JP2016077487A - Golf club head manufacturing method and golf club head thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a golf club head manufacturing method and a golf club head thereof in which a crystal grain size of a hitting surface of a face part is made small, and thereby a hitting sound and a sense of hitting are improved.SOLUTION: A punch 7 is pressed on a flat face part 12 of a golf club head 1 by embossing (coining). In the punch 7, twelve pieces of trapezoidal cross section protrusions 71 are formed at equal intervals in the strip-shape of a straight line in parallel to a microprotrusion 41 between the adjacent microprotrusions 41. When a score line forming step is completed, twelve pieces of score lines 2 are formed between the adjacent microprotrusion 41 and the position where the microprotrusion 41 has been present, the finishing such as polishing or plating is performed, and the manufacturing process of the golf club head 1 is completed.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a method for manufacturing a golf club head and the golf club head. More specifically, the golf club head manufactured by improving the hit feeling by compressing the crystal grains on the surface between the score lines of the face portion and making the crystal grains of the striking surface finer than the crystal grains of the base material. A method and its golf club head.

  One of the important factors in the performance of a golf club is the hitting sound and feel. In the case of an iron head, what is produced by forging a so-called soft iron produced by hot forging low carbon steel is said to have good hitting sound and feel. As the shape of the iron head, a muscle back type and a cavity back type are known. The cavity back type is inferior in the sound and feel compared to the muscle back type. On the other hand, in order to improve the hitting sound and feel, there is also a method of quenching or heat treatment with a laser to increase the strength of the face part, but even if the surface becomes hard due to this heat treatment, The forging effect may fade. The present applicant has proposed a cavity back-type iron head that has excellent comfortable sound and feel by increasing the hardness of a part of the face portion by cold forging (Patent Document 1).

  However, the proposed one is to form a face portion in contact with the ball in a dot shape with high hardness. For this reason, there is a limit to the occupation ratio of the high hardness area in the impact area where the ball directly contacts. For this reason, there is a limit to the improvement of the hitting sound and feel. On the other hand, a technique is also known in which forged lines are uniformly distributed on the face portion to obtain a good hit feeling (Patent Document 2).

  Also, the score line formed on the face portion has a great influence on the spin of the ball. The score line is a groove formed in the face part to release grass and water droplets sandwiched between the face part and the ball at the moment of impact, thereby increasing the adhesion of the ball and obtaining an appropriate spin. . The shape of this score line is defined by rules. Further, the interval between adjacent score lines is defined to be not less than three times the width of the score line groove and not less than 0.075 inch (1.905 mm). That is, a face portion which is a flat surface in direct contact with the ball and which is a flat portion at least twice the groove width is formed. The improvement of the face portion, which is a flat portion, leads to an improvement in hitting sound and hit feeling, and in turn reduces wear.

JP 2013-128765 A JP 2009-261908 A

The present invention has been made based on the technical background described above, and achieves the following objects.
An object of the present invention is to provide a golf club head manufacturing method and a golf club head thereof in which the crystal grain size of the hitting surface of the face portion is reduced to improve the hitting sound and feel.
Another object of the present invention is to provide a method of manufacturing a golf club head and an improved golf club head in which the area where the crystal grains on the striking surface of the face portion are made fine is increased to improve the hitting sound and feel. There is.

The said subject is solved by the following means.
That is, the golf club head manufacturing method according to the first aspect of the present invention is a golf club head manufacturing method manufactured by hot forging low carbon steel and having a recess formed on the back side of the face portion. In order to form a striking surface when striking the surface, a convex portion forming step of forming a plurality of convex portions on the face portion by the hot forging process in a substantially parallel and straight belt shape, and forming the striking surface For this reason, only the projections are flattened by cold forging to flatten the flattening process of refining the crystal grains of the metal structure, and between the projections adjacent to each other, A score line forming step of forming a score line substantially parallel to the longitudinal direction.

The method of manufacturing a golf club head according to the second aspect of the present invention is the method according to the first aspect, wherein the number of crystal grains in the vicinity of the flattened striking surface is 38 or more in a length range of 150 μm, and the average crystal grain size is Is about 4.0 μm or less, and the number of crystal grains other than the vicinity subjected to the flattening processing is 30 or less in a length range of 150 μm, and the average crystal grain size is about 5.0 μm or more. Features.
The iron golf club head of the third aspect of the present invention is manufactured by the method for manufacturing a golf club head of the first or second aspect of the present invention.

  Since the golf club head manufacturing method of the present invention and the golf club head squeeze a plurality of straight belt-shaped convex portions to refine crystal grains, a score line is formed between the convex portions. The area of the striking surface where the crystal grains are miniaturized increases, and the hitting sound and feel are improved.

FIG. 1 shows a golf club head manufactured by the manufacturing method of the present invention, FIG. 1 (a) is an overall front view, and FIG. 1 (b) is an AA cross-sectional view of FIG. 1 (a). FIG. 2 is an enlarged cross-sectional view of a P portion in FIG. 3A and 3B are explanatory views showing the manufacturing process of the present invention, in which FIG. 3A is a convex portion forming step for forming a plurality of straight belt-like convex portions on the face portion, and FIG. a) A flattening process that crushes the convex portion flatly in a subsequent process. 4A and 4B are explanatory views showing a post-process of FIG. 3B, FIG. 4A is a machining process in which the face portion is milled and flattened, and FIG. 4B is FIG. 4A. This is a score line forming step of forming a score line between the convex portion and the convex portion in a subsequent process, substantially parallel to the longitudinal direction of the convex portion. FIG. 5 shows a golf club head in the process of manufacture, which is a golf club head subjected to the convex portion forming step of FIG. 3 (a), where FIG. 5 (a) is an overall front view, and FIG. It is BB sectional drawing of 5 (a). FIG. 6 is an enlarged cross-sectional view of a Q portion in FIG. FIG. 7 shows a micrograph of a golf club head manufactured by the manufacturing method of the present invention, and FIG. 7A is a micrograph of a portion having a depth of 0.2 mm of a belt-like convex portion after flattening processing. 7 (b) is a photomicrograph of a portion having a depth of 0.2 mm between the belt-like convex portions after flattening. FIG. 8 shows a photomicrograph of a golf club head manufactured by the manufacturing method of the present invention, and is a photomicrograph of the center portion of the sole portion. FIG. 9 shows that the striking surface and the score line in which the crystal grains are refined are formed alternately and in parallel. FIG. 10 shows a photograph of the golf club head in the process of production, and is a photograph of the golf club head subjected to the flattening process in FIG. 3 (b) polished to a mirror finish and etched with a nital corrosive solution.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a golf club head manufactured by the manufacturing method of the present invention, FIG. 1 (a) is an overall front view, FIG. 1 (b) is a cross-sectional view taken along line AA in FIG. 1 (a), and FIG. It is the P section expanded sectional view of (b). The golf club head 1 shown in FIGS. 1 to 2 is an iron golf club head, and is a cavity back type iron golf club head having a recess 11 formed on the back surface. The golf club head 1 has a face portion 12 having a striking surface for hitting a ball, a hosel portion 13 which is a shaft connecting portion on the shaft side, a top portion 14 on an upper portion, a toe portion 15 on a front portion, and a ground surface. A sole portion 16 is formed in the lower portion and a heel portion 17 is formed in the rear portion. A shaft (not shown) is inserted into and connected to the hosel portion 13 of the golf club head 1.

  Twelve score lines (grooves) 2 are formed in the face portion 12 with the toe heel direction as a longitudinal direction and parallel to each other at equal intervals in a direction intersecting the toe heel direction. The depth D of the score line 2 (see FIG. 2) is 0.3 mm and is formed in a trapezoidal shape. The material of the golf club head 1 is a low carbon steel of S10C to S30C.

  Next, a method for manufacturing the above-described golf club head 1 will be described. FIG. 3A shows a convex portion forming step for forming a plurality of straight belt-shaped convex portions on the face portion 12. As shown in FIG. 3A, the punch 3 is pressed against the flat face portion 12 of the golf club head 1 by hot forging. In the punch 3, 13 cross-section arc-shaped recesses 31 are formed at equal intervals in a straight strip shape parallel to each other.

  5A and 5B show the golf club head 1 subjected to the convex forming process of FIG. 3A, in which FIG. 5A is an overall front view, and FIG. 5B is a cross-sectional view taken along line BB in FIG. Sectional drawing and FIG. 6 are the Q section expanded sectional views of FIG.5 (b). As shown in FIGS. 5 and 6, the face portion 12 has a toe heel direction as a longitudinal direction and is parallel to each other in a direction intersecting the toe heel direction by the convex portion forming step of FIG. Thirteen cross-section arc-shaped convex portions 4 are formed at equal intervals. The cross-section arc-shaped convex portion 4 has a width W (see FIG. 6) of 1.95 mm and a height H of 0.15 mm.

  FIG. 3B is an explanatory view showing a post-process of FIG. 3A, and is a flattening process step for flatly crushing the cross-section arc-shaped convex portion 4. As shown in FIG. 3B, the punch 5 is pressed against the cross-section arc-shaped convex portion 4 of the golf club head 1 by cold forging to crush the cross-section arc-shaped convex portion 4, and the metal structure of the cross-section arc-shaped convex portion 4 Refine crystal grains. A flat pressing surface 51 is formed on the punch 5.

  FIG. 4A is an explanatory view showing a post-process of FIG. 3B, and is a machining process in which the face portion 12 is milled and flattened. Even if the cross-section arc-shaped convex portion 4 is flattened in the flattening process in FIG. 3B, the small convex portion 41 having a height of 0.02 to 0.03 mm is formed by the spring back phenomenon. Remain in. As shown in FIG. 4A, the face portion 12 is machined with a milling tool 6, and the minute convex portions 41 are scraped off to make the face portion 12 flat.

  FIG. 4B is an explanatory diagram showing a post-process of FIG. 4A, and a score line is formed between the adjacent minute convex portions 41 in parallel with the longitudinal direction of the minute convex portions 41. This is a score line forming step. In the machining step of FIG. 4 (a), the minute projections 41 are scraped off and the face portion 12 is flat. As an actual step, the position between adjacent minute projections 41 is present. A score line is formed. That is, as shown in FIG. 4B, the punch 7 is pressed against the flat face portion 12 of the golf club head 1 by coining. In the punch 7, 12 cross-sectional trapezoidal convex portions 71 are formed at equal intervals in a straight strip parallel to the micro convex portions 41 so as to be between the adjacent micro convex portions 41. ing. When the score line forming step of FIG. 4B is completed, as shown in FIGS. 1 and 2, twelve score lines 2 are located between the positions where the adjacent minute convex portions 41 and the minute convex portions 41 exist. After that, finishing such as polishing and plating is performed, and the manufacturing process of the golf club head 1 is completed.

  FIG. 7 shows a photomicrograph of the golf club head 1 manufactured by the manufacturing method of the present invention described above, and FIG. 7A shows a depth 0 at a position where the band-shaped minute convex portion 41 after the flattening processing is present. Fig. 7 (b) shows the depth between the position of the band-shaped minute convex portion 41 and the minute convex portion 41 after the leveling process (position where the score line 2 is formed). It is a microscope picture of a 0.2 mm location. FIG. 8 shows a photomicrograph of the golf club head 1 manufactured by the manufacturing method of the present invention, and is a photomicrograph of the central portion at the position of the sole portion 16. In FIGS. 7 and 8, the magnification is 200 times. The crystal grains that appear white in FIGS. 7 and 8 are ferrite crystal grains, and the crystal grains that appear black are pearlite crystal grains.

  From the micrographs of FIGS. 7 and 8, the average crystal grain size was determined by the line intercept method (line segment method) defined by JIS. The line intercept method is a method in which a straight line is drawn on a photomicrograph, an average value of the lengths of the straight portions crossing each particle is calculated, and this is used as an average crystal grain size. As a result, the crystal grain at the position where the minute convex portion 41 in FIG. 7A was present had 40 crystal grains in a length range of 150 μm, and the average crystal grain size was 3.75 μm. In addition, the crystal grains between the positions where the micro-projections 41 and the micro-projections 41 in FIG. 7B are present (positions where the score line 2 is formed) are 35 crystal grains in a length range of 150 μm. The average crystal grain size was 4.3 μm.

  Further, the crystal grains at the position of the sole portion 16 (the position of the base material) in FIG. 8 had 27 crystal grains in a length range of 150 μm, and the average crystal grain size was 5.6 μm. FIG. 9 shows that the striking surface 42 and the score line 2 in which the crystal grains are miniaturized are formed alternately and in parallel. That is, by forming the refined striking surface 42 and the score line 2 in parallel without crossing each other, all the crystal grains are refined without losing the position where the minute convex portions 41 exist due to the formation of the score line. Therefore, the area occupied by the striking surface in which the crystal grains in the face portion 12 are miniaturized is increased, and the hitting sound and feel are improved, and the striking surface is increased in strength and toughness. Can be planned.

  FIG. 10 shows a photograph of the golf club head 1 in the process of production, and is a photograph of the golf club head 1 subjected to the flattening process shown in FIG. . As shown in FIG. 10, the position where the 13 minute convex portions 41 are provided is discolored in black and becomes striped, and the 13 minute convex portions 41 have finer crystal grains than other positions. I was able to confirm.

  As mentioned above, although the Example of this invention was described, this invention is not limited to this Example. For example, in the above-described embodiment, the score line forming step is performed after the flattening processing step, but the score line forming step is performed after the convex portion forming step, and then the flat portion is crushed flat. A processing step may be performed. Further, although the score line forming step is performed by coining, it may be performed by cutting with a milling tool or the like.

DESCRIPTION OF SYMBOLS 1 ... Golf club head 11 ... Concave part 12 ... Face part 13 ... Hosel part 14 ... Top part 15 ... Toe part 16 ... Sole part 17 ... Heel part 2 ... Score line 3 ... Punch 31 ... Sectional arc-shaped concave part 4 ... Sectional arc-shaped convex part DESCRIPTION OF SYMBOLS 41 ... Micro convex part 42 ... Impact surface 5 in which the crystal grain was refined ... Punch 51 ... Pressing surface 6 ... Milling tool 7 ... Punch 71 ... Trapezoid convex section

Claims (3)

In a method for manufacturing a golf club head manufactured by hot forging low carbon steel and having a recess formed on the back side of the face portion,
In order to form a striking surface when a ball is hit by the face part, a convex part forming step of forming a plurality of convex parts on the face part by the hot forging into a substantially parallel and straight belt shape,
In order to form the striking surface, only the convex portion is flattened by a cold forging process, and a flattening process step for refining crystal grains of the metal structure,
A golf club head manufacturing method comprising: a score line forming step of forming a score line between adjacent convex portions and a convex portion substantially parallel to a longitudinal direction of the convex portion. The method of manufacturing a golf club head according to claim 1,
The crystal grains in the vicinity of the flattened striking surface are 38 or more in a length range of 150 μm, and the average crystal grain size is about 4.0 μm or less,
The method for producing a golf club head, characterized in that the number of crystal grains other than the vicinity subjected to the leveling process is 30 or less within a length range of 150 μm and the average crystal grain size is about 5.0 μm or more. .   An iron golf club head manufactured by the golf club head manufacturing method according to claim 1.