JP4477793B2 - Golf club head and manufacturing method thereof - Google Patents

Description

【００２６】
表１から明らかなように、この種の圧延材は、圧下率が大きいほどその表面硬さが増すとともにその弾性応力限度が向上することが判る。圧延材料、とりわけβ型チタン合金は、冷間で圧延することにより、材料中に多数の転位などの格子欠陥が導入されるため、このように機械的強度が向上する。なお熱間圧延とするとき、再結晶化などが進行して転移が消失し優れた機械的特性が失われやすくなるため好ましくない。他方、ヤング率については、圧下率が変化しても実質的に一定となっている。
【００２７】
本発明では、ゴルフクラブヘッドのフェース部材にこのような圧延材の性質を利用する。即ち、例えばフェース部材７において、ゴルフボールと直接衝突する機会の多い例えばスイートスポットＳを含む中央領域Ａｃを、圧下率が大の高圧延部７ａとしたときには、大きな衝撃力が作用する該中央領域Ａｃにおいて、高い曲げ強度と表面硬さを発揮できヘッド１の耐久性を向上するのに役立つ。前記「スイートスポット」Ｓは、図２に示すように、ヘッド１の重心Ｇからフェース面Ｆに垂直に引いた法線Ｎが該フェース面Ｆと交わる点とする。また、フェース部材７の中央領域Ａｃの外側の領域Ａｐを、圧下率の小さい前記低圧延部７ｂとするときには、打球時においてフェース部材７の周辺領域を中央領域Ａｃに比して大きく撓ませることが可能となるため、打球感の向上（柔らかい打球感）と反発性能の向上とが期待できる。
【００２８】
また上記とは逆に、フェース部２の中央領域Ａｃを低圧延部７ｂとし、その外側の領域７ａを高圧延部７ａとしたときには、打球時にボールと直接接触する中央領域Ａｃをより撓みやすくすることができ、打球感を重視して向上させることもできる。またこの態様の場合、フェース部２の周辺を硬くしうるため、打球時にその部分の変形を抑えることができる。従って、例えばヘッド本体部９とフェース部材７との接合部（溶接部）に大きな応力集中が生じるのを防止しうる。このように、本発明のゴルフクラブヘッド１は、ヘッドの耐久性、反発性、打球感などをバランス良く向上しうる。
【００２９】
前記高圧延部７ａは、特に限定はされないが、好ましくは６５〜９５％、より好ましくは７０〜９０％程度の圧下率で圧延することが望ましい。前記高圧延部７ａの圧下率が６５％未満であると、圧延材１０の機械的特性の向上効果がやや不足する傾向があり、逆に９５％を超えると、機械的特性の向上には効果的ではあるが圧下率が大きくなる分、初期厚さが大の母材を必要とし材料ないし製造コストを増大させる傾向があるため好ましくない。また、このように圧下率が規制された高圧延部７ａが占める表面積が少なすぎると、耐久性の向上効果が得られ難くなるため、高圧延部７ａが占める全表面積Ｓ３と、フェース部２の全表面積Ｓ１との比（Ｓ３／Ｓ１）を０．５〜０．９、より好ましくは０．６〜０．７程度に設定することが特に望ましい。
【００３０】
また低圧延部７ｂも特に限定はされないが、好ましくは８０％以下、より好ましくは１０〜７０％、さらに好ましくは５０〜７０％程度の圧下率で圧延することが望ましい。低圧延部７ａの圧下率が８０％を超えるとフェース部材７の表面硬さが実質的に全域で向上してしまい、打球感や反発性能を悪化させる傾向があり、逆に１０％未満であると圧下率が小さすぎるため、母材の強度向上効果が期待できない傾向がある。さらに、低圧延部７ｂを前記外側の領域Ａｐに設ける場合、中央領域Ａｃの周囲に環状に連続的に形成することが望ましいが、途切れて形成されていても良い。
【００３１】
なお一例として、フェース部材７において、最大圧下率と最小圧下率との差が１５〜５０％程度、より好ましくは２０〜４０％程度であるのが好ましい。これによって、耐久性、反発性能のバランスを良好とする。またフェース部材７は、図３に略示するように、圧下率がフェース部材７の中央領域の高圧延部７ａからその周縁側に向かって徐々に小さくなる低圧延部７ｂ１、７ｂ２…となるように（例えば年輪状に）滑らかに変化するものが望ましい。これにより、フェース部材７において、硬さ、弾性限応力の急激な変化部を無くしさらに耐久性の向上などに役立つ。
【００３２】
本発明で用いるフェース部材７は、例えば図４（ａ）〜（ｃ）のような工程を含んで製造することができる。先ず、図４（ａ）、図５（ａ）、及びそのＡ−Ａ断面である図５（ｂ）に示すように、不均一厚さの母材ｍを準備する。本例の母材ｍは、平面視が円形状をなすともに、下面が平坦かつ上面がその中央部を最も隆起させたドーム状の曲面で形成されたものを示す。これにより、母材ｍは、厚さが最も大の厚肉部Ｍａと、この厚肉部Ｍａよりも厚さが小の薄肉部Ｍｂとを有する。
【００３３】
このような母材ｍは、例えば合金をアーク溶解炉で熔解する熔解工程において同形状のキャビティを有する金型で成形される。不均一厚さの母材ｍは、この例以外にも、例えば図６（ａ）、（ｂ）のように厚さが段階状に変化する部分を有するもの、図７、図８に示すように、厚さが滑らかに変化する部分を有するものなど種々の形状が採用できる。図４〜８では、平面視が円形状のものを例示したが、それに限定されるものではなく、平面視で楕円形状、長方形等であってもよく、フェース部材に加工しうる形状で有れば、いかなる形状でも良い。また、図４〜８では、下面が平坦かつ上面が曲面や段階的変化部分にて隆起するものを例示したが、これとは逆に上面が平坦かつ下面が曲面や段階的変化部分にて隆起するものや、上面と下面が共に曲面や段階的変化部分にて隆起するもの、さらには上面と下面の隆起の程度や隆起面形態が異なっているものでも良い。さらに、簿材の上面や下面の隆起が、曲面と段階的変化の部分の組み合わせからなる面による隆起であっても良いなど種々の形状の母材を用いうる。
【００３４】
次に母材ｍは、本例では図４（ｂ）に示したように一対のロールＲ、Ｒを用いて冷間圧延される。母材ｍは、圧延方向Ｋで圧延され、同図（ｃ）に示すように実質的に均一の厚さｔ’の圧延材１１として成形される。このように、不均一厚さの母材ｍを実質的に均一厚さに圧延することにより、母材ｍの厚肉部ｍａの圧下率は大きく、かつ薄肉部Ｍｂの圧下率は小さくなり、圧下率が異なる圧延材１１を容易に成形することができる。図９（Ａ）には、図４（ｃ）の圧延材１１のＸ−Ｘ断面を、同図（Ｂ）には、その各位置と圧下率との関係を示している。このように、圧延材１１の圧下率は、その端部で小さく、中央部で大きくなる。
【００３５】
前記冷間圧延加工は、本例では、１回の圧延工程での圧下量（厚さの減少量）を例えば０．１〜０．５mm程度とし、これを複数回繰り返すことにより所望の一定の厚さの圧延材１１を形成するものを示している。母材ｍは、その圧延方向Ｋに沿って伸ばされるが、冷間圧延の場合には、その圧延方向Ｋと直角な方向にはあまり大きな伸びは生じない。従って、図４に示した母材の場合、図３に示したように、その中央部分で圧下率が大となる高圧延部７ａとなり、他方その周囲が圧下率が徐々に小さくなる低圧延部７ｂ１、７ｂ２、…が形成できる。また圧延方向Ｋは単一の方向としても良いが、好ましくは互いに交差する２種以上の方向で圧延することが好ましい。圧延方向と、この圧延方向と直角な方向とでは、曲げに対する強度が異なり易いため、このように圧延方向を交差する２種以上とすることにより、材料の機械的強度などの異方性を極力減じる。また前記圧延方向の交差角度は４０〜９０゜とすることが望ましい。
【００３６】
冷間圧延加工は、特に材料を意図的に加熱せずに常温で圧延加工が行われる。冷間圧延加工としては、雰囲気温度と圧延加工の際に生じる材料の発熱を加味し、−２０〜１００℃、より好ましくは０〜１００℃、さらに好ましくは１５〜１００℃で加工することが望ましい。なおこの温度は、加工中に発熱する材料の温度を意味している。圧延加工時の温度が１００℃を超えると、材料の結晶中の転移の再配列や再結晶化が生じ、加工硬化が十分に期待し得ず、ひいては前記機械的強度の向上が充分に望めず、逆に−２０℃を下回ると圧延された圧延材の圧延方向と直角な側縁にひび割れ等が生じやすく材料の歩留まりが悪化しやすい傾向にある。
【００３７】
次に成形された圧延材１１は、本実施形態ではプレス加工され、所定の曲面（ロール、バルジ）に形成された後、図４（ｃ）の如くフェース部材７の形状Ｌに切り抜かれ、研磨加工などが施された後、前記ヘッド本体部９の開口に溶接される。なおプレス工程においても、圧延工程と同様に冷間で行うのが望ましい。またプレスと打ち抜きを行う順序を逆にしても良い。これにより本発明のヘッド１を製造することができる。
【００３８】
なお圧延材１１は、一定の厚さｔ′で圧延される場合の他、各部位で厚さが異なる非一定の厚さで形成することもできる。この場合、例えば溝状の凹みを有するロールなどを用いて圧延することができる。この場合においても、母材の形状により、圧下率を変化させることが可能になる。特に母材ｍの厚肉部を最も大きな圧下率で圧延することにより、容易に高圧延部７ａを形成できる。また、高圧延部７ａの外側に低圧延部７ｂが形成されるとき、上記実施形態のように環状に形成される場合の他、フェース部材の外側であれば、例えばフェース部材の上下（クラウンーソール）の領域や、フェース部材の左右（トウーヒール）の領域にのみに形成するものなど種々の態様で実施しうる。
【００３９】
以上本発明の実施形態についてウッド型のゴルフクラブヘッドを例に取り説明したが、本発明は、ウッド型のゴルフクラブヘッドに限定されるものではなく、アイアン型やパター型、ユーティリティ型の各ヘッドなどにおいても好適に適用しうるのは言うまでもない。またフェース部材は、本例では板状をなすものを示したが、その一部がクラウン部３、ソール部４又はサイド部５の一部を構成するようにもプレスで成形しうる。
【００４０】
【実施例】
次に本発明をより具現化した実施例について説明する。
（実施例１）
フェース部材を、前記式（１）を満たすチタン合金「Ｔｉ50Ｚｒ30Ｎｂ10Ｔａ10」（数字は原子％、原子半径差は最小−最大で約１１．７％）を用いて以下の手順で試作した。
図１０には、この材料を含む各種材料の引張応力−伸び曲線を、図１１には同引張強度とヤング率との関係を夫々示す。図１０、図１１から明らかなように、上記式（１）で表されるチタン合金は、純チタンないしチタン合金（Ｔｉ−６Ａｌ−４Ｖ）よりも高い引張強度（弾性限応力）を有しているにも拘わらず、ヤング率Ｅがそれらのほぼ半分以下と非常に低いものである。従って、このような高強度かつ低ヤング率という特徴を有するβ型チタン合金をヘッドのフェース部材に用いるだけでも、フェース部の耐久性を十分に確保しつつヘッドの反発係数が向上しうる。次に真空引きされかつアルゴン置換された雰囲気中のアーク溶解炉にて前記構成元素を溶解して図５に示すドーム状の母材（外径６０mm×最大厚さ３０mm×最小厚さ６mm）を成形した。そして、この母材を室温２０℃で圧延する冷間圧延を行い３mmの均一厚さの圧延材を成形した。この圧延材の圧下率は、中央部で約９０％、そこから周縁に向かって徐々に小さくなり周縁で約５０％に設定されている。
【００４１】
次に、この圧延材からトウ、ヒール方向のフェース巾１００mm、クラウン−ソール方向のフェース高さ５０mmでフェース部材の形状に打ち抜くとともに、これを室温２０℃で冷間プレス加工を施すことにより、９インチのフェースロール、フェースバルジを有するフェース部材を成形した。なおプレスは曲げ加工が主体であり、実質的な厚さの変化は生じていない。しかる後、フェース部材をヘッド本体部に溶接するとともに、フェース面を研磨してフェース部材の打球部の厚さを約２．７mmとしたウッド型ゴルフクラブヘッドを試作した。ヘッドの共通仕様は次の通りである。
ヘッド体積：３００cm³
ロフト角 ：１０゜
ヘッド本体：Ｔｉ−６Ａｌ−４Ｖのチタン合金をロストワックス精密鋳造法により製造
【００４２】
（実施例２〜５）
母材の寸法を変えることで圧下率を違えたものである。フェース部材の材料や製造工程は実施例１と同じである。
【００４３】
（従来例）
厚さを６mmで一定とした同一のチタン合金からなる母材を準備し、圧下率が５０％で一定となるように圧延した圧延材から同形状のフェース部材を試作した。
【００４４】
次に、上記各試作ヘッドに同一のシャフト（４６インチ、フレックスＳ）を装着してウッド型のゴルフクラブとし、これをツルーテンパー社製のスイングロボットに取り付けてヘッドスピード５４ｍ／ｓでゴルフボールをフェ０ス面の中央で試打する耐久テストを行った。評価は、５０００発未満でフェース部が破損したものを「×」、５０００発で破損がなかったものを「○」とした。
【００４５】
またヘッドの反発性能のテストは、Ｕ．Ｓ．Ｇ．Ａ．の Procedure for Measureing the Velocity Ratio of a Club Head for Conformance to Rule 4-1e, Revision 2 (February 8, 1999) に基づき行った。ボール初速は１６０フィート±０．５フィート（４８．７６８±０．１５２４ｍ／ｓ）に設定した。
テストの結果などを表２に示す。
【００４６】
【表２】

【００４７】
テストの結果、従来例では圧下率が比較的小さくかつ全域で一定であるため、機械的強度が充分でなく、耐久性にも劣る。他方、実施例のものは、耐久性を維持しつつ、反発性能、打球感に優れることが確認できた。
【００４８】
【発明の効果】
上述したように、請求項１記載の発明では、ボールを打球するフェース部に、圧延加工された圧延材からなるフェース部材を具えるとともに、該フェース部材は、圧下率が大きい高圧延部と、この高圧延部よりも圧下率が小さい低圧延部とを含む。従って、高圧延部で強度を増しフェース部の耐久性を向上しうるとともに、低圧延部によって反発性能、打球感などの悪化が防止できる。
【００４９】
また請求項２ないし３記載の発明では、厚さが大の厚肉部とこの厚肉部よりも厚さが小の薄肉部とを有する不均一厚さの母材を実質的に一定の厚さ或いは厚肉部を、最も大きな圧下率でそれぞれ圧延することにより、簡単な工程でフェース部材に高圧延部、低圧延部を製造することができる。従って、生産性の向上に役立つ。
【００５０】
また請求項４記載の発明のように、フェース部材は、高圧延部をスイートスポットを含む領域に形成するとともに、低圧延部をこの高圧延部の外側に形成したときには、ゴルフボールと直接衝突する機会の多い中央領域において、高い曲げ強度と表面硬さを発揮できヘッドの耐久性を向上する他、打球時に外側の領域を大きく撓ませることが可能となるため、打球感の向上と反発性能の向上とが期待できる。
【００５１】
また請求項５記載の発明のように、フェース部材に組成を限定したβ型チタン合金を用いたときには、より高圧延部では高強度にでき、しかも低いヤング率を維持することができるため、特に耐久性と反発性能とをバランス良く向上することができる。
【００５２】
また請求項６記載の発明のように、厚さが大の厚肉部とこの厚肉部よりも厚さが小の薄肉部とを有する不均一厚さの母材を圧延することにより、圧下率が大きい高圧延部とこの高圧延部よりも圧下率が小さい低圧延部とを含む圧延材を得る工程と、この圧延材からフェース部材を切り出す工程と、このフェース部材をヘッド本体部の打球面側に配して固着する工程とを含むことによって、各部位で圧下率が異なる圧延材を容易に成形しうるとともに、耐久性と反発性能とをバランス良く向上しうるゴルフクラブヘッドを生産性を損ねることなく製造できる。
【図面の簡単な説明】
【図１】本実施形態のゴルフクラブヘッドの基準状態における正面図である。
【図２】そのＹ−Ｙ線端面図である。
【図３】フェース部材の正面図である。
【図４】（ａ）〜（ｃ）はフェース部材の製造工程を示す略図である。
【図５】（ａ）は母材の平面図、（ｂ）はそのＡ−Ａ断面図である。
【図６】（ａ）は母材の平面図、（ｂ）はそのＡ−Ａ断面図である。
【図７】（ａ）は母材の平面図、（ｂ）はそのＡ−Ａ断面図である。
【図８】（ａ）は母材の平面図、（ｂ）はそのＡ−Ａ断面図である。
【図９】（Ａ）は図４（ｃ）のＸ−Ｘ断面図、（Ｂ）はその圧下率を示すグラフである。
【図１０】本実施例のチタン合金の引張応力−伸びの関係を示すグラフである。
【図１１】本実施例のチタン合金の引張応力−ヤング率の関係を示すグラフである。
【図１２】圧延工程を示す略図である。
【符号の説明】
１ ゴルフクラブヘッド
２ フェース部
３ クラウン部
４ ソール部
５ サイド部
６ シャフト取付部
７ フェース部材
７ａ 高圧延部
７ｂ 低圧延部
Ｓ スイートスポット
ｍ 母材[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a golf club head using rolled materials having different rolling reduction ratios for a face member and a manufacturing method thereof.
[0002]
[Prior art and problems to be solved by the invention]
In order to increase the flight distance of the hit ball, a face member made of a metal material having excellent resilience and durability is used for the face portion of the golf club head. Particularly in recent years, β-type titanium alloys such as Ti-15Mo-3Cr-3Sn-3Al have been attracting attention as metal materials having excellent resilience.
[0003]
Since this type of titanium alloy is excellent in cold plastic workability, for example, as shown in FIG. 12, a plate-like material prepared with a substantially uniform thickness between a pair of rotating rolls R, R is used. The base material m is caught by friction and cold-rolled to be formed as a small-thickness rolled material 10, and the rolled material 10 is pressed and punched into a predetermined shape and used as a face member. Further, since the rolled material 10 is usually rolled at a constant rolling reduction (degree of reduction in thickness due to rolling), the surface hardness, mechanical properties, etc. are substantially equal in each part of the face member. It is constant.
[0004]
The present inventors have made extensive studies in view of such a situation, and have found that this type of rolled material has a surface hardness that increases as the rolling reduction increases and an elastic limit stress improves. Based on such knowledge, the present invention is based on the fact that the face member includes a high-rolled portion having a large rolling reduction and a low-rolled portion having a rolling reduction smaller than that of the high-rolled portion. It is an object of the present invention to provide a golf club head capable of improving the above in a well-balanced manner and a manufacturing method thereof.
[0005]
[Means for Solving the Problems]
  The invention according to claim 1 of the present invention is provided with a face member made of a rolled material on a face part for hitting a ball, and the face member comprises:Represented by the following formula (1)A high rolling part having a large rolling reduction and a low rolling part having a lower rolling reduction than the high rolling part. The high rolling part and the low rolling part of the face member include a thick part having a large thickness and the thickness. A golf club head characterized by being formed by rolling a base material having a non-uniform thickness having a thin portion having a thickness smaller than that of a meat portion to a substantially constant thickness.
  Reduction ratio = {(h1−h2) / h1} × 100 [%] (1)
However, h1 is the thickness before rolling, and h2 is the thickness after rolling.
[0006]
  The invention according to claim 2The rolling reduction of the high rolling part is 65 to 95%, and the rolling reduction of the low rolling part is 10 to 70%.A golf club head according to claim 1.
[0007]
  According to a third aspect of the present invention, the face memberFormed the high rolling part in a region including a sweet spot and formed the low rolling part outside the high rolling part.Claim 1To any of 2The golf club head described.
[0008]
  According to a fourth aspect of the present invention, the face member isMade of titanium alloy represented by the following composition formulaClaims 1 toTo 3The golf club head described.
                  Ti100-xy M1x M2y (All figures are atomic%)
However, M1 is one or more elements selected from Zr and Hf,
M2 is one or more elements selected from V, Nb, Ta, Mo, Cr, W, and
x + y ≦ 50 (0 <x <50, 0 <y <50).
[0009]
  The invention according to claim 5 providesThe aboveThe face member is characterized in that the high rolled portion is formed in a region including a sweet spot, and the low rolled portion is formed outside the high rolled portion.Claim 1Golf club head.
[0010]
  Further, the invention described in claim 6 is that a base material having a non-uniform thickness having a thick part having a large thickness and a thin part having a thickness smaller than the thick part is formed to have a substantially constant thickness. By rollingRepresented by the following formula (1)A step of obtaining a rolled material having a high-rolled portion having a large rolling reduction and a low-rolled portion having a smaller rolling reduction than the high-rolled portion, and a step of cutting a face member including the high-rolled portion and the low-rolled portion from the rolled material And a step of fixing the face member to the ball striking surface side of the head main body.
  Reduction ratio = {(h1−h2) / h1} × 100 [%] (1)
However, h1 is the thickness before rolling, and h2 is the thickness after rolling.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a front view of a golf club head (hereinafter, simply referred to as “head”) 1 according to the present embodiment, and FIG. 2 is an end view taken along the line Y-Y. 2 shows a reference state placed on the horizontal plane HP at a lie angle α and a loft angle β.
[0012]
In the figure, a head 1 according to the present embodiment includes a face portion 2 that hits a ball, a crown portion 3 that is continuous with the upper edge 2a of the face portion 2 and forms the upper surface of the head, and a lower edge 2b of the face portion 2 that is connected to the head. A shaft portion on which a sole portion 4 that forms the bottom surface, a side portion 5 that extends between the crown portion 3 and the sole portion 4 from the toe 2t of the face portion 2 through the back face to the heel 2h, and a shaft (not shown) are mounted. Part 6. The head 1 of this embodiment is exemplified by a wood type made of a metal material and having a hollow shape inside.
[0013]
The head 1 is a head main body having a plate-like face member 7 made of a rolled material that forms at least a part of the face portion 2, in this example, a main portion, and an opening for arranging the face member 7 on the striking surface side. An example is shown in which the portion 9 is integrally fixed by welding, for example. In FIG. 1, the boundary of the face member 7 is indicated by a chain line, and the ratio (S2 / S1) of the total surface area S1 of the face portion 2 to the surface area S2 of the face member 7 is 0.7 or more, for example. More preferably, it is desirable to set it to 0.9 or more.
[0014]
The head main body 9 is formed from one member or by appropriately welding two or more members, and a titanium alloy is preferably used. In this example, the head main body 9 is integrally formed of α + β type titanium alloy (Ti-6Al-4V) by lost wax precision casting. Further, in this example, the shaft attachment portion 6 has a pipe shape protruding from the upper portion, and a shaft attachment hole 6a into which a shaft (not shown) can be inserted and fixed with an adhesive or the like is formed. Has been. Since the hole center line CL of the shaft mounting hole 6a substantially coincides with the axial center line of a shaft to be mounted later, in this specification, the lie angle α is determined based on the hole center line CL.
[0015]
In this example, the face member 7 is made of a β-type titanium alloy. In β-type titanium alloys, β-type crystals exist in a metastable state at room temperature. Since the β-type titanium alloy has a body-centered cubic structure (bcc) having a large number of slips, the resistance required for deformation is small compared to an α-type titanium alloy having a close-packed cubic structure with few slips. It is excellent in plastic workability, and is suitable as a rolled material.
[0016]
Examples of β-type titanium alloys include Ti-15V-3Cr-3Al-3Sn, Ti-22V-4Al, Ti-15Mo-5Zr-3Al, Ti-10V-2Fe-3Al, Ti-13V-11Cr-3Al, Ti— 8Mo-8V-2Fe-3Al, Ti-3Al-8V-6Cu-4Mo-4Zr, Ti-11.5Mo-6Zr-4.5Sn, Ti-15Mo-5Zr, etc. are mentioned.
[0017]
Particularly preferably, a β-type titanium alloy represented by the following composition formula (1) is desirable.
Ti100-x-y M1x M2y (All figures are atomic%) ... (1)
However, M1 is one or more elements selected from Zr and Hf,
M2 is one or more elements selected from V, Nb, Ta, Mo, Cr, W, and
x + y ≦ 50 (0 <x <50, 0 <y <50).
[0018]
As a result of the experiments by the present inventors, the titanium alloy represented by the above formula (1) has a high Young's modulus and a large elastic elongation and plastic elongation, while increasing the tensile strength and hardness. It was found to be suitable for a repulsive face member. The high strength and hardness of such a titanium alloy is mainly due to solid solution strengthening due to solid solution of elements having a large atomic radius difference, for example, an atomic radius difference of 10% or more from the above-mentioned combination, and a low Young's modulus. Is mainly because the constituent elements do not have an attractive interaction with each other, so atoms can move reversibly with low stress, and the large elastic elongation limit, etc. It is considered that reversible atomic transfer can occur up to a high strain region due to the property and increase in deformation stress is difficult to occur.
[0019]
In particular, since the constituent elements including at least two elements having a large difference in atomic radii as described above are dissolved, the rearrangement of atoms is difficult to occur and the diffusivity is lowered. Even when cooled, it is possible to obtain a β-type titanium alloy excellent in cold workability mainly containing a bcc solid solution single phase or a bcc solid solution. And such a solid solution can give high intensity | strength more effectively by giving a cold rolling process and producing work hardening.
[0020]
In the above formula (1), when the titanium content is less than 50 atomic%, the above-described alloy can exhibit excellent mechanical properties, but the specific gravity tends to increase. There is a tendency to increase the weight, increase the cost, and further increase the melting point. Further, when no element of Zr or Hf is contained, it tends to be difficult to dissolve a large amount of metal elements having a large atomic radius difference, and there is a tendency that solid solution strengthening cannot be performed. On the contrary, if the total content of the elements of Zr and Hf exceeds 50 atomic%, there are problems such as increase in specific gravity and increase in melting point.
[0021]
Furthermore, when one or two elements selected from V, Nb, Ta, Mo, Cr, and W are not included, the strength and the corrosion resistance are likely to decrease. Further, if the total content of these elements exceeds 50 atomic%, the specific gravity of the alloy increases, the melting point is increased, and the cost is likely to increase. Particularly preferred is a combination of Ti, Zr, Nb and Ta. That is, M1 is Zr, and M2 is Nb and Ta. Zr is more preferably 10 to 40 atomic%, and still more preferably 15 to 30 atomic%, and the balance is preferably composed of Nb and Ta.
[0022]
The thickness t (shown in FIG. 2) of the face member 7 is not particularly limited, but is, for example, 1.0 to 4.0 mm, more preferably 2.0 to 3.0 mm, and still more preferably 2. The thickness t is preferably 2 to 2.7 mm. If the thickness t is less than 1.0 mm, the practical strength is insufficient and the durability tends to be lowered. Conversely, if the thickness t exceeds 4.0 mm, the rigidity of the face portion 2 is excessively increased and the resilience performance is improved. It tends to decrease and the flying distance of the hit ball tends to decrease. In the present embodiment, the face member 7 is formed with a substantially uniform thickness.
[0023]
The face member 7 is formed from a rolled material. The rolled material is manufactured through a rolling process. The face member using the conventional rolled material has a substantially constant rolling reduction at each part. However, the face member 7 used in the present invention has a high rolling part 7a having a large rolling reduction and the high rolling part 7a. And a low rolling part 7b having a small rolling reduction.
[0024]
Table 1 shows the mechanical properties of each rolled material when the β-type titanium alloy was rolled with various rolling reductions. The mechanical properties are measured according to elastic limit stress (stress at the elastic limit of the stress-strain curve obtained from the bending test) and Vickers hardness (JIS Z2244 “Vickers hardness test method”), and the test load is 490 ( N))) and Young's modulus. Further, the rolling is cold rolling performed at room temperature, and the reduction ratio is as follows: when the thickness before rolling is h1, and the thickness after rolling is h2.
Reduction ratio = {(h1−h2) / h1} × 100 [%]
It is demanded by.
[0025]
[Table 1]

[0026]
As apparent from Table 1, it can be seen that this type of rolled material has a higher surface reduction and a higher elastic stress limit as the rolling reduction increases. Since rolling materials, especially β-type titanium alloys, are cold-rolled to introduce many lattice defects such as dislocations in the material, the mechanical strength is thus improved. Note that when hot rolling is performed, recrystallization or the like proceeds and the transition disappears and excellent mechanical properties are easily lost, which is not preferable. On the other hand, the Young's modulus is substantially constant even if the rolling reduction changes.
[0027]
In the present invention, such a property of the rolled material is utilized for the face member of the golf club head. That is, for example, when the central region Ac including, for example, the sweet spot S that frequently collides with the golf ball in the face member 7 is a high-rolled portion 7a with a large rolling reduction, the central region where a large impact force acts. In Ac, high bending strength and surface hardness can be exhibited, which helps to improve the durability of the head 1. As shown in FIG. 2, the “sweet spot” S is a point where a normal N drawn perpendicularly to the face surface F from the center of gravity G of the head 1 intersects the face surface F. Further, when the area Ap outside the central area Ac of the face member 7 is the low-rolled portion 7b having a small rolling reduction, the peripheral area of the face member 7 is greatly bent as compared to the central area Ac at the time of hitting. Therefore, it is possible to improve the feel at impact (soft feel at impact) and improve the resilience performance.
[0028]
Contrary to the above, when the central region Ac of the face part 2 is the low-rolled part 7b and the outer region 7a is the high-rolled part 7a, the central area Ac that is in direct contact with the ball at the time of hitting the ball is more easily deflected. It can also be improved with emphasis on the feel at impact. Further, in the case of this aspect, the periphery of the face portion 2 can be hardened, so that deformation of the portion can be suppressed at the time of hitting. Therefore, for example, it is possible to prevent a large stress concentration from occurring at the joint portion (welded portion) between the head main body 9 and the face member 7. As described above, the golf club head 1 of the present invention can improve the durability, resilience, feel at impact of the head, and the like in a well-balanced manner.
[0029]
The high-rolled portion 7a is not particularly limited, but is preferably rolled at a rolling reduction of about 65 to 95%, more preferably about 70 to 90%. If the rolling reduction of the high-rolled portion 7a is less than 65%, the effect of improving the mechanical properties of the rolled material 10 tends to be slightly insufficient, and conversely if it exceeds 95%, it is effective for improving the mechanical properties. Although the reduction ratio is large, it is not preferable because a base material having a large initial thickness is required and the material or manufacturing cost tends to increase. In addition, if the surface area occupied by the high rolling portion 7a in which the rolling reduction is regulated as described above is too small, it is difficult to obtain the effect of improving the durability. Therefore, the total surface area S3 occupied by the high rolling portion 7a and the face portion 2 are reduced. It is particularly desirable to set the ratio (S3 / S1) to the total surface area S1 to about 0.5 to 0.9, more preferably about 0.6 to 0.7.
[0030]
The low-rolled portion 7b is not particularly limited, but is preferably rolled at a rolling reduction of about 80% or less, more preferably 10 to 70%, and still more preferably about 50 to 70%. When the rolling reduction ratio of the low-rolled portion 7a exceeds 80%, the surface hardness of the face member 7 is substantially improved over the entire area, which tends to deteriorate the feel at impact and resilience performance, and conversely, it is less than 10%. And the rolling reduction is too small, the strength improvement effect of the base material tends not to be expected. Furthermore, when the low-rolled portion 7b is provided in the outer region Ap, it is desirable that the low-rolled portion 7b is continuously formed in an annular shape around the central region Ac, but it may be formed intermittently.
[0031]
As an example, in the face member 7, the difference between the maximum reduction ratio and the minimum reduction ratio is preferably about 15 to 50%, more preferably about 20 to 40%. This makes the balance between durability and resilience performance good. Further, as schematically shown in FIG. 3, the face member 7 becomes low-rolled portions 7 b 1, 7 b 2..., Whose rolling reduction gradually decreases from the high-rolled portion 7 a in the central region of the face member 7 toward the peripheral side. Those that change smoothly (for example, in an annual ring shape) are desirable. As a result, the face member 7 is useful for improving durability by eliminating a sudden change portion of hardness and elastic limit stress.
[0032]
The face member 7 used in the present invention can be manufactured including the steps as shown in FIGS. 4 (a) to 4 (c), for example. First, as shown in FIG. 4A, FIG. 5A, and FIG. 5B which is an AA cross section thereof, a base material m having a non-uniform thickness is prepared. The base material m in this example is a circular shape in plan view, and is formed of a dome-shaped curved surface whose bottom surface is flat and whose top surface is most raised. Thereby, the base material m has the thick part Ma with the largest thickness and the thin part Mb with a smaller thickness than the thick part Ma.
[0033]
Such a base material m is formed by a mold having a cavity having the same shape in a melting step of melting an alloy in an arc melting furnace, for example. In addition to this example, the base material m having a non-uniform thickness has a portion where the thickness changes stepwise as shown in FIGS. 6A and 6B, for example, as shown in FIGS. In addition, various shapes such as one having a portion whose thickness changes smoothly can be adopted. 4 to 8 exemplify a circular shape in plan view, but the shape is not limited thereto, and may be an oval shape, a rectangle, or the like in a plan view, and can be processed into a face member. Any shape is acceptable. 4 to 8 exemplify those in which the lower surface is flat and the upper surface is raised at a curved surface or a stepped change portion, on the contrary, the upper surface is flat and the lower surface is raised at a curved surface or a step change portion. It is also possible that the upper surface and the lower surface are both raised on a curved surface or a stepped change portion, and further, the degree of the bulge on the upper surface and the lower surface and the shape of the raised surface are different. Furthermore, the base material of various shapes can be used, such as the bulge of the upper and lower surfaces of the book material may be a bulge formed by a combination of a curved surface and a stepped portion.
[0034]
Next, the base material m is cold-rolled using a pair of rolls R and R as shown in FIG. The base material m is rolled in the rolling direction K, and is formed as a rolled material 11 having a substantially uniform thickness t ′ as shown in FIG. Thus, by rolling the non-uniform thickness of the base material m to a substantially uniform thickness, the reduction rate of the thick portion ma of the base material m is large and the reduction rate of the thin portion Mb is small, Rolled material 11 having different rolling reductions can be easily formed. FIG. 9A shows the XX cross section of the rolled material 11 of FIG. 4C, and FIG. 9B shows the relationship between each position and the rolling reduction. Thus, the rolling reduction of the rolled material 11 is small at the end portion and large at the center portion.
[0035]
In the present embodiment, the cold rolling process is performed in a single rolling step with a reduction amount (thickness reduction amount) of, for example, about 0.1 to 0.5 mm, and this is repeated a plurality of times to obtain a desired constant value. What forms the thickness of the rolled material 11 is shown. The base material m is stretched along the rolling direction K. However, in the case of cold rolling, no significant elongation occurs in a direction perpendicular to the rolling direction K. Therefore, in the case of the base material shown in FIG. 4, as shown in FIG. 3, a high-rolled portion 7 a having a large rolling reduction at the central portion thereof, and a low-rolling portion having a gradually reduced rolling reduction at the periphery thereof. 7b1, 7b2,... Can be formed. The rolling direction K may be a single direction, but it is preferable to perform rolling in two or more directions that intersect each other. Since the strength against bending tends to differ between the rolling direction and the direction perpendicular to the rolling direction, anisotropy such as the mechanical strength of the material is minimized as much as possible by using two or more types that intersect the rolling direction. Decrease. The crossing angle in the rolling direction is preferably 40 to 90 °.
[0036]
The cold rolling process is performed at room temperature without intentionally heating the material. As the cold rolling process, it is desirable to perform processing at −20 to 100 ° C., more preferably 0 to 100 ° C., more preferably 15 to 100 ° C. in consideration of the atmospheric temperature and heat generation of the material generated during the rolling process. . This temperature means the temperature of the material that generates heat during processing. If the temperature during the rolling process exceeds 100 ° C., rearrangement and recrystallization of the transition in the crystal of the material occurs, and work hardening cannot be expected sufficiently, and as a result, the mechanical strength cannot be sufficiently improved. On the other hand, if the temperature is lower than −20 ° C., cracks or the like are likely to occur at the side edge perpendicular to the rolling direction of the rolled material, and the yield of the material tends to deteriorate.
[0037]
Next, the formed rolled material 11 is pressed in this embodiment, formed into a predetermined curved surface (roll, bulge), and then cut into a shape L of the face member 7 as shown in FIG. After the processing or the like, the head body 9 is welded to the opening. In the pressing process, it is desirable to carry out cold as in the rolling process. Further, the order of pressing and punching may be reversed. Thereby, the head 1 of the present invention can be manufactured.
[0038]
Note that the rolled material 11 can be formed with a non-constant thickness that differs in thickness at each portion, in addition to the case where the rolled material 11 is rolled at a constant thickness t ′. In this case, it can be rolled using, for example, a roll having a groove-like recess. Even in this case, the rolling reduction can be changed depending on the shape of the base material. In particular, the high-rolled portion 7a can be easily formed by rolling the thick portion of the base material m at the largest reduction ratio. Further, when the low-rolled portion 7b is formed outside the high-rolled portion 7a, in addition to the case where the low-rolled portion 7b is formed in an annular shape as in the above-described embodiment, It can be carried out in various modes such as those formed only on the left and right (toe heel) regions of the face member.
[0039]
The embodiment of the present invention has been described by taking the wood type golf club head as an example. However, the present invention is not limited to the wood type golf club head, and each iron type, putter type, utility type head is used. Needless to say, the present invention can also be suitably applied. Although the face member has a plate shape in this example, the face member may be formed by pressing so that a part thereof constitutes a part of the crown part 3, the sole part 4 or the side part 5.
[0040]
【Example】
Next, an embodiment that further embodies the present invention will be described.
Example 1
A face member was prototyped by the following procedure using a titanium alloy “Ti50Zr30Nb10Ta10” satisfying the formula (1) (numbers are atomic%, atomic radius difference is minimum-maximum of about 11.7%).
FIG. 10 shows tensile stress-elongation curves of various materials including this material, and FIG. 11 shows the relationship between the tensile strength and Young's modulus. As is apparent from FIGS. 10 and 11, the titanium alloy represented by the above formula (1) has a higher tensile strength (elastic limit stress) than pure titanium or titanium alloy (Ti-6Al-4V). Nevertheless, the Young's modulus E is very low, almost less than half of them. Therefore, even if such a β-type titanium alloy having the characteristics of high strength and low Young's modulus is used for the face member of the head, the restitution coefficient of the head can be improved while sufficiently ensuring the durability of the face portion. Next, the constituent elements are melted in an arc melting furnace in a vacuum-evacuated and argon-substituted atmosphere, and a dome-shaped base material (outer diameter 60 mm × maximum thickness 30 mm × minimum thickness 6 mm) shown in FIG. 5 is obtained. Molded. Then, the base material was cold-rolled at a room temperature of 20 ° C. to form a rolled material having a uniform thickness of 3 mm. The rolling reduction of the rolled material is set to about 90% at the center, and gradually decreases toward the periphery from the center, and is set to about 50% at the periphery.
[0041]
Next, the rolled material was punched into a face member shape with a face width of 100 mm in the toe and heel directions and a face height of 50 mm in the crown-sole direction, and subjected to cold pressing at room temperature of 20 ° C. A face member having inch face rolls and face bulges was molded. Note that the press is mainly bending, and no substantial thickness change has occurred. Thereafter, the face member was welded to the head main body, and a wood type golf club head having a face surface polished to a thickness of about 2.7 mm was prototyped. The common specifications of the head are as follows.
Head volume: 300cm^Three
Loft angle: 10 °
Head body: Ti-6Al-4V titanium alloy manufactured by lost wax precision casting
[0042]
(Examples 2 to 5)
The rolling reduction was changed by changing the dimensions of the base material. The material and manufacturing process of the face member are the same as those in the first embodiment.
[0043]
(Conventional example)
A base material made of the same titanium alloy having a constant thickness of 6 mm was prepared, and a face member having the same shape was made from a rolled material rolled so that the rolling reduction was constant at 50%.
[0044]
Next, the same shaft (46 inches, Flex S) is attached to each of the prototype heads to make a wood-type golf club, which is attached to a swing robot manufactured by True Temper Co., Ltd., and a golf ball is played at a head speed of 54 m / s. An endurance test was performed with a test hit in the center of the face 0 face. In the evaluation, “X” indicates that the face portion was damaged at less than 5000 shots, and “◯” indicates that no damage occurred at 5000 shots.
[0045]
The test of the resilience performance of the head is described in U.S. Pat. S. G. A. The procedure for Measureing the Velocity Ratio of a Club Head for Conformance to Rule 4-1e, Revision 2 (February 8, 1999). The initial ball speed was set to 160 feet ± 0.5 feet (48.768 ± 0.1524 m / s).
Table 2 shows the test results.
[0046]
[Table 2]

[0047]
As a result of the test, in the conventional example, since the rolling reduction is relatively small and constant in the entire region, the mechanical strength is not sufficient and the durability is also inferior. On the other hand, it was confirmed that the examples had excellent resilience performance and feel at impact while maintaining durability.
[0048]
【The invention's effect】
As described above, in the first aspect of the present invention, the face portion for hitting the ball includes a face member made of a rolled material that has been rolled, and the face member includes a high-rolled portion having a large rolling reduction, And a low-rolled portion having a rolling reduction smaller than that of the high-rolled portion. Accordingly, the strength can be increased at the high rolling portion and the durability of the face portion can be improved, and deterioration of the resilience performance, feel at impact can be prevented by the low rolling portion.
[0049]
In the inventions of claims 2 to 3, a non-uniformly thick base material having a thick part having a large thickness and a thin part having a thickness smaller than the thick part is substantially constant. Alternatively, the high-thickness portion and the low-rolling portion can be produced on the face member by a simple process by rolling the thick-walled portion at the largest reduction ratio. Therefore, it is useful for improving productivity.
[0050]
According to a fourth aspect of the present invention, the face member directly collides with the golf ball when the high rolling portion is formed in the region including the sweet spot and the low rolling portion is formed outside the high rolling portion. In the central area where there are many opportunities, high bending strength and surface hardness can be demonstrated to improve the durability of the head, and it is possible to greatly deflect the outer area at the time of hitting, improving the shot feeling and resilience performance It can be expected to improve.
[0051]
In addition, when a β-type titanium alloy having a limited composition is used for the face member as in the invention described in claim 5, it is possible to achieve high strength in a higher rolled part and maintain a low Young's modulus. Durability and resilience performance can be improved with a good balance.
[0052]
In addition, as in the invention described in claim 6, by rolling a non-uniform thickness base material having a thick part having a large thickness and a thin part having a thickness smaller than the thick part, A step of obtaining a rolled material including a high-rolled portion having a large rate and a low-rolled portion having a reduction ratio smaller than that of the high-rolled portion, a step of cutting a face member from the rolled material, and a ball hitting ball of the head body portion Productivity by producing a golf club head that can easily form rolled materials having different rolling reduction ratios at each part and improve durability and resilience performance in a well-balanced manner. It can be manufactured without damaging.
[Brief description of the drawings]
FIG. 1 is a front view of a golf club head according to an embodiment in a reference state.
FIG. 2 is an end view of the YY line.
FIG. 3 is a front view of a face member.
FIGS. 4A to 4C are schematic views showing a manufacturing process of a face member.
FIG. 5A is a plan view of a base material, and FIG. 5B is a cross-sectional view taken along line AA.
6A is a plan view of a base material, and FIG. 6B is a cross-sectional view taken along the line AA of FIG.
7A is a plan view of a base material, and FIG. 7B is a cross-sectional view taken along line AA.
8A is a plan view of a base material, and FIG. 8B is a cross-sectional view taken along line AA.
9A is a cross-sectional view taken along line XX of FIG. 4C, and FIG. 9B is a graph showing the rolling reduction ratio.
FIG. 10 is a graph showing the relationship between tensile stress and elongation of the titanium alloy of this example.
FIG. 11 is a graph showing the relationship between tensile stress and Young's modulus of the titanium alloy of this example.
FIG. 12 is a schematic diagram showing a rolling process.
[Explanation of symbols]
1 Golf club head
2 Face part
3 Crown
4 Sole part
5 Side part
6 Shaft mounting part
7 Face members
7a High rolling section
7b Low rolling part
S Sweet spot
m Base material

Claims (6)

The face part for hitting the ball includes a face member made of a rolled material that has been rolled,
The face member includes a high rolled portion having a large rolling reduction represented by the following formula (1), and a low rolled portion having a rolling reduction smaller than the high rolled portion,
The high rolling portion and the low rolling portion of the face member have a substantially uniform base material having a non-uniform thickness having a thick portion having a large thickness and a thin portion having a thickness smaller than the thick portion. A golf club head formed by rolling at a thickness of.
Reduction ratio = {(h1−h2) / h1} × 100 [%] (1)
However, h1 is the thickness before rolling, and h2 is the thickness after rolling. The golf club head according to claim 1 , wherein the rolling reduction of the high rolling portion is 65 to 95%, and the rolling reduction of the low rolling portion is 10 to 70% . The said face member formed the said high rolling part in the area | region containing a sweet spot, and formed the said low rolling part in the outer side of this high rolling part, The Claim 1 thru | or 2 characterized by the above-mentioned. Golf club head. 4. The golf club head according to claim 1, wherein the face member is made of a titanium alloy represented by the following composition formula .
Ti100-xy M1x M2y (All figures are atomic%)
However, M1 is one or more elements selected from Zr and Hf,
M2 is one or more elements selected from V, Nb, Ta, Mo, Cr, W, and
x + y ≦ 50 (0 <x <50, 0 <y <50). 2. The golf club head according to claim 1, wherein the face member has the high rolled portion formed in an area including a sweet spot and the low rolled portion formed outside the high rolled portion. By rolling a base material having a non-uniform thickness having a thick part having a large thickness and a thin part having a thickness smaller than the thick part to a substantially constant thickness, the following formula (1 A step of obtaining a rolled material having a high rolling part with a large rolling reduction represented by) and a low rolling part with a lower rolling reduction than the high rolling part;
Cutting out the face member including the high rolling part and the low rolling part from the rolled material;
And a step of fixing the face member to the ball striking surface side of the head main body.
Reduction ratio = {(h1−h2) / h1} × 100 [%] (1)
However, h1 is the thickness before rolling, and h2 is the thickness after rolling.

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