JP2007507300A - Golf club having enhanced performance by friction stir processing - Google Patents

Abstract

  Friction stir processing (FSP) provides a hardened golf club face that transmits moments more efficiently between the golf club and the ball and imparts a high loft (for a given flight distance of the ball). Therefore, the pop-out speed is increased. The FSP cured surface also has higher wear resistance so that the golf club provides more consistent performance and lasts longer. It is possible to make it possible for the golfer to feel whether or not he / she can hit the sweet spot that has been subjected to the friction stir processing on the face.

Description

Field of Invention

  The present invention relates to the manufacture of golf clubs, and more particularly to the surface treatment of metal golf club heads to improve performance.

  Iron golf clubs are generally designed to fly a golf ball on a trajectory that maximizes the increase in ball height (ie, loft) for a given flight distance. In this case, the ball will hit the ground at a relatively large angle, and as a result, will tend to roll less and remain near the point where it hits the ground, so that the golfer will eventually There is a tendency to experience better control of position. For high quality golf clubs, when properly swung, the ball should fly “straight”, ie, its trajectory should draw an arc located in a vertical plane. This requires horizontal spin to be minimized so that the ball flies along a substantially “straight” trajectory and does not hook to the left or slice to the right. On the other hand, the ability to backspin (vertically) is desirable to allow the golfer to minimize ball rolling or to roll the ball backward with high control.

  The “face” of the golf club, which is the flat surface on the club head that strikes the ball, is angled differently to provide various distance to loft ratios. The club face angle relative to the vertical (during ball impact) tends to cover a large range for irons and be larger for shorter flight distances. The face of an iron typically has a horizontal groove, and the outer edge of this horizontal groove tends to “grab” the ball upon impact, resulting in greater backspin to the ball Can be done. These grooves also facilitate the removal of moisture, which changes the friction characteristics of the club face.

  Where other factors are constant, the comparison of loft to distance is primarily determined by the club face angle and the “jump speed” at which the ball leaves the face of the golf club. A faster pop-up speed allows a predetermined distance to be ensured using a club with a larger face angle. Conversely, for the same pop-out angle, a longer jump distance can be achieved with a fast pop-out speed. One way to increase the pop-up speed is to increase the hardness of the material including the club face so that the kinetic energy lost by inelasticity is minimized. However, due to the inclusion of irregular shapes, golf club heads are typically manufactured by burn-off precision casting that results in a material having a relatively large particle structure and low hardness.

  An insert made of a harder material may be affixed to the face of the golf club, but this does not provide ideal results. In particular, many of the benefits provided by the harder material may be offset by losses associated with energy transfer across the interface between the insert and the club head. The precise processing and secure mounting required to minimize such losses significantly increases manufacturing costs. The insert must also be relatively thick to withstand the impact of the ball without deformation. As the thickness increases, the degree of freedom to balance the weight distribution of the club is reduced. This loss of freedom is significant because the weight of the perimeter (around the club face) is often used to minimize the tendency to twist the club on impact and to impart horizontal spin to the ball. It is. A properly weighted club has a large “sweet spot” on the face to strike the ball in a straight path.

  One possible method for producing a golf club with high surface hardness is to forge the golf club head from a fine-grained workpiece of the golf club. Fineness can be achieved in metals by introducing a wide range of deformations. Many common metalworking operations such as rolling, forging, swaging and extrusion can be used for this purpose. However, such metalworking operations change the overall particle size of the material, and as a result, important bulk properties such as strength, ductility and impact resistance are also changed. The low impact resistance for golf clubs forged from fine metal masses significantly limits the durability and useful life of the club. Furthermore, achieving significant particle size reductions with these metalworking operations is not practical or economical. It should be noted that some crystal refinement occurs in the surface area of the workpiece during forging, where the degree of crystal refinement is small. Furthermore, the position of the deformed metal during forging of iron for golf clubs is mostly the hollow back surface and not in the club face. Thus, any molecular structure refinement achieved by forging during club manufacture does not substantially affect the grain size on the club face, resulting in significant improvements in hardness and golf club performance.

  Friction stir processing (FSP) involves passing a rotating FSP tool through a metal material to locally form a fine-grained microstructure that provides improved mechanical properties [F. D. Nicholas, Advanced Materials Processes 6/99, 69 (1999)]. FSP operations are typically performed at room temperature, but the friction and metal deformation involved increases the local temperature to just below the solid phase temperature, so that the friction stir processed material is Fully recrystallized but not melted. The friction stir process introduces a degree of deformation that is significantly greater than that which can be achieved by conventional metalworking, which provides exceptionally fine grain structure and greatly increased strength. Furthermore, the thin surface layer can be friction stir processed to improve hardness without significantly affecting the mechanical properties of the bulk metal. Friction stirring has been demonstrated for various metals and their alloys including aluminum, titanium, copper and steel. The FSP method has been used to locally improve the mechanical properties of cast metal parts in the high stress region, but has not been applied to increase the surface strength of golf clubs.

  The present invention provides a golf club improved by friction stir processing (FSP) and a method for improving the performance of a golf club by friction stir processing (FSP) to increase the hardness of at least a portion of the face of the golf club. . High surface hardness tends to increase the moment transmission efficiency between the club and the ball, providing a greater loft, longer flight distance and better control of the final position of the ball. The friction stir process also tends to remove voids and defects in the metal that would otherwise reduce moment transmission efficiency. The friction stir treated surface is also highly resistant to wear, which tends to improve golf consistency and extend club life. Another embodiment of the present invention is a practical club that provides skill feedback to the golfer with a more robust sensation felt when the ball is struck in a friction stir treated sweet spot.

  The friction stir processing according to the present invention may be performed after the golf club head is formed, for example, by casting or forging, or may be performed subsequently on a workpiece formed in the club head, for example, by forging. good. The depth of the FSP process is typically small enough so that the forging function, mechanical properties and impact resistance of the underlying bulk metal are not substantially affected. This provides a high degree of freedom with respect to golf club manufacture and peripheral weight, especially for forged clubs. It is generally necessary to make the area that has been friction stir processed, preferably by milling, a new surface. As part of the work of renewing the surface, a desired shape (eg, a groove) may be processed into a club face. The FSP process allows a high quality golf club to be manufactured at a low cost without application costs.

  Further features and advantages of the present invention will become apparent to those skilled in the art from the following detailed description taken in conjunction with the accompanying drawings.

Detailed Description of the Invention

  The technical terms used herein are generally well known to those skilled in the art. Forming involves deforming the metal workpiece into the desired shape by applying force or pressure to substantially conform the workpiece to the mold (punch, die or punch). The term “forming” includes “forging” as a subset. Forging involves applying a force or pressure and usually heat to transform a relatively thick metal workpiece into a desired shape. As used herein, the term “surface” refers to the surface area of a material. Thus, surface friction agitation treatment involves treating the material to a predetermined distance below the actual surface. The FSP tool is a rotating bit that moves through the workpiece material during the friction stir process.

  The present invention provides an improved golf club and method for improving the performance of a golf club by friction stir processing to increase the hardness of at least a portion of the club face surface of the golf club. The club face is the part of the club that contacts the golf ball during club operation. High surface hardness increases the moment transmission efficiency between the club and the ball, providing a higher loft, longer flight distance and better control of the final position of the ball. The friction stir process also tends to remove voids and defects in the metal that may otherwise reduce moment transmission efficiency. Since the friction-stirred surface layer is an integral part of the golf club surface, energy losses that occur at the interface between the insert and the club head are eliminated.

  The friction stir treated surface is also more wear resistant, which tends to improve golf consistency and extend club life. High wear resistance should be particularly advantageous for the outer edge of the groove in the club face designed to increase the backspin of the ball. Such edge wear is particularly rapid and has a substantial effect on performance. The FSP process is inexpensive to apply, which allows high quality golf clubs to be manufactured at a low cost.

  The friction stir treatment according to the present invention is preferably limited to a thin (1 to 3 mm thick) surface area of the metal so that the properties of the underlying bulk metal are not substantially affected. In this case, hardness is imparted to the club face surface region without substantially affecting the forging function, mechanical properties or impact resistance of the support material. This provides a high degree of freedom with respect to golf club manufacture and peripheral weight. For example, the bulk properties of metal workpieces used to forge club heads can lead to performance properties such as forging operations and good impact resistance while still maintaining the surface hardness required for high performance. Can be optimized. Thicker or thinner friction stir areas within the scope of the present invention may also be used.

  The friction stir processing according to the present invention may be performed before or after the golf club head is formed. In a preferred embodiment, a metal golf club head is first formed, for example by casting or forging, and then subjected to a friction stir treatment on at least a portion of the surface of the club face. Because the friction stir treated surface is typically non-uniform and somewhat rough, it is generally necessary to make the friction stir treated region a new surface, preferably by milling. As part of the process of making a new surface, the desired structure (eg, groove) may be created (or regenerated) in the club face. In another embodiment, a friction stir treatment is first applied to at least a portion of the surface of a metal workpiece (eg, a strip, plate or block) and then friction stir treatment in the club face, preferably by forging. Formed on a golf head having at least a portion of the region. In this case, the friction-stirred region is preferably a new surface before the molding operation, but the new surface can be formed after the club head is formed. The present invention further provides a golf club and manufacturing method that provides feedback regarding the skill of the golfer. For this embodiment, the “sweet spot” on the actual club face where the ball flies in an ideal trajectory is friction stir processed, while the rest of the club face is not subjected to friction stir processing. A skilled golfer will feel that the ball has been struck more firmly by the FSP-cured sweet spot as compared to the surrounding softer material. The difference in sensation when hitting the ball in the FSP-treated sweet spot provides quick feedback to improve the golfer's swing. The size of the FSP treated sweet spot for an actual club can be adapted to golfer proficiency and is smaller for high proficiency golfers. Furthermore, since the wear of FSP cured sweet spots is substantially reduced, the degree of wear observed for the surrounding softer material can be used as a long-term indicator of the golfer's skills. In this embodiment, the significant wear outside the sweet spot formed by the FSP surface treatment indicates that the ball was often hit outside the sweet spot where the material is softer. The softness of the base material that has not undergone FSP processing may be altered to provide the golfer with faster or slower skill feedback.

  Any friction stir processing equipment and conditions that provide an acceptable fine-grained microstructure can be used to practice the present invention. FSP tools of various shapes and sizes are commercially available. A typical FSP tool has a helical pin and a cylindrical shoulder. The structure on the pin tends to cause the workpiece material to flow toward the surface during the friction stir process and to have a diameter in the range of 2 mm to 15 mm. A pin structure on the FSP tool is not required but may be added for ease of operation. The shoulder includes the processed material and is re-forged and is designed to have a diameter in the range of 6 mm to 50 mm. Typical FSP tool materials are tool steel, polycrystalline cubic boron nitride, nickel-based superalloys, tungsten carbide and other tungsten-based alloys. FSP tools typically rotate at 150 to 2000 rpm and move along the surface of the workpiece at 50 to 7000 mm / min. Friction stirrers are commercially available from MTS General Tool and ESAB. Various tool designs can be used to achieve the same high hardness results, as would be understood by one skilled in the art.

  The relatively large area is typically friction stir processed by lasting including multiple parallel passes of the FSP tool along the surface of the workpiece. Raster device passes are typically done in layers, but this may not be necessary. As will be appreciated by those skilled in the art, the tool can be moved in a variety of other patterns such as, for example, a circle, a helix.

DESCRIPTION OF PREFERRED EMBODIMENTS

  Two 6-iron club faces equipped with 431 stainless steel heads were friction stir processed to a depth of 1.6 mm using a polycrystalline cubic boron nitride tool having an end face diameter of 12.5 mm. The tool was rotated at 900 rpm and passed at a tilt angle of 3 degrees along the centerline of the club face at a speed of 50 mm / min. It is determined that the surface temperature has approached 1100 ° C. The work piece was actively cooled and solidified by water cooling during the FSP operation to give a hardened microstructure. Two passes with 50% overlap were made to each face to give the largest sweet spot for hitting the ball. Such a rastering process was performed by milling to remove surface roughness and irregularities, and to form grooves required for ball spin control and water removal.

  Example 1 One of the friction stir treated club heads was sectioned for microscopic and hardness testing. FIG. 1 is an optical micrograph of a cross section showing a fine microstructure formed in a surface region by FSP treatment. FIG. 2 shows Rockwell “C” hardness values (hardness indentations shown in FIG. 1) measured at various distances from the surface using a Knoop hardness scale with a 500 g load. FSP treatment increased the hardness at the face from about 26 to 40 for the bulk material.

  Example 2 A No. 6 iron that was undamaged friction stir processing (FSP) by an object evaluator was compared to an (untreated) No. 6 iron of the same type of inventory. This object evaluator is a professional golf club finisher and skilled golfer. The object evaluator reported that balls hit by FSP-treated irons tended to obtain higher lofts and somewhat longer flight distances compared to stock 6 irons. . The evaluator also reported that the FSP-treated 6 iron hit the ball with a more uniform feel.

FIG. 1 is an optical micrograph of a cross-section of a club face of a friction stir treated golf club showing the fine microstructure formed in the surface region by FSP treatment. FIG. 2 shows the hardness of the steel as a function of the distance from the surface to the material in the friction stir treated steel.

Claims (19)

A method for improving the performance of a golf club, comprising:
Forming a golf club head having a club face;
Subjecting a predetermined region of the club face of the golf club to a friction stirring process;
Renewing the surface of the predetermined region that has been subjected to at least a friction stir treatment to provide a desired surface phase. The method of claim 1, comprising:
A method wherein the golf club head includes a metal selected from the group consisting of aluminum, titanium, nickel, copper, iron and alloys thereof. The method of claim 1, comprising:
A method wherein the step of manufacturing the head includes casting or forging. The method of claim 1, comprising:
The method wherein the friction stir processing step is performed using an FSP (friction stir processing) tool rotating at a speed of 150 to 2000 revolutions per minute. The method of claim 1, comprising:
Method wherein the friction stir processing step is performed using an FSP tool that is moved along the workpiece at a speed of 50 to 7000 mm per minute. The method of claim 1, comprising:
The method wherein the step of renewing the surface includes a milling step. The method of claim 1, comprising:
The method wherein the desired surface phase includes at least one groove. A method for improving the performance of a golf club, comprising:
Rubbing and stirring a predetermined area of the surface of the metal workpiece;
Manufacturing a golf club head having a surface including the predetermined region subjected to the friction stir treatment. The method according to claim 8, comprising:
The method wherein the metal workpiece includes a metal selected from the group consisting of aluminum, titanium, nickel, copper, iron and alloys thereof. The method according to claim 8, comprising:
The method wherein the metal workpiece has a shape selected from the group consisting of strips, plates and blocks. The method according to claim 8, comprising:
The method of manufacturing the golf club head comprising a forging step. The method according to claim 8, comprising:
The method wherein the friction stir processing step is performed using an FSP tool rotating at a speed of 150 to 2000 revolutions per minute. The method according to claim 8, comprising:
The method wherein the friction stir processing step is performed using an FSP tool that is moved along the surface of the workpiece at a rate of 50 to 7000 mm per minute. The method according to claim 8, comprising:
The method further includes the step of renewing at least the surface of the predetermined region that has undergone the friction stir treatment in order to provide a desired surface phase. 15. A method according to claim 14, comprising
A method wherein the step of renewing the surface is performed prior to the step of manufacturing the golf club head. 15. A method according to claim 14, comprising
A method wherein the step of renewing the surface is performed after the step of manufacturing the golf club head. 15. A method according to claim 14, comprising
The method wherein the desired surface phase includes at least one groove.   A golf club having improved performance, comprising a head with a face, wherein the face comprises a friction stir processed metal. The golf club according to claim 18,
A golf club, wherein the metal subjected to the friction stir treatment is selected from the group consisting of aluminum, titanium, nickel, copper, iron, and alloys thereof.

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