JP2003342654A - Titanium alloy - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a uniform, high-quality titanium alloy which contains few gas components and has an excellent elasticity, a high tensile elastic limit strength, a good processing yield and a low porosity. <P>SOLUTION: The titanium alloy comprises 30-60 mass% of at least one metallic element chosen from Zr, Hf, V, Nb, Ta, Cr, Mo and W and the balance being Ti and has an oxygen content of ≤2,000 ppm, a nitrogen content of ≤150 ppm, a hydrogen content of ≤200 ppm, an average Young's modulus of ≤75 GPa, a tensile elastic limit strength of ≥700 MPa and a crystalline structure comprising β phase as a main phase. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a titanium alloy,
The present invention relates to a titanium alloy which has a high tensile elastic limit strength and a low elastic modulus and has good workability, and therefore can be manufactured with a high processing yield.

[0002]

2. Description of the Related Art A titanium alloy having a high elastic strain limit and a low elastic modulus has a property of being lightweight and excellent in elasticity, so that it is used after being processed into eyeglass frames, ornaments and the like.

Regarding such titanium alloys, for example,
Japanese Patent Laid-Open No. 2001-247924 discloses a portable product using a titanium alloy having a low Young's modulus and a tensile elastic limit strength.

Specifically, V of 30% by mass to 60% by mass is used.
Alternatively, at least one of Zr, Hf, and Sc is 2
Titanium alloy containing 0 mass% or less, the average Young's modulus of which is 75 GPa or more, and the tensile elastic limit strength of which is 700 MPa or more is used for glasses, necklaces, tie pins,
It is used as a material for ornaments such as watches.

Such titanium alloys are, for example, Zr, Hf, V, Nb and T when the titanium alloy is 100% by mass.
It is an alloy containing 30 to 60 mass% of at least one metal element selected from a, Cr, Mo and W, and the balance being Ti.

Such a titanium alloy has a small specific gravity,
Since highly active Ti and a metal element having a large specific gravity and a high melting point are used as constituent elements, the melting point is high and the high specific gravity component is segregated by gravity, so that it is difficult to uniformly disperse each constituent component. It has been considered that the alloy is difficult to manufacture by the melting method.

For example, a small amount of titanium alloy can be manufactured by arc melting using a water-cooled copper hearth. On the other hand, in the case of large-scale production, a method of dissolving each constituent component at the same time using a consumable electrode method and manufacturing is adopted. According to this consumable electrode method, composition control of metal components used for electrodes is possible. Difficult and difficult to make a homogeneous titanium alloy.

Therefore, in the production of a large amount of titanium alloy, the powder metallurgy method has conventionally been mainly used. The powder metallurgy method mixes powders of each metal component, sinters and heat-treats the resulting mixture by a hot pressing method or the like to prepare a billet that is homogeneous and has few pores, and processes it into a rod or wire. use.

[0009]

However, the titanium alloy produced by this powder metallurgy method has impurities as impurities.
Since it contains a large amount of gas components such as oxygen, nitrogen, and hydrogen, it has the disadvantage that cracks are likely to occur during rolling, forging, and extrusion, which greatly reduces the processing yield and reduces the porosity. There was a problem of becoming expensive.

Further, when a conventional titanium alloy is used to manufacture a product requiring decorativeness such as a spectacle frame, non-metallic inclusions such as gas components are likely to cause scratches during processing, resulting in material yield. In addition, there is a problem in that the desired quality and shape cannot be obtained in terms of luster, decorativeness, and design.

As described above, in producing a titanium alloy, it is necessary to consider the influence of non-metallic inclusions such as gas components on the quality of the titanium alloy. However, the influence of the gas components on the quality of the titanium alloy is analyzed in detail. do it,
Regarding the technologies that have been defined together with the limit values of these gas components for producing high-quality titanium alloys, and the methods studied together with the method for producing high-quality titanium alloys by reducing the gas components, However, it was not reported.

On the other hand, as a method of producing a titanium alloy, a method of using a calcial crucible is also adopted. However, in the production of a titanium alloy by a calcial crucible, gravity segregation due to a difference in density of alloy components is likely to occur and a homogeneous titanium alloy It was difficult to obtain. Further, since the calcia crucible has deliquescent properties, the quality of the product is likely to be affected, and there is a problem in that handling is required.

The present invention has been made in order to solve the above-mentioned problems, and has a small amount of gas components, excellent elasticity, high tensile elastic limit strength, good processing yield, and uniform It is an object of the present invention to provide a high quality titanium alloy having a low porosity.

[0014]

[Means for Solving the Problems] The inventors of the present invention have tried and conducted comparative studies on various production methods such as induction electrolysis using calcia crucibles or dissolution by cold crucible,
We have conducted intensive studies on the relationship between the concentration of gas components in titanium alloys and the workability, the frequency of processing scratches, and the relationship with porosity.

As a result, by reducing the content of the gas component in the titanium alloy to a certain concentration or less, the titanium alloy is homogeneous and excellent in workability, has less non-metallic inclusions, and has a good yield during processing. It was found that a titanium alloy excellent in workability can be obtained.

Further, it has been found that, when a titanium alloy is manufactured by the melting method, it is possible to manufacture a high quality titanium alloy by taking advantage of the characteristics of the melting method by devising the manufacturing conditions.

That is, the titanium alloy of the present invention is composed of Zr,
A titanium alloy containing 30 to 60 mass% of at least one metal element selected from Hf, V, Nb, Ta, Cr, Mo and W, and the balance being Ti, and having an oxygen content of 2000 ppm or less. Yes, the nitrogen content is 150ppm
The hydrogen content is 200 ppm or less, the average Young's modulus is 75 GPa or less, and the tensile elastic limit strength is 7 or less.
It is characterized by having a crystal structure of at least 00 MPa and having a β phase as a main phase.

According to the research conducted by the present inventors, when the relationship between the frequency of occurrence of surface scratches and workability of titanium alloy products and the gas concentration was investigated in detail, the gas concentrations contained in the titanium alloy were found to be oxygen, nitrogen, Each concentration of hydrogen is 2000ppm or less,
It was found that when the content was 150 ppm or less and 200 ppm or less, generation of processing scratches and deterioration of workability were effectively prevented.

That is, it is more preferable that the concentration of each gas of oxygen, nitrogen and hydrogen in the alloy is 500 ppm or less, 120 ppm or less, 60 ppm or less. Titanium alloys with oxygen, nitrogen, and hydrogen gas concentrations of 500 ppm or less, 120 ppm or less, and 60 ppm or less are particularly prevented from surface scratches,
Workability is further improved. In addition, the porosity can be 0.5% or less. The porosity of the present invention is the ratio of the porosity per unit area as an area ratio as described later.

This titanium alloy has a low Young's modulus of 75 GPa or less. If the Young's modulus exceeds 75 GPa, the rigidity is high and the elasticity is reduced.

On the other hand, this titanium alloy has an alloy having a tensile elastic limit strength of 700 MPa or more. Since it has such a high tensile elastic limit strength, it is possible to provide a titanium alloy product excellent in mechanical strength.

This titanium alloy is characterized in that the crystal structure has a β phase as a main phase (50% or more is a β phase). In particular,
It has been found that the crystal structure of the metal is preferably a β single phase, and that the β single phase improves workability. In the present invention, “β single phase” means that the ratio of the peak height of α phase / peak height of β phase by X-ray diffraction is 1/100 or less (including zero). At this time, "α phase peak is not detected" and "α phase peak is below the detection limit"
State, that is, a state in which the ratio of the peak height of the α phase / the peak height of the β phase is zero is also included.

The titanium alloy of the present invention is preferably manufactured by a melting method.

For example, a titanium alloy produced by a melting method using a calcia crucible has a uniform concentration of gas components contained in the titanium alloy and a uniform porosity with a small porosity as compared with a titanium alloy produced by a powder metallurgy method. It is possible to produce alloys.

Further, according to the melting method, it is possible to provide a high-quality titanium alloy with less generation of surface processing scratches as compared with the titanium alloy by the powder metallurgy method.

Further, the titanium alloy of the present invention is more preferably manufactured by a melting method using a cold crucible.

According to the melting method using the cold crucible, it is possible to manufacture a high-quality titanium alloy with a further reduced gas concentration and good workability.

The dissolution method using a cold crucible is as follows.
It is a method of manufacturing an alloy material by a water-cooled copper crucible.

FIG. 1 shows a method for producing an alloy by cold crucible. The copper crucible 1 has an internal cavity 2
Is provided, and the refrigerant is circulated in the internal cavity 2. On the other hand, outside the crucible 1 is a high frequency induction heating coil 3
The high frequency induction heating coil 3 induces an eddy current in the metal material 4 inside the crucible 1 in a direction repulsive to the magnetic field. Joule heat is generated by the action of this eddy current, and the metal material 4 is melted and alloyed.

In the melting method using the cold crucible, the inner surface of the crucible 1 and the metal material 4 (molten metal) are always kept in a non-contact state (or a state close to this) during the heat melting of the metal material. . Therefore, metal material 4
There is very little contamination from the crucible 1 with respect to, and it is possible to effectively reduce the mixture of non-metallic inclusions such as gas components such as oxygen, nitrogen and hydrogen, and it is possible to greatly improve the workability of titanium alloys. .

According to the titanium alloy having the above-mentioned structure, since the gas component concentration is reduced to a predetermined value or less, it has a high tensile elastic limit strength, while it has a low elastic modulus and is therefore highly elastic and can be processed into a product. It is possible to provide a homogeneous titanium alloy with less processing scratches on the surface of the alloy, a good processing yield, and a good processing yield.

[0032]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the titanium alloy according to the present invention will be described below in detail with reference to Examples.

The present inventors produced various titanium alloys by the methods shown in the following examples and comparative examples, and comparatively examined the characteristics.

Example 1 A titanium material was put into a cold crucible (crucible) and melted in a vacuum to be completely melted.
% Nb-10% Ta-5% Zr-balance Ti: Zr, Nb, Ta pulverized to a particle size of several millimeters or less
A metal powder was added in small amounts so as not to cause surface solidification of the molten metal, completely melted, and then solidified in a crucible to produce a titanium alloy.

When the composition of this titanium alloy was analyzed by a composition analyzer, a titanium alloy having a composition substantially equivalent to the compounding ratio with respect to the main components was produced. Also, oxygen,
The concentrations of nitrogen and hydrogen are 680ppm, 120ppm,
It was 85 ppm.

The thus manufactured ingot having a diameter of 100 mm was hot-forged into a rod-shaped member having a diameter of 50 mm, and the rod-shaped member was surface-ground to a diameter of 47 mm. Next, this rod-shaped member was processed into a round bar having a diameter of 18 mm by cold swaging, and further subjected to peeling processing to remove irregularities and oxides on the surface portion and processed into a round bar having a diameter of 17 mm. Further, the surface of the round bar was electrolytically polished to reduce the surface roughness, and then the round bar was drawn to obtain a round bar having a diameter of 10 mm.

When the number of surface scratches per 100 m of this round bar and the processing yield were investigated, the number of surface scratches generated was very small at 2 per 100 m, and the processing yield was 70% or more, and the workability was improved. It turned out to be excellent. The "number of surface scratches" in this example is an average value of the number of scratches existing per 100 mm of a round bar having a diameter of 10 mm. Also, the "processing yield" is 100m in diameter.
It is the yield until a round bar with a diameter of 10 mm is produced from an m ingot.

Example 2 As in Example 1, the dissolution method using a cold crucible was carried out, and 35% Nb-5% Ta-5% Zr according to Example 2 was used.
A titanium alloy with the composition of the balance Ti was produced. The manufacturing method was the same as in Example 1 except that the mixing ratio of each raw material powder was changed.

When the composition of this titanium alloy was analyzed,
Regarding the main component, a titanium alloy having a composition almost equal to the compounding ratio was produced. Also, the concentrations of oxygen, nitrogen and hydrogen are
It was 700 ppm, 100 ppm, and 80 ppm, respectively.

When a round bar having a diameter of 10 mm was manufactured from this titanium alloy by the same processing method as in Example 1,
The processing yield was 70% or more, and the number of surface scratches generated per 100 m of the round bar was 2.

Example 3 In the same manner as in Example 1, the dissolution method using a cold crucible was used, and 35% Nb-5% Ta-balance Ti according to Example 3 was used.
A titanium alloy having the above composition was manufactured. The manufacturing method was the same as in Example 1 except that the mixing ratio of each raw material powder was changed.

When the composition of this titanium alloy was analyzed,
Regarding the main component, a titanium alloy having a composition almost equal to the compounding ratio was produced. Also, the concentrations of oxygen, nitrogen and hydrogen are
The values were 720 ppm, 120 ppm and 90 ppm, respectively.

A round bar having a diameter of 10 mm was manufactured from this titanium alloy by the same processing method as in Example 1.
The processing yield was 70% or more, and the number of surface scratches per 100 m of the round bar was 3.

[0044] By inducing electrolysis method using Example 4 Karushiarutsubo was prepared titanium alloy according to the fourth embodiment. That is, a titanium material is put into a calciar crucible that has been sufficiently dried by heating, and the titanium material is melted in a vacuum and completely melted, and 30% Nb-10% Ta-
Zr, Nb, and Ta metal powders pulverized to a particle size of several millimeters or less so as to have a composition of 5% Zr-the balance Ti were added little by little so as not to cause surface solidification of the molten metal, and completely melted. Then, the titanium alloy was manufactured by casting with a die having an inner diameter of 110 mm.

The titanium material was added 2.7% higher than the target composition in consideration of the loss due to the reaction with the calcia crucible.

When the composition of this titanium alloy was analyzed,
The concentrations of oxygen, nitrogen and hydrogen are 1320ppm and 1 respectively.
It was 30 ppm and 110 ppm.

The titanium alloy thus produced was ground into a rod-shaped member having a diameter of 100 mm, which was hot-forged into a rod-shaped member having a diameter of 50 mm, and the rod-shaped member was surface ground to a diameter of 47 mm. Next, this rod-shaped member was processed into a round bar having a diameter of 18 mm by cold swaging, and further processed into a round bar having a diameter of 17 mm by peeling.
Further, the surface of this round bar was electrolytically polished and then subjected to drawing to obtain a round bar having a diameter of 10 mm.

When the number of surface scratches generated per 100 m of this round bar and the processing yield were investigated, the number of surface scratches generated was 5 per 100 m, and the processing yield was 6.
It was 0% to 70%.

Example 5 In the same manner as in Example 4, a titanium alloy was produced by the induction melting method using a calcia crucible so as to have a composition of 35% Nb-5% Ta-5% Zr-balance Ti.

When the composition of this titanium alloy was investigated, the concentrations of oxygen, nitrogen and hydrogen were 1480 ppm and 14 respectively.
It was 0 ppm and 120 ppm.

A round bar having a diameter of 10 mm was manufactured from this titanium alloy by the same processing method as in Example 1.
The processing yield was 60% to 70%, and the number of surface scratches per 100 m of the round bar was 8.

Example 6 In the same manner as in Example 4, a titanium alloy was produced by the induction melting method using a calcia crucible so as to have a composition of 35% Nb-5% Ta-the balance Ti.

When the composition of this titanium alloy was investigated, the concentrations of oxygen, nitrogen and hydrogen were 1280 ppm and 14 respectively.
It was 0 ppm and 110 ppm.

When a round bar having a diameter of 10 mm was manufactured from this titanium alloy by the same processing method as in Example 1,
The processing yield was 60% to 70%, and the number of surface scratches per 100 m of the round bar was 6.

Comparative Example 1 Comparative Example 1 by the conventional induction electrolysis method using a calcia crucible
Was produced. That is, the calcia crucible that has been sufficiently heated and dried is placed in the atmosphere (temperature of 15 ° C to 28 ° C,
Humidity (37% to 72%) is left for 1 week, titanium material is put into this calcial crucible and melted in a vacuum to be completely melted, and 30% Nb-10% Ta-5% Zr-balance Ti Zr, Nb, Ta metal powder pulverized to a particle size of several millimeters or less so as to have the composition of
A titanium alloy was manufactured by casting in a 10 mm mold.

The titanium material was blended 3.8% higher than the target composition in consideration of the loss due to the reaction with the calcia crucible.

When the composition of this titanium alloy was investigated, the concentrations of oxygen, nitrogen and hydrogen were 2060 ppm and 16 respectively.
It was 0 ppm and 220 ppm.

The titanium alloy thus produced was ground into a rod-shaped member having a diameter of 100 mm, and this was hot-forged into a rod-shaped member having a diameter of 50 mm. The rod-shaped member was surface ground to a diameter of 47 mm. Next, this rod-shaped member was processed into a round bar having a diameter of 18 mm by cold swaging, and further processed into a round bar having a diameter of 17 mm by peeling.
Further, the surface of this round bar was electrolytically polished and then subjected to drawing to obtain a round bar having a diameter of 10 mm.

When the number of surface scratches per 100 m of this round bar and the processing yield were investigated, the number of surface scratches was 28 per 100 m, and the processing yield was 50% to 60%.

Comparative Example 2 A titanium alloy was produced by the conventional powder metallurgy method. That is, 30% Nb-10% Ta-5% Zr-balance Ti
Zr, Nb and Ta powders are mixed with pure Ti powder so as to have the composition of
(Cold isostatic pressing method) was used to compact into a round bar having a diameter of 90 mm. This powder compact was placed in vacuum at 1200 ° C for 8
The titanium alloy was manufactured by holding for a time and sintering.

When the composition of this titanium alloy was analyzed,
The concentrations of oxygen, nitrogen and hydrogen are 3620ppm and 1 respectively.
It was 90 ppm and 230 ppm.

The titanium alloy thus produced was hot forged into a rod-shaped member having a diameter of 50 mm, and the rod-shaped member was surface-ground to a diameter of 47 mm. Next, this rod-shaped member was processed into a round bar having a diameter of 18 mm by cold swaging. At this point, a part was cracked, so that part was removed. Further, a round bar having a diameter of 17 mm was processed by peeling. After electrolytically polishing the surface of this round bar,
It was drawn to obtain a round bar having a diameter of 10 mm.

When the number of surface scratches generated per 100 m of this round bar and the processing yield were investigated, the number of surface scratches generated was 44 per 100 m, and the processing yield was 50% or less.

Table 1 shows the test results of Examples 1 to 6 and Comparative Examples 1 and 2.

[0065]

[Table 1]

Based on Table 1 above, the characteristics of the titanium alloys of Examples 1 to 6 and Comparative Examples 1 and 2 will be considered.

The gas components contained in the titanium alloy varied significantly depending on the manufacturing method. The titanium alloys of Examples 1 to 3 produced using the cold crucible have the smallest gas components, oxygen 680 ppm to 720 ppm, and nitrogen 100 pp.
It was m to 120 ppm and hydrogen 80 ppm to 90 ppm.

On the other hand, the titanium alloys of Examples 4 to 6 produced by the induction electrolysis method using a calcia crucible contained a little more gas components than the titanium alloy using a cold crucible, and the oxygen concentration was 1280 ppm. ~ 1
Impurity oxygen was contained almost twice as much as the production method using 480 ppm and cold crucible.

Further, the titanium alloy of Comparative Example 1 using the calcia crucible which had been left in the air after being heated and dried had a high gas component concentration, an oxygen concentration of 2060 ppm and a nitrogen concentration of 16
Oxygen concentration is 3 times, nitrogen concentration is 1.3 times, hydrogen concentration is up to 2.6 times compared with gas concentration of titanium alloy of the same composition using cold crucible, 0 mm and hydrogen concentration 220 ppm, respectively. Increased.

On the other hand, when the powder metallurgical method of Comparative Example 2 was used, the oxygen concentration was about 5.3 times that of the titanium alloy of the same composition by using the cold crucible, and the nitrogen concentration was about 5 times. It contained a high-concentration gas component of about 1.5 times and about 2.7 times of hydrogen concentration.

Regarding the processing yield of the titanium alloy product, when the titanium alloy was manufactured by using the cold crucible, the processing yield was as good as 70% or more in all cases of Examples 1 to 3. On the other hand, in the case of manufacturing by calcia crucible, the working yields in Examples 4 to 6 were slightly reduced to 60% to 70%. Further, even when the calcia crucible was used, in the case of Comparative Example 1 in which the calcia crucible was left in the atmosphere, the processing yield was reduced to 50% to 60%.

Further, according to the powder metallurgy method of Comparative Example 2,
Cracks may occur during processing, processing yield is 50%
Below, it became very low compared to the titanium alloy using cold crucible.

On the other hand, comparing the number of processing scratches generated per 100 m of titanium alloy product, the number of titanium alloys due to the cold crucible of Examples 1 to 3 is suppressed to 2 to 3, whereas according to the Calciar crucible method. In Examples 4 to 6, the number was slightly increased to 5 to 8. Further, even when the calcial crucible was used, in the case of Comparative Example 1 in which the calcial crucible was left in the atmosphere, the number of processing scratches was significantly increased to 28.

On the other hand, the titanium alloy manufactured by the powder metallurgical method of Comparative Example 2 had 44 working scratches, which is much larger than those of other manufacturing methods, and the workability of the titanium alloy was significantly increased. Fell. It is considered that the cause of these decreases is due to the amount of gas components (oxygen, nitrogen, hydrogen) contained in the titanium alloy.

The present inventors further compared and examined the crystal structures and physical properties of the titanium alloys of Examples 1 to 6 and Comparative Examples 1 and 2.

First, the Young's modulus of each titanium alloy was compared. The Young's modulus is a physical property value showing the elastic modulus of a material, and a low Young's modulus means that the elastic modulus of the material is low, that is, a material having low rigidity and high elasticity.

As is clear from the results shown in Table 1, the Young's modulus is the lowest among the titanium alloys of Examples 1 to 3 using the cold crucible and is 51 GPa to 55 GPa, which is suitable for the production of a titanium alloy having high elasticity. It turned out.

On the other hand, the titanium alloys produced by the calciable crucibles of Examples 4 to 6 and Comparative Example 1 had a Young's modulus slightly higher than that of the cold crucible and showed 52 GPa.
The Young's modulus was 56 GPa, and the Young's modulus of the titanium alloy prepared by the powder metallurgy method of Comparative Example 2 was 58 GPa, which was a high Young's modulus.

That is, it was confirmed that the titanium alloy produced by the melting method, particularly the cold crucible, had a reduced Young's modulus and was excellent in elasticity.

Next, the tensile elastic limit strengths of the titanium alloys of Examples 1 to 6, Comparative Examples 1 and 2 were compared and examined.

2A and 2B show the stress-strain curve of the titanium alloy of the present invention and the stress-strain curve of a general non-ferrous metal, respectively.

In the non-ferrous metal material, the stress that causes a predetermined permanent strain is made to correspond to the yield stress. This is called proof stress and is generally defined by the stress σ _P corresponding to 0.2% strain (FIG. 2 (B)).

The tensile elastic limit strength is 0. 0 in a tensile test in which loading and unloading of a test piece are repeated.
It is represented by 2% proof stress σ _P. That is, the tensile elastic limit strength σ _P
With the following stress, the relationship between stress and strain is said to be elastic.

However, in the case of the titanium alloy of the present invention, as shown in FIG. 2 (A), the relationship between stress and strain does not show a constant proportional relationship but shows a curved shape. Therefore, in this titanium alloy, it was actually 0.2% in the tensile test.
The stress σ _e that causes strain is defined as 0.2% proof stress = tensile elastic limit strength.

Regarding the tensile elastic limit strength, Comparative Example 1
And in the titanium alloy of Comparative Example 2, as high as 770 MPa, in the case of the titanium alloys of Examples 1 to 6, 740 MPa to 7
It was 50 MPa. It was found that the titanium alloys of Examples 1 to 6 have a high tensile elastic limit strength of 700 MPa or more.

Next, the porosities of the titanium alloy products of Examples 1 to 6 and Comparative Examples 1 and 2 were compared.

The porosity is 1 for the cross section of the titanium alloy product.
Observation was performed at a magnification of 000, observation was performed on at least 5 non-overlapping observation planes having a unit area of 50 μm × 50 μm, and a value obtained by averaging the ratio of the total area of pores was used.

In the titanium alloys of Examples 1 to 3 produced by cold crucible, the porosity was 0.0% to 0.
Almost no void was observed at 2%. The porosity of 0.0% in Example 2 means that no porosity was observed on the observation surface.

On the other hand, in the case of Examples 4 to 6 using the calcia crucible, the porosity tended to increase to 0.3% to 0.5%, and the calcia crucible left in the air was used. In the case of Comparative Example 1 which had the above, the porosity was 2.4%.

Furthermore, in the case of the titanium alloy of Comparative Example 2 by the powder metallurgy method, the porosity was 3.5%, and it was confirmed that the porosity of the titanium alloy product by the manufacturing method greatly changed.

That is, since the porosity in the titanium alloy is reduced by reducing the gas component contained in the titanium alloy, it is possible to provide a high-quality titanium alloy that is homogeneous and has few pores. It is possible.

On the other hand, the crystal structures of the titanium alloys of Examples 1 to 6, Comparative Examples 1 and 2 were measured by the X-ray diffraction method.

As a result, when the X-ray peaks of the titanium alloys of Examples 1 to 6 and Comparative Examples 1 and 2 were compared,
The α-phase peak was 1/100 or less (including zero) of the β-phase peak, and it was confirmed that the α-phase peak was substantially a β-single phase.

From the comparative examination of the physical properties of the titanium alloys of Examples 1 to 6, Comparative Examples 1 and 2, the following findings were obtained.

According to the titanium alloy of the present invention, since the gas component concentration is reduced, it is possible to obtain a titanium alloy having a low porosity, a high tensile elastic limit strength, a low rigidity and a high elasticity. it can. This titanium alloy has a crystal structure having a β phase as a main phase and effectively prevents the occurrence of processing scratches on the product surface during product processing. Further, the processing yield is good and the manufacturing cost is reduced.

The method for producing the titanium alloy of the present invention includes:
The dissolution method using a cold crucible is most suitable. According to the cold crucible, the inner surface of the crucible and the metal material (molten metal) are kept in non-contact with each other, and interferences (contamination of impurities) from the crucible are reduced. To be prevented. In addition, the titanium alloy manufactured using cold crucible has a high processing yield during manufacturing, effectively prevents the occurrence of processing scratches during product processing, and manufactures high-quality titanium alloy with low porosity. It is possible.

As the method for producing the titanium alloy of the present invention, a melting method such as dielectric melting using a calcial crucible may be used. The titanium alloy manufactured by the melting method has less gas components mixed therein and can be manufactured with good workability as compared with the titanium alloy manufactured by the powder metallurgy method. However, since the calcia crucible has a deliquescent property, it is necessary to heat and dry it before use to prevent contamination such as mixing of a gas component into the molten metal.

The titanium alloy of the present invention produced in this manner is rich in elasticity, excellent in workability, and reduced in production cost. Therefore, for example, it is used as a material for spectacle frames, golf clubs or tennis rackets, or as a timepiece. It can also be used as a material for a band, etc.

[0099]

As described above, since the titanium alloy according to the present invention has the gas component concentration reduced to a predetermined value or less, it has a high tensile elastic limit strength, while having a low elastic modulus, it has elasticity. It is possible to provide a titanium alloy that is rich and has few processing scratches on the alloy surface when processed into a product, has a good processing yield, and is homogeneous.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a method for producing a titanium alloy according to the present invention using a cold crucible.

FIG. 2A is a stress-strain diagram of the titanium alloy according to the present invention, and FIG. 2B is a stress-strain diagram of a general non-ferrous metal.

[Explanation of symbols]

1 crucible 2 Internal cavity 3 High frequency induction heating coil 4 Metal materials (molten alloy)

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) C22C 27/04 101 C22C 27/04 101 102 102 27/06 27/06 28/00 28/00 Z (72 ) Inventor Tomohisa Arai 8 Shinsugita-cho, Isogo-ku, Yokohama-shi, Kanagawa Incorporated company Toshiba Corporation Yokohama office

Claims (5)

[Claims] 1. Zr, Hf, V, Nb, Ta, Cr, M
3 at least one metal element selected from o and W
It is a titanium alloy containing 0 to 60 mass% and the balance being Ti, the oxygen content is 2000 ppm or less, the nitrogen content is 150 ppm or less, and the hydrogen content is 20.
0 ppm or less, the average Young's modulus is 75 GPa or less,
A titanium alloy having a tensile elastic limit strength of 700 MPa or more and a crystal structure having a β phase as a main phase. 2. The titanium alloy according to claim 1, wherein the titanium alloy is manufactured by a melting method. 3. The titanium alloy according to claim 1, wherein the titanium alloy is manufactured by a melting method using a cold crucible. 4. The titanium alloy according to claim 1, wherein the titanium alloy has a β single phase crystal structure. 5. The titanium alloy according to claim 1, wherein the titanium alloy has a porosity of 0.5% or less.