ensured.

  Hereinafter, the effects of the present invention will be made clearer by examples. In addition, this invention is not limited to a following example, In the range which does not change the summary, it can change suitably and can implement.

Example 1
FIG. 1 is an example of an appearance photograph of an ingot 100 used in the experiment. Each ingot was made by high frequency melting using an yttria crucible. The prepared procedure will be described.

  The raw materials used for melting were sponge Ti, Al pellets, Fe, Zr, Si granular raw materials, and Mo, W, TiN powder raw materials. The total amount of raw materials was about 800 g. The melting operation was performed by evacuating the melting furnace chamber and introducing argon gas. After all the raw materials were dissolved, the material was held for about 3 minutes, and the dissolved raw materials were poured into a cast iron mold. As the mold, a cast-in part having a cylindrical shape with a diameter of 40 mm and a height of 100 mm was used. When pouring, an alumina funnel was placed on the top and filled with the molten metal halfway through the funnel. The molten metal in the funnel became a hot water for reducing casting defects of the ingot in the mold. In FIG. 1, an upper conical portion 100A is a feeder portion solidified in a funnel, and is a rod-like portion 100B (hereinafter referred to as an ingot 100B) cut at a position C shown in FIG. The following tests were carried out using

  The ingot 100B was hot forged after being heated to 1200 ° C. The forging direction was upsetting forging in the longitudinal direction L of the ingot 100B, and the ingot 100B having a length of 100 mm was forged to 25 mm by only one compression. An example of an appearance photograph of the material 110 after forging is shown in FIG.

  Next, the entire forged material 110 was heated at 1100 ° C. for 1 hour (first heat treatment) and then oil-cooled (solution treatment). Thereafter, an aging treatment (second heat treatment) was carried out at 500 ° C. for 100 hours.

  The following (a) to (c) were evaluated for the forged material after the aging treatment.

(A) Evaluation by Vickers hardness measurement with a load of 50 kgf on a test piece cut out from a cross-section of a forging material and polished.
Specifically, when the diamond indenter was pressed against the test piece with a load of 50 kgf, the length of the diagonal line of the recessed part was measured, and the area of the recessed part was calculated from this length, and the load and area The Vickers hardness is obtained using the value.

(B) Evaluation by observation with an optical microscope or the like for the presence or absence of cracks at the end of the indented portion (end of the indentation) at the time of measuring the Vickers hardness with a load of 50 kgf for the purpose of simple evaluation of toughness.

(C) Evaluation by a room temperature Charpy impact test of an unnotched specimen processed from a forged material after aging treatment.
Specifically, the test piece is destroyed by hitting a hammer, the energy (Charpy impact value) required for the destruction is measured, and this is used as an index for evaluating the toughness of the test piece.

  In the same procedure as in Example 1, Ti-based alloys (ingots) having a composition different from that of the Ti-based alloy of Example 1 were produced as samples of Comparative Examples 1 to 12 and Examples 2 to 24. The above evaluations (a) to (c) were performed on them. Tables 1 and 2 summarize the compositions and various evaluation results for the forging materials produced as Comparative Examples 1 to 12 and Examples 1 to 24, respectively.

  In the evaluation of the above (a), an alloy having a Vickers hardness of HV580 or higher was determined to be an appropriate alloy, and an alloy having a Vickers hardness of less than HV580 was determined to be an inappropriate alloy.

  In the evaluation of (b) above, it was determined that a crack did not occur was an appropriate alloy, and a crack was determined to be an inappropriate alloy.

In the evaluation of the above (c), as a watch exterior material currently in practical use, the impact value of KV30 of the cemented carbide with the lowest toughness is 6.0 J / cm ² , which is above this reference value. It was judged that the alloy was an appropriate alloy, and an alloy that showed less than this reference value was determined to be an inappropriate alloy.

  The sample of Comparative Example 1 (Alloy No. 1) has an alloy index of 10.3, which is lower than the lower limit value 10.5 of the alloy index defined in the above embodiment. Therefore, since the Vickers hardness is less than HV580 and the hardness is insufficient, the sample of Comparative Example 1 is determined to be an inappropriate sample.

  The sample of Comparative Example 2 (Alloy No. 2) has an alloy index of 17.2, which exceeds the upper limit value of 17.0 for the alloy index defined in the above embodiment. Therefore, a crack is generated at the end of the indentation at the time of measuring the Vickers. From this, the sample of Comparative Example 2 is determined to be an inappropriate sample.

  The sample of Comparative Example 3 (alloy number 3) has an Fe composition ratio of 2.5 atomic%, which is lower than the lower limit value of 3.0 atomic% of the Fe composition ratio defined in the above embodiment. Therefore, since the Vickers hardness is less than HV580 and the hardness is insufficient, the sample of Comparative Example 3 is determined to be an inappropriate sample.

  The sample of Comparative Example 4 (Alloy No. 4) has an Fe composition ratio of 8.5 atomic%, which exceeds the upper limit of 8.0 atomic% of the Fe composition ratio defined in the above embodiment. Therefore, a crack is generated at the end of the indentation at the time of measuring the Vickers. From this, the sample of Comparative Example 4 is determined to be an inappropriate sample.

  In the sample of Comparative Example 5 (Alloy No. 5), the Mo composition ratio is 3.5 atomic%, which is lower than the lower limit value of 4.0 atomic% of the Mo composition ratio defined in the above embodiment. . Therefore, since the Vickers hardness is less than HV580 and the hardness is insufficient, the sample of Comparative Example 5 is determined to be an inappropriate sample.

In the sample of Comparative Example 6 (Alloy No. 6), the Mo composition ratio is 9.5 atomic%, which exceeds the upper limit value of 9.0 atomic% of the Mo composition ratio defined in the above embodiment. Therefore, cracks occur at the end of the indentation at the time of Vickers measurement, the Charpy impact value is less than 6 J / cm ² , and the toughness is insufficient, so the sample of Comparative Example 6 is determined to be an inappropriate sample. Is done.

  The sample of Comparative Example 7 (Alloy No. 7) has a W composition ratio of 3.5 atomic%, which exceeds the upper limit of 3.0 atomic% of the W composition ratio defined in the above embodiment. For this reason, cracks occur at the end of the indentation at the time of Vickers measurement. From this, the sample of Comparative Example 7 is determined to be an inappropriate sample.

  In the sample of Comparative Example 8 (alloy number 8), the Al composition ratio is 5.5 atomic%, which is lower than the lower limit value of 6.0 atomic% of the Al composition ratio defined in the above embodiment. . Therefore, since the Vickers hardness is less than HV580 and the hardness is insufficient, the sample of Comparative Example 8 is determined to be an inappropriate sample.

The sample of Comparative Example 9 (alloy number 9) has an Al composition ratio of 12.5 atomic%, which exceeds the upper limit of 12.0 atomic% of the Al composition ratio defined in the above embodiment. Therefore, cracks are generated at the end of the indentation at the time of Vickers measurement, and the Charpy impact value is less than 6 J / cm ² and the toughness is insufficient. Therefore, the sample of Comparative Example 9 is determined to be an inappropriate sample. Is done.

  The sample of Comparative Example 10 (Alloy No. 10) has a Si composition ratio of 2.0 atomic%, which exceeds the upper limit of 1.5 atomic% of the Si composition ratio defined in the above embodiment. Therefore, a crack is generated at the end of the indentation at the time of Vickers measurement. From this, the sample of Comparative Example 10 is determined to be an inappropriate sample.

  In the sample of Comparative Example 11 (Alloy No. 11), the N composition ratio is 0.35 atomic%, which is lower than the lower limit of 0.4 atomic% of the N composition ratio defined in the above embodiment. . Therefore, since the Vickers hardness is less than HV580 and the hardness is insufficient, the sample of Comparative Example 11 is determined to be an inappropriate sample.

In the sample of Comparative Example 12 (Alloy No. 12), the composition ratio of N is 1.75 atomic%, which exceeds the upper limit of 1.5 atomic% of the N composition ratio defined in the above embodiment. Therefore, cracks occur at the end of the indentation at the time of Vickers measurement, and the Charpy impact value is less than 6 J / cm ² , and the toughness is insufficient. Therefore, the sample of Comparative Example 12 is determined to be an inappropriate sample. Is done.

In the samples of Examples 1 to 24 (alloy numbers 13 to 36), the composition ratios (at%) of all the contained elements are all within the range defined in the above embodiment, and the alloy index is also It is within the range defined in the above embodiment. Therefore, the Vickers hardness is HV580 or more and the hardness is sufficient, the crack is not generated at the end of the indentation at the time of Vickers measurement, and the Charpy impact value is 6 J / cm ² or more. Toughness is sufficient. Therefore, all the samples of Examples 1 to 24 are determined to be appropriate samples.

  The Ti-based alloy of the present invention requires hardness and toughness, and can be widely used as a material constituting an exterior part of a watch used in contact with a human body.

DESCRIPTION OF SYMBOLS 100 ... Ingot 100A ... Conical part 100B of ingot ... Bar-shaped part 110 of ingot ... Forging material

Claims (3)

Fe includes at least one of Fe, Mo, and W, Fe is 3.0 atomic% to 8.0 atomic%, Mo is 4.0 atomic% to 9.0 atomic%, and W is 0 atomic% 3.0 atomic% or less, Al is 6.0 atomic% or more and 12.0 atomic% or less, Zr is 0 atomic% or more and 2.0 atomic% or less, Si is 0 atomic% or more and 1.5 atomic% or less. % Or less, N is contained in a proportion of 0.4 atomic% or more and 1.5 atomic% or less, and Ti and inevitable impurities are included as the balance,
A Ti-based alloy having an alloy index represented by Al + 0.5Si + 2.5N + 0.5Fe + 0.3Mo + 0.3W + 0.3Zr in atomic percent of 10.5 or more and 17.0 or less. It is a manufacturing method of Ti system alloy according to claim 1,
A first heat treatment step in which heat treatment is performed at a temperature of 900 degrees to 1200 degrees;
Solution treatment process by water cooling or oil cooling,
And a second heat treatment step in which heat treatment is performed at a temperature of 400 ° C. or more and 600 ° C. or less.   A timepiece component comprising the Ti-based alloy according to claim 1.