JP3452798B2 - High-strength β-type Ti alloy - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention has a basic composition of β-type Ti alloy, in particular, a Ti-15Mo-5Zr-3Al-based β-type Ti alloy, and has a high strength β-type Ti with further enhanced strength.
Regarding the alloy, this Ti alloy can be effectively utilized as a face material of a golf club head.

[0002]

2. Description of the Related Art At present, a typical Ti alloy, which is widely used as a face material for a Ti golf club head, is
It is a Ti-15Mo-5Zr-3Al-based β-type Ti alloy, and this Ti alloy has a high level of strength of 1400 to 1600 MPa, but is further improved in order to further improve the performance of the Ti golf club. Strengthening is required. However, in the case of this type of β-type Ti alloy, if it is a linear material, it is possible to further increase the strength by changing the processing conditions and heating conditions, but the face material of the golf club head is plate-shaped. However, even if the processing conditions and heating conditions are changed, the degree of freedom is small, so it is almost impossible to expect strength modification by adjusting heating and processing conditions like linear objects, and to further improve strength. There is no choice but to rely on modification from the viewpoint of alloy composition.

[0003]

SUMMARY OF THE INVENTION The present invention has been made by paying attention to the above circumstances, and its purpose is to provide Ti-
Targeting 15Mo-5Zr-3Al-based β-type Ti alloys, β-type showing high strength exceeding conventional levels by enhancing its hot workability and cold workability and controlling those working conditions well. To provide a Ti alloy.

[0004]

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

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION Conventional Ti-15Mo-5Zr-
The 3Al-based β-type Ti alloy has an optimum alloy composition determined by comprehensively considering hot workability, cold workability, and strength improvement characteristics by age hardening. As long as it is adopted, from the viewpoint of alloy composition, β type Ti of that composition
It is difficult to obtain strength and workability that exceed those of alloys.

By the way, when the Mo content is decreased, the precipitation of the α phase is accelerated, and the coarse α phase is likely to be precipitated during the hot working, which not only deteriorates the hot workability but also deteriorates the cold workability. Further, when the Mo content is increased, the β phase is stabilized and the precipitation strengthening ability of the α phase is reduced, and it becomes difficult to obtain satisfactory strength. Further, Zr is an alloying element that forms a solid solution in both the α phase and the β phase and exhibits a strengthening effect, and if the content thereof is insufficient, satisfactory strength cannot be obtained, and conversely, if the Zr content is too large, Although the strength after aging treatment is improved, hot workability and cold workability are significantly reduced, and it becomes unsuitable for practical use in terms of workability.

Further, Al has a function of strengthening the precipitated α phase, and when the content thereof is insufficient, the strength after age hardening becomes insufficient, while when the Al content is too large, the strength after age hardening is significantly increased. However, the cold workability becomes extremely poor, which makes it extremely difficult to process the final product shape.

Thus, the conventional Ti-15Mo-5Zr-
It is considered that the 3Al-based β-type Ti alloy has an optimum alloy composition determined by comprehensively considering hot workability, cold workability, and strength after age hardening. As long as it is, 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 other alloying elements to the Ti-15Mo-5Zr-3Al-based β-type Ti alloy without substantially changing the base composition. By doing so, it is thought that the strength after aging treatment can be further increased without impairing both of the above properties, and the research has been advanced along that line.

As a result, as described above, Ti-15Mo-5 was obtained.
When a Zr-3Al-based β-type Ti alloy is used as a base composition and an appropriate amount of Sn is contained in the base composition, the strength after aging treatment can be further enhanced without lowering the hot and cold workability of the base alloy. Was confirmed. And such S
It is confirmed that the modifying effect by the addition of n is effectively exhibited by adding Sn in an amount of 0.5% or more, more preferably 1.0% or more, and the effect of improving the strength reaches the peak by adding about 3%. It was However, if the Sn content is too high,
Not only does the age hardening property show a downward trend, but
Since the cold workability is also adversely affected, the Sn content is preferably 5.0% or less, more preferably 4.5% or less.

Although it has not been theoretically confirmed as to what is the reason why such an excellent effect of modifying by adding Sn is brought about, for the base alloy without addition of Sn and the alloy with addition of Sn, the metal after age hardening has been obtained. Judging from the results of observing the tissue, the following can be considered.

That is, a Ti-15Mo-5Zr-3Al base alloy and a β-type T containing a proper amount of Sn in the base alloy.
According to the observation of the metal structure of the i alloy after age hardening, the α phase is relatively coarse and non-uniform in the former, whereas the α phase is uniform and fine in the latter. By including an appropriate amount of Sn, the deformation during plastic working becomes uniform throughout, the introduction of α-phase precipitation sites becomes more uniform, and α-phase precipitation occurs evenly 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 above-mentioned base alloy, the strength after age hardening is further enhanced, and the cold workability is adversely affected even though the age hardening performance is improved. In other words, the strength after age hardening can be significantly increased while maintaining the excellent cold workability of the base alloy.

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 can be slightly increased by adding a small amount of β-stabilizing elements other than, the strength-improving effect comparable to Sn cannot be obtained, and addition of a large amount stabilizes the β-phase and improves the age hardening characteristics. It is damaged and the strength after aging becomes poor. However, in the present invention, together with Sn, for example, C
Add a small amount of 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 base alloy
If the amount of stabilizing elements is too large, the β phase is stabilized and the age hardening performance is significantly impaired. Therefore, the content of these β stabilizing elements must be suppressed to about 1% or less, preferably about 0.5% or less. I won't.

Further, in the present invention, Ti-15Mo-5Zr-3Al, which is known to have high strength as a base alloy, is used.
Although a β-type Ti alloy of the system was selected, this alloy is not limited to the chemical composition of 1 point, and it is also possible to slightly increase or decrease the amount of each alloying element within the range shown below. It is included in the technical scope of the present invention. The reasons for defining 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 ensuring the excellent workability which is a characteristic of β-type Ti alloys. Precipitation is accelerated, and a coarse α phase is likely to precipitate during hot working, which not only deteriorates hot workability but also deteriorates cold workability. However, Mo
If the content is too large, the β phase will be stabilized, the precipitation strengthening ability of the α phase will be reduced, and the strength after aging treatment will be insufficient, so it must be suppressed to 17% or less. A more preferable lower limit of Mo content is 14%, and a more preferable upper limit thereof is 16% in order to achieve both workability and strength after aging treatment.

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 effect. It is an element indispensable for ensuring high strength, and its effect is obtained. It should be contained in an amount of 3% or more, and more preferably 4% or more in order to effectively exert the effect. But Z
If the r content is too large, the strength after aging treatment is improved, but the hot workability and cold workability are significantly deteriorated. Therefore, it should be kept to 7% or less, more preferably 6% or less. I have to.

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% is required to effectively bring out the effect. Above, more preferably 2.5% or more should be contained. However, if the Al content is too large, the strength after age hardening is significantly increased, but on the other hand, the cold workability becomes extremely poor and the 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 in the above content ratio, and the balance is substantially T.
It is a β-type Ti alloy composed of i, and in the present invention, a specific amount of Sn is further contained as another element in the present invention, as long as it does not impair the characteristics of the alloy of the present invention described above.
Further, it may contain a small amount of other allowable elements or unavoidable impurity elements.

The Ti alloy of the present invention thus obtained takes advantage of its excellent hot and cold workability and high strength property after aging treatment, and further the lightness and corrosion resistance inherent in the Ti alloy, By utilizing its excellent workability, can be widely used as, for example, leaf springs for automobiles and riser pipes for oil drilling. Above all, this titanium alloy can increase the strength after aging treatment without impairing the excellent workability of the Ti-15Mo-5Zr-3Al-based β-type Ti alloy that is the base, and adopts, for example, coil rolling. Even when processed into a plate shape, the strength can be sufficiently increased. Therefore, by applying it as a face material for a Ti golf head, which has recently received a great deal of attention, it is possible to further increase the flight distance with a high strength and a high coefficient of restitution. It can be used extremely effectively as a face material.

[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, and may be appropriately applied within a range compatible with the gist of the above and the following. Modifications can be made and implemented, and all of them are included in the technical scope of the present invention.

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

In this hot rolling process, the hot rolling property is evaluated by the presence or absence of the occurrence of edge cracks, and the base alloy (Ti-
15Mo-5Zr-3Al-based β-type Ti alloy) was considered to be good (◯), and if ear cracking was remarkable, it was considered to be bad (x). In addition, half of the obtained hot-rolled sheet was trimmed at both side edges and then cold-rolled by 10% without annealing to evaluate the cold workability. ), Those with ear cracks are considered defective (x), and the other half are subjected to aging treatment at 500 ° C. for 8 hours and then the Vickers hardness is measured. Those in which a clear increase in hardness was recognized were rated as good (◯). The results are collectively shown in Table 1.

[0024]

[Table 1]

From Table 1, the following analysis can be performed. No. 1 to
No. 3 is an example alloy satisfying the requirements of the present invention, and has good hot workability and cold workability with respect to the base alloy (No. 4), and the hardness after aging treatment is the base alloy. It can be seen that it is clearly improved.

In contrast to these, 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 hot and cold workability is poor because the α phase is rapidly precipitated and a coarse α phase is formed due to insufficient stabilization of the β phase.

No. 6: A comparative alloy with an excessive amount of Mo and good hot and cold workability, but the stability of the β phase was too high, and the α phase precipitation strengthening effect by the aging treatment was insufficient, resulting in insufficient strength. Has become.

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

No. 8: Comparative alloy with too much Zr content, the strength after aging treatment is increased by the solid solution strengthening effect, but the hot workability and cold workability are poor.

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

No. 10: Comparative alloy containing too much Al, and the strength after age hardening was significantly increased, but cold workability was extremely deteriorated due to excessive strengthening of the precipitated α phase.

No. 11: This is a comparative alloy in which the Sn content is insufficient, and no modification effect on the base alloy is observed.

No. 12: Comparative alloy with too much Sn content, the hot workability deteriorates rather than the cold workability as a square, and the strength also decreases due to the 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 observed.

No. 14: Although it is a comparative alloy in which the Cr content is increased, the stabilization of the β phase inhibits the precipitation strengthening effect of the α phase, and the strength after aging treatment is significantly reduced.

[0037]

The present invention is constructed as described above, and T
i-15Mo-5Zr-3Al-based β-type Ti alloy is used as a base, and an appropriate amount of Sn is added to the base.
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, the Ti alloy of the present invention exhibits a high level of strength even if it is a plate-like material, and thus can be extremely effectively utilized as a face material for a golf club head, which has recently been in rapid demand.

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-3-53037 (JP, A) High-strength and high-toughness titanium alloy, metal, Japan, Agne Co., Ltd., July 1, 1990, Volume 60 No. 7, p. 21-22 (58) Fields investigated (Int.Cl. ⁷ , DB name) C22C 14/00 A63B 53/04

Claims (2)

(57) [Claims] 1. In mass%, Mo: 13 to 16 %, Zr:
3-7%, Al: 1.5-4.5% and Sn: 0.5
A high-strength β-type Ti alloy characterized by containing ˜5% and the balance being substantially Ti. 2. The high-strength β-type Ti alloy according to claim 1, which is used as a material for a golf club head.