US Patent 6929566 Golf club head and method of manufacturing the same

A method of manufacturing a golf club head comprises: making a billet of a titanium alloy Ti-6Al-4V by machining an ingot of the titanium alloy; forging the billet into a face plate within a temperature range of from (the beta transformation temperature −150 degrees C.) to (the beta transformation temperature −20 degrees C.); and jointing the face plate and a head main body, whereby the golf club head comprise a face portion for hitting a ball, at least part of which is made of an alpha and beta type titanium alloy Ti-6Al-4V including alpha phase crystal structure whose average grain size is not less than 20 micrometers but less than 70 micrometers.