JPH11343528A - High-strength beta-type titanium alloy - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase the aged strength while maintaining excellent hot workability and cold workability by incorporating Mo, Zr, Al and Sn respectively in specified amts. SOLUTION: A Ti-15Mo-5ZR-3Al β-type Ti alloy is used as the base composition, and an appropriate amt. of Sn is incorporated into it. The Sn to increase the aged strength is incorporated by >=0.5 mass %, preferably by >=1.0 mass %. Since cold workability is adversely affected when the Sn content is too high, the content is adjusted to <=5.0%, preferably to <=4.5%. The preferable lower-limit Mo content is adjusted to 14% and the preferable upper-limit to 16%. Zr is incorporated by 3-7%, preferably by 4-6%. Al is incorporated by >=1.5%, preferably by >=2.5% and more preferably by <=4.5%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a high-strength β-type Ti alloy having a basic composition of a β-type Ti alloy, particularly a Ti-15Mo-5Zr-3Al-based β-type Ti alloy, the strength of which is further enhanced.
The present invention relates to an alloy, and this Ti alloy can be effectively used particularly as a material for a face of a golf club head.

[0002]

2. Description of the Related Art At present, a typical Ti alloy generally used as a face material for a golf club head made of Ti is:
This is a Ti-15Mo-5Zr-3Al-based β-type Ti alloy, which has a high level of strength, such as 1400 to 1600 MPa, but further improves the performance of the Ti golf club. Increased strength is required. However, in the case of this type of β-type Ti alloy, if it is a linear object, it is possible to further increase the strength by changing the processing conditions, heating conditions, and the like, but the face material of the golf club head is plate-shaped. Even if the processing conditions, heating conditions, etc. are changed, the degree of freedom is small, so that strength improvement by adjusting the heating and processing conditions, such as linear objects, can hardly be expected. We have to rely on reforming from the viewpoint of alloy composition.

[0003]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances.
For 15Mo-5Zr-3Al-based β-type Ti alloy, its hot workability and cold workability are enhanced, and by properly controlling the working conditions, the β-type exhibiting a high strength exceeding the conventional level. It is to provide a Ti alloy.

[0004]

Means for Solving the Problems The titanium alloy according to the present invention, which can solve the above-mentioned problems, has a mass percentage of M
o: 13 to 17%, Zr: 3 to 7%, Al: 1.5 to
High strength β containing 4.5% and Sn: 0.5-5%
There is a gist in the place of the type Ti alloy, and this Ti alloy can be effectively used as a material for golf club heads, etc. by utilizing its excellent workability and excellent strength after aging treatment.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Conventional Ti-15Mo-5Zr-
The 3Al-based β-type Ti alloy has an optimum alloy composition determined in consideration of the hot workability and cold workability, and furthermore, the strength improvement characteristics by age hardening. As long as it is adopted, β-type Ti
It is difficult to obtain strength and workability exceeding that of alloys.

By the way, when the Mo content is reduced, the precipitation of the α phase is accelerated, and the coarse α phase is easily precipitated during the hot working, so that not only the hot workability is lowered but also the cold workability is deteriorated, When the Mo content is increased, the β phase is stabilized, and the precipitation strengthening ability of the α phase is reduced, making it difficult to obtain a satisfactory strength. Also, Zr is an alloying element that forms a solid solution in both the α phase and the β phase and exhibits a strengthening action. If the content is insufficient, satisfactory strength cannot be obtained, and if the Zr content is too large, Although the strength after the aging treatment is improved, the hot workability and the cold workability are significantly reduced, and the workability is not suitable for practical use.

[0007] Further, Al has an effect of strengthening the precipitated α phase, and if its content is insufficient, the strength after age hardening becomes insufficient, while if the Al content is too large, the strength after age hardening is greatly increased. However, since the cold workability is extremely poor, it is extremely difficult to work into a final product shape.

As described above, the conventional Ti-15Mo-5Zr-
The 3Al-based β-type Ti alloy is considered to have determined the optimum alloy composition after considering the hot workability, cold workability, and strength after age hardening, and adopts a combination of the above alloy elements. As far as possible, it is not easy to achieve both workability and strength by controlling the content of each element.

Therefore, the present inventors changed the viewpoint of the research direction and added another alloy element to the base composition of the Ti-15Mo-5Zr-3Al-based β-type Ti alloy without substantially changing it. By doing so, we thought that it would be possible to further increase the strength after aging treatment without hindering both of the above properties, and proceeded with research along that line.

As a result, as described above, Ti-15Mo-5
By using a Zr-3Al-based β-type Ti alloy as a base composition and adding an appropriate amount of Sn to the base composition, the strength after aging treatment can be further increased without lowering the hot and cold workability of the base alloy. Was confirmed. And such S
The modification effect by the addition of n is effectively exhibited by adding Sn at 0.5% or more, more preferably 1.0% or more, and it is confirmed that the strength improvement effect reaches a peak by addition of about 3%. Was. However, if the Sn content is too large,
Not only does the age hardening characteristic tend to decrease,
Since this also has an adverse effect on the cold workability, it is desirable that the Sn content be suppressed to 5.0% or less, more preferably to about 4.5% or less.

Although the reason why such an excellent modification effect by the addition of Sn is brought about is not theoretically confirmed, the base alloy after the addition of Sn and the alloy with the addition of Sn have the following properties. Judging from the results of observation of the tissue, the following can be considered.

That is, a Ti-15Mo-5Zr-3Al base alloy and a β-type T alloy containing an appropriate amount of Sn.
According to the observation of the metal structure after age hardening for the i-alloy, the former has a relatively coarse and non-uniform α phase, whereas the latter has a uniform and fine α phase. By containing an appropriate amount of Sn, the deformation during plastic working becomes uniform as a whole and the introduction of α-phase precipitation sites becomes more uniform, and α-phase precipitation occurs uniformly on the entire surface of β-phase. We believe that the strengthening effect was further enhanced.

In any case, by including an appropriate amount of Sn in the base alloy, the strength after age hardening is further increased, and in spite of such improvement in age hardening performance, the cold workability is adversely affected. In other words, the strength after age hardening can be greatly increased while maintaining the excellent cold workability of the base alloy.

Incidentally, Ti-15, which is the base of the alloy of the present invention,
For the Mo-5Zr-3Al-based β-type Ti alloy, Sn
Although the strength after aging treatment is slightly increased by adding a small amount of a β stabilizing element other than the above, the strength improvement effect comparable to Sn is not obtained, and when added in a large amount, the β phase is stabilized and the age hardening characteristics are improved. It is impaired and the strength after aging becomes poor. However, in the present invention, for example, C
adding a small amount of a β-stabilizing element such as r, Fe, Ni, Co,
It is also effective to further increase the strength after the aging treatment. However, the above β other than Mo contained in Sn or the base alloy
If the amount of the stabilizing element is too large, the β phase is stabilized, and the age hardening performance is significantly impaired. No.

Further, in the present invention, Ti-15Mo-5Zr-3Al, which is known to exhibit high strength as a base alloy, is used.
Although a β-type Ti alloy was selected, this alloy is, of course, not limited to a one-point chemical composition, and the amount of each alloy element can be slightly increased or decreased within the range shown below. It is included in the technical scope of the present invention. The reasons for determining the component composition of the base Ti alloy used in the present invention are summarized as follows.

Mo: 13 to 17% Mo is a β-stabilizing element, and is an element indispensable for securing excellent workability characteristic of β-type Ti alloys. Precipitation is accelerated, and a coarse α phase is easily precipitated during hot working, so that not only the hot workability is reduced, but also the cold workability is deteriorated. But Mo
If the content is too large, the β phase is stabilized, the precipitation strengthening ability of the α phase is reduced, and the strength after the aging treatment becomes insufficient. Therefore, the content must be suppressed to 17% or less. In order to achieve both workability and strength after aging, the lower limit of the Mo content is more preferably 14%, and the more preferable upper limit is 16%.

Zr: 3 to 7% Zr is an alloying element that forms a solid solution in both the α phase and the β phase and exhibits a strengthening action, and is an element indispensable for securing high strength. To be effective, the content should be 3% or more, more preferably 4% or more. But Z
If the r content is too large, the strength after aging treatment is improved, but the hot workability and the cold workability are significantly deteriorated. Therefore, the r content must be suppressed to 7% or less, more preferably 6% or less. Must.

Al: 1.5 to 4.5% Al is an essential element for strengthening the precipitated α phase and increasing the strength after aging treatment, and 1.5% for effectively exhibiting its effect. More preferably, the content should be 2.5% or more. However, if the Al content is too large, the strength after age hardening is greatly increased, but on the other hand, the cold workability becomes extremely poor, and processing into the final product shape becomes extremely difficult. More preferably, it should be suppressed to 4.5% or less.

The base alloy used in the present invention is Mo,
Zr and Al are contained at the above content ratio, and the balance is substantially T
i is a β-type Ti alloy consisting of i. In the present invention, a specific amount of Sn is further contained as another element, but as long as the above-mentioned properties of the present alloy are not impaired,
Further, it may contain a small amount of other allowable elements or unavoidable impurity elements.

The Ti alloy of the present invention thus obtained makes use of its excellent hot and cold workability and high strength properties after aging treatment, as well as the lightness and corrosion resistance inherent to the Ti alloy. Utilizing its excellent workability, it can be widely used as, for example, a leaf spring for an automobile or a riser pipe for oil drilling. Above all, this titanium alloy can increase the strength after aging treatment without impairing the excellent workability of the base Ti-15Mo-5Zr-3Al-based β-type Ti alloy. Since the strength can be sufficiently increased even when it is processed into a plate shape, by applying it as a material for the face of a Ti golf head, which has recently attracted particular attention, it is possible to further increase the flight distance with a high strength, a high coefficient of restitution, It can be used very effectively as a face material that can be used.

[0021]

EXAMPLES Next, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the following examples, but may be appropriately adjusted within a range that can conform to the purpose of the preceding and following examples. Modifications can be made and implemented, all of which are included in the technical scope of the present invention.

Example A Ti alloy having an alloy composition shown in Table 1 was melted with a button, cast, heated to 1200 ° C., hot-rolled at a rolling reduction of 50%, and then held at 1050 ° C. for 10 minutes. Was further hot-rolled to produce a hot-rolled sheet having a total rolling reduction of 75%.

In this hot rolling step, the hot rolling property is evaluated based on the occurrence of edge cracks, and the base alloy (Ti-
15Mo-5Zr-3Al-based β-type Ti alloy) was evaluated as good (○), and if the edge cracks were remarkable, as poor (×). Half of the obtained hot-rolled sheet was evaluated for cold workability by performing 10% cold rolling without annealing after trimming both side edges. ), Those with ear cracks were regarded as defective (×), the other half was subjected to aging treatment at 500 ° C. for 8 hours, and then measured for Vickers hardness. Those with a clear increase in hardness were evaluated as good (○). The results are collectively shown in Table 1.

[0024]

[Table 1]

Table 1 can be analyzed as follows. No. 1 to
No. 3 is an example alloy which satisfies the requirements of the present invention, which has both good hot workability and cold workability with respect to the base alloy (No. 4), and has a hardness after aging treatment of the base alloy. It can be seen that it is clearly improved.

On the other hand, no. Nos. 5 to 14 are comparative alloys lacking any of the specified requirements of the present invention, and at least one of workability and hardness after aging treatment is poor, and the object of the present invention cannot be achieved.

No. 5: Comparative alloy with insufficient Mo content, in which the precipitation of α phase is rapid and the coarse α phase is formed due to insufficient stabilization of β phase, so that hot and cold workability is poor.

No. 6: Comparative alloy with too much Mo content, good hot and cold workability, but the stability of β phase is too high and the effect of strengthening α phase precipitation by aging treatment is insufficient, resulting in insufficient strength. Has become.

No. 7: Comparative alloy with insufficient Zr content, good hot and cold workability, but low strength due to insufficient solid solution strengthening action on α phase and β phase.

No. 8: A comparative alloy having too much Zr. The strength after aging treatment is increased by the solid solution strengthening effect, but the hot and cold workability is poor.

No. 9: Comparative alloy with insufficient Al content and good workability, but strength after aging treatment is inferior because the effect of strengthening the precipitated α phase is not sufficiently exhibited.

No. 10: Comparative alloy with too much Al content, the strength after age hardening is greatly increased, but the cold workability is extremely deteriorated due to excessive strengthening of the precipitated α phase.

No. 11: This is a comparative alloy having an insufficient amount of Sn, and has no effect of modifying the base alloy.

No. 12: Comparative alloy with too much Sn content, cold workability is rather degraded in terms of hot workability, and strength is also lowered due to deterioration of age hardening characteristics.

No. 13: A comparative alloy to which a small amount of Cr was added as another β-stabilizing element, but almost no strengthening effect on the base alloy was recognized.

No. 14: A comparative alloy having a high Cr content, but the β phase stabilization hinders the precipitation strengthening effect of the α phase and significantly reduces the strength after aging treatment.

[0037]

The present invention is configured as described above,
Based on an i-15Mo-5Zr-3Al-based β-type Ti alloy and containing an appropriate amount of Sn,
While maintaining the excellent hot workability and cold workability of the base alloy, the strength after aging treatment can be further increased, and the demand for higher strength can be met. In particular, since the Ti alloy of the present invention exhibits a high level of strength even in the form of a plate, it can be used very effectively as a face material for a golf club head, whose demand has been rapidly increasing recently.

Claims (2)

[Claims] 1% by mass, Mo: 13 to 17%, Zr:
3-7%, Al: 1.5-4.5% and Sn: 0.5
A high-strength β-type Ti alloy characterized by containing about 5%. 2. The high-strength β-type Ti alloy according to claim 1, which is used as a material for a golf club head.