Golf club and production method thereof

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Technical field to which the invention belongs]

The present invention relates to a golf club and a method for manufacturing the golf club, and in particular, a structure of a metal golf club head in which the average crystal grain size on the back surface side of the face center is smaller than the average crystal grain size on the front surface side of the face center and the golf. Regarding the manufacturing method of the club head.

【0002】

[Conventional technology]

Conventionally, various methods for manufacturing a head portion of a golf club have been known. Casting is one of the methods for manufacturing the head portion. In this manufacturing method, a head material is melted at a high temperature, and the molten metal is cast into a shell formed by melting wax to form a golf club head.

【0003】

There is also a method of manufacturing the face portion of the head portion of the golf club from a plate material. In this method, for example, a head component such as a crown portion and a sole portion other than the face portion is molded by the above casting method. On the other hand, the plate material is die-cut to form a face portion. Then, a golf club head is manufactured by joining the head component portion and the face portion.

【0004】

There is also a method of forging the face portion of the head portion of the golf club. In this method, for example, a round bar is forged to form a face material, the head component portion and the face material are joined, and further heat treatment is performed to increase the strength of the head portion.

【0005】

[Problems to be Solved by the Invention]

However, since a large number of voids are present in the face portion formed by casting, not only the strength of the face portion is lowered, but also the variation in strength is large. Therefore, the face portion is liable to be damaged by the impact force generated at the time of hitting the ball, and it is necessary to increase the wall thickness of the face portion in order to avoid such damage to the face portion.

【0006】

If the wall thickness of the face portion is increased, the weight of the portion other than the face portion must be reduced, and a large head portion cannot be manufactured. In addition, when the wall thickness of the face portion is increased, the face portion is less likely to bend, the repulsive performance of the head portion is lowered, and the flight distance of the ball is also lowered.

【0007】

When the face portion is produced using the plate material, the plate material is generally rolled by a roll machine, so that the crystal grains of the plate material are relatively uniform and small. Since the strength of the plate material depends on the size of the crystal grains, the strength of the face portion corresponds to the strength of the plate material after rolling, and is relatively high.

【0008】

However, the strength of the plate material after rolling has anisotropy that it is high in the rolling direction and low in the direction perpendicular to the rolling direction. Since the strength of the face portion is affected by the low strength in the vertical direction, it is difficult to thin the face portion. Therefore, it is difficult to improve the repulsive performance of the head portion, and it is also difficult to manufacture a large head portion.

【0009】

When the face part is manufactured by round bar forging, it is possible to reduce the crystal grains of the face part, but in normal forging, the block material made of round bar or square bar is processed into a flat face shape, so the face The amount of plastic deformation in the central portion is large, and the crystal grains in the central portion of the face are finer than those in the peripheral portion of the face. Therefore, the strength of the face portion is highest in the central portion and low in the peripheral portion. Further, during forging, the portion close to the surface of the material is in contact with the die, so that plastic deformation is small, and as shown in FIG. 7, the crystal grains become finer and the strength increases toward the inside.

【0010】

However, as shown in FIG. 8, when the ball 10 hits the center portion of the face portion 2 at the time of hitting the ball, the center portion bends to the rear side. Tensile stresses are applied, and these stresses decrease from the front surface or the back surface of the face portion 2 toward the inside.

【0011】

Therefore, in the face produced by forging, the portion to which stress is applied is weak, and the portion to which stress is not applied becomes strong. Therefore, it is difficult to make the face thin, and it is difficult to improve the repulsive performance of the head or to increase the size of the head.

【0012】

The present invention has been made to solve the above problems. An object of the present invention is to provide a golf club having excellent resilience performance and having a large head portion, and a method for manufacturing the golf club.

【0013】

[Means for solving problems]

In one aspect, the golf club according to the present invention includes a metal head portion having a face portion, and the average crystal grain size of the back surface side portion in the center portion of the face portion is the front surface side portion in the center portion of the face portion. Is smaller than the average grain size of. In the specification of the present application, the "average crystal grain size" refers to a 100-fold magnified photograph expressed using a two-dimensional number of crystal grains contained in a square region having a side of 25 mm.

【0014】

Normally, a ball is hit on the surface (ball striking surface) of the center portion of the face portion of the golf club head, and the center portion of the face portion bends to the rear side when the ball is hit. Therefore, as shown by an arrow in FIG. 8, tensile stress acts on the back surface of the center portion of the face portion, and compressive stress acts on the surface of the center portion of the face portion. On the contrary, in the peripheral portion of the center portion of the face portion, tensile stress is generated on the front surface and compressive stress is generated on the back surface. The inventor of the present application investigated the cut cross section of the damaged face portion in order to confirm the relationship between these stresses and the breakage of the face portion. It was found that in most cases, the face portion was damaged. Therefore, it can be said that the damage of the face portion depends on the resistance to the tensile stress of the back surface side portion in the center portion of the face portion. Therefore, it was decided to reduce the average crystal grain size of the back surface side portion in the center portion of the face portion. As a result, the strength of the back surface side portion of the face portion can be improved, and the resistance to tensile stress can be improved.

【0015】

The average crystal grain size on the front surface side in the center portion of the face portion is twice or more and 100 times or less the average crystal grain size on the back surface side, and preferably 10 times or more and 100 times or less the average crystal grain size on the back surface side. Yes, and more preferably, it is 50 times or more and 100 times or less the average crystal grain size on the back surface side.

【0016】

The average crystal grain size on the back surface side in the center portion of the face portion is 0.1 μm or more and less than 50 μm. The average crystal grain size on the back surface side is preferably 0.1 μm or more and 20 μm or less, and more preferably 0.1 μm or more and 10 μm or less.

【0017】

By reducing the average crystal grain size on the back surface side in the center portion of the face portion in this way, the strength of the back surface side portion can be increased, and the resistance to tensile stress can be enhanced.

【0018】

Further, it is preferable that the average crystal grain size on the front surface side in the peripheral portion located around the center portion of the face portion is smaller than the average crystal grain size on the back surface side in the peripheral portion. This is because tensile stress acts on the peripheral portion of the center portion of the face portion, and it is desirable to strengthen that portion.

【0019】

As described above, the center portion of the face portion bends backward when the ball is hit, but at this time, as shown by the arrow in FIG. 8, tensile stress acts on the surface side of the peripheral portion located around the center portion of the face portion. To do. Therefore, by making the average crystal grain size on the front surface side in the peripheral portion of the face portion smaller than the average crystal grain size on the back surface side in the peripheral portion, the strength on the front surface side in the peripheral portion of the face portion can be increased. .. Thereby, the resistance to the tensile stress on the surface side in the peripheral portion of the face portion can be improved.

【0020】

A convex portion may be provided on the back surface side of the center portion of the face portion. In this case, the average crystal grain size of the portion near the surface of the convex portion is made smaller than the average crystal grain size of the surface side in the center portion of the face portion. By providing such a convex portion, the durability of the face portion can be improved, the repulsion characteristic of the face portion can be improved, and the flatness of the surface side of the face portion can be easily ensured. ..

【0021】

In another aspect, the golf club according to the present invention includes a metal head portion having a face portion, and is relative to the cross section of the center portion of the face portion and the cross section of the peripheral portion located around the center portion. There is a first region having a large average crystal grain size and a second region having a relatively small average crystal grain size. Then, in the cross section of the center portion, the first region is located on the front surface side of the center portion, the second region is located on the back surface side of the center portion, and in the cross section of the peripheral portion, the second region is the surface of the peripheral portion. It is located on the side, and the first region is located on the back side of the peripheral part. This second region is a band-shaped region, and preferably extends continuously from the back surface side of the center portion toward the front surface side of the peripheral portion. Further, when the convex portion is provided on the back surface side of the center portion, it is preferable that the second region extends within the convex portion.

【0022】

The method for manufacturing a golf club according to the present invention includes a step of plastically deforming a metal material into a plate shape by forging so that the plastic flow on the back surface side of the center portion is larger than the plastic flow on the front surface side of the center portion, and the forging. A step of forming the metal material into the shape of the face portion in the head portion of the golf club by subjecting the subsequent metal material to mechanical processing or plastic processing is provided.

【0023】

By making the plastic flow on the back surface side of the center portion of the metal material larger than the plastic flow on the front surface side in this way, the average crystal grain size on the back surface side of the center portion of the metal material can be adjusted to the front surface side of the center portion of the metal material. It can be smaller than the average crystal grain size in. By performing machining such as cutting or plastic working such as forging, sheet metal, bending, and pressing on this metal material, the average crystal grain size on the back surface side of the center portion becomes the average crystal grain size on the front surface side of the center portion. A smaller face portion of a golf club head can be made.

【0024】

The forging step includes a step of suppressing plastic flow on the surface side of the center portion of the metal material by plastically deforming the metal material so as to form a convex portion on the surface side of the center portion of the metal material.

【0025】

By plastically deforming the metal material so as to form a convex portion on the surface side of the center portion of the metal material as described above, it is possible to suppress the plastic flow on the surface side of the center portion. At this time, since there is no element that positively suppresses the plastic flow on the back surface side of the metal material, the metal material flows freely. Therefore, the plastic flow on the back surface side of the center portion of the metal material can be promoted as a result, and the average crystal grain size on the back surface side of the center portion of the metal material is larger than the average crystal grain size on the front surface side of the center portion. Can also be made smaller.

【0026】

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described. The present invention improves the strength of the back surface side portion of the face center by reducing the average crystal grain size of the back surface (the surface opposite to the ball striking surface) side portion of the face center of the metal golf club head, thereby improving the face. The part is made thinner to improve the resilience performance of the head, and the head is made larger (for example, 300 cm).³~ 500cm³) Is what you are trying to do.

【0027】

If the golf club, even a wood-type even in the iron type the present invention is applicable is possible for. FIG. 1 is a perspective view of a head portion 1 in a wood-type golf club to which the present invention is applied. As the shape of the shaft and the grip of the golf club, well-known shapes that have been generally used in the past can be used, and thus the illustration thereof will be omitted.

【0028】

The head portion 1 has a metal hollow outer shell structure, and as shown in FIG. 1, has a face portion 2, a toe portion 3, a crown portion 4, a heel portion 5, and a sole portion 6.

【0029】

FIG. 2 shows the cross-sectional structure of the face portion 2 along the line II-II in FIG. Note that FIG. 2 schematically shows a first region 7a having a relatively large average crystal grain size and a second region 7b having a relatively small average crystal grain size in the cross section of the face portion 2.

【0030】

In FIG. 2, the surface located on the upper side of the face portion 2 is the ball striking surface, and the surface located on the lower side of the face portion 2 and facing the internal space of the head portion 1 is the back surface. When a ball is hit on the surface of the center portion 2a of the face portion 2, the center portion 2a of the face portion 2 bends to the rear side (lower side in FIG. 2). As a result, tensile stress acts on the back surface of the center portion 2a of the face portion 2, and compressive stress acts on the surface of the center portion 2a of the face portion 2.

【0031】

As described above, the damage of the face portion 2 at the center portion 2a largely depends on whether or not it is resistant to the tensile stress of the back surface of the center portion 2a of the face portion 2, and therefore the center portion 2a of the face portion 2 It is necessary to increase the strength of the back surface side in.

【0032】

In a metal member, the strength can be increased by reducing the average crystal grain size. Therefore, in order to increase the strength of the back surface side of the face portion 2, the average of the back surface side portions of the center portion 2a of the face portion 2 is increased. The crystal grain size may be reduced.

【0033】

At this time, the average crystal grain size may be uniformly reduced over the entire face portion 2, but in the present embodiment, the average crystal grain size on the back surface side of the center portion 2a of the face portion 2 is selectively reduced. There is.

【0034】

More specifically, as shown in FIG. 2, the second region having a relatively small average crystal grain size is left in the cross section of the center portion 2a of the face portion 2 while the first region 7a having a relatively large average crystal grain size is left. 7b is provided, the first region 7a is arranged on the front surface side of the center portion 2a of the face portion 2, and the second region 7b is arranged on the back surface side of the center portion 2a of the face portion 2.

【0035】

As a result, the average crystal grain size on the back surface side of the center portion 2a of the face portion 2 can be reduced, and the strength on the back surface side of the face center on which tensile stress acts at the time of hitting the ball can be increased. As a result, the resistance to tensile stress on the back surface side of the face center can be improved, and damage to the face portion 2 can be suppressed.

【0036】

On the other hand, in the example shown in FIG. 2, the first region 7a and the second region 7b are also present in the cross section of the peripheral portion 2b located around the center portion 2a, respectively. In the peripheral portion 2b of the face portion 2, the second region 7b may be located on the front surface side of the peripheral portion 2b, and the first region 7a may be located on the back surface side of the peripheral portion 2b.

【0037】

The second region 7b is a strip-shaped region in the example shown in FIG. 2, and extends continuously from the back surface side of the center portion 2a of the face portion 2 toward the front surface side of the peripheral portion 2b.

【0038】

Next, the average crystal grain size of the face portion 2 according to the present invention will be described in more detail.

【0039】

The average crystal grain size of the front surface side portion of the center portion 2a of the face portion 2 is about 2 to 3 times or more and 100 times or less of the average crystal grain size of the back surface side portion, and preferably the average crystal grain size of the back surface side portion. It is 10 to 20 times or more and 100 times or less, and more preferably 30 to 50 times or more and 100 times or less the average crystal grain size of the back surface side portion.

【0040】

By setting the average crystal grain size of the front surface side portion and the average crystal grain size of the back surface side portion so as to satisfy the above relationship, the strength of the back surface side of the center portion 2a of the face portion 2 can be increased.

【0041】

The average crystal grain size of the back surface side portion of the center portion 2a of the face portion 2 is 0.1 μm or more and less than 50 μm, preferably 0.1 μm or more and 20 μm or less, and more preferably 0.1 μm or more and 10 μm or less. .. By reducing the average crystal grain size of the back surface side portion of the center portion 2a of the face portion 2 in this way, the strength of the back surface side can be effectively increased.

【0042】

Next, a modified example of the cross-sectional structure of the face portion 2 shown in FIG. 2 will be described with reference to FIG.

【0043】

As shown in FIG. 6, a convex portion 11 may be provided on the back surface side of the center portion 2a of the face portion 2. In this case, the second region 7b extends in the convex portion 11, and the average crystal grain size of the portion near the surface of the convex portion 11 is smaller than the average crystal grain size on the surface side of the center portion 2a of the face portion 2. Become.

【0044】

By providing the convex portion 11 on the back surface side of the center portion 2a of the face portion 2 as described above, the thickness of the center portion 2a of the face portion 2 can be increased and the second region 7b can be extended in the convex portion 11. Can be done. As a result, the durability of the face portion 2 can be improved and the repulsive characteristics of the face portion 2 can also be improved. Further, when the face portion 2 is formed, the plastic flow of the metal material on the back surface side of the center portion 2a of the face portion 2 can be promoted, and by forming the convex portion 11, the average of the portions near the surface of the convex portion 11 is formed. The flatness on the surface side of the face portion 2 can be easily ensured while the crystal grain size is made smaller.

【0045】

Next, a method for manufacturing a golf club according to the present invention will be described with reference to FIGS. 4 and 5. 4 and 5 are cross-sectional views showing a characteristic manufacturing process in the method for manufacturing a golf club according to the present invention.

【0046】

First, a β-titanium (15V-6Cr-4AL) round bar (metal material) having a diameter of 21 mm and a length of 140 mm is prepared, and the round bar and the mold are heated to a predetermined temperature. After that, the round bar is installed in the die and roughly forged into a plate shape by a 1600t press. As a result, the round bar is plastically deformed into a plate shape to obtain the metal material 8 having the shape shown in FIG.

【0047】

At this time, as shown in FIG. 4, the metal material 8 is plastically deformed so as to form a convex portion 9 on the surface side of the center portion 8a of the metal material 8. As a result, the plastic flow of the metal material 8 on the back surface side of the center portion 8a can be made larger than the plastic flow of the metal material 8 on the front surface side of the center portion 8a.

【0048】

This is because the mold suppresses the plastic flow of the metal material 8 on the front surface side of the center portion 8a of the metal material 8, but the element that substantially suppresses the plastic flow of the metal material 8 on the back surface side of the metal material 8 is. This is because the metal material 8 freely flows because it does not exist.

【0049】

As described above, by making the plastic flow on the back surface side of the center portion 8a of the metal material 8 larger than the plastic flow on the front surface side of the center portion 8a, the strain during forging on the back surface side becomes large, and the center of the metal material 8 is centered. The average crystal grain size on the back surface side portion of the portion 8a can be made smaller than the average crystal grain size on the front surface side portion of the center portion 8a. In the peripheral portion 8b of the metal material 8, the metal material 8 flows in the same manner as on the back surface side of the metal material 8.

【0050】

Next, the forged product shown in FIG. 4 is machined. Specifically, for example, the convex portion 9 is removed by cutting, or the metal material 8 is further forged to flatten the convex portion 9. As a result, as shown in FIG. 5, the metal material 8 can be formed into the shape of the face portion 2 in the head portion 1 of the golf club.

【0051】

As described above, the crystals on the back surface side of the center portion 8a of the metal material 8 can be refined by one forging. Therefore, the crystals on the back surface side can be further refined by performing heat treatment such as solution treatment or aging treatment. Can be transformed into.

【0052】

In order to obtain the structure shown in FIG. 2, further forging may be performed so as to push the convex portion 9 shown in FIG. 4 into the metal material 8. Further, in order to obtain the structure shown in FIG. 6, a concave portion corresponding to the above-mentioned convex portion 11 is provided in a mold for forming the back surface side of the metal material 8, and the metal material having the form shown in FIG. 4 is used. 8 can be further forged.

【0053】

The inventor of the present application has actually produced the face portion 2 by the method of the present invention and confirmed the metal structure of the cross section thereof, and the results will be described.

【0054】

FIGS. 3 (a) to 3 (c) show the metallographic structure of each part in the thickness direction of the cross section of the face part 2. FIG. 3A shows the metal structure of the cross section of the face portion 2 on the surface side of the center portion 2a, and FIG. 3B shows the metal of the cross section located at the center portion of the center portion 2a of the face portion 2 in the thickness direction. The structure is shown, and FIG. 3 (c) shows the metal structure of the cross section on the back surface side of the center part 2a of the face part 2.

【0055】

As shown in FIGS. 3 (a) to 3 (c), it can be seen that the crystal grains on the back surface side of the center portion 2a of the face portion 2 are much finer than the crystal grains on the front surface side. At this time, the Vickers hardness on the front surface of the center portion 2a of the face portion 2 was Hv380, and the Vickers hardness on the back surface of the center portion 2a of the face portion 2 was Hv300.

【0056】

While the face portion 2 of the golf club head is manufactured as described above, the head constituent portions such as the crown portion 4 and the sole portion 6 other than the face portion 2 are formed by casting or the like. Then, the head portion 1 of the golf club can be manufactured by joining the head component portion and the face portion 2 by welding or the like. After that, the head portion 1 is joined to the grip and the shaft to complete the golf club.

【0057】

The inventor of the present application compared the durability strength between the head portion (product of the present invention) 1 having the face material of the present invention and the head portion (conventional product) 1 having a normal face material. Shown. In the durability strength test this time, the number of hits was examined until the face portion 2 was damaged by hitting the ball at a head speed of 38 m / s. The conventional product uses a head part made of 15V-6Cr-4AL titanium material with a face thickness of 2.9 mm, and the product of the present invention uses a head part made of 15V-6Cr-4AL titanium material with a face thickness of 2.9 mm. used.

【0058】

[table 1]

<img file="JP2003144591A_D0001.tif" />【0059】

As shown in Table 1, in the conventional product, the face portion 2 was damaged by hitting 3000 times, whereas in the product of the present invention, the face portion 2 was damaged by hitting 5000 times. Therefore, according to the present invention, it has become possible to significantly improve the durability strength of the face portion 2.

【0060】

Since the durability strength can be increased in this way, the thickness of the face portion 2 can be reduced. As a result, the face portion 2 can be easily bent, and the coefficient of restitution can be improved. In addition, the head portion 1 can be enlarged.

【0061】

In the above-described embodiment, in order to increase the plastic flow on the back surface side of the center portion of the metal material 8 and miniaturize the crystal, the convex portion 9 shown in FIG. 4 is on the front surface side of the center portion of the metal material 8. However, other methods may be used to increase the plastic flow on the back surface side of the center portion of the metal material 8. Further, as the material of the face portion 2, iron, stainless steel, aluminum, magnesium-copper alloy, etc. other than titanium can be adopted.

【0062】

Although the embodiments of the present invention have been described above, it should be considered that the embodiments disclosed this time are examples in all respects and are not restrictive. The scope of the present invention is indicated by the scope of claims, and includes all modifications within the meaning and scope equivalent to the scope of claims.

【0063】

[Effect of the invention]

According to the present invention, since the strength of the back surface side of the face portion can be improved, the resistance to the tensile stress on the back surface side can be improved. As a result, the face portion can be thinned, and the head portion can be enlarged while improving the repulsion performance of the head portion.

[Simple explanation of drawings]

[Figure 1]

It is a perspective view of the head part of the golf club to which this invention is applied.

[Figure 2]

It is an enlarged cross-sectional view along the line II-II in FIG.

[Fig. 3]

(a) is a diagram showing the metal structure of the cross section on the surface side of the face center, (b) is a diagram showing the metal structure of the cross section located at the center in the thickness direction of the face center, and (c) is a diagram showing the metal structure of the cross section located at the center in the thickness direction of the face center. It is a figure which shows the metal structure of the cross section on the back surface side of.

[Fig. 4]

It is sectional drawing which shows the characteristic 1st process in the manufacturing process of the golf club which concerns on this invention.

[Fig. 5]

It is sectional drawing which shows the characteristic 2nd process in the manufacturing process of the golf club which concerns on this invention.

[Fig. 6]

It is sectional drawing which shows the modification of the face part structure shown in FIG.

[Fig. 7]

(a) is a diagram showing the metal structure of the cross section of the face center on the surface side of the conventional face formed by forging, and (b) is the central portion in the thickness direction of the face center in the conventional face formed by forging. It is a figure which shows the metal structure of the cross section which is located, (c) is the figure which shows the metal structure of the cross section on the back surface side of the face center in the conventional face formed by forging.

[Fig. 8]

It is a schematic diagram which shows the state which the face part is deformed at the time of hitting a ball, and the tensile stress or the compressive stress is generated in the face part by it.

[Explanation of symbols]

1 head part, 2 face part, 2a, 8a center part, 2b, 8b peripheral part, 3 toe part, 4 crown part, 5 heel part, 6 sole part, 7a 1st area, 7b 2nd area, 8 metal material, 9,11 Convex, 10 balls.