JP2002085602A - Golf club head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the durability of a golf club head. SOLUTION: At least a part of a face section F striking ball is formed out of a complex 4 including nano-crystal grains of a ceramic as a dispersant in a base material made of a titanium alloy.

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 having improved durability.

[0002]

2. Description of the Related Art In recent years,
In the face part hitting the ball of the golf club head,
Titanium alloys are frequently used. Titanium alloy has a small Young's modulus in spite of having high strength and high hardness as compared with stainless steel and the like. For this reason, the titanium alloy can reduce the thickness of the face portion by utilizing the feature of high strength, and easily bend the face portion at the time of hitting the ball in combination with the feature of low Young's modulus. As a result, the resilience efficiency of the ball at the time of hitting the ball can be increased, and the flight distance can be increased. The feature of high hardness improves the trauma resistance of the face portion.

However, as a result of various experiments by the inventors,
Titanium alloy has excellent static mechanical strength,
It has been found that there is a slight problem in the metal fatigue properties, that is, even if the stress is lower than the elastic limit, the material may be easily weakened while the stress is repeatedly applied. In particular, in a titanium alloy subjected to cold rolling or the like, metal fatigue characteristics are liable to be reduced due to the inherent processing strain.

In order to improve the fatigue resistance of a golf club head using such a titanium alloy for the face, it is effective to increase the thickness of the face. However, when the thickness of the face portion is increased, the bending characteristics of the face portion obtained by thinning are lost, so that the resilience efficiency with the ball is reduced and the effect of increasing the flight distance is also reduced. Further, for example, it is possible to alleviate the work strain inside the alloy by heat treatment, but in this case, there is a problem that the work hardening is eased and the mechanical properties of the titanium alloy are reduced.

The present invention has been devised in view of the above problems, and at least a part of a face portion for hitting a ball is formed of a composite comprising a titanium alloy and ceramic nanocrystal grains. On the basis of this, it is an object of the present invention to provide a golf club head capable of improving durability and fatigue resistance while taking advantage of a titanium alloy.

[0006]

According to a first aspect of the present invention, at least a part of a face portion for hitting a ball includes a base material made of a titanium alloy and nanocrystalline grains of ceramics as a dispersing material. A golf club head formed of a composite.

[0007] The term "nano-crystal grains" used herein means an average particle diameter of 5 nm or more and 300 nm or less, particularly preferably 45-300 nm.
150 (nm) particles or powder.

According to a second aspect of the present invention, the nano crystal grains are made of one or more of carbides, nitrides or borides of a metal element belonging to Group 4 of the periodic table, and the titanium alloy is The golf club head according to claim 1, wherein the golf club head 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).

According to a third aspect of the present invention, in the golf club head according to any one of the first to third aspects, the nanocrystalline grains have an average particle size of 5 to 300 (nm). is there.

According to a fourth aspect of the present invention, the composite is formed as a plate-like face member by performing cold working with a cross-sectional reduction rate of 10% or more. 4. The golf club head according to any one of 3.

According to a fifth aspect of the present invention, in the face part, the thickness of the composite forming the face part is 1.
The golf club head according to any one of claims 1 to 4, wherein the golf club head has a thickness of 0 to 4.0 mm.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view of a golf club head (hereinafter, may be simply referred to as “head”) 1 of the present embodiment, FIG. 2 is a cross-sectional view thereof, and FIG. 3 is a schematic view of a fine structure of the face member of FIG. Each is shown. In the figure, a head 1 of the present embodiment is exemplified by a wood type having a hollow portion i inside. In the present embodiment, a head body 2 and a face member 3 constituting a main part of a face portion F are illustrated. An example of the configuration is shown.

The head body 2 includes a crown 2a forming an upper part of the head, a sole 2b forming a bottom of the head, and a side part 2 connecting between the crown 2a and the sole 2b.
c, a neck portion 2d protruding toward the heel of the crown portion 2a, and an opening 5 in which the face member 3 is disposed. In this embodiment, the opening 5 is formed with a backup portion 6 that supports only the peripheral edge of the face member 3, but the backup portion 6 can be omitted. Further, the head body 2 of this example can be formed of various crystalline metals or amorphous metals such as aluminum alloy, titanium, titanium alloy, stainless steel, resin, and a composite material thereof.

As shown in FIG. 3, the face member 3 is formed of a composite 4 composed of a titanium alloy 4a as a base material and nanocrystalline grains 4b of ceramics as a dispersing material. ing. In general, fatigue fracture when stress is repeatedly applied to a titanium alloy is such that cracks grow inside as stress is applied to surface defects generated on the surface of the titanium alloy, and ultimately cannot withstand the applied stress. Caused by destruction. In order to improve the fatigue characteristics of such a titanium alloy, it is effective to suppress the crack growth inside the titanium alloy in terms of the crystal structure. The composite 4 of the present invention includes the nanocrystal grains 4b of ceramics dispersed in the titanium alloy matrix, so that the growth of fine cracks generated in the titanium alloy phase is prevented by the nanocrystal grains 4b of ceramics. A so-called "pinning effect". Thereby, since the titanium alloy 4a is effectively reinforced, the fatigue resistance of the face member 3 is greatly improved.

The titanium alloy 4a used in this embodiment
Is not particularly limited as long as it has the largest amount of titanium in the metal composition. For example, in addition to Ti-6Al-4V,
As a higher strength titanium alloy, Ti-15V-3Cr
-3Al-3Sn, Ti-15Mo-5Zr-3Al,
Ti-10V-2Fe-3Al, Ti-4.5Al-3
V-2Mo-2Fe (SP700), Ti-22V-4
Al (DAT51) or the like can be used.

It is particularly preferable to use a titanium alloy represented by the following composition formula (1) for the composite 4. 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
One or more elements selected from the group consisting of: and x + y ≦ 5
0 (0 <x <50, 0 <y <50).

As a result of various experiments, the present inventors have found that the titanium alloy represented by the above formula has a significantly lower Young's modulus and a large elastic elongation and a plastic elongation while increasing the tensile strength and the hardness. I found it. The high strength and hardness of such a titanium alloy is mainly for solid solution strengthening by dissolving elements having a large atomic radius difference, and the low Young's modulus is mainly for the constituent elements having no attractive interaction with each other. In addition to the fact that atoms can be reversibly moved with low stress, and the large elastic elongation limit, etc., the reversible movement of atoms due to the diversity of reversible movement sites due to various types of elements that do not interact has a high range up to the strain region. It is thought that this can be caused by the fact that it can occur and that the deformation stress does not easily rise.

As an example, “Ti
a Zrb Nbc Md ”titanium alloy (T
(i-Zr alloy) was subjected to cold working of rolling and elongation, yielding 980 MPa, tensile strength of 1070 MPa, Young's modulus of 40 GPa, elastic elongation of 1.7%, plastic elongation of 15% and 350 Hv It was confirmed that an alloy having a Vickers hardness of 5% was obtained. Table 1 shows such titanium alloys, pure titanium, and titanium alloys (Ti-6) which are currently the mainstream materials for wood-type golf club heads.
Al-4V) are shown in comparison. FIG. 4 shows tensile stress-elongation curves of these materials, and FIG. 5 shows the relationship between tensile strength and Young's modulus, including other metal materials.

[0019]

[Table 1]

As apparent from Table 1 and FIG. 4, such a titanium alloy has a Young's modulus E of less than half of that of pure titanium or titanium alloy, despite having a higher tensile strength σf than that of pure titanium or titanium alloy. Of 40 MPa, which is very low, and shows that the elastic elongation is large and the hardness and the like are also large. That is, by using a titanium alloy having such characteristics of high strength and low Young's modulus for at least a part of the face portion F of the golf club head 1, the durability and trauma resistance of the face portion F are sufficiently ensured. In addition, the coefficient of restitution of the head is improved, the initial velocity of the ball is increased, and the flight distance can be increased.

In the above formula (1), the contents of the respective elements are limited based on the following reasons. First, when the content of titanium is less than 50 atomic%, the above-described alloy can exhibit excellent mechanical properties, but tends to have a large specific gravity, so that when it is applied to a head, the weight increases and the cost increases. In addition, the melting point tends to be increased. Further, if the elements Zr and Hf are 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, Zr, H
If the total content of the element f exceeds 50 atomic%, there are disadvantages such as an increase in specific gravity and an increase in melting point.

When one or two elements selected from V, Nb, Ta, Mo, Cr and W are not contained, the strength and the corrosion resistance are liable to be reduced. Further, when the total content of these elements exceeds 50 atomic%, the specific gravity of the alloy becomes large, the melting point becomes high, and the cost tends to increase.

Next, the ceramic nanocrystal grains 4b used in the composite 4 are made of a metal element of Group 4 of the periodic table, ie, Ti, Zr, Hf, La or Ac, especially Ti,
Preference is given to carbides, nitrides or borides of Zr and Hf. Specifically, TiB ₂ , TiC, TiCN, ZrC, Zr
B ₂ , HfN, and HfC are suitable, and one or more of these can be used as a dispersant.

In general, ultrafine crystals such as nanocrystals tend to be unstable due to miniaturization and cannot maintain the characteristics of macrocrystals. For this reason, it is essential that the nanocrystals be stable in order to sufficiently exhibit the pinning effect. Therefore, in the present invention, nanocrystalline grains of ceramics, in which bonds between atoms are strong and nanocrystals are very stable, are used.

The average particle diameter of the ceramic nanocrystal grains 4b is desirably, for example, 5 to 300 (nm). When the particle diameter is less than 5 (nm), the nanocrystal grains 4b tend to be crystallographically unstable, and the pinning effect for suppressing the growth of cracks in the titanium alloy tends to decrease. When the diameter exceeds 300 (nm), the nanocrystalline grains 4b of the ceramic tend to be a starting point of a crack, and the effect of improving fatigue resistance tends to be hardly obtained. From such a viewpoint, the average particle size of the nanocrystal grains 4b is more preferably 20 to 200 (nm), and further preferably 30 to 15 (nm).
0 (nm), particularly preferably 45 to 150 (nm). The average particle size of the nanocrystal grains 4b is represented by the average of the particle sizes of the nanocrystal grains contained in a certain region of the titanium alloy phase.

The composite 4 preferably has a volume content of the ceramic nanocrystal grains 4b of 5 to 40%. When the volume content of the nanocrystal grains 4b of the ceramics is less than 5%, the effect of suppressing the crack growth in the titanium alloy tends to decrease. Are agglomerated, and this portion serves as a starting point of destruction, and the mechanical properties tend to decrease. From such a viewpoint, it is more desirable that the composite 4 has a volume content of the nanocrystal grains 4b of the ceramics of 10 to 30%, more preferably 15 to 25%.

The face member 3 has a substantially constant thin thickness, for example, 1.0 to 4.0 mm, more preferably 1.0 to 4.0 mm.
It has a thickness t of about 2.8 mm, more preferably 1.0 to 2.5 mm, and is formed in a plate shape constituting a main part of the face portion F while reducing the thickness. in this way,
Since the face member 3 of the present embodiment is made of the composite 4 and has high strength, the face strength is maintained even when the face portion F is thinner than usual, and the face portion F is effectively bent while reducing the weight. Can be. Therefore, fatigue resistance can be improved while increasing the flight distance of the hit ball. The face member 3
When the thickness t is less than 1.0 mm, the strength of the face portion F cannot be secured, and there is a risk of breakage. On the other hand, when the thickness t exceeds 4.0 mm, the strength and fatigue resistance of the face portion F can be secured. In addition, the rebound characteristics with the ball are reduced, and the effect of increasing the flight distance of the hit ball is likely to be reduced.

The face member 3 is provided on the head main body 2.
And is firmly joined to the head main body 2 by a fixing means such as adhesion, caulking, welding or the like. The face member 3 forms at least a part of the face portion F for hitting a ball, in this example, substantially the entire area of the face portion F. In particular, when the face member 3 is formed of the composite 4, the ratio (S1 / S2) of the surface area S1 of the composite 4 to the total surface area S2 of the face F is 0.5.
It is preferably set to 0 or more, more preferably 0.70 or more, and further preferably 0.90 or more. Thereby, the composite body 4 can be arranged on the face portion F over a wide range, and both improvement in fatigue resistance and increase in flight distance are more preferably achieved.

As a method of forming the composite 4, for example, a ceramic alloy nanocrystal powder is added to a titanium alloy having a predetermined composition, and an ingot of the composite is produced by arc melting. It can be performed by processing into a predetermined shape. In the present embodiment, the ingot is cold-rolled by a cold rolling mill to produce a thin plate, and the thin plate is subjected to, for example, punching to form the face member 3.
The face member 3 is welded to the head body 2 to manufacture the golf club head 1. The ingot of the composite 4 can also be manufactured by a suspension dissolution method.

The composite 4 has a cross-sectional reduction rate of 10%.
Or more, more preferably 30% or more, still more preferably 5% or more.
It is preferable that the face member 3 is processed while being cold-worked such as rolling or elongation of 0% or more, particularly preferably 70% or more, and hardened. Thereby, the face member 3 is preferable in that the tensile strength can be further improved by work hardening while maintaining a low Young's modulus.
The cold working may include various things such as forging, extrusion, and deep drawing, in addition to rolling and stretching. In principle, the sectional reduction rate is 1- (A1) where A1 is a sectional area perpendicular to the longitudinal direction before processing and A2 is the same sectional area after processing.
/ A2), but the width hardly changes during rolling, so that the width is determined by the thickness reduction rate for convenience.

The fine powder ceramics can be appropriately manufactured by a known method, and the manufacturing method is not limited. For example, fine powder ceramics can be produced by evaporating the raw material metal in a noble gas atmosphere and performing a nitriding, carbonizing, or boring treatment during or after this evaporation step. The composite 4 only needs to be a composite of the titanium alloy 4a and the ceramic nanocrystal grains 4b, and it does not matter how the composite 4 is manufactured.

In the above embodiment, a wood type golf club head has been described as an example.
Is applicable to an iron type golf club head 1 as shown in FIGS. 6A and 6B, for example. The head 1 of these examples also includes a head body 2 and a face member 3 disposed on the front surface of the head body 2 and made of the composite 4. The head body 2
Holds the periphery of the face member 3 in this example,
The substantial back surface of the face member 3 is not supported. In such an iron-type head 1 and the wood-type head 1 of the embodiment, when the back surface of the face member 3 is substantially empty, the strength of the face member 3 is particularly required. Therefore, the effect when the present invention is applied is further enhanced.

When the back surface of the face member 3 is substantially vacant, a low Young's modulus and a thinner wall due to the excellent properties of the titanium alloy provide excellent resilience and durability. Are compatible. The present invention can be applied not only to a wood type and an iron type but also to a putter type and a utility type head.

[0034]

EXAMPLE A face member having the basic structure shown in FIGS. 1 and 2 was trial-produced using a titanium alloy shown in Table 2 and a composite using nanocrystal grains of ceramics, respectively. Ti-6Al-4
A wood type golf club head was manufactured by welding to a V) head. The face member is formed by arc melting a titanium alloy (both Ti ₅₀ Zr ₃₀ Nb ₁₀ Ta ₁₀ ) and a ceramic nanocrystal powder to form a composite ingot, which is formed into a cold ingot having a cross-sectional reduction rate of 70%. It was manufactured by rolling into a thin plate and punching.

The same shaft was fixed to each of the test heads to produce a wood type golf club as a trial, and each club was mounted on a swing robot manufactured by True Temper, and the head speed was set to 54 (m / s). ), And a durability test was conducted in which the golf ball was hit 5000 times.
After hitting 5000 balls, the face member was not damaged at all, を: fine cracks were seen, Δ: the face portion was broken by less than 5,000 hits, and × was evaluated. Further, for comparison, a wood-type golf club using a face member made of only a titanium alloy that is not composited with ceramic nanocrystal grains (Comparative Examples 1 and 2)
A similar test was also performed for. Table 2 shows the specifications and test results of the composite.

[0036]

[Table 2]

As shown in Table 1, no damage to the face was observed in the durability test in any of the examples, but the nanocrystal grains of the ceramics had a small particle size and the addition amount was small. Example 2, Example 3 in which the addition amount of ceramic nanocrystals is slightly larger, Example 6 and Example 14 in which the addition amount of ceramic nanocrystals is slightly smaller, Example 10 in which the particle size of ceramic nanocrystals is slightly larger In Example 14 and the like, small cracks were generated although they were not damaged. However, in view of the head speed at which the test was performed, the head in which these cracks occurred had sufficient practical durability.

[0038]

As described above, in the golf club head of the present invention, at least a part of the face portion for hitting the ball is formed by a composite of a titanium alloy and ceramic nanocrystal grains. The nanocrystalline grains of the ceramics exhibit a pinning effect of preventing the growth of cracks due to fatigue generated in the metal crystal phase, and can greatly improve the fatigue resistance of the titanium alloy. Thus, it is possible to provide a golf club head that launches a ball with high rebound by, for example, thinning the face portion while improving durability.

According to the second aspect of the present invention, by limiting the alloy composition to a certain range, the durability of a titanium alloy having higher strength and a lower Young's modulus can be improved, and the face portion can be made thinner to improve resilience. And durability can be secured at the same time.

According to a third aspect of the present invention, the nano crystal grains have an average particle diameter of 5 to 300 (nm), so that the nano crystal grains can be crystallized stably and cracks in the titanium alloy can be reduced. In addition to ensuring the pinning effect of suppressing the progress, the nanocrystalline grains can be prevented from becoming the starting point of the crack, and the effect of improving the fatigue resistance can be enhanced.

According to a fourth aspect of the present invention, the composite is formed as a plate-shaped face member by performing cold working with a cross-sectional reduction rate of 10% or more. While maintaining the ratio, the tensile strength can be further improved by work hardening.

According to the fifth aspect of the present invention, the strength and fatigue resistance of the face portion are improved by setting the thickness of the composite forming the face portion to 1.0 to 4.0 mm. , And a decrease in resilience characteristics with the ball can be prevented.

[Brief description of the drawings]

FIG. 1 is a front view illustrating a golf club head according to an embodiment.

FIG. 2 is a sectional view thereof.

FIG. 3 is an enlarged view showing a microstructure of a composite.

FIG. 4 is a graph showing a relationship between tensile stress and elongation of a titanium alloy or the like.

FIG. 5 is a graph showing a relationship between tensile strength and Young's modulus of a titanium alloy or the like.

FIG. 6 (A) is a front view showing an embodiment of an iron type golf club head, and FIG. 6 (B) is an XX end view thereof.

[Description of Signs] 1 golf club head 2 head body 3 face member 4 composite 4a titanium alloy 4b nanocrystal grains of ceramic F face

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hisashi Kakiuchi 3-6-9, Wakihama-cho, Chuo-ku, Kobe City, Hyogo Prefecture Within Sumitomo Rubber Industries, Ltd. (72) Inventor Akihisa Inoue No. 35 Kawauchi House 11-806 F term (reference) 2C002 AA02 AA03 CH01 MM04 MM06 MM07 PP02

Claims (5)

[Claims] 1. A golf club head wherein at least a part of a face portion for hitting a ball is formed of a composite material comprising a base material made of a titanium alloy and nanocrystalline grains of ceramics as a dispersing material. 2. The nanocrystalline grains are made of one or more of carbides, nitrides, or borides of a metal element belonging to Group 4 of the periodic table, and the titanium alloy is represented by the following composition formula. The golf club head according to claim 1, wherein: 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). 3. The nanocrystalline grains have an average particle size of 5 to 30.
The golf club head according to claim 1, wherein the golf club head is 0 (nm). 4. The composite according to claim 1, wherein the composite is formed as a plate-shaped face member by performing cold working with a cross-sectional reduction rate of 10% or more. Golf club head. 5. The golf club according to claim 1, wherein the thickness of the composite forming the face portion is 1.0 to 4.0 mm. head.