JP2002325870A - Golf club head and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a golf club which is improved in tensile strength of the face part. SOLUTION: A face member 7 comprising a titanium alloy formed by press- working a cold-rolled material at a temperature not higher than 400 deg.C is used for at least a part of the face part 2 of this golf club head 1 to hit a ball.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a golf club head using a titanium alloy for a face portion and a method of manufacturing the same.

[0002]

2. Description of the Related Art In a wood type golf club head, in order to increase the flight distance of a hit ball, a metal material having good resilience is used for a face portion hitting the ball. In recent years, as a metal material excellent in resilience, β such as Ti-15Mo-3Cr-3Sn-3Al has been used.
Type titanium alloys are being used extensively.

[0003] Generally, the workability of a metal material improves as the temperature increases. Therefore, conventionally, even in the case of β-type titanium alloy, a thin plate-shaped rolled material is manufactured by first rolling at a high temperature of around 1000 ° C., and this rolled material is press-formed again at a high temperature of around 1000 ° C. It is formed into the shape of the face member.

[0004]

As a result of various experiments by the present inventors, when a titanium alloy is cold-rolled, effective work hardening can be obtained, and mechanical strength and fatigue resistance can be greatly improved. I found that. However, it has also been found that the improvement of the mechanical strength of the titanium alloy thus obtained disappears when the material is heated to a certain temperature.

The present invention has been devised in view of such a situation. At least a part of a face portion for hitting a ball is formed by pressing a cold-rolled rolled material at a certain temperature or lower. It is an object of the present invention to provide a golf club head that can improve mechanical strength and fatigue resistance based on using a face member made of a formed titanium alloy.

[0006]

According to the first aspect of the present invention, at least a part of a face portion for hitting a ball is formed by pressing a cold-rolled rolled material at 400 ° C. or less. A golf club head using a face member made of a titanium alloy formed by the method described above.

According to a second aspect of the present invention, there is provided the golf club head according to the first aspect, wherein a reduction in the cold rolling is 10 to 95%.

The invention according to claim 3 is the golf club head according to claim 1 or 2, wherein the titanium alloy is represented by the following composition formula. Ti100-xy M1x M2y (all numerical values are atomic%) where M1 is one or more elements selected from Zr and Hf, and M2 is V, Nb, Ta, Mo, Cr, W
And x + y ≦ 50 (0 <x <50, 0 <y <50).

Further, the invention according to claim 4 comprises a step of cold rolling the titanium alloy to obtain a rolled material, and a step of pressing the rolled material at 400 ° C. or less without heat treatment to form a face member. Fixing the face member to the striking face side of the head main body.

[0010]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a golf club head (hereinafter, may be simply referred to as “head”) 1 of the present embodiment.
FIG. 2 is a front view of the head 1 taken along a line YY, and FIG.
Indicates a reference state placed on the horizontal plane HP.

Referring to FIG. 1, a head 1 of the present embodiment includes a face portion 2 for hitting a ball, a crown portion 3 connected to an upper edge 2a of the face portion 2 and forming an upper surface of the head, and a lower edge 2b of the face portion 2. A sole 4 extending from the toe 2t of the face 2 to the heel 2h through the back face, between the crown 3 and the sole 4, and a shaft (not shown). And a shaft mounting portion 6. The head 1 of the present embodiment is exemplified by a wood type head made of a metal material and having a hollow inside.

The head 1 has a plate-like face member 7 serving as at least a part of the face portion 2, in this example, a main portion, and a main body portion 9 having an opening for arranging the face member 7 on the hitting surface side. An example is shown that is formed by integrally fixing and. In FIG. 1, the boundary of the face member 7 is indicated by a chain line, and the total surface area S
1 to the surface area S2 of the face member 7 (S2 / S1)
Is desirably set to, for example, 0.9 or more.

The main body 9 is formed by appropriately welding one member or two or more members, and is preferably made of a titanium alloy. In this example, the head body 9 is α +
As a β-type titanium alloy, an example in which Ti-6Al-4V is integrally formed by lost wax casting is illustrated. The shaft mounting portion 6 is formed so as to protrude upward in this embodiment, and has a shaft mounting hole 6a in which a shaft (not shown) can be inserted and fixed with an adhesive or the like. Since the hole center line CL of the shaft mounting hole 6a substantially coincides with the axial center line of the shaft to be mounted later, the lie angle α is determined based on the hole center line CL in this specification.

In this embodiment, the face member 7 is formed of a β-type titanium alloy. Since the β-type titanium alloy has a body-centered cubic structure (bcc) having a large number of slips, the resistance required for deformation is smaller than that of the α-type titanium alloy having a close-packed cubic structure with a small amount of slip, and the cold or hot Excellent workability between layers.

Examples of such β-type titanium alloys include, for example, Ti-15V-3Cr-3Al-3Sn, Ti-1
5Mo-5Zr-3Al, Ti-10V-2Fe-3A
1, Ti-13V-11Cr-3Al, Ti-8Mo-
8V-2Fe-3Al, Ti-22V-4Al, Ti-
15Mo-5Zr and the like. Particularly preferably, a titanium alloy represented by the following composition formula (1) is desirable. Ti100-xy M1x M2y (all numerical values are atomic%) (1) where M1 is one or more elements selected from Zr and Hf, and M2 is V, Nb, Ta, Mo, Cr, W
And x + y ≦ 50 (0 <x <50, 0 <y <50).

As a result of the experiments by the present inventors, the titanium alloy represented by the above formula (1) has a significantly low Young's modulus and a large elastic elongation and plastic elongation while increasing the tensile strength and hardness. As a result, it has been found that it is suitable for a face member having high repulsion. The high strength and hardness of such titanium alloys is mainly due to solid solution strengthening by dissolving elements having a large atomic radius difference, for example, an element having an atomic radius difference of 10% or more from the above combination, and a low Young's modulus Is mainly because the constituent elements have no attractive interaction with each other, so that atoms can move reversibly with low stress.In addition, the large elastic elongation limit etc. It is considered that the reversible atom transfer can occur up to a high strain region due to the property and the deformation stress hardly increases.

In particular, the solid solution of the constituent elements containing at least two elements having a large difference in atomic radius as described above makes it difficult for rearrangement of atoms to occur and lowers the diffusivity. In addition, even when slowly cooled, it is possible to obtain a β-type titanium alloy mainly containing a bcc solid solution single phase or a bcc solid solution and having excellent cold workability. And it turned out that such a solid solution can easily provide more effective high strength by performing cold rolling and causing work hardening.

In the above formula (1), when the content of titanium is less than 50 atomic%, excellent mechanical properties of the above alloy can be exhibited, but the specific gravity tends to be large, so that the head has When applied, it tends to increase the weight, increase the cost, and further increase the melting point. If the element of Zr or Hf is not contained, it tends to be difficult to form a solid solution of a metal element having a large difference in atomic radius in a large amount, and solid solution strengthening tends to be impossible. Conversely, when the total content of the elements Zr and Hf exceeds 50 atomic%, there are disadvantages such as an increase in specific gravity and an increase in melting point. Furthermore, when one or two elements selected from V, Nb, Ta, Mo, Cr, and W are not contained, a decrease in strength and a decrease in corrosion resistance are likely to occur. Further, when the total content of these elements exceeds 50 atomic%, the specific gravity of the alloy is increased, the melting point is increased, and the cost is easily increased. Particularly preferably, Ti, Zr,
It is a combination of Nb and Ta. That is, M1 is Zr, and M2 is Nb and Ta. Zr is more preferably 10 to 40 atomic%, further preferably 15 to 30 atomic%, and the balance is preferably composed of Nb and Ta.

In the present embodiment, the titanium alloy represented by the formula (1) is cold-rolled to obtain a rolled material, and the rolled material is pressed at 400 ° C. or lower without heat treatment. The face member 7 is formed. As a result of diligent research, the titanium alloy and the like are subjected to cold rolling, thereby introducing lattice defects such as a large number of dislocations into the material, thereby improving the mechanical strength and fatigue resistance properties. It has been found that such improvements can be eliminated by heating the rolled material to 400 ° C. or higher.

In the rolling process, for example, as shown in FIG. 3, the material M is engaged between a pair of rotating rolls R by friction to reduce the thickness or the cross-sectional area. Also,
The cold rolling is a process in which a material is rolled at room temperature without intentionally heating the material, and is distinguished from a warm or hot rolling process in which a material is heated and rolled. Specifically, as the cold rolling, taking into account the ambient temperature and the heat generated by the material during the rolling, −20 to 100 ° C., more preferably 0 to 100 ° C., and even more preferably 15 to 100 ° C. It is desirable to process. This temperature means the material temperature during processing.

If the temperature at the time of the cold rolling exceeds 100 ° C., rearrangement and recrystallization of the transition in the crystal of the material occur, so that work hardening cannot be sufficiently expected, and as a result, the mechanical strength is improved. And the improvement of fatigue resistance cannot be expected sufficiently, and conversely -20
If the temperature is lower than 0 ° C., cracks or the like are likely to occur on the side edges perpendicular to the rolling direction of the rolled material, and the yield of the material tends to deteriorate.

In the cold rolling step, a material M such as a titanium alloy ingot or a bloom obtained from the ingot is prepared. The thickness, shape, and the like of the material M are adjusted in advance by cutting or the like. Further, in the cold rolling process, the deformation resistance of the material is larger than that in the hot rolling process, so that the rolling reduction (thickness reduction amount) in one rolling process is, for example, 0.1 to 0.1.
0.5mm, and by repeating this multiple times,
It is preferable to form a rolled material 10 having a desired thickness. In the present embodiment, a rolled material 10 having a thickness of about 3 mm is prepared.

On the other hand, if the rolling reduction in cold working is too small, the dislocation density of the titanium alloy cannot be increased, and the effect of improving the mechanical strength by work hardening will be reduced. For this reason,
Preferably, the rolling reduction of the rolling process is 10% or more, more preferably 20% or more, and further preferably 50% or more. On the other hand, if the rolling reduction is too large, there is no particular problem from the viewpoint of improving the strength of the material, but since large processing equipment is required, practically, in combination with any of the above lower limits, 95% or less, Preferably 90
% Or less, particularly preferably 85% or less. By regulating the rolling reduction at the time of cold rolling in this way, the tensile strength can be further improved by work hardening while maintaining the low Young's modulus of the titanium alloy.
The rolling reduction is determined by the following formula: rolling reduction = {(h1−h2) / h1} × 100 [%], where h1 is the thickness before rolling and h2 is the thickness after rolling.

In the cold rolling, the rolling direction K
(Shown in FIG. 3) may be in a single direction, but is preferably rolled in two or more directions crossing each other. In the rolling direction and the direction perpendicular to this rolling direction,
Since the strengths against bending tend to be different, it is preferable that the anisotropy such as the mechanical strength of the material is reduced as much as possible by using two or more kinds that intersect the rolling direction. Further, it is desirable that the crossing angle of the rolling direction is 40 to 90 °.

In the present invention, the face member 7 is formed by pressing the cold-rolled material 10 at a temperature of 400 ° C. or less. If the temperature during the pressing exceeds 400 ° C., new crystal grains without distortion will be generated in the titanium alloy, which will grow in the region where the dislocations are high, and eventually all the material will be covered with the new crystal grains. This is because the mechanical strength and fatigue resistance of the titanium alloy enhanced by cold rolling are lost. More preferably, the temperature at the time of press working is 350 ° C. or lower, more preferably 300 ° C. or lower, and further preferably 2 ° C. or lower.
By performing the treatment at a temperature of 00 ° C. or less, particularly preferably 100 ° C. or less, and more preferably at room temperature, it is possible to maintain the enhanced mechanical strength of the titanium alloy. The lower limit temperature at the time of press working is not particularly limited, but if the temperature is extremely low, toughness is impaired. Therefore, in combination with any of the above upper limit temperatures, for example, -20 ° C. or higher, preferably 0 ° C. C. or higher, more preferably 15 ° C. or higher, particularly preferably 20 ° C. or higher.
This temperature is the temperature of the rolled material 10.

In the press working, for example, as shown in FIG. 4 (a), the rolled material 10 is placed between a lower die D1 and an upper die D2, and as shown in FIG. For example, the surface pressure of the mold D2 is about 25 to 45 MPa and the pressing time is 1 to 1.
Push down to about 10 seconds. Thereafter, the upper mold D2 is separated from the lower mold D1 as shown in FIG. Thus, the face member 7 curved at a predetermined curvature can be press-formed. After pressing, a part of the face member may be cut or the like.

As described above, the face member 7 of this embodiment is subjected to the press working at a temperature of 400 ° C. or less after the cold rolling as described above. No heat treatment such as baking was performed. In other words,
In the process from the cold rolling process to finishing the face member 7, the titanium alloy as the material is not heated to a temperature exceeding 400 ° C. For this reason, in the face member 7 of the present embodiment, the excellent mechanical strength of the titanium alloy work-hardened by the work strain generated by the cold rolling can be maintained as it is. By using such a titanium alloy having excellent mechanical strength or fatigue resistance for the face member 7, the thickness of the face member 7 can be reduced. Thereby, the resilience performance of the face portion can be enhanced, and the flight distance of the hit ball can be improved.

The thickness t of the face member 7 (shown in FIG. 2)
Is not particularly limited, for example, 1.0 to
The thickness t is preferably 4.0 mm, more preferably 2.0 to 3.0 mm, and still more preferably 2.2 to 2.7 mm. If the thickness t is less than 1.0 mm, the practical strength tends to be insufficient and the durability tends to decrease. Conversely, if the thickness t exceeds 4.0 mm, the rigidity of the face portion 2 is excessively increased, and the resilience performance is reduced. There is a tendency that the distance of the hit ball tends to decrease due to a decrease.

The face member 7 made of the titanium alloy thus obtained generally has a bending strength k of 500.
To about 4000 MPa, more preferably 700 to 3000 MPa, and still more preferably 800 to 2 MPa.
It is desirable to set it to 500 MPa. Such bending strength can be variously adjusted depending on the rolling reduction and the temperature during press working. When the bending strength is less than 500 MPa,
The strength tends to be insufficient, and when the strength exceeds 4000 MPa, the cold working tends to be difficult.

When the absolute thickness t of the face member 7 is small even when the bending strength k is large, or when the bending strength k is extremely low even when the thickness t of the face member 7 is large. All tend to have insufficient practical strength as the head 1. From such a viewpoint, the face member 7
K × t of the bending strength k of the member and the thickness t of the face member 7
(MPa · mm) value is 500 to 16000, more preferably 1250 to 12500, and particularly preferably 2000 to 16000.
It is desirably 7000.

The face member 7 formed as described above
Is preferably formed on the ball striking face side of the main body 9 by a fixing means such as, for example, bonding, caulking, welding, pressing, brazing or the like. Since the range of welding is limited to the periphery of the face member 7, the mechanical strength of the weld does not substantially decrease.

Although the embodiment of the present invention has been described by taking a wood type golf club head as an example, the present invention
It is needless to say that the present invention is not limited to the wood type golf club head, but can be suitably applied to iron type, putter type, utility type heads and the like. Although the face member has a plate shape in this example, the face member may be formed so that a part thereof forms a part of the crown portion 3, the sole portion 4, or the side portion 5.

[0033]

Next, an embodiment of the present invention will be described. As a titanium alloy satisfying the above formula (1), "Ti50
A composition of "Zr30Nb10Ta10" (difference in atomic radius is about 11.7% at minimum-maximum) was prototyped by the following method. First, the above-mentioned constituent elements are melted in a vacuum arc melting furnace in an atmosphere evacuated and replaced with argon, and an alloy having the above composition is formed into a lump (shape: width 100 mm × length 70 mm × thickness 1).
0 mm), and then cold-rolled at a rolling reduction of about 70% to produce a prototype of a rolled plate having a width of 100 mm, a length of 100 mm and a thickness of 3 mm.

Next, when the mechanical strength of the rolled material was measured, the yield strength was 980 MPa, the tensile strength was 1070 MPa, the Young's modulus was 40 GPa, the elastic elongation was 1.7%,
5% plastic elongation and Vickers hardness 350Hv, bcc
The solid solution had a volume fraction of 90% or more. Table 1 shows the properties of such a titanium alloy and a conventional product (pure titanium, and α + β-type titanium alloy (Ti-6Al-4V) which is currently the mainstream material for wood-type golf club heads). The comparison is shown. FIG. 5 shows the tensile stress-elongation curves of these materials, and FIG. 6 shows the relationship between tensile strength and Young's modulus, including other metal materials.

[0035]

[Table 1]

As is apparent from Table 1 and FIGS. 5 to 6, the titanium alloy represented by the above formula (1) has a higher tensile strength σf than pure titanium or a titanium alloy. It can be seen that the Young's modulus E is as low as 40 MPa, which is less than half of those, and that the elasticity or plastic elongation is large and the hardness is also large. That is, by using a titanium alloy having such characteristics of high strength and low Young's modulus as the face member 7 of the head 1, the durability and the trauma resistance of the face portion 2 are sufficiently secured, and the coefficient of restitution of the head is reduced. This is particularly preferable in that it can improve the initial velocity of the ball, and thereby increase the flight distance. Further, such a titanium alloy has low deformation resistance and large plastic elongation, and thus has excellent rolling workability in a cold state, and can easily form a rolled material having a draft of 10% or more, for example.

Next, a plurality of the above-mentioned rolled materials are prepared, and the rolled material is prepared at room temperature (23
℃), 100 ℃, 200 ℃, 300 ℃, 400 ℃, 50
After being kept in each environment of 0 ° C. for 30 minutes, each rolled material was formed with a hydraulic press so that both face rolls and face bulges became 9 inches (228.6 mm). The press-formed product is cut into the shape of a face member, welded to the head body, and the face surface is polished to reduce the thickness of the hitting portion of the face member to about 2.7.
A wood-type golf club head of mm was prototyped. The common specifications of the head are as follows. Head volume: 300cm ³ Loft angle: 10 ゜ Head body: Ti-6Al-4V titanium alloy manufactured by lost wax precision casting

The same shaft (46) is attached to such a head.
Inch, Flex S) was attached to a wood-type golf club, which was attached to a swing robot manufactured by True Temper Co., and was subjected to a durability test in which a golf ball was hit at a head speed of 54 m / s. In the evaluation, "X" indicates that the face portion was damaged in less than 5,000 shots, and "O" indicates that the face portion was damaged between 5,000 and 10,000 shots.

The mechanical strength was 3 in each of the above environments.
JIS Z2204 from the rolled material after holding for 0 minutes
A No. 3 test piece was cut out in accordance with the above, and a bending test was performed to measure a bending elastic limit stress (n = 3). Table 2 shows the test results and the like.

[0040]

[Table 2]

As a result of the test, in the example in which the rolled material of the cold-rolled titanium alloy was pressed at a temperature from room temperature to 400 ° C., the durability and the bending elastic limit stress were improved. You can see that. In contrast, 500 ° C
In Comparative Example 1 in which press working was performed and in Comparative Example 2 in which hot rolling was performed at a temperature of 1000 ° C., the durability was low.
Also, it can be confirmed that the bending elastic limit stress is small.

Further, Table 3 shows the results of the same test as in Table 2 performed for other compositions. Also in this example, it can be confirmed that the example has a high bending stress limit and is excellent in durability.

[0043]

[Table 3]

[0044]

As described above, according to the first aspect of the present invention, at least a part of the face portion for hitting a ball includes
A face member made of a titanium alloy formed by pressing a cold-rolled material at 400 ° C. or lower is used. Such a face member is excellent in durability by directly combining the high mechanical strength and fatigue resistance characteristics imparted to the titanium alloy by cold rolling, and the face thickness can be reduced due to the high strength. The performance can be improved and the flight distance of the hit ball can be improved.

Further, when the face member is formed through a cold rolling process with a draft of 10% or more, the face member is more effectively formed by work hardening, and has a bending strength and a tensile strength. Can be further improved.

When the composition of the titanium alloy is limited to a certain range as in the third aspect of the present invention, excellent cold rolling workability and higher strength and low Young's modulus can be achieved at the same time. Therefore, the durability can be improved while the resilience is improved by making the face member thinner.

Further, the invention according to claim 4 comprises a step of cold rolling the titanium alloy to obtain a rolled material, and a step of pressing the rolled material at 400 ° C. or less without heat treatment to form a face member. And fixing the face member to the striking face side of the head main body, thereby allowing the face member to have the high mechanical strength and fatigue resistance imparted to the titanium alloy by cold rolling as it is. It is possible to manufacture a golf club head having excellent durability, high strength, a small face thickness, improved rebound performance, and improved flight distance of a hit ball.

[Brief description of the drawings]

FIG. 1 is a front view of a golf club head according to an embodiment in a reference state.

FIG. 2 is an end view taken along the line YY.

FIG. 3 is a schematic view showing a rolling process.

FIGS. 4A to 4C are cross-sectional views showing a pressing step.

FIG. 5 is a graph showing a relationship between tensile stress and elongation of the titanium alloy of the present embodiment.

FIG. 6 is a graph showing the relationship between tensile strength and Young's modulus of the titanium alloy of the present embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Golf club head 2 Face part 3 Crown part 4 Sole part 5 Side part 6 Shaft attachment part 7 Face member

Claims (4)

[Claims] 1. A face member made of a titanium alloy formed by pressing a cold-rolled rolled material at a temperature of 400 ° C. or less for at least a part of a face portion for hitting a ball. And golf club head. 2. The rolling reduction in the cold rolling is from 10 to 9
The golf club head according to claim 1, which is 5%. 3. The golf club head according to claim 1, wherein the titanium alloy is represented by the following composition formula. Ti100-xy M1x M2y (all numerical values are atomic%) where M1 is one or more elements selected from Zr and Hf, and M2 is V, Nb, Ta, Mo, Cr, W
One or more elements selected from the group consisting of: and x + y ≦ 5
0 (0 <x <50, 0 <y <50). 4. A step of cold rolling the titanium alloy to obtain a rolled material, a step of pressing the rolled material at 400 ° C. or less without heat treatment to form a face member, and a step of forming the face member into a head body. Fixing the golf club head to the striking surface side of the golf club head.