JP2646325B2 - Manufacturing method of titanium alloy plate for golf driver head - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a titanium alloy plate having a specific composition range required for inexpensively producing a titanium alloy-based golf driver head. A golf driver head with excellent performance can be produced from the produced titanium alloy plate by press molding and welding.

[0002]

2. Description of the Related Art Golf driver heads were initially made of persimmon (persimmon tree) or the like, but in recent years hollow heads have become the mainstream, and metal heads using stainless steel or the like have attracted attention. This metal head is more durable than Persimmon and has a longer flight distance, so it is expected that demand will further increase in the future. At present, stainless steel is the main material for metal heads, but recently heads made of titanium or titanium alloy have appeared. Titanium alloys are lighter and have higher strength than stainless steel, so the degree of freedom in design is increased, and it is generally possible to manufacture a larger head than a stainless steel head. As a result, the sweet spot is widened, and a stable hit ball can be obtained.

To date, among titanium alloys, the one used as a material for a driver head is Ti alloy.
-6Al-4V alloy (hereinafter referred to as 64AT) and T
i-4.5Al-3V-2Fe-2Mo alloy. 6
4AT is most frequently used in various fields among titanium alloys, and has a particularly high track record as an aircraft material. However, since this alloy cannot be cold-worked, manufacturing a 1-5 mm plate generally required as a head material requires a great deal of labor and a great deal of cost. Therefore, in reality, for example, JP-A-3-2
64A by casting as described in 30845
A head made of T is manufactured. However, also in this case, since titanium is easily oxidized, it cannot be cast in the atmosphere, and furthermore, it easily reacts with the mold, so that a very advanced technique is required, resulting in an increase in cost. Further, since the structure of the cast product cannot be controlled as compared with the rolled material, the cast product has a disadvantage that the strength is weak. On the other hand, Ti-4.5
Since the Al-3V-2Fe-2Mo alloy can be subjected to superplastic working, it is easier to obtain higher strength than a cast product. However, this requires a special device for superplastic working, and requires much time for superplastic working, so that it is not suitable for mass production.

In order to efficiently produce a large number of hollow heads made of titanium-based material, as in the case of producing a stainless steel head, a plate or coil which is cold-rolled and has a desired thickness and structure is prepared. It is optimal to punch a target shape by cold or warm press and then assemble the processed parts by welding. Unfortunately, no titanium material has been found so far except pure titanium. Pure titanium can be cold-rolled and cold-pressed easily, so there was no problem in terms of manufacturing as a material for hollow heads, but its strength is not so high, so it has a serious impact on the strength after head assembly. There was a problem.

[0005] Under these circumstances, the present applicant has proposed that a new titanium alloy for a golf driver head contains 10% to less than 25% by weight of vanadium and optionally 2 to 5%.
% Aluminum, 2-5% chromium and 2-4% by weight
Successful development of a titanium alloy further comprising one or more selected from the group consisting of tin by weight tin and the balance of titanium and unavoidable impurities.

[0006]

As described above, in order to manufacture a golf driver head at a low cost, a thin plate having a thickness of 1 to 4 mm is punched out by a press in the same manner as in the manufacture of a conventional stainless steel head. It is considered that the most appropriate method is to put out and connect them by welding. The method of mass-producing such a cold-rollable near-beta titanium alloy or a thin sheet of beta-titanium alloy has not been clarified, but, for example, "Beta Titanium" published in 1983.
Alloys in the 80's, describes a method for producing thin sheets of this type of titanium alloy: (1) For slabs of nominal 10.2 to 15.2 cm (4 to 6 inches) thickness. Forging and conditioning as needed. (2) The slab is nominally 3.0-4.6 mm (0.12-
(0.18 inch) hot rolled band. (3) Perform cold rolling straightening, atmospheric annealing, blasting, pickling, grinding and trimming as necessary. (4) cold rolling to a desired gauge thickness (this can incorporate intermediate continuous vacuum annealing depending on the final gauge thickness; thickness reduction by cold rolling in the range of 60 to 70% is possible. ), (5) Continuous vacuum annealing is performed for those having a gauge thickness of less than 1.8 mm (0.070 inch). For higher gauge thicknesses, batch vacuum annealing followed by atmospheric solution annealing, grinding and pickling to reduce hydrogen is required. (6) Cut to size, inspect and ship. In short, a titanium alloy thin plate is formed into an ingot having a predetermined composition, and then is forged and hot-rolled to a thickness of 3 to 4.6 mm.
The coil is cold-rolled to a predetermined thickness, the coil is subjected to continuous vacuum annealing or vacuum annealing in a batch manner, followed by atmospheric solution annealing, and then cut into sheets. Is done.

[0007] When such a conventionally known method for producing a cold-rollable near-beta titanium alloy or a thin sheet of a beta-titanium alloy is applied to the above-mentioned titanium alloy (hereinafter, simply referred to as the present alloy) used in the present invention, serious problems arise. It has been found that various problems arise. First, it has been found that when the titanium alloy is subjected to a solution treatment in a coil state, a very strong curl (coil habit) occurs. Even in the case of pure titanium, a curl occurs, but this can be eliminated by applying a light process such as a leveler or a skin pass. However, the alloy used in the present invention has a high yield strength and a relatively low Young's modulus, so that the springback is very strong, and it is impossible to remove the curl by light working such as a leveler or skin pass. all right. If strong working is added, the curl can be reduced, but the work hardening deteriorates the press formability, making it unsuitable for a golf driver head plate.

When the solution treatment is performed in a continuous line that is not wound around a coil, the above-mentioned problem of curling is solved, but it has been found that a new problem arises. It was recognized that this alloy was liable to absorb hydrogen, especially when pickling. Hydrogen absorption of pure titanium or the like is problematic because it causes embrittlement. However, hydrogen embrittlement hardly occurs in the present titanium alloy, and it was initially thought that hydrogen absorption was not a problem. However, in practice, it has been found that the absorbed hydrogen is released from the material at the time of welding to join the pressed plate members, causing a small hydrogen explosion, making welding impossible. Since a very large force is applied to the head of a golf driver at the time of hitting and this is repeated thousands of times, high reliability is particularly required for a welded portion. For that purpose, the hydrogen concentration needs to be 130 ppm or less. This alloy must pass through a hot rolling process, and must be passed through an acid pickling line to remove the oxide scale and alpha case generated at that time. At this time, the hydrogen concentration of the alloy increases to several hundred ppm, and
In order to achieve the target hydrogen concentration of ppm or less, it is essential to incorporate a dehydrogenation step. In the case of the present alloy, dehydrogenation can be performed only by heat treatment in a vacuum or an inert atmosphere (eg, argon) . However, in the case of a continuous line, it became clear that sufficient dehydrogenation could not be performed. First, in continuous annealing in the atmosphere, not only dehydrogenation cannot be performed, but also oxide scale is newly formed, and it is necessary to pass through the pickling line again, so there is no room for adoption. In an argon atmosphere, hydrogen can be removed by reducing the pressure, but the rate is slow, and it is difficult to dehydrogenate to a desired hydrogen concentration of 130 ppm or less here in a short time such as continuous annealing. A method using the continuous vacuum annealing line proposed in the above-mentioned conventional method is also conceivable, but it is difficult to obtain a high vacuum in this line, and when the alloy is treated at a temperature higher than the transformation point of the present alloy, discoloration (light oxidation) generally occurs. In addition to this, it is necessary to perform pickling again, and further, the continuous vacuum annealing line requires enormous equipment and cost, and has no practical value.

[0009] It is an object of the present invention to establish a method capable of maintaining flatness and dehydrogenating to a sufficiently low level without producing a curl problem in the production of the present titanium alloy sheet for a golf driver head. It is to be.

[0010]

Means for Solving the Problems In order to solve the above-mentioned problems, the present inventors have conducted a thorough examination of the manufacturing process, and as a result, have not performed heat treatment after cold rolling, but have cut all the sheets, and By performing a final heat treatment that combines solution annealing and dehydrogenation, a titanium alloy sheet for a golf driver head is particularly required for (1) solution treatment, (2).
It has been confirmed that a thin plate can be manufactured which satisfies the requirement of having flatness and (3) dehydrogenating to 130 ppm or less.

Based on this finding, the present invention comprises from 10% to less than 25% by weight of vanadium and optionally 2% by weight.
-5% by weight aluminum, 2-5% by weight chromium and 2
And producing a cold-rolled coil of a titanium alloy for a golf driver head further comprising one or more selected from the group consisting of -4% by weight tin and the balance of titanium and unavoidable impurities. A method for producing a titanium alloy plate for a golf driver head, comprising: performing heat treatment for solution treatment and dehydrogenation in a state of the plate after cutting the coil into a titanium alloy plate. The dehydrogenation is preferably performed so that the hydrogen concentration is 130 ppm or less. The heat treatment is preferably performed at a temperature not lower than the transformation point of the titanium alloy and not higher than 850 ° C.

In order to remove oil adhering at the time of cold rolling, the titanium alloy sheet is kept at a temperature in the range of 200 to 400 ° C. for 30 minutes or more during the temperature rise for heat treatment of the titanium alloy sheet. At this time, the oil adhering can be removed. Further, in order to prevent adhesion between the plates during the heat treatment, it is recommended to insert a spacer between the plates during the heat treatment of the titanium alloy plate.

[0013]

The Ti alloy containing 10 to less than 25% by weight of V, which is the basis of the present alloy, is a cold-rollable titanium alloy. Here, the lower limit of the amount of vanadium added is 10% by weight.
The reason for this is that if it is less than 10% by weight, good cold rollability cannot be obtained. Further, the reason why the upper limit of the amount of vanadium added is set to less than 25% by weight is that even if it is added more than that, no improvement in the cold rolling property is observed, and conversely, the strength tends to decrease. In addition, since the price of vanadium is considerably higher than that of titanium, it is preferable to suppress the amount of vanadium added as much as possible from the viewpoint of cost. The preferred vanadium content is 13-20% by weight.

The results of a test in which the cold workability of vanadium was investigated are shown below. Various amounts of vanadium were added to titanium, an ingot was prepared by arc melting, hot-rolled at 900 ° C, scale removed, heated to 830 ° C (in an inert atmosphere), and then water-quenched. The concentration is 0.1 ~
0.15% by weight, and Fe,
Table 1 shows the results of examining the cold workability of H, N, C, etc.).

[0015]

[Table 1]

[0016] Titanium alloys with a low V concentration have poor cold rollability and cause considerable edge cracking. V concentration is 10% by weight
, The cold rolling property is improved, but the tendency does not change even if the V content is increased to 25% by weight or more.

When the oxygen content exceeds 0.25% by weight, the elongation starts to extremely decrease, and the cold rolling property and the cold pressability become very poor.

Although the above alloys can be used sufficiently as a head material, improvement can be achieved in several points by adding one or more of chromium, aluminum and tin.

It has been confirmed that the addition of chromium to the Ti-V alloy further increases the elongation. This significantly improves the cold pressability, in particular. However, in order to obtain the effect, it is necessary to add chromium in an amount of 2% by weight or more.
If it is added in an amount of more than 10% by weight, it tends to become brittle,
The upper limit needs to be 5% by weight.

For example, various concentrations of C are added to Ti-18% V.
After adding r, and making an ingot by arc melting, 90
FIG. 1 shows a change in elongation (total elongation) of a test material obtained by hot rolling at 0 ° C., removing scale, heating to 800 ° C. (in an inert atmosphere), and then water quenching by a tensile test. Obviously, Cr
It is confirmed that the elongation is increased by adding. The effect is particularly confirmed when the Cr concentration is 2% or more, and the elongation is remarkably increased up to around 5%. If it exceeds 5%, the elongation does not increase so much, and conversely, the hot and cold deformation resistance increases and the number of ear cracks increases. From the above, the lower limit of the added amount of Cr is set to 2% by weight, and the upper limit is set to 5% by weight. The addition of Cr significantly improves cold pressability.

Further, the addition of aluminum to a Ti-V alloy is mainly due to economic effects. That is, the price of a single metal of vanadium is very high, and if it is used as an additive, the price of the alloy becomes very high. On the other hand, when an Al-V master alloy can be used as an additive, this master alloy is considerably cheaper than a vanadium simple metal, and as a result, a Ti-V-Al alloy requires less expensive raw material. Become. In addition, Ti-V alloys show a phenomenon of age hardening in a certain temperature range. However, when aluminum is added to the alloy, age hardening is promoted, which contributes to an increase in strength. Here, the lower limit of the aluminum addition amount is set to 2% by weight.
Even if a% Al mother alloy is used, a very large amount of V metal alone must be added, and the cost merit disappears. Further, the upper limit of the aluminum addition amount is set to 5% by weight, because above this, the cold workability becomes difficult.

As an example, various concentrations of Al are added to Ti-17% V-3% Cr, an ingot is prepared by arc melting, hot-rolled at 900 ° C., and scale is removed.
FIG. 2 shows changes in mechanical properties of the test material (solution-hardened material) heated to 00 ° C. (in an inert atmosphere) and then water-quenched by a tensile test. The specimen was aged (500 ° C).
FIG. 3 shows changes in mechanical properties of the age-hardened material after (× 8 hours).

In FIG. 2 in the case of the material after solution heat treatment,
The addition of Al only slightly contributes to the improvement of elongation. Notably, the A in FIG.
This is the effect of l. Clearly, the addition of Al causes an increase in strength. In golf heads, aging treatment is sometimes performed because of the required strength. By appropriately controlling the amount of Al added, a material having ductility and high strength can be obtained.

Finally, the effect of adding Sn will be described. S
n does not significantly affect the mechanical properties, but Ti-V
This has the effect of suppressing the precipitation of a brittle ω phase, which is easily formed when aging treatment is performed on a system alloy. To achieve this effect, 2% by weight
It is necessary to add the above Sn. On the other hand, even if it is added more than 4% by weight, the effect of suppressing the precipitation of the brittle ω phase does not change, the specific strength decreases due to the increase in specific gravity, and it is unsuitable as a material for a driver head. The upper limit is 4% by weight
And

As described above, in order to efficiently manufacture a driver head, it is optimal to work into a target shape by a cold or warm press and assemble the parts by welding. In this step, welding is always included, but it has been found that if a large amount of hydrogen is contained in the alloy, small explosion of hydrogen occurs during welding, and good welding cannot be performed. As described above, the alloy of the present invention easily absorbs hydrogen more than pure titanium, and particularly absorbs a large amount of hydrogen in the pickling step.
Then, when the influence on the welding was changed by changing the hydrogen concentration, it was found that welding was possible if the concentration was 130 ppm or less. On the other hand, a change in the hydrogen concentration has a subtle effect on the characteristics of the golf driver head. This is because the Young's modulus decreases slightly as the hydrogen concentration decreases,
It is considered that this affected the aging temperature. In any case, the lower limit of the hydrogen concentration is preferably set to 0.002% by weight and the upper limit is set to 0.013% by weight.
In the range of 003 to 0.009% by weight, good welds can be obtained and a certain level of shot feeling can be experienced.

For example, Ti-15% V-4% Cr-3A
Using a material obtained by changing the hydrogen concentration of an l-3Sn alloy,
Table 2 shows the results of the TIG welding performed in the r atmosphere.
While the hydrogen concentration was low, TIG welding could be performed without any problem. However, a small spark that seems to be a reaction of hydrogen began to be observed at a hydrogen concentration of 0.013%, and at a concentration of 0.05% or more, a small explosion of hydrogen caused welding. The part became incomplete. It was found that when the hydrogen concentration exceeded 0.1%, almost no welding was possible. From these results, the upper limit of the hydrogen concentration was set to 0.013%.
And

[0027]

[Table 2]

Although the composition range has been mainly described above, the structure is also an important factor. When this alloy is used as a material for a golf driver head, since cold pressing is first performed, cracking occurs if the alloy has a single β phase and does not have an equiaxial structure. In general, after maintaining the material at or above the β transformation point, water-cooling or air-cooling can provide a β-single phase with good workability and an equiaxed structure. For example, Ti-15% V-4% Cr-3% Al-3
% Sn-0.15% O alloy solution-treated plate (crystal grain size 100 µm) and aging treatment (500 ° C x 8 hours)
When the resulting plate was cold-pressed, all of the aged plates cracked. This indicates that the head material preferably has a β single phase and has an equiaxial structure. However, if an aging treatment is performed on a material having an appropriate composition, benefits such as an increase in strength can be obtained without cracking.

In manufacturing the thin plate for a golf driver head according to the present invention, an alloy material having a required composition is formed into an ingot by arc melting and then forged and hot-rolled.
A coil of 5 mm is manufactured, the coil is pickled, and cold-rolled to produce a cold-rolled coil having a thickness of 1 to 4 mm. After degreasing, the coil is cut into a plate, and a final heat treatment for solution and dehydrogenation is performed in a plate state in a vacuum furnace or a furnace under a reduced pressure of argon.

The heat treatment is performed at a temperature equal to or higher than the transformation point, and is preferably set to 850 ° C. or lower. If the heat treatment is performed at a high temperature exceeding 850 ° C., the material is discolored, the crystal grain size becomes too large, and the flatness tends to deteriorate.

The alloy is liable to seize oil during cold rolling and cannot be removed by ordinary degreasing. If the above-described heat treatment is performed while the oil remains, the baked oil may ooze out from the material surface and discolor the titanium surface. As a result of detailed observation, it was confirmed that the oil began to be released at 200 ° C. or higher, and that the titanium surface did not discolor at 400 ° C. or lower. Therefore, it is useful to incorporate a process of maintaining the temperature of the titanium alloy plate at a temperature in the range of 200 to 400 ° C. during the heating to the heat treatment temperature and volatilizing and removing the attached oil. In order to volatilize and remove the adhering oil, it is necessary to hold the oil for at least 30 minutes, preferably for 1 hour or more.

The heat treatment is usually performed in a state where the plates are piled up in a furnace. When a load is applied to the contact portion, the plates easily come into close contact with each other. In order to prevent this, it is recommended to insert a spacer between the plates. As the spacer, for example, a stainless steel wire mesh is preferably used. If you insert a plate instead of wire mesh,
Poor ventilation, causing discoloration and also solution,
A situation where dehydrogenation is not sufficiently performed may occur.

After the heat treatment, the solution of the titanium alloy sheet is completed by air cooling, water quenching, rapid cooling with argon gas, or the like. Thereafter, aging treatment can be performed. A part having a required shape is produced by cold or warm press, and these are joined by welding to produce a head. With the present invention, such operations can be performed easily and reliably. The golf driver is manufactured by assembling the obtained head to a shaft and assembling the golf driver.

Using the prototype, the hitting characteristic of a golf ball, which is the most characteristic of the head, was tested. Ti-1
5% V-3.1% Cr-3.6% Al-3Sn-0.1
1% O alloy (0.1% Fe, 0.007% as impurities)
C, 0.011% N, and 0.004% H) were produced by arc melting, and then hot and cold rolled and cut to produce a 1 to 3 mm plate. After heating this to 800 ° C,
Using a plate cooled by air cooling, a head was prepared by cold pressing and welding, and then assembled into a golf driver and tested. As a result, the flying distance was increased by about 10% compared with the conventional titanium alloy golf driver. Also, the sweet spot has become much wider.

The very good characteristics were obtained because a high ideal strength and a nearly ideal head shape were obtained by welding and assembly, and the Young's modulus was 8000 to 900.
Despite being a low value of 0 Kgf / mm ² (after solution solution) compared to stainless steel and other titanium alloys, the yield strength is considerably high, that is, the springback property is very strong. It is presumed that it is.

[0036]

EXAMPLE 15% of vanadium, 3% of chromium, 3% of aluminum and 3% of tin were added to a titanium raw material, an ingot was produced by arc melting, forging and 900 ° C.
Was carried out to obtain a coil having a thickness of 4 mm. At this time, an oxide case and an alpha case with a thickness of several tens of μ were present on the surface of the material. This was removed by pickling using an aqueous solution of hydrofluoric acid and sulfuric acid, and as a result, the hydrogen concentration in the material became 500 ppm or more. From this, three types of coils having a thickness of 1 mm, 2 mm and 3 mm were produced by cold rolling. After degreasing, the hydrogen concentration of the material was measured but showed little change.

These coils were cut into plates, and the plates were arranged in a vacuum furnace and heat-treated. The heat treatment was performed by holding at 800 ° C. for 30 minutes and then quenching with argon gas. In the obtained material structure, no alpha case was observed, and it was a beta single phase. When the hydrogen concentration was analyzed, it was found that dehydrogenation had been performed to a level of 50 ppm, which was not a problem. With the exception of some materials, the materials retained their metallic luster and no discoloration occurred.

Since some of the materials were discolored by baking of oil, the heat treatment conditions were adjusted so that it took three hours for the material temperature to reach 400 ° C. after reaching 200 ° C., and then the material temperature was raised to 800 ° C. Changed to increase the temperature. As a result, all the materials retained their metallic luster and no discoloration occurred.

Next, a stainless steel wire mesh was inserted between the plates in order to perform heat treatment in a piled state with the alloy plates stacked in a furnace. It was possible to avoid close contact between the boards.

The press formability of the obtained material was good, no hydrogen explosion occurred during welding, and the head could be easily manufactured by cold pressing and welding.

[0041]

As described above, according to the method of the present invention, a titanium alloy sheet for a golf driver head is required to (1) be solution-treated, (2) have a flatness, and (3) have a flatness.
Dehydrogenation has been performed to 130 ppm or less,
(4) A thin plate that satisfies the requirement of a clean surface can be manufactured at low cost, and the head can be mass-produced relatively inexpensively by a method similar to a conventional method of manufacturing a stainless steel head. In combination with the material properties, it is possible to manufacture a driver having a performance exceeding that of a conventionally sold titanium alloy driver at a relatively low cost.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between Cr concentration and elongation of a Ti-18V-Cr alloy.

FIG. 2 is a graph showing the relationship between Al concentration and mechanical properties of a solution-hardened material obtained by adding Al to Ti-17% V-3% Cr.

FIG. 3 is a graph showing the relationship between Al concentration and mechanical properties of an age hardened material obtained by adding Al to Ti-17% V-3% Cr.

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Hirohiro Mitsuyoshi 3rd Kurami, Samukawa-cho, Koza-gun, Kanagawa Pref. 5-49716 (JP, A) JP-A-6-240390 (JP, A) JP-B-64-7151 (JP, B2)

Claims (5)

(57) [Claims] 1. A composition comprising from 10% to less than 25% by weight of vanadium, optionally 2 to 5% by weight of aluminum,
Producing a cold-rolled coil of a titanium alloy for golf driver heads further comprising one or more selected from among 5% by weight chromium and 2 to 4% by weight tin and comprising the balance titanium and unavoidable impurities; A method for producing a titanium alloy sheet for a golf driver head, comprising cutting the titanium alloy cold-rolled coil into a titanium alloy sheet and performing heat treatment for solution and dehydrogenation in the state of the sheet. 2. The method for producing a titanium alloy plate for a golf driver head according to claim 1, wherein the heat treatment is carried out at a temperature not lower than the transformation point of the titanium alloy and not higher than 850 ° C. 3. The method according to claim 1, wherein the titanium alloy sheet is kept at a temperature in the range of 200 to 400 ° C. for 30 minutes or more during the temperature rise for heat treatment of the titanium alloy sheet to remove oil adhering during cold rolling. 3. The method for producing a titanium alloy plate for a golf driver head according to claim 1, wherein: 4. The method for manufacturing a titanium alloy plate for a golf driver head according to claim 1, wherein a spacer is inserted between the plates during heat treatment of the titanium alloy plate. 5. The dehydrogenation is carried out at a hydrogen concentration of 0.002 to 0.0.
The method for producing a titanium alloy plate for a golf driver head according to claim 1, which is performed so as to be 13% by weight.