Golf club head and method for manufacturing the same
A golf club head and a manufacturing method therefor in which the coefficient of restitution can be easily adjusted to desirable values for example the upper limit specified by Golf the Rules without impairing the durability and the directional stability. The head comprises a face member having a ball striking club face, and a main member at the front of which the face member is disposed, wherein the face member is produced from a titanium alloy, and the main member is produced from another titanium alloy having a larger specific gravity than that of the face member's titanium alloy.
1. A golf club head having a hollow structure comprising a face portion, a crown portion, a sole portion, a side portion, and a hosel portion, and composed of
a main member provided with a top opening in the crown portion and a front opening in the face portion,
a face member covering the front opening and forming a club face for striking a ball, and
a crown member covering the top opening, wherein
said face member is made of a first titanium alloy,
said main member is made of a second titanium alloy having a larger specific gravity than that of said first titanium alloy,
said crown member is made of a third titanium alloy different from the first and second titanium alloys,
the main member is a casting of the second titanium alloy integrally including the sole portion, the side portion, the hosel portion, a periphery part of the crown portion around the top opening, and a periphery part of the face portion around the front opening,
the sole portion has a thickness of at least 0.65 mm,
the side portion has a thickness of at least 0.65 mm,
the crown member has a thickness of at most 0.60 nun,
the area of the crown member is at least 50% of the area of the crown portion, and
the face member has a Young's modulus Y 1 of 120 to 150 GPa and a tensile strength of 950 to 2,200 MPa.
2. The golf club head according to claim 1 , wherein said first titanium alloy is composed of 4.5 to 5.5% by weight of aluminum, 0.5 to 1.5% by weight of iron and the remaining amount of titanium inclusive of unavoidable impurities.
3. The golf club head according to claim 1 , which has a head volume of at least 400 cc, a head weight of 170 to 200 g and a coefficient of restitution in a range of not less than 0.800 but less than 0.830.
4. The golf club head according to claim 1 , wherein
the face portion is provided with a thicker central portion including the sweet spot, and a thin annular peripheral portion surrounding the central portion, wherein the central portion has a thickness in a range of from 2.90 to 3.5 mm, and the peripheral portion has a thickness of not more than 2.70 mm, and
the face portion is further provided between said central portion and peripheral portion with a thickness-transitional portion having a variable thickness gradually changes from the central portion to the peripheral portion.
5. The golf club head according to claim 1 , wherein
a moment of inertia of the head around a vertical axis passing through the center of gravity of the head is in a range of from 4,100 to 5,700 gram sq. cm.
6. The golf club head according to claim 1 or 4 , wherein
the Young's modulus Y 1 of the face member is at least 1.05 times the Young's modulus Y 2 of the main member.
7. The golf club head according to claim 1 or 4 , wherein
the Young's modulus Y 3 of the crown member is smaller than the Young's modulus Y 2 of the main member.
8. The golf club head according to claim 1 or 4 , wherein
the Young's modulus Y 1 of the face member is at least 1.05 times the Young's modulus Y 2 of the main member, and
the Young's modulus Y 3 of the crown member is smaller than the Young's modulus Y 2 of the main member.
9. The golf club head according to claim 1 , wherein
the Young's modulus Y 3 of the crown member is at most 110 GPa.
10. A method for manufacturing the golf club head of claim 1 comprising: heating the first titanium alloy at a temperature of from 930 to 950 deg. C. for 3 to 30 minutes; and hot forging the heated first titanium alloy into said face member.