Golf club head

Abstract

A golf club head has a loft no less than 38°. The golf club head also comprises a material having a material composition that includes an Iron content that by weight is highest of all constituents. The material composition also has a Chromium content no less than 10.5% by weight and a Nickel content no greater than 0.5% by weight.

Description

[0001] This application is a continuation-in-part of U.S. patent application Ser. No. 18 / 771,457, which is a non-provisional of U.S. Provisional Application No. 63 / 614,154, filed on Dec. 22, 2023, the disclosures of each of which are incorporated herein by reference in its entirety.BACKGROUND

[0002] Golf clubs from a technical perspective undergo a unique set of rigors. For example, golf clubs are evaluated in their ability to meet performance thresholds such as efficient transfer of energy to a golf ball upon impact. Golf clubs are also evaluated in terms of their ability to provide forgiveness on off-centered shots or mis-hits. Further, golf clubs in some cases are evaluated in their ability to impart specific spin characteristics or other attributes to a golf ball upon impact for shaping flight trajectory and / or ball roll characteristics. Apart from performance, club heads are expected to withstand repeated use, e.g. resist wear, rust, and material fatiguing. Some club heads are also expected to permit a degree of adjustability by plastic deformation, e.g. hosel bending to adjust loft and / or lie.

[0003] Golf club manufacturers desire to achieve success across all or as many of these aspects of use as possible. But the varied nature of these functional desirables, and provision of limitations, e.g. regarding mass, physical dimensions, and cost, often lead to design conflicts and tradeoffs. For example, increasing the forgiveness of a club head, e.g. by increasing its moment of inertia about preferred axes often comes at the cost of desirable feel. Similarly, adapting a club head to impart beneficial spin and wear resistance may likely involve a material selection that could adversely affect other considerations. For example, conventional materials that offer high hardness, high yield strength and adequate machineability often fall short in other key areas such as malleability or softness, which is preferable regarding the provision of adjustability or bendability.

[0004] To minimize the severity of such design trade-offs, manufacturers have considered selectively varying club head materials about the structure of the club head to better match material properties with structural function. For example, iron-type club heads, e.g. wedges, have implemented face inserts of a material different from that of a main body to which the face insert is secured. Accordingly, the face insert may be selected to exhibit properties ideal for impact, such as relatively high hardness, low density, adequate wear resistance, and adequate machineability. Yet, the material of the main body may appropriately depart from those properties and instead be selected to exhibit e.g. a higher density and greater malleability.

[0005] Selectively positioning different materials about the structure of a club head, although with apparent benefit, is not without detriment. First, increasing the number of components constituting a club head increases its cost and complexity in manufacture. As a result, margins of error in manufacturing may increase as may locations of failure e.g. given the imposition of adhesives, mechanical fasteners and heat-affected zones resulting from welding or brazing. Also, departure of a club head from solid structure toward componentized structure may result in deleterious loss of feel and poor acoustics or vibratory properties.SUMMARY

[0006] An object, therefore, of the present disclosure is to provide material compositions, and implementations thereof, that are in themselves suitable for varied use aspects expected of golf club heads. Accordingly, benefits associated with selectively corresponding material properties with particular club head structure may be achieved, while detriments associated with unduly componentized structure may be minimized or avoided.

[0007] In one aspect, a golf club head includes a unitary component formed of a stainless steel material. The unitary component has variable hardness. A first portion of the component exhibits a first hardness H1 no less than 50 HRC. A second portion of the component exhibits a second hardness H2 no greater than 85 HRB.

[0008] In another aspect of the present disclosure, a method includes forming a component of a golf club head. The component comprises a stainless steel material. The method includes selectively surface hardening the component such that a first portion of the component exhibits a first hardness H1 no less than 50 HRC and a second portion of the component exhibits a second hardness H2 no greater than 85 HRB.

[0009] In another aspect of the present disclosure, a component for a golf club head includes a stainless steel material. The stainless steel material has a Nickel content no greater than 0.25% by mass.

[0010] In another aspect of the present disclosure, a component for a golf club head includes a stainless steel material. The stainless steel material has a Carbon content no less than 0.25% by mass.

[0011] In another aspect of the present disclosure, a component for a golf club head includes a stainless steel material. The stainless steel material has an austenization temperature no less than 800° C.

[0012] These and other features and advantages of the golf club heads, their compositions, and manufacturing methods thereof according to the various aspects of the present disclosure will become more apparent upon consideration of the following description, drawings, and appended claims. The description and drawings described below are for illustrative purposes only and are not intended to limit the scope of the present invention in any manner.BRIEF DESCRIPTION OF THE DRAWINGS

[0013] FIG. 1 shows a front elevation view of an exemplary golf club head in accordance with one or more aspects of the present disclosure.

[0014] FIG. 2 shows a rear elevation view of the exemplary golf club head of FIG. 1.

[0015] FIG. 3 shows a flow chart of a method of manufacturing a golf club head in accordance with one or more aspects of the present disclosure.

[0016] FIG. 4 shows a chart providing material properties of an exemplary steel composition and known steel compositions in accordance with one or more aspects of the present disclosure.

[0017] FIG. 5 shows a line chart providing relationship information between tempering temperature and hardness for the exemplary steel composition of FIG. 4 and another known steel composition.

[0018] FIG. 6 shows a chart providing relationship information between Carbon content, tempering temperature, and “as-quenched” hardness for the exemplary steel composition of FIG. 4 and other known steel compositions.

[0019] FIG. 7 shows a front elevation view of an exemplary golf club head in accordance with one or more aspects of the present disclosure.

[0020] FIG. 8 shows a rear elevation view of the exemplary golf club head of FIG. 7.

[0021] FIG. 9 shows a toe elevation view of the exemplary golf club head of FIG. 7.

[0022] FIG. 10 shows a heel elevation view of the exemplary golf club head of FIG. 7.

[0023] FIG. 11A shows a cross-sectional view of an exemplary golf club head of FIG. 7 through plane A-A′ being a first-lofted club head of a correlated set of differently-lofted golf club heads.

[0024] FIG. 11B shows a cross-sectional view of an exemplary golf club head of FIG. 7 through plane A-A′ being a second-lofted club head of a correlated set of differently-lofted golf club heads.

[0025] FIG. 12A shows a rear perspective view of a plaque of the exemplary club head of FIG. 7.

[0026] FIG. 12B shows a front perspective view of the plaque of the exemplary club head of FIG. 7.DETAILED DESCRIPTION

[0027] In one aspect of the present disclosure, referring to FIGS. 1 and 2, a club head 100 is shown. The golf club head 100 includes a front portion 122 including a striking face 102, a top portion 106 and a sole portion 108 opposite the top portion 106. The sole portion 108 is configured to rest on a virtual ground plane, e.g. ground plane 108, when in a reference position. The golf club head 100 further include a heel portion 112 and a toe portion 110 opposite the heel portion 112. A hosel portion 104 extends from heel portion 112. The hosel portion 104 includes a hosel bore (not shown) configured to receive a golf shaft (not shown). The golf club head 100, once combined with a golf shaft may form a golf club. The hosel portion 104 defines a virtual hosel axis 124 being a central axis defined by the hosel bore. The hosel axis 124 in relation to the remaining structure of the club head 100 defines a club head loft and lie.

[0028] As used herein, “reference position” refers to a position of the golf club head, e.g. club head 100, wherein a hosel centerline lies in an imaginary vertical hosel plane relative to a ground plane 102, the hosel plane intersects a striking face plane along a line parallel the scorelines, and the scorelines 113 generally extend parallel to the ground plane 102

[0029] Preferably, the club head 100 is an iron-type club head, e.g. having a loft between 20° and 66°. More preferably, the club head 100 is a wedge-type club head, e.g. having a loft between 40° and 66°. Additionally, or alternatively, the club head 100 bears a lie between about 62° and about 66°, more preferably between 61° and 63°. However, the structures and material compositions described herein may readily apply to other types of golf club heads, e.g. woods including drivers, fairway woods, and hybrids, as well as putters, rescue clubs, etc.

[0030] The golf club head preferably comprises a steel material, preferably a stainless steel material. Typically, readily-available grades of stainless steel are applied in golf club head construction, particularly for iron-type, including wedge-type, club heads. For example, AISI 431 alloy steel is a commonly used material in golf club heads and components thereof. However, in consideration of the unique set of rigors and constraints associated with golf club heads, particularly wedge-type golf club heads, as well as the desire to minimize the severity of design trade-offs, steel compositions different from conventional materials, say AISI 431, may be advantageous. For all purposes herein, a steel alloy is considered to be a stainless steel if its Chromium content is at least 10.5% by mass.

[0031] Preferably, a majority (i.e. greater than 50%) of the club head 100, by mass, is comprised of such steel, more preferably at least 85% of the club head 100, even more preferably substantially the entirety of the club head 100 (e.g. accounting for minor auxiliary components such as paints, thin coatings, mouse glue, ferrules, etc.). Alternatively or additionally, such steel preferably constitutes a unitary component of the club head 100, more preferably a unitary component that includes a first portion forming at least a portion of the striking face 102, even more preferably also including a second portion forming at least a portion of the hosel portion 104 and yet even more preferably including a third portion forming at least a portion of the rear portion 116 of the club head 100. The club head 100 is preferably solid in shape having an upper blade portion 118 and lower muscle portion 120 proximate the sole portion 108. In some aspects, substantially the entirety of the club head 100 is unitarily formed of such steel. As discussed above, reducing the number of the components required in the build of the club head 100 may provide benefits in reducing manufacturing cost, reducing manufacturing tolerances, and reducing locations susceptible to failure, while maintaining desirable feel, acoustics and vibratory characteristics.

[0032] Preferably, though, the composition of the steel described above is selected such that it provides material properties that are particularly beneficial for use in a golf club head. Conventionally available grades of steel have some adequate properties regarding club heads but are also believed to have properties not particularly relevant to golf club head use. For at least these reasons, tailoring steel composition for use associated with club heads may provide benefits with no or little detriment. Also, preferably, tailoring steel composition for use associated with club heads may permit greater flexibility in varying club head properties on a structure-by-structure basis.

[0033] As described above, the golf club head 100 is preferably an iron-type club head, more preferably a wedge-type club head. Accordingly, adapting main body material composition to the specific use aspects of such club heads may result in outweighed benefit. Particular attention is drawn to hardness characteristics, wear resistance and density for their believed relevance to wedge-type club heads. However, other characteristics may be taken into consideration also.

[0034] Hardness is an example of a property of which desirable application is unique in the case of golf club heads. On one hand, a striking face, e.g. striking face 102, preferably comprises a relatively hard surface. Yet, other portions of a club head, e.g. club head 100, are preferably softer and / or more malleable, e.g. the hosel portion 104. Such malleability supports adjustability by plastically deforming the club head, e.g. modifying loft and / or lie by hosel bending. This duality in hardness desirability is a unique aspect of golf club head functionality and is believed to justify deviation from conventional material composition.

[0035] One concern regarding conventional steels is their limitations in providing for manipulation of hardness. For example, 431 Stainless Steel exhibits an austenization temperature of about 720° C., which in turn enables tempering at a temperature no greater than about 700° C.; exceeding this temperature deleteriously raises the likelihood of austenite transformation and rehardening. Thus, maintaining malleable qualities while achieving a striking face of relatively high hardness may be challenging.

[0036] Such limitations on hardening are believed closely correlated with Nickel content in steels, other material constituents notwithstanding. Nickel is believed to be a strong austenite promoter. This in turn is believed to affect, by decreasing, an austenization temperature. In turn, this is believed to raise the minimum achievable hardness by such steel in a quenched and tempered state. For example, 431 Stainless Steel is believed only capable of being softened to about 85 HRB by quenching and tempering. Remedial processes may counteract this deficiency, such as a softening processes that includes holding such steels at temperatures about their austenization temperature and slowly cooling. However, these remedial processes are not without detriment themselves, e.g. reduced wear resistance. Such remedial processes also complicate, and increase the cost of, manufacturing. Thus, a steel composition capable of achieving desirable variation in hardness, by virtue of quenching and tempering, alone, is preferable.

[0037] Accordingly, the steel composition of the club head 100 preferably comprises a Nickel content no greater than 0.5% by mass, more preferably no greater than 0.35% by mass. However, notably, even reducing Nickel composition to no greater than 0.25% by mass, or more preferably about 0.2% by mass, the club head 100 may be capability of exhibiting superior properties, e.g. hardness variation and wear resistance, with little believed detriment. Accordingly, an exemplary preferably range of Nickel content of the steel composition of the golf club head 100 is between 0.07% and 0.27% by mass. Provided such a Nickel content, the steel can exhibit an austenization temperature no less than 800° C., preferably no less than 850° C., and even more preferably equal to about 870° C. As a result, the steel may likely be capable of being tempered at temperatures of at least 800° C. This may result in a capability to soften the steel to 90 HRB or less after quenching and tempering (e.g. 89 HBR or less), substantially increasing bendability, e.g. to accommodate loft and / or lie adjustment by hosel bending. Preferably, the steel exhibits material properties permitting up to about 4° of angular adjustment of the hosel portion whether in loft adjustment or lie adjustment. Generally, in some alternative aspects, the content of Nickel may be reduced to be below 0.2% without significant detriment, particularly in the case of a wedge-type club head. However, lower limits of Nickel content may correspond to unacceptable impact energy and should be evaluated on that basis.

[0038] Hardness characteristics of steel are also believed substantially affected by Carbon content. Other material constituents notwithstanding, increasing Carbon may generally be considered to increase maximum achievable hardness of a steel in a quenched state. For example, 431 Stainless Steel is believed to have a Carbon content of about 0.1% by mass and to exhibit a maximum hardness in a quenched state of around 40 HRC. 8620 Stainless Steel is believed to have a Carbon content of about 0.2% by mass and to exhibit a maximum hardness in a quenched state of about 45 HRC. Preferably, the steel of the club head 100 has a Carbon content of no less than 0.13% by mass, more preferably no less than 0.15% by mass, even more preferably no less than 0.20% by mass, and yet even more preferably no less than 0.25% by mass. Other constituents notwithstanding, the steel of the club head 100 in a quenched state can exhibit a hardness no less than 50 HRC, more preferably no less than 55 HRC, even more preferably no less than 60 HRC and yet even more preferably between 60 HRC and 65 HRC.

[0039] In addition to its own direct benefits, Carbon is believed, to a degree, to be an effective substitute for Nickel. Thus Carbon permits the advantageous reduction in Nickel content as described above. In addition to such hardness benefits, such Carbon content ranges are believed to contribute to improved wear resistance and reduced material density.

[0040] If, however, Carbon content is too high, deleterious effects may result. For example, manufacturing issues such as problems with weldability and solidification may be presented. Also, Carbon content, in association with Nickel and other constituents, is believed to contribute to the steel's austenization temperature. Specifically, a relatively high Carbon content may lower austenization temperature as it is believed to be a strong austenite promoter. As a result, the steel may be deleteriously limited in its above-mentioned capability to be softened by tempering to a hardness no greater than 90 HRB. Thus, the steel of the club head 100 preferably has a Carbon content between 0.13% and 0.50% by mass, more preferably between 0.22% and 0.50% by mass, even more preferably between 0.22% and 0.27% by mass. However, higher Carbon contents, e.g. in a range of 0.45% to 0.50%, may be particularly preferable in cases where capability of achieving higher hardnesses are prioritized over lower minimum hardness, e.g. for purposes of adjustability as described above.

[0041] Notwithstanding other factors correlated with wear resistance, increased hardness itself is believed correlated in part with greater wear resistance. Thus, the capability of quenching the above steel to achieve a higher hardness in turn may increase wear resistance and strength. This may be particularly true in the case of specific heat treat processes such as laser etching or laser peening in combination with the Carbon contents described above.

[0042] The content of Chromium is also believed to contribute to material properties of steel uniquely relevant to golf club heads. This is particularly true regarding hardness and wear resistance, including resistance to rust. Preferably, the content of Chromium present in the steel of club head 100 is selected primarily based on improving these properties, as described below in further detail.

[0043] As described above, the club head 100 preferably exhibits a relative high

[0044] hardness at striking face locations, and relative low hardness at other locations, e.g. the hosel portion 104 and / or the rear portion 116. Chromium, in addition to Nickel and Carbon as described above, may contribute to achieving these desired club head properties. For example, steel composition, apart from its per se hardness properties, may also indirectly affect hardness. For example, steel composition may dictate which surface processing options, e.g. surface hardening or case hardening, may be effectively applied and their degree of success. For example, in some aspects, the striking face 102 undergoes a surface hardening process, preferably a nitriding process. In some aspects, other surface hardening processes may be applied, either in substitution or in addition to nitriding, such as carburizing, carbonitriding, normalizing, case hardening, induction hardening, cyaniding, flame hardening and laser hardening. However, nitriding is preferable as it is believed to be cost-effective and to achieve the most satisfactory results. Because of the presence of Chromium, a nitriding process is capable of permitting Chromium Nitride to form on the striking face 102. In turn, this permits the striking face 102 to exhibit a surface hardness of no less than 1200 HV (0.05). Otherwise, e.g. for a conventional carbon steel, maximum achievable hardness may be significantly less, e.g. about 800 HV (0.05).

[0045] Nitriding may also bear drawbacks. For example, nitriding stainless steel has been shown to decrease corrosion resistance. However, considering the overall use characteristics of a club head, particularly the wedge-type club head 100 of FIG. 1, the hardness benefits achieved by virtue of steel composition and surface hardening, e.g. nitriding, are believed to outweigh this potential detriment.

[0046] Regarding rust, preferably, the steel composition is adapted to reduce or minimize propagation of rust or natural oxidation. In some alternative aspects, rusting or oxidizing of the striking face 102 of the club head 100 may be viewed as a positive development. For example, a niche market exists for golf club heads with striking faces exhibiting rust or having characteristics specifically selected to promote rust. Such client base of golfers favors the particular texture, appearance, and / or surface roughness characteristics associated with a rusted face. However, in general, preferably, the club head 100 is configured to reduce the onset or propagation of rust. It is believed that club heads susceptible to rust wear faster than club heads not so susceptible. This may be because rust on a striking face is believed to wear faster than regions not exhibiting rust, resulting in a greater rate of volume loss of the rusted club head. This is of particular concern regarding scoreline structure. The presence of Chromium in the steel reduces the onset and propagation of rust, thus likely reducing rate of wear.

[0047] Based on the above considerations, the steel implemented in the club head 100 preferably includes Chromium in an amount no less than 13% by mass, more preferably no less than 14% by mass, even more preferably no less than 16% by mass. Additionally, or alternatively, the steel includes Chromium in an amount no greater than 21% by mass, more preferably no greater than 18% by mass. A preferable range of Chromium content in the steel of golf club head 100 is between 16.5% and 18.0% by mass. A Chromium content that is too high may frustrate the steel's transition to martensitic crystalline structure, may result in a steel that is too brittle, and / or may deleteriously result in sigma phase formation during tempering.

[0048] In addition to the considerations described above affecting rust reduction and wear, the Chromium contents described above—in association with the described Carbon and Nickel contents—desirably reduce overall steel density. The density of a metallic material is primarily affected by two attributes: (1) the composition of the alloy; and (2) the formation in which its atoms are arranged.

[0049] A simplified method to estimate the actual density of an alloy is to calculate density as derived solely from constituent content information, herein referred to as an alloy's “theoretical density.” Because theoretical density provides useful aggregate information about an alloy's composition, it is considered a useful material property in its own right, regardless of whether it may differ from an actual, measured density of the same alloy. Theoretical density is determined by taking the percent by weight of each constituent element and divide it by the density of the constituent element to return the total volume of each element. Then, assume a 100 g sample and divided by the sum of the volumes as shown in Equation 1 below:ρalloy=100⁢ g∑wt. %Element⁢1·1⁢ gρElement⁢ 1+wt. %Element⁢ 2·1⁢ gρElement⁢ 2⁢ …Preferably, the theoretical density of the steel composition implemented in golf club head 100 is no greater than 7.56g / cc.

[0051] The other key contributor (i.e. (2) as described above) to steel density is the structure in which the atoms are arranged or the structure's crystal structure. For this reason, in part, an alloy's actual density may differ from its theoretical density describe above. The steel of the club head 100, based on its constituent compositions described above, once tempered and / or quenched, is preferably a mixture of Ferrite, which has body centered cubic structure (BCC), and Martensite—or substantially entirely, or entirely—Martensite. Martensite exhibits body centered tetragonal (BCT) structure in the quenched state and body centered cubic (BCC) structure in the tempered state. Thus, the relative proportions of Martensite's crystal structure is dependent on the amount of tempering after quenching. BCC and BCT structures have an atomic packing factor, i.e. amount of atom volume per unit cell, of 0.68. Because the packing factors for BCC and BCT structures are similar, overall material density is believed primarily governed by composition of the alloy.

[0052] Another common metallic crystal structure is face centered cubic (FCC) which has an atomic packing factor greater than BCC or BCT, of 0.74, indicative of a close packed structure. Austenite has an FCC structure so it will generally have a higher density than the blended composition of the steel of the club head 100, even though its theoretical density according to the above Equation 1 would be lower.

[0053] Based on the above, the actual density of the steel is preferably no greater than 7.85 g / cm2, more preferably no greater than 7.67 g / cm2 and even more preferably no greater than 7.60 g / cm2. Reducing density increases discretionary mass of the club head 100, i.e. mass not primarily required for the structural integrity of the club head thus capable of being placed in locations for purposes of enhancing the various mass properties of the club head 100, e.g. the location of the center of gravity and moments of inertia about relevant axes passing through the center of gravity.

[0054] The constituent composition of Nitrogen in the steel of the club head 100 is also significant. Nitrogen may affect steels in a similar manner as does Carbon. This is due to their similar size, i.e. Nitrogen and Carbon may both be considered interstitial elements. Accordingly, as with Carbon, Nitrogen is a strong austenite promoter. Thus, increasing Nitrogen composition beyond a certain point may deleteriously result in increased minimum quenched and tempered hardness. Further, if too high in content, Nitrogen may result in partitioning problems of the steel during welding and solidification due to its small size and relatively high diffusion rates. Further, if too high in content, Nitrogen may also result in the steel alloy's loss of ductility, undesirable toughness, and corrosion resistance by the formation of CrN. Nitrogen may influence the maximum strength of stainless steels, albeit to a believed lesser extent than Carbon.

[0055] Based on the above considerations, the steel of the club head 100 preferably includes Nitrogen content in an amount no greater than 0.035% by mass, more preferably no greater than 0.15% by mass, even more preferably within the range of about 0% to 0.06% by mass. Because of its shared characteristics with Carbon, the combined content of Carbon and Nitrogen also bears significance. Preferably, this combined content in the steel of the club head 100 is no less than 0.13%, more preferably no less than 0.17% by mass, even more preferably no less than 0.19% by mass, yet even more preferably no less than 0.24% by mass. As an example, a preferably range of Nitrogen content in the steel composition of the golf club head 100 is between 0.0% and 0.06%. Additionally, or alternatively, the combined content of Nitrogen and Carbon in the steel of club head 100 is within the range of 0.13% to 0.75% by mass, more preferably within the range of 0.24% to 0.35% by mass. In this case, if such content is too low, the steel may not be capable of hardening to a desirable degree, may exhibit reduced wear residence and may exhibit undesirably high density.

[0056] The above description details preferable steel composition embodiments for use in golf club head 100. Table 1 below summarizes several exemplary steel compositions corresponding to the above description. Exemplary Steel A corresponds to a first, general example of the steel used in golf club head 100.TABLE #1CarbonChromiumNickelSteel(% by mass)(% by mass)(% by mass)Exemplary0.2616.6.15Steel A8620 SS0.18-0.230.4-0.60.4-0.7431 Stainless0.07316.11.66Steel

[0057] A more detailed assessment of the chemical composition of Exemplary Steel A is shown below in Table #2. Some properties of club head 100 are shown in FIG. 4, for alternative cases in which the golf club head 100 is composed of known steels as well as the exemplary steel described herein.TABLE #2Extended Chemical Composition of Exemplary Steel A (% by mass)CSiSPMnNiCrMoCuTiNFePreferred0.22-0.6-0-0-0.3-0.07-16.5-0.1-0.1-00-Bal.Range0.271.00.030.030.70.2718.00.30.30.06Target0.250.8000.50.15170.170.1500Bal.

[0058] Based on the above constituent contents, the exemplary steel composition of golf club head 100 is capable, after quenching, tempering and case hardening, of exhibiting a maximum hardness of no less than 50 HRC, more preferably no less than 55 HRC, yet even more preferably within the range of 60 HRC and 65 HRC. With regard to the Vickers hardness scale, such maximum hardness is preferably no less than 500 HV1 (or no less than 650 HV0.05, more preferably no less than 700 HV0.05). The same steel composition of the golf club head 100, by virtue of its constituent composition, is capable of exhibiting a minimum hardness of no greater than 90 HRB, more preferably no greater than 8 5HRB. With regard to the Vickers hardness scale, such minimum hardness is preferably no greater than 185 HV1 (or no greater than 260 HV0.05,more preferably no greater than 250 HV0.05). Preferably, the component of the club head 100 comprised of this steel includes a first location on the striking face 102 of the club head 100, preferably a second location at a hosel portion 104, and preferably a third location at a rear portion 116 of the club head. In such embodiments, e.g. by virtue of selective surface processing, preferably, the first location has a hardness no less than 50 HRC more preferably no less than 55 HRC, even more preferably within the range of 60 HRC to 65 HRC. Alternative or additionally, the steel component's maximum hardness preferably coincides with the first location, e.g. is located on the striking face 102. Preferably, the second location (and optionally the third location) has a hardness no greater than 90 HRB, more preferably no greater than 85 HRB. Alternatively or additionally, the steel component's minimum thickness is preferably located on a portion other than the striking face 102, and preferably located at the hosel portion 104. However, in some aspects, the location of minimum hardness of the steel component is on the rear portion 116 or another portion of the club head 100.

[0059] In addition or alternatively, a ratio of the steel's maximum hardness (capable by virtue of quenching) to the steel's minimum hardness (capable by virtue of quenching and tempering) determined where both maximum and minimum values are expressed in quantities in association with the Rockwell C Hardness (HRV) Scale) is preferably no less than 4.5, more preferably no less than 6, even more preferably no less than 9, yet even more preferably no less than 12. In some particular embodiments, preferably such ratio is within the range of 12 to 16.25. Expressed another way, the ratio of such maximum hardness to such minimum hardness is preferably no less than 0.5 HRC / HRB (i.e. where maximum hardness is measured and expressed using the HRC scale and minimum hardness is measured and expressed using the HRB scale). Expressed another way, the ratio of such maximum hardness to such minimum hardness is preferably no less than 2.5, more preferably no less than 2.6 (i.e. where maximum hardness and minimum hardness are measured and expressed using the HV1 scale).

[0060] FIG. 3 illustrates a process flow chart 200 describing preferable steps taken in the formation of the club head 100 using the exemplary steel composition aspects described herein. While the steps of process 200 are organized sequentially and preferably intended to occur chronologically in the sequence shown, it is contemplated that one or more steps may occur in a different sequence or be omitted. Further, in some aspects, additional steps or processes may occur chronologically before, after, or between any process step shown and described.

[0061] In step 202, an intermediate club head body is formed by casting, e.g. investment or lost-wax casting. Next, optionally, in step 204, welding is applied to add material and / or repair any regions of the intermediate cast club head body due to artifacts or defects of the casting process. For example, welding material may be applied as filler for regions exhibiting porosity issues. The welding material is preferably a stainless steel material. However, other materials may alternatively be used but, if so, preferably in combination with additional post-processing.

[0062] Next, optionally, in step 206, the intermediate club head body is polished preferably removing any remnants of gates or other artifacts resulting from the casting process 202.

[0063] Next, in step 208, the intermediate club head body undergoes heat treating 208. Preferably, the heat treating process 208 includes at least a quenching process 208A and a tempering process 208B. Initially, in step 208A, preferably the intermediate club head body is held at a temperature of about 1040° C. for a duration of about 90 min to about 120 min, more preferably about 90 min. Subsequently, the intermediate club head body is quenched preferably by immersion in an N2 solution. The result is transition to a harder martensitic structure throughout the majority (i.e. greater than 50%) of the club head body by mass, more preferably throughout no less than 60% by mass, and even more preferably throughout substantially the entirety of the intermediate club head body.

[0064] Next, in step 208B, the intermediate club head body undergoes tempering. In this step, the intermediate club head body is held at a temperature no less than 800° C., more preferably no less than 850° C., even more preferably within the range of 865° C. to 870° C. and yet even more preferably at a temperature of about 870° C. for about 2 hrs. Preferably, subsequently, the intermediate club head body is cooled in an N2 solution. This step tempers the martensite thus softening the intermediate club head body.

[0065] In some embodiments, in step 208, the intermediate club head body undergoes plural heat treat cycles. Applying multiple heat treat cycles is preferable in some cases to both maintain a relatively high potential for face hardness of the steel at the striking face 102 and permitting a final club head hardness that is even further reduced at locations including e.g. the hosel portion 104 and / or the rear portion 116. Such plural cycles may include multiple tempering cycles. As shown e.g. in FIG. 6, applying a double tempering process results in reduced hardness relative single tempering at same temperatures. For example, double tempering at a temperature of about 863° C. for about a 2 hr period results in a hardness of 80 HRB, whereas single tempering at the same temperature and duration results in a hardness of about 96 HRB. A multiple cycle heat treat process may e.g. include the sub-steps shown below in Table #4:TABLE #4TemperatureDurationResultingStepProcess(° C.)(Hrs)Hardness1Heat in Vacuum Furnace1040247 HRC to2N2 Quench and CoolTo 10050 HRCor below3Heat in Vacuum or 870287 HRBGeneral Furnace4N2 Quench and CoolTo 100or below5Heat in Vacuum or830 C.280 HRBGeneral Furnace6N2 Quench and CoolTo RoomTemperature

[0066] Next, in step 210, the striking face 102 is preferably surface milled. Next, in step 212, the hosel / neck region of the intermediate club head body is polished to effect a blended appearance between the striking face 102 and the hosel portion 104. Next, in step 214, scorelines are machined into the striking face 102, preferably by milling.

[0067] Next, in step 216, the striking face 102 undergoes face hardening. Preferably, the face hardening step 216 includes a nitriding process 216A and additional hardening operations, such as laser hardening or laser peening peening in step 216B.

[0068] The step of nitriding 216A occurs at a temperature of preferably no less than about 550° C., more preferably no less than about 575° C., even more preferably at about 580° C., and for a duration of about 50 min. However, alternative or additional face hardening or other protective or cosmetic surface finishing processes are contemplated, such as carburizing, carbonitriding, normalizing, case hardening, induction hardening, cyaniding, flame hardening and coating with PVD, ceramics, and / or diamond). Because of the various constituent compositions described above, the steel applied in the golf club head 100 is believed to exhibit sufficient wear / rust resistance per se, thus not considered to necessitate plating for that purpose. On the other hand, e.g. in the case of 8620 Steel, Nickel and Chromium plating is generally considered necessary for purposes of increasing wear / rust resistance to an acceptable degree.

[0069] Preferably, in step 216B, laser hardening is applied to the nitrided striking face. In this step, for a short period of time (e.g. a few seconds) focused heat energy is directed to the striking face 102. Cooling of the striking face 102 subsequent the laser peening process is preferable using e.g. a gas or water. This laser hardening process preferably affects material extending a depth from the striking face 102 of no less than 0.5 mm, more preferably no less than 0.7 mm, even more preferably about 0.8 mm. Such laser hardening process further hardens the striking face 102, e.g. to a hardness of no less than 50 HRC, more preferably no less than 52 HRC. Based on the above steps, the striking face 102 of the club head 100 preferably achieves hardness and wear resistance values in accordance with embodiments of the club head 100 described above.

[0070] As a result of the face hardening process, hardness through the club head 100, more specifically throughout any component comprised of the inventive steels described herein, exhibit a hardness gradient throughout its thickness. Preferably, the club head 100 exhibits martensitic structure at a depth from the striking face (i.e. measured rearward in a direction perpendicular to a virtual striking face plane generally coplanar with the striking face 102) of no less than 50% of the overall depth of the club head 100, more preferably no less than 90% of the overall depth of the club head 100, and even more preferably substantially the entire overall depth of the club head 100. In specific embodiments in which the striking face 102 undergoes nitriding, preferably the nitriding process results in a CrN layer on the striking face 102 of a thickness no less than 0.02 mm, more preferably no less than 0.03 mm, and even more preferably about 0.04 mm.

[0071] Referring to FIGS. 7 through 12B, a golf club head 300 is shown having a heel portion 312, a toe portion 310 opposite the heel portion 312, a striking face 302 at a front portion 322 and a rear portion 316 opposite the front portion 322 (see specifically FIG. 8). A hosel portion 304 extends from the heel portion 312 and includes a hosel bore configured to receive and secure to the golf club head a tip end of a conventional golf shaft (not shown). The hosel bore defines a virtual (central) hosel axis 324. The golf club head 300 is shown in the reference position and thus the hosel axis 324 lies in a virtual vertical hosel plane 334 (see FIG. 9).

[0072] The golf club head 300 preferably comprises an inventive steel composition for example an inventive steel composition described above with regard to the aspects of FIG. 4. In particular, at least a majority of the mass of the club head 300 is composed of the inventive steel composition described with regard to FIG. 4, and more preferably substantially the entirety of the club head 300 is composed of such inventive composition. In aspects in which the golf club head 300 is only partially comprised of the inventive steel composition, such composition is preferably located at least at the striking face 302. In such cases, optionally, such composition is additionally located at the hosel portion 304. In some such cases, the inventive steel composition is a component that is co-forged with, co-molded with, welded to, brazed to, mechanically fastened to, or otherwise secured to, other components to for a complete golf club head.

[0073] Referring to FIG. 8, the rear portion 316 of the golf club head 300 is shown. The rear portion 316 includes an upper blade portion 318 and a lower muscle portion 320. In some aspects, the golf club head 300 is a wedge-type club head, e.g. having a loft no less than 38°,and more preferably between about 38° and 64°. Accordingly, the upper blade portion 318 and lower muscle portion 320 promote a traditional wedge-like appearance desirable by many golfers. Such structure contributes to advantageous feel and acoustic / vibratory response typically associated with and desired of wedge-type club heads.

[0074] However, in some aspects, the golf club head 300 is more specifically a game improvement type wedge-type club head. While the golf club head 300 preferably embodies features traditional of a wedge-type club head, the golf club head 300 preferably additional includes features that improve forgiveness and other characteristics typically desired by golfers with an average to high handicap. For example, the golf club head 300 includes a perimeter weighting feature 324 defining a rear cavity 326. The perimeter weighting feature 324 preferably extends about substantially the entire periphery of the rear portion 316 of the club head 300, including both the upper blade portion 318 and the lower muscle portion 320. However, the lower muscle portion 320 preferably still includes a stepped up portion mass portion 326 to maintain the traditional wedge-like appearance of the club head 300 and to maintain desirable feel and acoustic characteristics.

[0075] The striking face 302 further comprises a leading edge 332 and a face center 328. The leading edge 332 denotes the junction between the striking face 302 and the sole portion 308 and constitutes the locus of points each being the specific forwardmost point of the striking face 302 of each front-to-rear vertical cross-section through the striking face 302. The leading edge, as a whole, includes a forwardmost-point 336 (see FIG. 9). “Face center,” as used in, refers to a point located on the striking face 302 that is: (a) vertically aligned with the forwardmost point 336 of the leading edge 332; and (b) vertically midway between an upper extent and a lower extent of the scorelines 338 of the striking face 302.

[0076] The golf club head 300 further includes a center of gravity 330. The center of gravity 330 is preferably positioned as described in U.S. patent application Ser. No. 15 / 342,822, herein incorporated by reference in its entirety. Specifically, the center of gravity is laterally spaced from the face center 328 by a distance D1 no greater than 6 mm, more preferably no greater than 4 mm, and even more preferably no greater than 2 mm from the face center. Additionally, in some aspects, the center of gravity is located heelward of the face center 328 (i.e. has a positive x value) (see e.g. FIG. 7). Additionally, or alternatively, the center of gravity 330 is spaced rearward from the striking face 302 by a distance D2 that is no greater than 2 mm, measured in a front-to-rear direction and perpendicular to the face plane 338. More preferably, D2 is no greater than 1 mm and, in some aspects D2 is negative (signifying a center of gravity 330 located forward of the striking face 302).

[0077] Alternatively, or in addition, the golf club head 300 further includes an auxiliary recess preferably extending from an abutment surface of the internal bore of the hosel 304, as described in U.S. patent application Ser. No. 18 / 229,972. Alternatively, or additionally, the striking face 302 of the golf club head 300 is preferably textured to exhibit metrological characteristics 20 ribbedbed in U.S. patent application Ser. No. 18 / 771,444.

[0078] Referring specifically to FIGS. 8 through 11, the muscle portion 320 of the club head 300 includes an upper surface 340 and a lower (sole) surface 342. A recess 346 is preferably located in the upper surface 340 and extends toward the lower (sole) surface 342. In some aspects the recess 456 is covered with an insert or plaque 344.

[0079] In some aspects, the golf club head 300 constitutes plural golf club heads forming a correlated set of golf club heads, e.g. a set of wedges. In some aspects, such plural correlated golf clubs heads bear similar features but vary progressive in loft. For example, FIGS. 11A and 11B show two club heads of a correlated set of golf club heads, e.g. wedges. These club heads 11A and 11B bear similar aesthetic, structural and mass-related features, but differ in loft. Preferably the golf club head of FIG. 11A has a loft of 56° and the golf club head 300b of FIG. 11B has a loft of 58°. In each case, the golf club head is shown in vertical cross-section through a virtual plane A-A′ passing through the face center 328 as shown in FIG. 7.

[0080] As shown e.g. in FIG. 11A, the plaque 344a is secured to the main body of the club head, via placement within recess 346a to form a hollow region 348a. Preferably, the hollow region is substantially fully enclosed by the plaque 344a and the main body of the club head 300, more preferably entirely enclosed. The golf club head of FIG. 11B preferably has a loft greater than the loft of the club head of FIG. 11B. By way of example, the loft of the club head 300b may be 58°. Additional club heads are anticipated as optionally comprised within the correlated set, which plurality of golf club heads may range in loft from bout 38° to about 60°.

[0081] The plaque 344b as located within the recess 346b of the club head 300b of FIG. 11B preferably also forms a hollow region 348b. Preferably the depth of the hollow region from insert to main body measured in the front-to-rear directions varies with loft within the correlated set. For example, the depth D3a of the hollow region 348a is greater than the depth of the hollow region 348b by at least 1 mm, more preferably at least 2 mm. Alternatively, or in addition, the depth D3a is preferably at least 1.5 times greater than D3b, more preferably at least 2.0 times D3b. Thus, preferably, hollow region depth preferably decreases with increasing loft for at least two, more preferably three and even more preferably all club heads within a correlated set of golf club heads that each differ in loft from each other.

[0082] Despite this preferred variation in hollow region depth, for purposes of reducing manufacturing costs, structurally identical plaques are preferably used for plural club heads, varying with loft, within the correlated set of golf club heads. Preferably for a correlated set of at least 3 golf clubs that each differ from each other in loft, at least 2 of the club heads bear such plaques that are structurally identical, more preferably 3 of the club heads bear structurally identically plaques and / or each club head of the correlated set bears a structurally identifical plaque.

[0083] Additionally, or alternatively, the plaque 300 is recessed beneath the outermost edge of the recess 346. In this manner, the plaque may be well-supported and structurally viable given typical repeated impacts of the golf club head with a golf ball. Yet, the higher rising and thicker recess wall, constituting the muscle portion, provides for greater manipulation of discretionary mass. Preferably, in some aspects, the recess wall is varied such that the wall is thicker proximate the toe end, which inter alia promotes a toe-ward shift in location of the club head center of gravity. This may in some cases, counter-act the natural heelward position of the center of gravity due to provision of the hosel 304.

[0084] In some aspects, the recess 346 preferably also includes a stepped down region forming a ledge 350. The plaque 344 accordingly preferably includes an inset stepped region complementary to the ledge 350 to securely mate with the recess 346. The ledge is preferably located at least at the rear surface of the recess 346, but may alternatively extend along the majority of the periphery of the insert and in some cases along the entirety of the periphery of the recess 346. In aspects where the ledge only partially extends about the periphery of the recess 346, the ledge 350 preferably transitions by blending into the remaining region of the inner surface of the recess 346. The presence of the left 350 provides more secure seating and precise placement of the plaque 344, while also providing for greater mass in the sole 308, thus increasing forgiveness of the club head 300.

[0085] Referring to FIGS. 12A and 12B, the plaque 344 preferably includes an upper surface 352 and a lower surface 354. The upper surface is generally planar, but may include facets, steps and undulation. The upper surface 352 may also include indicia and be visible to the golfer as it is preferably exposed when secured to the main body of the club head 300. The lower surface 354 is preferably not visually exposed once secured to the main body of the club head 300. The lower surface 354 may comprise additional hollow portions, e.g. a thin-walled cellular matrix structure to further increase discretionary mass that may be relocated to more advantageous locations about the club head 300.

[0086] The plaque 344 may comprise a unitary composition, however preferably comprises plural components secured together by mechanical fasteners, chemical adhesive and / or co-molding. Preferably, the plaque assembly as a whole comprises an overall density less than a density of the main body of the club head 300. In some aspects, the density of the plaque is less than 7 g / cm3, more preferably no greater than 5 g / cm3 and even more preferably between about 2 g / cm3 and 5 g / cm3. The majority of the plaque preferably comprises a polymeric material, for example TPU, polyamide, polyamide, rubber, polybutadiene, propylene, ethylene. The polymeric component Is preferably co-molded with a thin, metallic plate, e.g. of aluminum, that forms a substantial portion (and in some aspects substantially the entirety) of the visually exposed surface of the plaque 344.

[0087] Referring to FIG. 7, the virtual hosel axis 304 intersects the virtual ground plane 328 at an intersection point 356. A virtual vertical plane 358 perpendicular to the striking face plane 338 (see FIG. 9) passes through the intersection point 356. The club head 300 further includes a toe-wardmost point 360. A second virtual vertical plane (i.e. “toe plane”) 362 perpendicular to the striking face plane 338 passes through the toe-wardmost point 360. Preferably, the recess 346, and optionally the plaque 344, extend(s) laterally a majority of the distance between the virtual toe plane 362 and the virtual vertical heel plane 358, more preferably at least 65% of such distance, even more prefererably at least 75% of such distance, and yet even more preferably at least 85% of such distance. In increasing the lateral extent of the recess 346 and plaque 344, a traditional look is maintained and feel is believed more consistently exhibited at various impact locations on the striking face 302.

[0088] Additionally, or alternatively, the golf club head 300 is preferably forgiving on off-centered shots, based in part on the feature described above, as well as other considerations. The moment of inertia about a vertical axis passing through the center of gravity 330, Izz, is preferably no less than 3000 g·cm2, more preferably no less than 3500 g·cm2 and even more preferably no less than 4000 g·cm2. A moment of inertia about an axis extending in the heel-to-toe direction and passing through the center of gravity 330, Iyy, is preferably no less than 1000 g·cm2, more preferably no less than 1150 g·cm2, and even more preferably no less than 1200 g·cm2. Additional or alternative mass-related features are anticipated, for example those described in U.S. application Ser. No. 18 / 220,972, herein incorporated by reference in its entirety.

[0089] In the foregoing discussion, the present invention has been described with reference to specific exemplary aspects thereof. However, it will be evident that various modifications and changes may be made to these exemplary aspects without departing from the broader spirit and scope of the invention. It is contemplated that the exemplary steel compositions described herein may be applied in like scenarios, e.g. in use cases known to be functionally similar to the golf club head functionality described herein. For example, such steel compositions may be applied to figure skating or ice skating blades where strength and ductility may be necessary given typical cyclical loading and desirability for forging or cold working. Yet surface hardening may also be beneficial in such cases. Similarly, such steel compositions may be applied to edges used in skis, snowboards, and related snow-glideable equipment for similar reasons. Particularly in the case of snow-glideable equipment, such edges must exhibit sufficient malleability to be formed about irregular or complex perimetric shapes yet exhibit sufficient surface hardness and wear resistance / rust resistance given their expected repeated interaction with snow and ice. Accordingly, the foregoing discussion and the accompanying drawings are to be regarded as merely illustrative of the present invention rather than as limiting its scope in any manner.

Examples

Embodiment Construction

[0027]In one aspect of the present disclosure, referring to FIGS. 1 and 2, a club head 100 is shown. The golf club head 100 includes a front portion 122 including a striking face 102, a top portion 106 and a sole portion 108 opposite the top portion 106. The sole portion 108 is configured to rest on a virtual ground plane, e.g. ground plane 108, when in a reference position. The golf club head 100 further include a heel portion 112 and a toe portion 110 opposite the heel portion 112. A hosel portion 104 extends from heel portion 112. The hosel portion 104 includes a hosel bore (not shown) configured to receive a golf shaft (not shown). The golf club head 100, once combined with a golf shaft may form a golf club. The hosel portion 104 defines a virtual hosel axis 124 being a central axis defined by the hosel bore. The hosel axis 124 in relation to the remaining structure of the club head 100 defines a club head loft and lie.

[0028]As used herein, “reference position” refers to a posit...

[0001] This application is a continuation-in-part of U.S. patent application Ser. No. 18 / 771,457, which is a non-provisional of U.S. Provisional Application No. 63 / 614,154, filed on Dec. 22, 2023, the disclosures of each of which are incorporated herein by reference in its entirety.BACKGROUND

[0002] Golf clubs from a technical perspective undergo a unique set of rigors. For example, golf clubs are evaluated in their ability to meet performance thresholds such as efficient transfer of energy to a golf ball upon impact. Golf clubs are also evaluated in terms of their ability to provide forgiveness on off-centered shots or mis-hits. Further, golf clubs in some cases are evaluated in their ability to impart specific spin characteristics or other attributes to a golf ball upon impact for shaping flight trajectory and / or ball roll characteristics. Apart from performance, club heads are expected to withstand repeated use, e.g. resist wear, rust, and material fatiguing. Some club heads are also expected to permit a degree of adjustability by plastic deformation, e.g. hosel bending to adjust loft and / or lie.

[0003] Golf club manufacturers desire to achieve success across all or as many of these aspects of use as possible. But the varied nature of these functional desirables, and provision of limitations, e.g. regarding mass, physical dimensions, and cost, often lead to design conflicts and tradeoffs. For example, increasing the forgiveness of a club head, e.g. by increasing its moment of inertia about preferred axes often comes at the cost of desirable feel. Similarly, adapting a club head to impart beneficial spin and wear resistance may likely involve a material selection that could adversely affect other considerations. For example, conventional materials that offer high hardness, high yield strength and adequate machineability often fall short in other key areas such as malleability or softness, which is preferable regarding the provision of adjustability or bendability.

[0004] To minimize the severity of such design trade-offs, manufacturers have considered selectively varying club head materials about the structure of the club head to better match material properties with structural function. For example, iron-type club heads, e.g. wedges, have implemented face inserts of a material different from that of a main body to which the face insert is secured. Accordingly, the face insert may be selected to exhibit properties ideal for impact, such as relatively high hardness, low density, adequate wear resistance, and adequate machineability. Yet, the material of the main body may appropriately depart from those properties and instead be selected to exhibit e.g. a higher density and greater malleability.

[0005] Selectively positioning different materials about the structure of a club head, although with apparent benefit, is not without detriment. First, increasing the number of components constituting a club head increases its cost and complexity in manufacture. As a result, margins of error in manufacturing may increase as may locations of failure e.g. given the imposition of adhesives, mechanical fasteners and heat-affected zones resulting from welding or brazing. Also, departure of a club head from solid structure toward componentized structure may result in deleterious loss of feel and poor acoustics or vibratory properties.SUMMARY

[0006] An object, therefore, of the present disclosure is to provide material compositions, and implementations thereof, that are in themselves suitable for varied use aspects expected of golf club heads. Accordingly, benefits associated with selectively corresponding material properties with particular club head structure may be achieved, while detriments associated with unduly componentized structure may be minimized or avoided.

[0007] In one aspect, a golf club head includes a unitary component formed of a stainless steel material. The unitary component has variable hardness. A first portion of the component exhibits a first hardness H1 no less than 50 HRC. A second portion of the component exhibits a second hardness H2 no greater than 85 HRB.

[0008] In another aspect of the present disclosure, a method includes forming a component of a golf club head. The component comprises a stainless steel material. The method includes selectively surface hardening the component such that a first portion of the component exhibits a first hardness H1 no less than 50 HRC and a second portion of the component exhibits a second hardness H2 no greater than 85 HRB.

[0009] In another aspect of the present disclosure, a component for a golf club head includes a stainless steel material. The stainless steel material has a Nickel content no greater than 0.25% by mass.

[0010] In another aspect of the present disclosure, a component for a golf club head includes a stainless steel material. The stainless steel material has a Carbon content no less than 0.25% by mass.

[0011] In another aspect of the present disclosure, a component for a golf club head includes a stainless steel material. The stainless steel material has an austenization temperature no less than 800° C.

[0012] These and other features and advantages of the golf club heads, their compositions, and manufacturing methods thereof according to the various aspects of the present disclosure will become more apparent upon consideration of the following description, drawings, and appended claims. The description and drawings described below are for illustrative purposes only and are not intended to limit the scope of the present invention in any manner.BRIEF DESCRIPTION OF THE DRAWINGS

[0013] FIG. 1 shows a front elevation view of an exemplary golf club head in accordance with one or more aspects of the present disclosure.

[0014] FIG. 2 shows a rear elevation view of the exemplary golf club head of FIG. 1.

[0015] FIG. 3 shows a flow chart of a method of manufacturing a golf club head in accordance with one or more aspects of the present disclosure.

[0016] FIG. 4 shows a chart providing material properties of an exemplary steel composition and known steel compositions in accordance with one or more aspects of the present disclosure.

[0017] FIG. 5 shows a line chart providing relationship information between tempering temperature and hardness for the exemplary steel composition of FIG. 4 and another known steel composition.

[0018] FIG. 6 shows a chart providing relationship information between Carbon content, tempering temperature, and “as-quenched” hardness for the exemplary steel composition of FIG. 4 and other known steel compositions.

[0019] FIG. 7 shows a front elevation view of an exemplary golf club head in accordance with one or more aspects of the present disclosure.

[0020] FIG. 8 shows a rear elevation view of the exemplary golf club head of FIG. 7.

[0021] FIG. 9 shows a toe elevation view of the exemplary golf club head of FIG. 7.

[0022] FIG. 10 shows a heel elevation view of the exemplary golf club head of FIG. 7.

[0023] FIG. 11A shows a cross-sectional view of an exemplary golf club head of FIG. 7 through plane A-A′ being a first-lofted club head of a correlated set of differently-lofted golf club heads.

[0024] FIG. 11B shows a cross-sectional view of an exemplary golf club head of FIG. 7 through plane A-A′ being a second-lofted club head of a correlated set of differently-lofted golf club heads.

[0025] FIG. 12A shows a rear perspective view of a plaque of the exemplary club head of FIG. 7.

[0026] FIG. 12B shows a front perspective view of the plaque of the exemplary club head of FIG. 7.DETAILED DESCRIPTION

[0027] In one aspect of the present disclosure, referring to FIGS. 1 and 2, a club head 100 is shown. The golf club head 100 includes a front portion 122 including a striking face 102, a top portion 106 and a sole portion 108 opposite the top portion 106. The sole portion 108 is configured to rest on a virtual ground plane, e.g. ground plane 108, when in a reference position. The golf club head 100 further include a heel portion 112 and a toe portion 110 opposite the heel portion 112. A hosel portion 104 extends from heel portion 112. The hosel portion 104 includes a hosel bore (not shown) configured to receive a golf shaft (not shown). The golf club head 100, once combined with a golf shaft may form a golf club. The hosel portion 104 defines a virtual hosel axis 124 being a central axis defined by the hosel bore. The hosel axis 124 in relation to the remaining structure of the club head 100 defines a club head loft and lie.

[0028] As used herein, “reference position” refers to a position of the golf club head, e.g. club head 100, wherein a hosel centerline lies in an imaginary vertical hosel plane relative to a ground plane 102, the hosel plane intersects a striking face plane along a line parallel the scorelines, and the scorelines 113 generally extend parallel to the ground plane 102

[0029] Preferably, the club head 100 is an iron-type club head, e.g. having a loft between 20° and 66°. More preferably, the club head 100 is a wedge-type club head, e.g. having a loft between 40° and 66°. Additionally, or alternatively, the club head 100 bears a lie between about 62° and about 66°, more preferably between 61° and 63°. However, the structures and material compositions described herein may readily apply to other types of golf club heads, e.g. woods including drivers, fairway woods, and hybrids, as well as putters, rescue clubs, etc.

[0030] The golf club head preferably comprises a steel material, preferably a stainless steel material. Typically, readily-available grades of stainless steel are applied in golf club head construction, particularly for iron-type, including wedge-type, club heads. For example, AISI 431 alloy steel is a commonly used material in golf club heads and components thereof. However, in consideration of the unique set of rigors and constraints associated with golf club heads, particularly wedge-type golf club heads, as well as the desire to minimize the severity of design trade-offs, steel compositions different from conventional materials, say AISI 431, may be advantageous. For all purposes herein, a steel alloy is considered to be a stainless steel if its Chromium content is at least 10.5% by mass.

[0031] Preferably, a majority (i.e. greater than 50%) of the club head 100, by mass, is comprised of such steel, more preferably at least 85% of the club head 100, even more preferably substantially the entirety of the club head 100 (e.g. accounting for minor auxiliary components such as paints, thin coatings, mouse glue, ferrules, etc.). Alternatively or additionally, such steel preferably constitutes a unitary component of the club head 100, more preferably a unitary component that includes a first portion forming at least a portion of the striking face 102, even more preferably also including a second portion forming at least a portion of the hosel portion 104 and yet even more preferably including a third portion forming at least a portion of the rear portion 116 of the club head 100. The club head 100 is preferably solid in shape having an upper blade portion 118 and lower muscle portion 120 proximate the sole portion 108. In some aspects, substantially the entirety of the club head 100 is unitarily formed of such steel. As discussed above, reducing the number of the components required in the build of the club head 100 may provide benefits in reducing manufacturing cost, reducing manufacturing tolerances, and reducing locations susceptible to failure, while maintaining desirable feel, acoustics and vibratory characteristics.

[0032] Preferably, though, the composition of the steel described above is selected such that it provides material properties that are particularly beneficial for use in a golf club head. Conventionally available grades of steel have some adequate properties regarding club heads but are also believed to have properties not particularly relevant to golf club head use. For at least these reasons, tailoring steel composition for use associated with club heads may provide benefits with no or little detriment. Also, preferably, tailoring steel composition for use associated with club heads may permit greater flexibility in varying club head properties on a structure-by-structure basis.

[0033] As described above, the golf club head 100 is preferably an iron-type club head, more preferably a wedge-type club head. Accordingly, adapting main body material composition to the specific use aspects of such club heads may result in outweighed benefit. Particular attention is drawn to hardness characteristics, wear resistance and density for their believed relevance to wedge-type club heads. However, other characteristics may be taken into consideration also.

[0034] Hardness is an example of a property of which desirable application is unique in the case of golf club heads. On one hand, a striking face, e.g. striking face 102, preferably comprises a relatively hard surface. Yet, other portions of a club head, e.g. club head 100, are preferably softer and / or more malleable, e.g. the hosel portion 104. Such malleability supports adjustability by plastically deforming the club head, e.g. modifying loft and / or lie by hosel bending. This duality in hardness desirability is a unique aspect of golf club head functionality and is believed to justify deviation from conventional material composition.

[0035] One concern regarding conventional steels is their limitations in providing for manipulation of hardness. For example, 431 Stainless Steel exhibits an austenization temperature of about 720° C., which in turn enables tempering at a temperature no greater than about 700° C.; exceeding this temperature deleteriously raises the likelihood of austenite transformation and rehardening. Thus, maintaining malleable qualities while achieving a striking face of relatively high hardness may be challenging.

[0036] Such limitations on hardening are believed closely correlated with Nickel content in steels, other material constituents notwithstanding. Nickel is believed to be a strong austenite promoter. This in turn is believed to affect, by decreasing, an austenization temperature. In turn, this is believed to raise the minimum achievable hardness by such steel in a quenched and tempered state. For example, 431 Stainless Steel is believed only capable of being softened to about 85 HRB by quenching and tempering. Remedial processes may counteract this deficiency, such as a softening processes that includes holding such steels at temperatures about their austenization temperature and slowly cooling. However, these remedial processes are not without detriment themselves, e.g. reduced wear resistance. Such remedial processes also complicate, and increase the cost of, manufacturing. Thus, a steel composition capable of achieving desirable variation in hardness, by virtue of quenching and tempering, alone, is preferable.

[0037] Accordingly, the steel composition of the club head 100 preferably comprises a Nickel content no greater than 0.5% by mass, more preferably no greater than 0.35% by mass. However, notably, even reducing Nickel composition to no greater than 0.25% by mass, or more preferably about 0.2% by mass, the club head 100 may be capability of exhibiting superior properties, e.g. hardness variation and wear resistance, with little believed detriment. Accordingly, an exemplary preferably range of Nickel content of the steel composition of the golf club head 100 is between 0.07% and 0.27% by mass. Provided such a Nickel content, the steel can exhibit an austenization temperature no less than 800° C., preferably no less than 850° C., and even more preferably equal to about 870° C. As a result, the steel may likely be capable of being tempered at temperatures of at least 800° C. This may result in a capability to soften the steel to 90 HRB or less after quenching and tempering (e.g. 89 HBR or less), substantially increasing bendability, e.g. to accommodate loft and / or lie adjustment by hosel bending. Preferably, the steel exhibits material properties permitting up to about 4° of angular adjustment of the hosel portion whether in loft adjustment or lie adjustment. Generally, in some alternative aspects, the content of Nickel may be reduced to be below 0.2% without significant detriment, particularly in the case of a wedge-type club head. However, lower limits of Nickel content may correspond to unacceptable impact energy and should be evaluated on that basis.

[0038] Hardness characteristics of steel are also believed substantially affected by Carbon content. Other material constituents notwithstanding, increasing Carbon may generally be considered to increase maximum achievable hardness of a steel in a quenched state. For example, 431 Stainless Steel is believed to have a Carbon content of about 0.1% by mass and to exhibit a maximum hardness in a quenched state of around 40 HRC. 8620 Stainless Steel is believed to have a Carbon content of about 0.2% by mass and to exhibit a maximum hardness in a quenched state of about 45 HRC. Preferably, the steel of the club head 100 has a Carbon content of no less than 0.13% by mass, more preferably no less than 0.15% by mass, even more preferably no less than 0.20% by mass, and yet even more preferably no less than 0.25% by mass. Other constituents notwithstanding, the steel of the club head 100 in a quenched state can exhibit a hardness no less than 50 HRC, more preferably no less than 55 HRC, even more preferably no less than 60 HRC and yet even more preferably between 60 HRC and 65 HRC.

[0039] In addition to its own direct benefits, Carbon is believed, to a degree, to be an effective substitute for Nickel. Thus Carbon permits the advantageous reduction in Nickel content as described above. In addition to such hardness benefits, such Carbon content ranges are believed to contribute to improved wear resistance and reduced material density.

[0040] If, however, Carbon content is too high, deleterious effects may result. For example, manufacturing issues such as problems with weldability and solidification may be presented. Also, Carbon content, in association with Nickel and other constituents, is believed to contribute to the steel's austenization temperature. Specifically, a relatively high Carbon content may lower austenization temperature as it is believed to be a strong austenite promoter. As a result, the steel may be deleteriously limited in its above-mentioned capability to be softened by tempering to a hardness no greater than 90 HRB. Thus, the steel of the club head 100 preferably has a Carbon content between 0.13% and 0.50% by mass, more preferably between 0.22% and 0.50% by mass, even more preferably between 0.22% and 0.27% by mass. However, higher Carbon contents, e.g. in a range of 0.45% to 0.50%, may be particularly preferable in cases where capability of achieving higher hardnesses are prioritized over lower minimum hardness, e.g. for purposes of adjustability as described above.

[0041] Notwithstanding other factors correlated with wear resistance, increased hardness itself is believed correlated in part with greater wear resistance. Thus, the capability of quenching the above steel to achieve a higher hardness in turn may increase wear resistance and strength. This may be particularly true in the case of specific heat treat processes such as laser etching or laser peening in combination with the Carbon contents described above.

[0042] The content of Chromium is also believed to contribute to material properties of steel uniquely relevant to golf club heads. This is particularly true regarding hardness and wear resistance, including resistance to rust. Preferably, the content of Chromium present in the steel of club head 100 is selected primarily based on improving these properties, as described below in further detail.

[0043] As described above, the club head 100 preferably exhibits a relative high

[0044] hardness at striking face locations, and relative low hardness at other locations, e.g. the hosel portion 104 and / or the rear portion 116. Chromium, in addition to Nickel and Carbon as described above, may contribute to achieving these desired club head properties. For example, steel composition, apart from its per se hardness properties, may also indirectly affect hardness. For example, steel composition may dictate which surface processing options, e.g. surface hardening or case hardening, may be effectively applied and their degree of success. For example, in some aspects, the striking face 102 undergoes a surface hardening process, preferably a nitriding process. In some aspects, other surface hardening processes may be applied, either in substitution or in addition to nitriding, such as carburizing, carbonitriding, normalizing, case hardening, induction hardening, cyaniding, flame hardening and laser hardening. However, nitriding is preferable as it is believed to be cost-effective and to achieve the most satisfactory results. Because of the presence of Chromium, a nitriding process is capable of permitting Chromium Nitride to form on the striking face 102. In turn, this permits the striking face 102 to exhibit a surface hardness of no less than 1200 HV (0.05). Otherwise, e.g. for a conventional carbon steel, maximum achievable hardness may be significantly less, e.g. about 800 HV (0.05).

[0045] Nitriding may also bear drawbacks. For example, nitriding stainless steel has been shown to decrease corrosion resistance. However, considering the overall use characteristics of a club head, particularly the wedge-type club head 100 of FIG. 1, the hardness benefits achieved by virtue of steel composition and surface hardening, e.g. nitriding, are believed to outweigh this potential detriment.

[0046] Regarding rust, preferably, the steel composition is adapted to reduce or minimize propagation of rust or natural oxidation. In some alternative aspects, rusting or oxidizing of the striking face 102 of the club head 100 may be viewed as a positive development. For example, a niche market exists for golf club heads with striking faces exhibiting rust or having characteristics specifically selected to promote rust. Such client base of golfers favors the particular texture, appearance, and / or surface roughness characteristics associated with a rusted face. However, in general, preferably, the club head 100 is configured to reduce the onset or propagation of rust. It is believed that club heads susceptible to rust wear faster than club heads not so susceptible. This may be because rust on a striking face is believed to wear faster than regions not exhibiting rust, resulting in a greater rate of volume loss of the rusted club head. This is of particular concern regarding scoreline structure. The presence of Chromium in the steel reduces the onset and propagation of rust, thus likely reducing rate of wear.

[0047] Based on the above considerations, the steel implemented in the club head 100 preferably includes Chromium in an amount no less than 13% by mass, more preferably no less than 14% by mass, even more preferably no less than 16% by mass. Additionally, or alternatively, the steel includes Chromium in an amount no greater than 21% by mass, more preferably no greater than 18% by mass. A preferable range of Chromium content in the steel of golf club head 100 is between 16.5% and 18.0% by mass. A Chromium content that is too high may frustrate the steel's transition to martensitic crystalline structure, may result in a steel that is too brittle, and / or may deleteriously result in sigma phase formation during tempering.

[0048] In addition to the considerations described above affecting rust reduction and wear, the Chromium contents described above—in association with the described Carbon and Nickel contents—desirably reduce overall steel density. The density of a metallic material is primarily affected by two attributes: (1) the composition of the alloy; and (2) the formation in which its atoms are arranged.

[0049] A simplified method to estimate the actual density of an alloy is to calculate density as derived solely from constituent content information, herein referred to as an alloy's “theoretical density.” Because theoretical density provides useful aggregate information about an alloy's composition, it is considered a useful material property in its own right, regardless of whether it may differ from an actual, measured density of the same alloy. Theoretical density is determined by taking the percent by weight of each constituent element and divide it by the density of the constituent element to return the total volume of each element. Then, assume a 100 g sample and divided by the sum of the volumes as shown in Equation 1 below:ρalloy=100⁢ g∑wt. %Element⁢1·1⁢ gρElement⁢ 1+wt. %Element⁢ 2·1⁢ gρElement⁢ 2⁢ …Preferably, the theoretical density of the steel composition implemented in golf club head 100 is no greater than 7.56g / cc.

[0051] The other key contributor (i.e. (2) as described above) to steel density is the structure in which the atoms are arranged or the structure's crystal structure. For this reason, in part, an alloy's actual density may differ from its theoretical density describe above. The steel of the club head 100, based on its constituent compositions described above, once tempered and / or quenched, is preferably a mixture of Ferrite, which has body centered cubic structure (BCC), and Martensite—or substantially entirely, or entirely—Martensite. Martensite exhibits body centered tetragonal (BCT) structure in the quenched state and body centered cubic (BCC) structure in the tempered state. Thus, the relative proportions of Martensite's crystal structure is dependent on the amount of tempering after quenching. BCC and BCT structures have an atomic packing factor, i.e. amount of atom volume per unit cell, of 0.68. Because the packing factors for BCC and BCT structures are similar, overall material density is believed primarily governed by composition of the alloy.

[0052] Another common metallic crystal structure is face centered cubic (FCC) which has an atomic packing factor greater than BCC or BCT, of 0.74, indicative of a close packed structure. Austenite has an FCC structure so it will generally have a higher density than the blended composition of the steel of the club head 100, even though its theoretical density according to the above Equation 1 would be lower.

[0053] Based on the above, the actual density of the steel is preferably no greater than 7.85 g / cm2, more preferably no greater than 7.67 g / cm2 and even more preferably no greater than 7.60 g / cm2. Reducing density increases discretionary mass of the club head 100, i.e. mass not primarily required for the structural integrity of the club head thus capable of being placed in locations for purposes of enhancing the various mass properties of the club head 100, e.g. the location of the center of gravity and moments of inertia about relevant axes passing through the center of gravity.

[0054] The constituent composition of Nitrogen in the steel of the club head 100 is also significant. Nitrogen may affect steels in a similar manner as does Carbon. This is due to their similar size, i.e. Nitrogen and Carbon may both be considered interstitial elements. Accordingly, as with Carbon, Nitrogen is a strong austenite promoter. Thus, increasing Nitrogen composition beyond a certain point may deleteriously result in increased minimum quenched and tempered hardness. Further, if too high in content, Nitrogen may result in partitioning problems of the steel during welding and solidification due to its small size and relatively high diffusion rates. Further, if too high in content, Nitrogen may also result in the steel alloy's loss of ductility, undesirable toughness, and corrosion resistance by the formation of CrN. Nitrogen may influence the maximum strength of stainless steels, albeit to a believed lesser extent than Carbon.

[0055] Based on the above considerations, the steel of the club head 100 preferably includes Nitrogen content in an amount no greater than 0.035% by mass, more preferably no greater than 0.15% by mass, even more preferably within the range of about 0% to 0.06% by mass. Because of its shared characteristics with Carbon, the combined content of Carbon and Nitrogen also bears significance. Preferably, this combined content in the steel of the club head 100 is no less than 0.13%, more preferably no less than 0.17% by mass, even more preferably no less than 0.19% by mass, yet even more preferably no less than 0.24% by mass. As an example, a preferably range of Nitrogen content in the steel composition of the golf club head 100 is between 0.0% and 0.06%. Additionally, or alternatively, the combined content of Nitrogen and Carbon in the steel of club head 100 is within the range of 0.13% to 0.75% by mass, more preferably within the range of 0.24% to 0.35% by mass. In this case, if such content is too low, the steel may not be capable of hardening to a desirable degree, may exhibit reduced wear residence and may exhibit undesirably high density.

[0056] The above description details preferable steel composition embodiments for use in golf club head 100. Table 1 below summarizes several exemplary steel compositions corresponding to the above description. Exemplary Steel A corresponds to a first, general example of the steel used in golf club head 100.TABLE #1CarbonChromiumNickelSteel(% by mass)(% by mass)(% by mass)Exemplary0.2616.6.15Steel A8620 SS0.18-0.230.4-0.60.4-0.7431 Stainless0.07316.11.66Steel

[0057] A more detailed assessment of the chemical composition of Exemplary Steel A is shown below in Table #2. Some properties of club head 100 are shown in FIG. 4, for alternative cases in which the golf club head 100 is composed of known steels as well as the exemplary steel described herein.TABLE #2Extended Chemical Composition of Exemplary Steel A (% by mass)CSiSPMnNiCrMoCuTiNFePreferred0.22-0.6-0-0-0.3-0.07-16.5-0.1-0.1-00-Bal.Range0.271.00.030.030.70.2718.00.30.30.06Target0.250.8000.50.15170.170.1500Bal.

[0058] Based on the above constituent contents, the exemplary steel composition of golf club head 100 is capable, after quenching, tempering and case hardening, of exhibiting a maximum hardness of no less than 50 HRC, more preferably no less than 55 HRC, yet even more preferably within the range of 60 HRC and 65 HRC. With regard to the Vickers hardness scale, such maximum hardness is preferably no less than 500 HV1 (or no less than 650 HV0.05, more preferably no less than 700 HV0.05). The same steel composition of the golf club head 100, by virtue of its constituent composition, is capable of exhibiting a minimum hardness of no greater than 90 HRB, more preferably no greater than 8 5HRB. With regard to the Vickers hardness scale, such minimum hardness is preferably no greater than 185 HV1 (or no greater than 260 HV0.05,more preferably no greater than 250 HV0.05). Preferably, the component of the club head 100 comprised of this steel includes a first location on the striking face 102 of the club head 100, preferably a second location at a hosel portion 104, and preferably a third location at a rear portion 116 of the club head. In such embodiments, e.g. by virtue of selective surface processing, preferably, the first location has a hardness no less than 50 HRC more preferably no less than 55 HRC, even more preferably within the range of 60 HRC to 65 HRC. Alternative or additionally, the steel component's maximum hardness preferably coincides with the first location, e.g. is located on the striking face 102. Preferably, the second location (and optionally the third location) has a hardness no greater than 90 HRB, more preferably no greater than 85 HRB. Alternatively or additionally, the steel component's minimum thickness is preferably located on a portion other than the striking face 102, and preferably located at the hosel portion 104. However, in some aspects, the location of minimum hardness of the steel component is on the rear portion 116 or another portion of the club head 100.

[0059] In addition or alternatively, a ratio of the steel's maximum hardness (capable by virtue of quenching) to the steel's minimum hardness (capable by virtue of quenching and tempering) determined where both maximum and minimum values are expressed in quantities in association with the Rockwell C Hardness (HRV) Scale) is preferably no less than 4.5, more preferably no less than 6, even more preferably no less than 9, yet even more preferably no less than 12. In some particular embodiments, preferably such ratio is within the range of 12 to 16.25. Expressed another way, the ratio of such maximum hardness to such minimum hardness is preferably no less than 0.5 HRC / HRB (i.e. where maximum hardness is measured and expressed using the HRC scale and minimum hardness is measured and expressed using the HRB scale). Expressed another way, the ratio of such maximum hardness to such minimum hardness is preferably no less than 2.5, more preferably no less than 2.6 (i.e. where maximum hardness and minimum hardness are measured and expressed using the HV1 scale).

[0060] FIG. 3 illustrates a process flow chart 200 describing preferable steps taken in the formation of the club head 100 using the exemplary steel composition aspects described herein. While the steps of process 200 are organized sequentially and preferably intended to occur chronologically in the sequence shown, it is contemplated that one or more steps may occur in a different sequence or be omitted. Further, in some aspects, additional steps or processes may occur chronologically before, after, or between any process step shown and described.

[0061] In step 202, an intermediate club head body is formed by casting, e.g. investment or lost-wax casting. Next, optionally, in step 204, welding is applied to add material and / or repair any regions of the intermediate cast club head body due to artifacts or defects of the casting process. For example, welding material may be applied as filler for regions exhibiting porosity issues. The welding material is preferably a stainless steel material. However, other materials may alternatively be used but, if so, preferably in combination with additional post-processing.

[0062] Next, optionally, in step 206, the intermediate club head body is polished preferably removing any remnants of gates or other artifacts resulting from the casting process 202.

[0063] Next, in step 208, the intermediate club head body undergoes heat treating 208. Preferably, the heat treating process 208 includes at least a quenching process 208A and a tempering process 208B. Initially, in step 208A, preferably the intermediate club head body is held at a temperature of about 1040° C. for a duration of about 90 min to about 120 min, more preferably about 90 min. Subsequently, the intermediate club head body is quenched preferably by immersion in an N2 solution. The result is transition to a harder martensitic structure throughout the majority (i.e. greater than 50%) of the club head body by mass, more preferably throughout no less than 60% by mass, and even more preferably throughout substantially the entirety of the intermediate club head body.

[0064] Next, in step 208B, the intermediate club head body undergoes tempering. In this step, the intermediate club head body is held at a temperature no less than 800° C., more preferably no less than 850° C., even more preferably within the range of 865° C. to 870° C. and yet even more preferably at a temperature of about 870° C. for about 2 hrs. Preferably, subsequently, the intermediate club head body is cooled in an N2 solution. This step tempers the martensite thus softening the intermediate club head body.

[0065] In some embodiments, in step 208, the intermediate club head body undergoes plural heat treat cycles. Applying multiple heat treat cycles is preferable in some cases to both maintain a relatively high potential for face hardness of the steel at the striking face 102 and permitting a final club head hardness that is even further reduced at locations including e.g. the hosel portion 104 and / or the rear portion 116. Such plural cycles may include multiple tempering cycles. As shown e.g. in FIG. 6, applying a double tempering process results in reduced hardness relative single tempering at same temperatures. For example, double tempering at a temperature of about 863° C. for about a 2 hr period results in a hardness of 80 HRB, whereas single tempering at the same temperature and duration results in a hardness of about 96 HRB. A multiple cycle heat treat process may e.g. include the sub-steps shown below in Table #4:TABLE #4TemperatureDurationResultingStepProcess(° C.)(Hrs)Hardness1Heat in Vacuum Furnace1040247 HRC to2N2 Quench and CoolTo 10050 HRCor below3Heat in Vacuum or 870287 HRBGeneral Furnace4N2 Quench and CoolTo 100or below5Heat in Vacuum or830 C.280 HRBGeneral Furnace6N2 Quench and CoolTo RoomTemperature

[0066] Next, in step 210, the striking face 102 is preferably surface milled. Next, in step 212, the hosel / neck region of the intermediate club head body is polished to effect a blended appearance between the striking face 102 and the hosel portion 104. Next, in step 214, scorelines are machined into the striking face 102, preferably by milling.

[0067] Next, in step 216, the striking face 102 undergoes face hardening. Preferably, the face hardening step 216 includes a nitriding process 216A and additional hardening operations, such as laser hardening or laser peening peening in step 216B.

[0068] The step of nitriding 216A occurs at a temperature of preferably no less than about 550° C., more preferably no less than about 575° C., even more preferably at about 580° C., and for a duration of about 50 min. However, alternative or additional face hardening or other protective or cosmetic surface finishing processes are contemplated, such as carburizing, carbonitriding, normalizing, case hardening, induction hardening, cyaniding, flame hardening and coating with PVD, ceramics, and / or diamond). Because of the various constituent compositions described above, the steel applied in the golf club head 100 is believed to exhibit sufficient wear / rust resistance per se, thus not considered to necessitate plating for that purpose. On the other hand, e.g. in the case of 8620 Steel, Nickel and Chromium plating is generally considered necessary for purposes of increasing wear / rust resistance to an acceptable degree.

[0069] Preferably, in step 216B, laser hardening is applied to the nitrided striking face. In this step, for a short period of time (e.g. a few seconds) focused heat energy is directed to the striking face 102. Cooling of the striking face 102 subsequent the laser peening process is preferable using e.g. a gas or water. This laser hardening process preferably affects material extending a depth from the striking face 102 of no less than 0.5 mm, more preferably no less than 0.7 mm, even more preferably about 0.8 mm. Such laser hardening process further hardens the striking face 102, e.g. to a hardness of no less than 50 HRC, more preferably no less than 52 HRC. Based on the above steps, the striking face 102 of the club head 100 preferably achieves hardness and wear resistance values in accordance with embodiments of the club head 100 described above.

[0070] As a result of the face hardening process, hardness through the club head 100, more specifically throughout any component comprised of the inventive steels described herein, exhibit a hardness gradient throughout its thickness. Preferably, the club head 100 exhibits martensitic structure at a depth from the striking face (i.e. measured rearward in a direction perpendicular to a virtual striking face plane generally coplanar with the striking face 102) of no less than 50% of the overall depth of the club head 100, more preferably no less than 90% of the overall depth of the club head 100, and even more preferably substantially the entire overall depth of the club head 100. In specific embodiments in which the striking face 102 undergoes nitriding, preferably the nitriding process results in a CrN layer on the striking face 102 of a thickness no less than 0.02 mm, more preferably no less than 0.03 mm, and even more preferably about 0.04 mm.

[0071] Referring to FIGS. 7 through 12B, a golf club head 300 is shown having a heel portion 312, a toe portion 310 opposite the heel portion 312, a striking face 302 at a front portion 322 and a rear portion 316 opposite the front portion 322 (see specifically FIG. 8). A hosel portion 304 extends from the heel portion 312 and includes a hosel bore configured to receive and secure to the golf club head a tip end of a conventional golf shaft (not shown). The hosel bore defines a virtual (central) hosel axis 324. The golf club head 300 is shown in the reference position and thus the hosel axis 324 lies in a virtual vertical hosel plane 334 (see FIG. 9).

[0072] The golf club head 300 preferably comprises an inventive steel composition for example an inventive steel composition described above with regard to the aspects of FIG. 4. In particular, at least a majority of the mass of the club head 300 is composed of the inventive steel composition described with regard to FIG. 4, and more preferably substantially the entirety of the club head 300 is composed of such inventive composition. In aspects in which the golf club head 300 is only partially comprised of the inventive steel composition, such composition is preferably located at least at the striking face 302. In such cases, optionally, such composition is additionally located at the hosel portion 304. In some such cases, the inventive steel composition is a component that is co-forged with, co-molded with, welded to, brazed to, mechanically fastened to, or otherwise secured to, other components to for a complete golf club head.

[0073] Referring to FIG. 8, the rear portion 316 of the golf club head 300 is shown. The rear portion 316 includes an upper blade portion 318 and a lower muscle portion 320. In some aspects, the golf club head 300 is a wedge-type club head, e.g. having a loft no less than 38°,and more preferably between about 38° and 64°. Accordingly, the upper blade portion 318 and lower muscle portion 320 promote a traditional wedge-like appearance desirable by many golfers. Such structure contributes to advantageous feel and acoustic / vibratory response typically associated with and desired of wedge-type club heads.

[0074] However, in some aspects, the golf club head 300 is more specifically a game improvement type wedge-type club head. While the golf club head 300 preferably embodies features traditional of a wedge-type club head, the golf club head 300 preferably additional includes features that improve forgiveness and other characteristics typically desired by golfers with an average to high handicap. For example, the golf club head 300 includes a perimeter weighting feature 324 defining a rear cavity 326. The perimeter weighting feature 324 preferably extends about substantially the entire periphery of the rear portion 316 of the club head 300, including both the upper blade portion 318 and the lower muscle portion 320. However, the lower muscle portion 320 preferably still includes a stepped up portion mass portion 326 to maintain the traditional wedge-like appearance of the club head 300 and to maintain desirable feel and acoustic characteristics.

[0075] The striking face 302 further comprises a leading edge 332 and a face center 328. The leading edge 332 denotes the junction between the striking face 302 and the sole portion 308 and constitutes the locus of points each being the specific forwardmost point of the striking face 302 of each front-to-rear vertical cross-section through the striking face 302. The leading edge, as a whole, includes a forwardmost-point 336 (see FIG. 9). “Face center,” as used in, refers to a point located on the striking face 302 that is: (a) vertically aligned with the forwardmost point 336 of the leading edge 332; and (b) vertically midway between an upper extent and a lower extent of the scorelines 338 of the striking face 302.

[0076] The golf club head 300 further includes a center of gravity 330. The center of gravity 330 is preferably positioned as described in U.S. patent application Ser. No. 15 / 342,822, herein incorporated by reference in its entirety. Specifically, the center of gravity is laterally spaced from the face center 328 by a distance D1 no greater than 6 mm, more preferably no greater than 4 mm, and even more preferably no greater than 2 mm from the face center. Additionally, in some aspects, the center of gravity is located heelward of the face center 328 (i.e. has a positive x value) (see e.g. FIG. 7). Additionally, or alternatively, the center of gravity 330 is spaced rearward from the striking face 302 by a distance D2 that is no greater than 2 mm, measured in a front-to-rear direction and perpendicular to the face plane 338. More preferably, D2 is no greater than 1 mm and, in some aspects D2 is negative (signifying a center of gravity 330 located forward of the striking face 302).

[0077] Alternatively, or in addition, the golf club head 300 further includes an auxiliary recess preferably extending from an abutment surface of the internal bore of the hosel 304, as described in U.S. patent application Ser. No. 18 / 229,972. Alternatively, or additionally, the striking face 302 of the golf club head 300 is preferably textured to exhibit metrological characteristics 20 ribbedbed in U.S. patent application Ser. No. 18 / 771,444.

[0078] Referring specifically to FIGS. 8 through 11, the muscle portion 320 of the club head 300 includes an upper surface 340 and a lower (sole) surface 342. A recess 346 is preferably located in the upper surface 340 and extends toward the lower (sole) surface 342. In some aspects the recess 456 is covered with an insert or plaque 344.

[0079] In some aspects, the golf club head 300 constitutes plural golf club heads forming a correlated set of golf club heads, e.g. a set of wedges. In some aspects, such plural correlated golf clubs heads bear similar features but vary progressive in loft. For example, FIGS. 11A and 11B show two club heads of a correlated set of golf club heads, e.g. wedges. These club heads 11A and 11B bear similar aesthetic, structural and mass-related features, but differ in loft. Preferably the golf club head of FIG. 11A has a loft of 56° and the golf club head 300b of FIG. 11B has a loft of 58°. In each case, the golf club head is shown in vertical cross-section through a virtual plane A-A′ passing through the face center 328 as shown in FIG. 7.

[0080] As shown e.g. in FIG. 11A, the plaque 344a is secured to the main body of the club head, via placement within recess 346a to form a hollow region 348a. Preferably, the hollow region is substantially fully enclosed by the plaque 344a and the main body of the club head 300, more preferably entirely enclosed. The golf club head of FIG. 11B preferably has a loft greater than the loft of the club head of FIG. 11B. By way of example, the loft of the club head 300b may be 58°. Additional club heads are anticipated as optionally comprised within the correlated set, which plurality of golf club heads may range in loft from bout 38° to about 60°.

[0081] The plaque 344b as located within the recess 346b of the club head 300b of FIG. 11B preferably also forms a hollow region 348b. Preferably the depth of the hollow region from insert to main body measured in the front-to-rear directions varies with loft within the correlated set. For example, the depth D3a of the hollow region 348a is greater than the depth of the hollow region 348b by at least 1 mm, more preferably at least 2 mm. Alternatively, or in addition, the depth D3a is preferably at least 1.5 times greater than D3b, more preferably at least 2.0 times D3b. Thus, preferably, hollow region depth preferably decreases with increasing loft for at least two, more preferably three and even more preferably all club heads within a correlated set of golf club heads that each differ in loft from each other.

[0082] Despite this preferred variation in hollow region depth, for purposes of reducing manufacturing costs, structurally identical plaques are preferably used for plural club heads, varying with loft, within the correlated set of golf club heads. Preferably for a correlated set of at least 3 golf clubs that each differ from each other in loft, at least 2 of the club heads bear such plaques that are structurally identical, more preferably 3 of the club heads bear structurally identically plaques and / or each club head of the correlated set bears a structurally identifical plaque.

[0083] Additionally, or alternatively, the plaque 300 is recessed beneath the outermost edge of the recess 346. In this manner, the plaque may be well-supported and structurally viable given typical repeated impacts of the golf club head with a golf ball. Yet, the higher rising and thicker recess wall, constituting the muscle portion, provides for greater manipulation of discretionary mass. Preferably, in some aspects, the recess wall is varied such that the wall is thicker proximate the toe end, which inter alia promotes a toe-ward shift in location of the club head center of gravity. This may in some cases, counter-act the natural heelward position of the center of gravity due to provision of the hosel 304.

[0084] In some aspects, the recess 346 preferably also includes a stepped down region forming a ledge 350. The plaque 344 accordingly preferably includes an inset stepped region complementary to the ledge 350 to securely mate with the recess 346. The ledge is preferably located at least at the rear surface of the recess 346, but may alternatively extend along the majority of the periphery of the insert and in some cases along the entirety of the periphery of the recess 346. In aspects where the ledge only partially extends about the periphery of the recess 346, the ledge 350 preferably transitions by blending into the remaining region of the inner surface of the recess 346. The presence of the left 350 provides more secure seating and precise placement of the plaque 344, while also providing for greater mass in the sole 308, thus increasing forgiveness of the club head 300.

[0085] Referring to FIGS. 12A and 12B, the plaque 344 preferably includes an upper surface 352 and a lower surface 354. The upper surface is generally planar, but may include facets, steps and undulation. The upper surface 352 may also include indicia and be visible to the golfer as it is preferably exposed when secured to the main body of the club head 300. The lower surface 354 is preferably not visually exposed once secured to the main body of the club head 300. The lower surface 354 may comprise additional hollow portions, e.g. a thin-walled cellular matrix structure to further increase discretionary mass that may be relocated to more advantageous locations about the club head 300.

[0086] The plaque 344 may comprise a unitary composition, however preferably comprises plural components secured together by mechanical fasteners, chemical adhesive and / or co-molding. Preferably, the plaque assembly as a whole comprises an overall density less than a density of the main body of the club head 300. In some aspects, the density of the plaque is less than 7 g / cm3, more preferably no greater than 5 g / cm3 and even more preferably between about 2 g / cm3 and 5 g / cm3. The majority of the plaque preferably comprises a polymeric material, for example TPU, polyamide, polyamide, rubber, polybutadiene, propylene, ethylene. The polymeric component Is preferably co-molded with a thin, metallic plate, e.g. of aluminum, that forms a substantial portion (and in some aspects substantially the entirety) of the visually exposed surface of the plaque 344.

[0087] Referring to FIG. 7, the virtual hosel axis 304 intersects the virtual ground plane 328 at an intersection point 356. A virtual vertical plane 358 perpendicular to the striking face plane 338 (see FIG. 9) passes through the intersection point 356. The club head 300 further includes a toe-wardmost point 360. A second virtual vertical plane (i.e. “toe plane”) 362 perpendicular to the striking face plane 338 passes through the toe-wardmost point 360. Preferably, the recess 346, and optionally the plaque 344, extend(s) laterally a majority of the distance between the virtual toe plane 362 and the virtual vertical heel plane 358, more preferably at least 65% of such distance, even more prefererably at least 75% of such distance, and yet even more preferably at least 85% of such distance. In increasing the lateral extent of the recess 346 and plaque 344, a traditional look is maintained and feel is believed more consistently exhibited at various impact locations on the striking face 302.

[0088] Additionally, or alternatively, the golf club head 300 is preferably forgiving on off-centered shots, based in part on the feature described above, as well as other considerations. The moment of inertia about a vertical axis passing through the center of gravity 330, Izz, is preferably no less than 3000 g·cm2, more preferably no less than 3500 g·cm2 and even more preferably no less than 4000 g·cm2. A moment of inertia about an axis extending in the heel-to-toe direction and passing through the center of gravity 330, Iyy, is preferably no less than 1000 g·cm2, more preferably no less than 1150 g·cm2, and even more preferably no less than 1200 g·cm2. Additional or alternative mass-related features are anticipated, for example those described in U.S. application Ser. No. 18 / 220,972, herein incorporated by reference in its entirety.

[0089] In the foregoing discussion, the present invention has been described with reference to specific exemplary aspects thereof. However, it will be evident that various modifications and changes may be made to these exemplary aspects without departing from the broader spirit and scope of the invention. It is contemplated that the exemplary steel compositions described herein may be applied in like scenarios, e.g. in use cases known to be functionally similar to the golf club head functionality described herein. For example, such steel compositions may be applied to figure skating or ice skating blades where strength and ductility may be necessary given typical cyclical loading and desirability for forging or cold working. Yet surface hardening may also be beneficial in such cases. Similarly, such steel compositions may be applied to edges used in skis, snowboards, and related snow-glideable equipment for similar reasons. Particularly in the case of snow-glideable equipment, such edges must exhibit sufficient malleability to be formed about irregular or complex perimetric shapes yet exhibit sufficient surface hardness and wear resistance / rust resistance given their expected repeated interaction with snow and ice. Accordingly, the foregoing discussion and the accompanying drawings are to be regarded as merely illustrative of the present invention rather than as limiting its scope in any manner.

Examples

Embodiment Construction

[0027]In one aspect of the present disclosure, referring to FIGS. 1 and 2, a club head 100 is shown. The golf club head 100 includes a front portion 122 including a striking face 102, a top portion 106 and a sole portion 108 opposite the top portion 106. The sole portion 108 is configured to rest on a virtual ground plane, e.g. ground plane 108, when in a reference position. The golf club head 100 further include a heel portion 112 and a toe portion 110 opposite the heel portion 112. A hosel portion 104 extends from heel portion 112. The hosel portion 104 includes a hosel bore (not shown) configured to receive a golf shaft (not shown). The golf club head 100, once combined with a golf shaft may form a golf club. The hosel portion 104 defines a virtual hosel axis 124 being a central axis defined by the hosel bore. The hosel axis 124 in relation to the remaining structure of the club head 100 defines a club head loft and lie.

[0028]As used herein, “reference position” refers to a posit...

Claims

1. A golf club head comprising:a loft no less than 38°; anda material having a material composition such that:(a) an Iron content by weight is highest of all constituents;(b) a Chromium content is no less than 10.5% by weight; and(c) a Nickel content is no greater than 0.5% by weight.

2. The golf club head of claim 1, further comprising a rear portion having a perimeter-weighted element.

3. The golf club head of claim 1, further comprising:a striking face having a face center;a center of gravity;a distance D1 being a lateral distance between the center of gravity and the face center, when the golf club head is in a reference position, D1 being no greater than 6 mm.

4. The golf club head of claim 3, wherein D1 is no greater than 4 mm.

5. The golf club head of claim 1, further comprising:a hosel portion having a hosel bore configured to receive a golf shaft, the hosel bore having a side surface and an abutment surface; andan auxiliary recess extending sole-ward from the abutment surface.

6. The golf club head of claim 1, further comprising:a main body having a rear portion and a recess located in the rear portion;a plaque secured to the recess forming a substantially enclosed hollow portion.

7. The golf club head of claim 6, wherein the plaque has an overall density less than 7 g / cm3.

8. The golf club head of claim 6, further comprising:a striking face having scorelines thereon, the scorelines defining a toe-most extent and a heel-most extent, the plaque extending a lateral distance that is a majority of a lateral distance between the heel-most extent and the toe-most extent.

9. The golf club head of claim 1 that, when oriented in a reference position, further comprises:a center of gravity; anda moment of inertia, Izz, about a vertical virtual axis passing through the center of gravity, Izz being no less than 3000 g·cm2. 10 The golf club head of claim 1 that, when oriented in a reference position, further comprises:a center of gravity; anda moment of inertia, Iyy, about a virtual axis passing through the center of gravity and extending in the heel to toe direction, Iyy being no less than 1200 g·cm2.

11. A golf club head comprising:a center of gravity;a moment of inertia, Iyy, about a virtual axis passing through the center of gravity and extending in the heel to toe direction, Iyy being no less than 1200 g·cm2; anda material having a material composition such that:(a) an Iron content by weight is highest of all constituents;(b) a Chromium content is no less than 10.5% by weight; and(c) a Nickel content is no greater than 0.5% by weight.

12. The golf club head of claim 11, further comprising:a striking face having a face center;a center of gravity;a distance D1 being a lateral distance between the center of gravity and the face center, when the golf club head is in a reference position, D1 being no greater than 4 mm.

13. The golf club head of claim 11, further comprising:a main body having a rear portion and a recess located in the rear portion;a plaque secured to the recess forming a substantially enclosed hollow portion.

14. The golf club head of claim 13, wherein the plaque has an overall density less than 7 g / cm3.

15. The golf club head of claim 13, further comprising:a striking face having scorelines thereon, the scorelines defining a toe-most extent and a heel-most extent, the plaque extending a lateral distance that is a majority of a lateral distance between the heel-most extent and the toe-most extent.

16. The golf club head of claim 11 that, when oriented in a reference position, further comprises:a center of gravity; anda moment of inertia, Izz, about a vertical virtual axis passing through the center of gravity, Izz being no less than 3000 g·cm2.

17. A golf club head comprising:a striking face having a face center;a center of gravity;a distance D1 being a lateral distance between the center of gravity and the face center, when the golf club head is in a reference position, D1 being no greater than 4 mm; anda material having a material composition such that:(a) an Iron content by weight is highest of all constituents;(b) a Chromium content is no less than 10.5% by weight; and(c) a Nickel content is no greater than 0.5% by weight.

18. The golf club head of claim 17, further comprising:a main body having a rear portion and a recess located in the rear portion;a plaque secured to the recess forming a substantially enclosed hollow portion.

19. The golf club head of claim 18, wherein the plaque has an overall density less than 7 g / cm3.

20. The golf club head of claim 17 that, when oriented in a reference position, further comprises:a center of gravity; anda moment of inertia, Izz, about a vertical virtual axis passing through the center of gravity, Izz being no less than 3000 g·cm2.

Images