JPH03267077A - Manufacture of golf club - Google Patents

Abstract

PURPOSE:To provide a golf club excellent in a stable ball following property in driving the ball, strength and fatigue property by adjusting a hosel bending angle of the golf club made of an alloy having thermoelastic type martensite transformation within a specified temperature range, thereby correcting a lie angle and loft angle. CONSTITUTION:A golf club H made of 500mum or less of average grain diameter of an alloy generating thermoelastic type martensite transformation is manufactured by hot forging for example. A coupling section of a head body and hosel 1 is heated at 300-1200 deg.C and the hosel 1 is bent under the condition of lowered hardness to correct a lie angle and loft angle, Thus, the lie angle and loft angle of the golf club head can be corrected without generating crack and wrinkles.

Description

[Detailed Description of the Invention] "Industrial Application Field" The present invention relates to a method for manufacturing a golf club head using an alloy that undergoes thermoelastic martensitic transformation, and utilizes hot forging in a specific temperature range. By doing so, it has excellent elongation and fracture stress resistance, good fatigue properties, and allows for correction of lie angle and loft angle without causing cracks or wrinkles.

``Prior Art'' Conventionally, a patent application has been filed in Japanese Patent Laid-Open No. 59-222172 for the use of an alloy that produces thermoelastic martensite with excellent elongation and fracture stress resistance for golf club heads.

In this patent application, Cu-Z n-based, Cu-A
Technology for manufacturing golf club heads by casting using alloys that produce thermoelastic martensitic transformation, such as I-based, Cu-3b-based, Cu-8i-based, Ni-Zn-based, and NiTl%NiA1 alloys. has been disclosed.

Therefore, when an iron-type golf club head is manufactured using an alloy that undergoes the thermoelastic martensitic transformation, the following three methods can be considered as possible manufacturing methods.

■Machining method A method in which a block is made from an alloy that produces thermoelastic martensite, and this block is machined by cutting or grinding to form a golf club head shape. ■Casting method A method of manufacturing by preparing a molten metal of an alloy that undergoes thermoelastic martensitic transformation and casting this molten metal into a mold having a molding cavity shaped like a golf club head.

■Powder metallurgy method A method of preparing a powder of an alloy that undergoes thermoelastic martensitic transformation, placing the powder in a mold, heating it, pressurizing it, and sintering it to manufacture a golf club head in the desired shape.

"Problem to be Solved by the Invention" However, the machining method described in (2) has problems in that the processing cost is too high and the mass productivity is low. Moreover, when cutting a golf club head from a block of an alloy that undergoes thermoelastic martensitic transformation, the crystal structure of the alloy block is oriented in random directions, resulting in differences in the orientation of the crystal structure for each product. Therefore, the deformation state of the golf club head when hitting a ball differs depending on the product, and there is a problem that stable ball tracking performance cannot be obtained.

In addition, the casting method described in (2) tends to cause segregation during casting, and some columnar crystals are generated, so the crystal grain size distribution tends to be uneven, which may cause problems in strength and fatigue properties.

Also, depending on the conditions during casting, a columnar structure may develop, but the direction in which this columnar structure develops depends on the shape of the mold and the cooling conditions of the molten metal, and is usually perpendicular to the face of the golf club. In addition, the direction of the golf club head is often uneven, so the deformation state of the golf club head when hitting the ball differs depending on the product.
Golf club heads obtained by the casting method have a problem in that sufficiently stable ball tracking performance cannot be obtained.

Furthermore, in golf clubs, the angle of the hosel is usually adjusted to adjust the lie angle and loft angle to suit the user's preference or to correct manufacturing defects. There is.

However, the crystal grain size of golf club heads obtained by casting using alloys that undergo thermoelastic martensitic transformation is relatively large, ranging from 0.5 to 5 mm, making it difficult to correct the bending angle of the hosel. When force is applied, bending stress concentrates on the grain boundaries at the joint between the hosel and the head body, causing cracks and wrinkles to form in the joint, whether cold or hot working. There was a problem with the product being defective.

In the powder metallurgy method described in (2), although the composition becomes uniform, defects such as bores are likely to be introduced, and strength and fatigue properties may still be problematic. Moreover, golf club heads obtained by powder metallurgy have a granular structure in which fine particles are bonded together, and many fine voids exist in the grain boundaries in a disorderly manner. This causes a problem in that the state changes, making it impossible to obtain a golf club with stable ball tracking performance.

The present invention has been made to solve the above problems,
In addition to being able to demonstrate stable ball tracking when hitting the ball,
To provide golf clubs with excellent strength and fatigue characteristics,
A further object of the present invention is to provide a method for manufacturing a golf club that allows the lie angle and loft angle to be easily corrected.

"Means for Solving the Problems" In order to solve the problems described above, the present invention has a head main body and a hosel integrally formed of a superelastic alloy, and the average crystal grain size of the alloy that causes thermoelastic martensitic transformation is reduced. 500μ
A method for manufacturing a golf club made of less than 300 m
The hosel is bent in a temperature range of ~1200°C to adjust the bending angle of the hosel and correct the lie angle and loft angle.

1 action' 300 to 1 alloy that causes thermoelastic martensitic transformation
Since the head body is manufactured by forging at 200° C., the head body is manufactured in a state where the hardness of the alloy that causes thermoelastic martensitic transformation is low, making it easy to process.

Furthermore, by heating the hosel at 300 to 1200°C and bending it, the angle of the hosel can be adjusted without causing cracks or wrinkles while the alloy that undergoes thermoelastic martensitic transformation has a lower hardness and is easier to work with. The lie angle and loft angle can be corrected.

Since at least the face portion of the head body is made of an alloy that undergoes thermoelastic martensitic transformation,
Excellent superelastic properties and fatigue properties.

In the resulting head body, the fibrous structure of the alloy that undergoes thermoelastic martensitic transformation is oriented approximately parallel to the face surface, so the face deforms uniformly around the hitting point, preventing the ball from flying. Therefore, it is possible to obtain a golf club that has excellent tracking ability to the ball and is easy to control when hitting the ball.

The present invention will be explained in more detail below.

FIGS. 1 and 2 show an example of an iron-type golf club head manufactured by implementing the present invention. In the golf club head H of this example, the entire head undergoes thermoelastic martensitic transformation. Composed of alloy.

In this golf club head I4, l is a hosel,
2 is the heel, 3 is the face surface, 4 is the toe,
5 each indicates a sole.

When stress is applied to an alloy that undergoes thermoelastic martensitic transformation in a temperature range equal to or higher than its (martensitic) reverse transformation temperature, stress is induced in the martensitic phase in the matrix as the strain increases. When the stress is then unloaded, the induced martensitic phase transforms back into the parent phase as the strain decreases, and the shape recovers, exhibiting a so-called superelastic effect.

In other words, the superelastic effect means that even if stress exceeding the elastic limit is applied to an alloy that undergoes thermoelastic martensitic transformation and the composition is deformed, as soon as the stress is unloaded, the plastic strain is resolved.
This is the effect of returning to the original shape.

The amount of strain that can be restored by an alloy that undergoes thermoelastic martensitic transformation is extremely larger (about I order of magnitude) than that of ordinary spring materials.

To further explain about alloys that undergo thermoelastic martensitic transformation, there is a relationship between stress and strain acting on this alloy that shows a hysterinosloop as shown in Figure 3. Points indicate hyperelastic elongation. On the other hand, in the relationship between stress and strain for a general metal material 1s+, as shown in Figure 4, point E indicates elastic elongation, point B indicates plastic elongation, and these values are thermoelastic. This is much smaller than the superelastic elongation of alloys that undergo martensitic transformation.

That is, superelastic elongation refers to elongation that can be recovered when stress is applied to an alloy that undergoes thermoelastic martensitic transformation and the alloy is strained to the elongation of general metal materials, for example, about 0.5% or more. Therefore, a material with excellent superelastic properties is a material with large superelastic elongation.

Today, as alloys that cause thermoelastic martensitic transformation, β-phase alloys of various prefectures such as Cu-based, Ni-based, and Ag-based, or the compounds NiTi, NiAl, and the like are known. Here, specifically, Cu-Z n-based 4
．． 5% Z n-Cu or 4% A126% Zn-Cu
, Cu-Al based 12.5 Al-Cu or 403
%Ni-13, 4%A1-cu, Cu-6b type 3
6%5b-Cu, 68%S + Cu of Cu-9i system
66% of the sN i-Z n system Z n-N i,,N i
-T n-based 55-57% Ni-Ti, 63.51%
Examples include Ni-A1.

Next, a method for manufacturing the golf club head I will be described.

In order to manufacture the golf club head 11 using the alloy that causes thermoelastic martensitic transformation, a round bar 7 made of an alloy ingot that causes thermoelastic martensitic transformation as shown in FIG. 5 is prepared. Note that the alloy ingot used here may have a shape other than a round bar, such as a prismatic shape or a block shape. Further, this alloy ingot may be manufactured by any method such as a forging method, a casting method, or a powder metallurgy method. Also, what is its organization and condition?6.

Next, this round bar 7 is hot-forged at 300-1200[deg.]C, preferably 400-1200[deg.]C, and processed into the shape of a golf club head H as shown in FIG.

When this hot forging is performed, a die of a forging device is struck in the radial direction of the round bar 7 shown in FIG. 5 to deform it as shown in FIG. 6 to manufacture a golf club head. That is, round bar 7
The other end of the round bar 7 forms a golf club head toe I so that one end forms the toe 4 side of the golf club head 11.
Forging is performed to form a face portion at the center of the round bar 7 so as to form the hosel 1 side of the round bar 7.

By performing the forging process as described above, the fibrous structure of the alloy that undergoes thermoelastic martensitic transformation can be oriented substantially parallel to the face surface 3 of the face portion. The reason for this is that when forging, the metal structure of the round bar 7 is
This is because the alloy is deformed in the direction shown by the arrow in the figure, and the metal structure of the alloy is aligned in a fibrous shape along this deformation.

Furthermore, when manufacturing the golf club head I-1 by forging, the thickness of the part including the face surface 3 may be the same as the thickness of other parts (for example, the thickness of the toe 4 side and the thickness of the heel 2 side). It is preferable to process it so that it becomes thinner in comparison.

By forging in this way, the forging ratio of the face portion including the face surface 3 can be made larger than the forging ratio of other parts, and as a result, the forging ratio of the face portion including the face surface 3 can be made larger than the forging ratio of other parts. The fibrous structure of the alloy that causes thermoelastic martensitic deformation can be oriented substantially in parallel.

By orienting the fibrous structure in this way, when the face surface 3 deforms when hitting a ball, the face surface 3 deforms uniformly on the left and right sides around the ball hitting point, improving the ball tracking ability of the face surface 3. ”

In addition, in the fibrous structure (fibrous crystal), the particle size (fiber diameter) is preferably 500 μm or less, and 50 μm or less.
m or less is more preferable. To adjust the grain size, the forging ratio by die forging may be adjusted. By increasing the forging ratio by die forging to create crystals with small grain size, the recrystallization temperature (approximately 800℃
) The grain size can also be adjusted by growing crystals by heat treatment at a temperature above.

In addition, the aspect ratio of the fibrous structure (the length of the fibrous crystal (
ρ)/diameter (d)) is preferably 3 or more, more preferably IO or more.

Furthermore, the angle α between the fibrous structure and the face surface 3 is 0.
The range of ≦α≦306 is preferable, and it is effective if about 40% or more of the total length a of the fibrous tissue falls within the range indicated by α. Therefore, when we say that the fibrous structures are approximately parallel to the face surface 3, we mean that the entire fibrous structures are completely parallel to the face surface 3, and approximately 4 of the total length e of each fibrous structure.
0% or more includes cases where the angle with the face surface 3 is 30° or less.

"Manufacturing Example" A golf club head was manufactured using a NiTi alloy round bar by forging the round bar at 600° C. by striking it with a die from the outside in the radial direction as shown in FIG.

FIG. 7 is a schematic diagram of a metal structure photograph taken in a cross section on the side near the toe of the face 3 of this golf club. This shows a state in which crystal grains are connected in a fibrous manner.

In contrast, FIG. 8 is a schematic diagram of a photograph of the metallographic structure in a cross section of a portion of the face near the toe of a conventional golf club head D manufactured by a casting method using stainless steel (17-4PA). . The cross-sectional structure of this golf club head D shows a state in which a large number of irregularly shaped crystal grains are mixed together. Conventional golf club heads made of stainless steel have a large average crystal grain size of about 1 mm and a non-uniform grain size distribution.

On the other hand, in the golf club head H shown in FIG. 7 according to the present invention, a fine fibrous structure with an average crystal grain size of 20 μm is developed substantially parallel to the face surface 3.

From the above, by forging as explained based on FIGS. 5 and 6, the fibrous structure of the alloy metal that causes thermoelastic martensitic transformation approximately parallel to the face surface 3 can be created. It has become clear that orientation can be achieved.

Figure 9 shows an alloy (
The results of measuring hardness changes in a high temperature range of NiTi alloy) are shown below. From the results shown in FIG. 9, it can be seen that the alloy has 4
Hardness begins to decrease from around 00℃, and after 600℃
It was found that the hardness decreased to about /10. Therefore, it has become clear that the temperature when forging the above alloy is preferably 400°C or higher, and most preferably 600°C or higher. Note that the temperature limit during hot forging needs to be below the melting point of the NiTi alloy, so it is 1200°C.
The following settings are required.

Figure 10 shows an alloy (
The results of measuring the elongation of NiTi alloy) in a high temperature range are shown below. From the results shown in FIG. 1O, it was found that heating to 400° C. or higher increases the elongation of the alloy that causes thermoelastic martensitic transformation and improves the workability.

FIG. 1I shows the relationship between the average grain size and superelastic elongation of the NiTi alloy golf club head. According to Figure 11, the average crystal grain size is 500 μm.
It is clear that the superelastic elongation can be increased to 2% or more by setting the average crystal grain size to 50 μm or less, and that the superelastic elongation is 4% or more by setting the average crystal grain size to 50 μm or less.

FIG. 12 shows the fatigue characteristics when the golf club head made of NiTi alloy is repeatedly strained so that a strain of 2% is applied thereto. From FIG. 12, it is clear that by setting the average crystal grain size to 500 μm or less, it is possible to manufacture a golf club head that has durability of 104 times or more.

FIG. 13 shows the relationship between the tensile strength of the golf club head and the aspect ratio of the fibrous structure. 1st
From Figure 3, it is clear that the tensile strength can be improved by increasing the aspect ratio to 3 or more.

FIG. 14 shows the relationship between the flight distance and aspect ratio of the golf club head calculated from the test shot results. 14th
From the figure, it is clear that flight distance is improved by setting the aspect ratio to 3 or more.

Summarizing the above two results, it has been found that by implementing the method of the present invention, a golf club head having the following characteristics can be manufactured.

Tensile strength: 80 kg/mm2 or more Superelastic elongation: 5% or more Fatigue properties (at strain 0.5%): 104 times or more In contrast, the following properties were obtained with a conventional golf club head made of stainless steel.

5 6 Tensile strength 50 kg/mm2 Elastic elongation 1.5% or more Fatigue properties (strain 0.5
% time 102 times or more.'' From the above, it has been found that by implementing the method of the present invention, it is possible to manufacture a golf club that has a longer flying distance, greater tensile strength, and higher fatigue strength than conventional golf clubs.

Next, the hosel of the golf club head manufactured as described above is bent to correct the lie angle (the angle indicated by the symbol Q in FIG. 1) and the loft angle (the angle indicated by the symbol R in FIG. 2). A test was conducted to perform the following. Generally, the correction angle between the lie angle and the loft angle is at most 10° for the lie angle and 5° for the loft angle.
Therefore, in this correction test, the lie angle correction angle was set to 15°, and the loft angle correction angle was set to 10°, and the test was conducted to see if correction was possible without causing cracks or wrinkles. I did it.

As the first correction test, the heating temperature during correction (during bending) was set at 300°C, and the average crystal grain size of the golf club head was set at 20 to 100°C as shown in Table 1.
Tests were conducted on golf club heads with different positions of 0 μm.

To adjust the grain size, we used die forging to increase the forging ratio to produce crystals with a small grain size, and then used heat treatment to grow the crystals to a temperature higher than the recrystallization temperature to adjust the grain size.

In addition, as a second modification test, a modification test was conducted on a golf club head with an average crystal grain size of 500 μm, in which the heating temperature during modification (during bending) was set at a range of 20 to 1200°C as shown in Table 2. carried out.

The above results are shown in Tables 1 and 2.

Table 1 Table 2 In Tables 1 and 2, the hosel marked with ○ means that the hosel could be bent into a shape that poses no practical problems without causing any cracks or wrinkles in the bent portion. Those marked with an X mark have cracks or wrinkles in the bent portion.

From the results shown in Tables 1 and 2, the heating temperature during bending was set at 300 to 1200°C or higher, and the average crystal grain size was
It has been found that when the thickness is 00 μm or less, the hosel can be bent without cracking or wrinkling, and the lie angle and loft angle can be easily corrected.

Incidentally, in the following description, an example in which the present invention is applied to an iron-type golf club head has been described, but it goes without saying that the present invention may also be applied to a wood-type golf club head.

When applying the present invention to a wood-type golf club head, a metal made of an alloy that undergoes thermoelastic martensitic transformation is applied to the portion of the head body that is to become the ball hitting point, and the surrounding portion, that is, the fugoose portion. A golf club head is configured to attach a plate, and in this metal plate,
A golf club head may be manufactured by forging the alloy so that its fibrous structure is substantially parallel to the face surface. Furthermore, when manufacturing an iron-type golf club, the entire head need not be manufactured from an alloy that undergoes thermoelastic martensitic transformation, but only the face portion may be manufactured from this alloy.

“Effects of the Invention-1 As explained above, the present invention hot-forges an alloy ingot that undergoes thermoelastic martensitic transformation in the temperature range of 300 to 1200°C, so it is processed by reducing the hardness of this alloy. It is possible to manufacture golf club heads using the forging method.This makes it possible to manufacture golf club heads with dense crystal grains and excellent tensile strength, superelastic elongation, and fatigue properties. Obtainable.

Therefore, it is possible to provide a golf club that can extend the flight distance and has improved durability compared to conventional golf clubs.

Furthermore, according to the method of the present invention, the hosel is bent while the joint between the head body and the hosel is heated to 300 to 1200°C to reduce its hardness, so no cracks or cracks occur. You will be able to modify the lie angle and loft angle of the golf club head.

Furthermore, since the head made of a superelastic alloy with dense crystal grains with an average grain size of 500 μm or less is bent in the above temperature range, stress concentration at the grain boundaries of the bending part is reduced, reducing the hardness. Since the bending process can be performed in the same state, the lie angle and loft angle can be corrected without creating warps or wrinkles.

Therefore, it is possible to provide a golf club made of an alloy that has a lie angle and a loft angle that match the user's preference and that causes thermoelastic martensitic transformation, and also when manufactured with a lie angle and a loft angle that are different from the designed values. However, there is an effect that these can be easily corrected.

[Brief explanation of drawings]

Fig. 1 is a front view showing an example of a golf club head obtained by carrying out the method of the present invention, Fig. 2 is a side view showing an example of the same golf club head, and Fig. 3 is a thermoelastic martensitic transformation. Figure 4 is a diagram showing the relationship between strain and stress in the resulting alloy; Figure 4 is a diagram showing the relationship between strain and stress in general metal materials; Figure 5 does not show the round bar that is the material of the golf club head of the present invention. A perspective view, FIG. 6 is a side view for explaining the manufacturing method of the golf club head of the present invention, and FIG. 7 is a schematic diagram of the metal structure when a part of an example of the golf club head is shown in cross section. , Figure 8 is a schematic diagram of the metal structure when a part of a conventional stainless steel golf club head is taken in cross section. Figure 9 is a line showing the relationship between temperature and hardness of an alloy that undergoes thermoelastic martensitic transformation. Figure 1O is a line diagram showing the relationship between temperature and elongation of an alloy that undergoes thermoelastic martensitic transformation, Figure 1+ is a line diagram showing the relationship between average grain size and superelastic elongation of the golf club head of the present invention. Figure 12 is a diagram showing the relationship between average grain size and fatigue properties of the same golf club head, Figure 13 is a diagram showing the relationship between aspect ratio and tensile strength of the same golf club head, and Figure 14 is a diagram showing the relationship between the aspect ratio and tensile strength of the same golf club head. is a diagram showing the relationship between the aspect ratio and flight distance of the same golf club head. ■1... Golf club head, l... hosel, 2...
・・Heel, 3・Face, 4・Toe, 5・
Sole, Q... lie angle, R... loft angle, 7... round bar, a... fibrous structure.

Claims (1)

[Scope of Claims] A method for manufacturing a golf club in which a head body and a hosel are integrally formed of an alloy that undergoes thermoelastic martensitic transformation, and the average crystal grain size of the alloy is formed to be 500 μm or less, comprising: A method for manufacturing a golf club, which comprises bending the hosel in a temperature range of 300 to 1200°C to adjust the bending angle of the hosel and correct the lie angle and loft angle.