RE: ShopTalk: porosity-grain structure

[Tom Wishon]

TOM:   I’ll chime in on this because I have a pretty fair amount of experience in this area.  First of all, the grain structure of the metal from which a clubhead is formed is primarily an internal thing.  One a head’s surface is polished and finished, whatever edges of the grain structure that exist on the face are a moot point because the process of polishing and finishing a head changes the surface condition to the point that it in essence, “covers up” the grain structure.  Now when you talk about ironheads, grain structure has nothing whatsoever to do with the actual performance of the shot.  It can affect things like loft/lie bendability, how much the head might ding or mar, etc., because the grain structure can be an outcome of the forming and heat treatment of the head that determines the head’s final material mechanical properties like strengths, elongation, hardness, etc.  But because most all irons are so “solid” there is nothing from a grain structure standpoint that can ever affect the performance of the shot.    In woods, where you are seeing thin walls as a major part of the construction of the head, yes it can have a bearing on the performance of the shot.  But here too, this is all a product of the forming methods used and then the heat treatment of the head after it is formed.  Heat treatment done after forming on virtually all metal woodheads to be able to slightly change the grain structure/molecular structure of the metal from which the head was made so that it ends up with the right combination of mechanical properties.  Wall thicknesses, especially the face, have to be designed with the final mechanical properties of the metal in mind.  Thus it is possible that if the forming process of the head is not carefully monitored and performed, and then if the post forming heat treatment is not done properly, the final strength, ductility, etc (mechanical properties) won’t get to the level they need to be to allow that wall thickness to perform as intended in the design.  Mess up these processes and the face could deform, break or not deflect the proper amount to ensure a good ball velocity to swing speed ratio in the use of the head.    Because all forming methods like forging or casting, and all heat treatment processes do affect the molecular structure of the metal, they do thus affect the grain structure of the metal at the same time.  And it is the metal’s final grain structure and molecular structure that ultimately determines what it’s mechanical properties will be.    TOM W   -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of [EMAIL PROTECTED] Sent: Tuesday, November 23, 2004 9:34 AM To: [EMAIL PROTECTED] Subject: RE: ShopTalk: porosity-grain structure   I have a question that related to your posting about porosity-grain structure.  Is it desirable to have the grain structure on the face as small as possible?  As the grain structure decreases won’t the surface become so smooth that it is slick?  If a slick surface on irons is desired, why do we sand blast the face?  These questions may show my total ignorance of club design, but your posting raised them in my mind.   Tom   -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of [EMAIL PROTECTED] Sent: Tuesday, November 23, 2004 2:34 AM To: [EMAIL PROTECTED] Subject: ShopTalk: porosity-grain structure   Hi All, I've been testing a lot of titanium faces, in a variety of materials, thickness', and aging processes, as well as body materials for some time now, concerning drivers, not irons, and one thing we are concerned with in the face is surface hardness vs core hardness, surface hardness has always been somewhat higher due to either the forging process pressing the outer most layers more so than the inner most which results in the grain structure being broader in the core than it is on the surface or in some rare cases an alpha case situation on the surface, but the closer the two the tighter the grain structure or more precisely put the lack of porosity, and a lack of porosity is a good thing. If you could get a face that when measured under micro hardness testing measured the same on the surface as it did in the core than you would have the best quality specimen, assuming those core measurements were up there with your other hi surface measurements. The last test we did on our most recent project we achieved this and none of us believed it because in the collective years of the people involved we had never seen this. If you were to think of a face made of say styrofoam (porous) vs a face made of metal (less porous) then you could imagine that the one lacking in porosity would be more solid, and thus it goes, reduce the pourosity/increase the solidity. Now there is of course the point of "peak" i.e. if it doesn't fail at 1" why make it 2" but we don't yet know what is best, we are only trying to learn. What in the world does this have to do with the current irons thread? Probably something. If you could chose between two irons that were equally appealing to you and you could do micro hardness or other testing to prove one had a tighter grain structure definitely pick the one with the tighter grain structure. Just be aware that you are going to shoot the same score no matter which one you pick. David