Iron Forgings, metallurgy, basics and confusions...

[rhowardprd]

Below, I have tried to present some information about the metallurgy of forged irons which, after reading around in this forum, I think members may find interesting.

This topic was sparked after reading around in the best iron reviews where the great debate continues over what is the best looking, best feeling or best performing forged iron.

Please feel free to debate the following or disagree as you like; but I think that if you read through the facts and let them sit for awhile, you might start to see more into your own experiences with these irons.

Okay, here goes;

Did you ever notice that the more expensive an iron head is the softer the carbon steel? But the softer the steel the more feel you get? And the smaller the head the more feel? The denser the metal the more feel? And denser metals are heavier and harder? There seems to be a contradiction here, somehow. Curious?

Have you ever heard of coin forging versus machine forging or false forging?

Well, here's some of what I learned in a machine shop about all this. Some of this may sound like voodoo because even the top engineers have not completely figured it out. So please bear with me.

First a little metallurgy. Steel is an admixture not an element. It is made up of ferric iron and carbon. Stainless steel also has chromium in it. Carbon steel suggests that it has a high or dominant amount of carbon. The chemistry looks like this -- carbon has only 4 electrons and positrons -- it bonds in 4 directions to create various tetrahedrons, like a 4 sided pyramid. This versatile structure allows life on earth because it is so attachable in 4 directions, thus allowing complex proteins to be formed like so many tinker toys. However, carbon's use in making steel is different. Iron atoms are much larger. Say if an iron atom is a cannon ball, then a carbon is a pellet. When you stack the cannon balls like oranges in a supermarket, the cannon balls can roll off each other. But carbon in the form of graphite gets inside the spaces between the cannon balls and gums up the works. Graphite or coal or charcoal is not a tetrahedron but a complex sheet of carbon rings. As industrial grade coal dust it's really looks like ragged bits and pieces of sheets of carbon.

Why is this important? Well, the more you gum up iron with carbon bits, the less the iron atoms can roll around or shear away. Yes, you can increase the tensile strength of steel this way.

Now, in metallurgy, the science of atoms and bits of graphite turn into more of a magic formula game, and one of trial and error. Certain amounts and forms of carbon are good to increase steel's ability to be strong yet flex, or to hold an edge or to withstand tremendous pressures.

So, the question for the golf club maker is what is the best formula for making golf irons? You want steel that is dense, soft, accurate and that can transfer energy and provide feel and feedback.

Now, many top boutique club makers, machine shops and/or foundries have been testing formulas and methods of making iron heads for years. Some are secret, while many are misleading and off point. Example, Srixon says its 506 heads are coined forged six times. but probably 2 are for hardening, 2 for shaping and 2 for graphics.

Which gets us to hardening. Did you know that one of the very first practical uses of coin forging besides for coins was for what? Yes, cannon making. The barrels had to be hardened to take great explosions. So the harder the cannon barrel the more explosive material could be used and the further the shell could travel. Battle ship cannons were especially made of high carbon and multiple hammering. In fact, a 30,000 pound press was focused on each square inch of the barrels of the USS Missouri. It took the forge operator a week to hammer one barrel. The result was that the cannon could fire shells 10 miles.

So, coin forging is all about hardening and therefore strengthening. Strengthening is nessassary to allow the metal to withstand the impact of explosives or in golf of 100 mph swings.

So, where does the feel come in? And what about soft feeling but hard forged?

It's actually a big misunderstanding that has resulted in this seeming ambiguity or mix-up.

That is how can a harder, stronger metal -- a forged high carbon steel iron head, now be so soft feeling?

Answer: its about vibration killing density without lattices speading out the shock.

A club head can feel hard or harsh as in a cast club -- because the steel used depends for its strength on high temperature crystal patterns forming in the steel matrix or lattice. That is, when certain formulas of steel are molten and cooled quickly a higher percentage of lattice formations occur. This is what tempering is. Quick cooling causes the iron atoms to line up more evenly with the carbon and chromium and other alloy elements. When this happens an impact in one spot on the surface can more readily carry over to other parts of the surface.

However, when the strength of the steel depends on compaction -- or coin forging by compacting a pure mix of carbon and iron in the right formula -- then you get strength and density without much of a crystal structure. The pile of oranges at the supermarket that represented iron atoms stacked up, now has carbon bits that act like glue in the spaces between the oranges. And the strength comes from the structure being gummed up, and not from a lattice being formed. The cannon balls or oranges can slide independent of each other. So, any shearing force is localized.

The result for the golf club head is that the sweet spot or center of gravity spot feels soft, with less vibration and that softness or solid feel can be remembered physically. when this feeling is paired with hand eye coordination elements -- the whole memory can be stored as a unit; so when practicing -- if one part of the unit is missing we translate that to an incompleteness. And thus this can help us hone in on a better swing. If you understand the term of art, fuzzy logic, that is close to what is going on in learning the golf swing by feel.

Lastly, in the forum discussions on best iron heads, there is a lot of anticipation of the next best thing. I noticed that the top forged irons are now a combination of forging or compressing the lower half of the head, while routing out the upper half. The intention is to make a more forgiving club while keeping the forged iron feel.

But, there's a problem with this, IMHO. When you take away the metal in the top half or cavity half of the club head -- you take away the forging quality or density or compaction of that part of the head. The first club head to do this, I would guess, was the Tourstage MR23 US spec. Before that MP30s did not have deep enough cavities to compare, nor did the original Yonex Tour Forged of the 90s, as crude as it was.

This has lead me to suspect that the reason for the on-again, off-again love affair with the original MR23 US spec -- occurs because the club head itself is rewarding when you hit the truly forged rise at the center, and disappointing when you don't, disappointing because the remainder of the design is routed out and not genuinely compressed, it is not dense or coined like the bottom. The cavity is not coined.

So, you now see boutique club makers struggling with designs to harmonize what can give a truly forged feel in a cavity back and what designs fail or do not give enough feel, or the correct feel often enough.

It appears that the answer is how much routing is too much, and how much actual forging will a cavity back player stand for? If you know what I mean.

On the other hand, I think there is one club in history that did it all. Its the MR23 non-US spec, the one with the diamond design on the back. This club is rare. I bet most members have not even heard of it??? But before the US spec there was an MR23 that was wholly forged, compressed, or entirely coined, with little or no routing at all; and it still had a significant amount of cavity and perimeter weighting to it, without having to cut out the cavity and thus destroy the feel and density.

Has anyone heard of this pre US spec MR23? The diamond back?

I understand that it was tour only and was so expensive to make that Bridgestone stopped production mid year of its first year.

I also understand that this was the purest feeling cavity back ever made.

Well, the chemistry and metallurgy would make sense that it would be the best cavity back if it is the only one that is truly coined into a cavity design.

Okay, any thoughts on all this? And I hope this info on chemistry and metallurgy has given any one interested a little food for thought.

So, the answer as to why we keep changing irons is -- we want the feel of the pure forged dense carbon steel that was made dense by compaction. But when we use routed cavity backed forge blades -- the feeling can be elusive from one day to the next depending on how much we have honed our hand eye coordination on that particular day.

Edited July 28, 2007 by rhowardprd

[bushy]

Intersting stuff thanks. I love the feel of my Mizunos but need all the forgiveness I can get

[Spoon]

nice informative post. thanks for sharing.

[putt4doh]

Very interesting read. Even more interesting first post...

Just curious, but where did you obtain all this metallurgical knowledge? It seems highly specified, but given my limited knowledge of chemistry also seems highly plausible---although I've never quite heard it presented this way.

Thanks much for the info.

[+TourSpecGolfer]

Most of us already know its all about vibration but the info you received from the machine shop is just scratching the surface. As I have always said feel in design comes from several things: Material, Loft, and Sole Design and thats stuff a metallurgy expert can't account for. For the most part coin forging is usually reserved for blends. Blended steel is almost on the lower end because in order to make the blend the steel is further liquified.

The less pressing that is done to a forged club the better, currently only Endo does a true double press and Chuo ( Mizuno ) does double yet with the cookie cutter after. Graphics are not pressed in most cases but rather engraved, basic sole design is pressed though. You can take 1018 but if its forged 4 times it wont be as soft as 1025 pressed twice.

Many forum members are in awe of the MR-23's, TSG was almost started on that product alone, but truth is there are dozens of clubs that Endo has produced including the MR-23 that have that feel or a tad better. But why does that set feel so good? Well besides the design, material and loft it was the copper underlayer, There are two reasons people use an underlay of copper, one and the most common is to hide pitted steel, the second is to increase the soft feel, If someone is willing to strip the finish and copper from an MR23 and let us know that would be great. The diamond back isn't Tour only but rather ALL MR-23 model irons were produced for 1 year only. Maru stopped using it due to offset ( rumor ) Here is the thing, while people were paying 1250 for a set in America these were collecting dust in Japan in used golf shops, still to this day they are and even 5 years ago this was the case.

Much of your info is spot on, but let me add that undercuts reduce that good feel we desire and a solid and compact head like you mentioned seems to do best. There are several other aspects like hardness rating between carbon steel batches before and after it is made into a billet. Its like fine fish, you can buy tuna or you can buy O-toro, similar fish Atlantic deep vs pacific but I would take the O-toro any day because it has a higher fat content making it softer. Replace Fat with Carbon content and it gives us a good idea.

Also let me add the shaft, flex, and setup plays a big part in feel, you can have the same iron at the same spec and usually the softer shaft will make a club feel less harsh at impact. If that shaft has properties that dampen vibration or a finish or a material that does something similar it will also feel softer.

Im no metallurgy or forging expert but I have watched and participated in the process a couple of times and asked a variety of questions really picking it apart. Some of my data may be wrong but for the most part im repeating what factory and actual production managers, and golf specific auto cad designers have told me.

[ajaykkr]

Amazing coincidence! that a set of Mr-23 happen to be on sale on ebay (appears to be by the OP)

[rhowardprd]

Amazing coincidence! that a set of Mr-23 happen to be on sale on ebay (appears to be by the OP)

This is not a coincidence, I wanted to make sure that the MR23 data on Ebay was correct. That's why I posted this info here, along with a general respect for this board.

I came to this board specifically because a potential bidder emailed me from Ebay and told me about this board. he also said the MR23 US spec was a limited production, so I put that in to the Ebay auction as a correction.

And after reading the comments above, I intend to correct the MR23 diamond auction further by putting in some of the detail given from TSG.

In reply to TSG, here are a few things that I understand to be true which follow or slightly conflict with his given knowledge above.

1. Copper coating as an underlayer is generally not for feel. It is for plating efficiency. It may be that someone noticed that copper coating gave a better feel so they increased the thickness of the copper coating. But I have my doubts here. Why? Well, a tenth of a millimeter of copper just is not thick enough or dynamically active or resonant enough or dense enough to change feel substantillly. Whereas, copper undercoating is necessary to get an even distribution of chrome plating. Copper is highly conductive and plating uses electricity. So, many products are copper coated before plating to ensure uniformity of coating, and thus sheen and luster. But, yes, covering pits may be one other use; however, the condensing done by the 15 ton press should have taken the pits out in the first place. Sterling silver electroplating has a copper underlayer, for example.

2. Second, TSG reports that, "...The less pressing that is done to a forged club the better, currently only Endo does a true double press...'"

Well, that is arguable, and perhaps really unknown. My original post here suggests otherwise. But let's take a look at this because this issue is the thing itself, the gravamen.

First, Srixon advertises as a point of sale that it strikes each head 6 times compared to Mizuno with only 4 strikes. Next, we know that the more that steel is struck the harder it becomes -- except that there comes a point where the steel will fracture. And that is the key. How to make steel as dense as possible without it fracturing.

Fractures are caused by increasing the crystal properties of a metal. Crystals fracture and sometimes shatter because the crystal structure carries the breaking energy through the structure. How far through the structure? Well, as far as the crystal pattern goes without it being interrupted. Example, you can stop a crack in a window pane by somehow fusing the end of the crack, this interrupts the crystal structure by creating thatched or opposing grains.

Which brings us to how steel fractures or is prevented from fracturing. Steel comes in many varieties as you know. Steel can be very glass like or not very glass lke depending on the formula. And as you might guess, steel that is not very glass like is the most difficult to fracture.

Steel that is easy to fracture also is the harshest for a golf club head. Why? Because vibrations carry the impact throughout the head -- as more iron atoms are connected directly to each other -- owing to crystal structure. Whereas, free carbon which is just held together by carbon acting as a glue -- does not have much crystal structure at all, and will not transfer as much vibration. Remember the bits of carbon graphite that are like bits of a jagged sheet of carbon rings? Those bits are the glue that can hold the iron atoms together without resorting to crystal chaining. Crystal chaining uses stronger chemical bonds which make the steel behave more like glass.

So, the long and short of the matter is -- the more crystal patterns in steel the more it will carry vibrations throughout its form. The less crystal patterns the more the shock will be localized.

Lastly, it may be true that the more you press an iron head the more it is likely to form crystal structures. So, there is probably some optimal amount of pressing that has to be discovered by experiment. In battleships, the cannons are designed to reduce the crystal structures in the steel so if there is bending in one part of the barrel it will not cause a failure or crack down the length of the barrel, that is, the weakened part of the barrel is localized and can be repaired, usually be re-forging or re-hammering the expansion.

Then this begs the question -- why are off center hits on forged club heads so stinging? Well, that's a conundrum.

It seems that if you hit the sweet spot -- the spot acts as the site of center percussion, like a drum head. But if you hit the edge of the forged club head -- you get a nasty shock. Why if the dense steel has shock isolating properties? Well, I think this off center shocking occurs less and less with modern forgings. I own a set of 1960 something Macgregor VIPs and also Hogan blades and they both give nasty shocks, while off center hits on Mizuno MP30s and Srixon 506's are much less harsh.

So, how does this all add up? Balance. Even isolated iron atoms held together by carbon bits that gum up the stacking or grains -- even these have enough crystal properties to provide a shock, and since the forged steel is so dense (has so much substance in a small space) the shock is amplified. Also, the form -- since the sweet spot acts as a center of percussion -- when the edge is struck -- the shock wave flows through the center and to the hosel without percussing like a drum head. The shock shoots right up the shaft instead of rebounding off the sweet spot and into the ball.

Whereas, with cast cavity backs -- center percussion and rebounding effects and dense steel are all forgotten in favor of a uniform metal reaction. It's a trade off.

So, the hunt of the perfect forged iron head continues.

New heads by boutique companies -- are working trade offs too by carving shallow cavities or top cavities to lure cavity back players into the market. While cavity back companies are introducing forgings with welded on perimeter weights, i.e., Callaway X-Tour.

Moreover, there is one advantage to thick dense forgings we have not mentioned. That is this -- the more mass you put directly behind the ball, behind the sweet spot, the more energy is focused and released -- the more pure the feeling of a well solid shot. This means having a cavity or partial cavity behind the sweet spot is not optimal.

This brings us back to the MR23 diamond back. Here with this club, the whole head has been forged, compressed and made dense uniformly without carving out a cavity -- but by pressing in a cavity. So, is this the way to go? I understand that the diamond back was stopped in production half way because it was too expensive to make or turned out that way. It may be laying around in shops in Japan unsold because no one wanted to pay $1,250 USD for what looked appeared to be pure ornamentation. I think this is wrong. It's not pure ornamentation. The diamond pressing is functional and perhaps the best compromise for cavity back players -- in terms of metallurgy. The crying shame is that to lure cavity back players to the forged world -- you may need more than that -- more? Yes, like a better swing, (LOL).

Edited July 28, 2007 by rhowardprd

[LilCallaway]

Moreover, there is one advantage to thick dense forgings we have not mentioned. That is this -- the more mass you put directly behind the ball, behind the sweet spot, the more energy is focused and released -- the more pure the feeling of a well solid shot. This means having a cavity or partial cavity behind the sweet spot is not optimal.

This discussion has been quite informative to say the least. I've chosen not to do research on what is the best iron head produced as my head will start to hurt and in the end, I probably can't afford it anyway. Even if the best head fell into my lap, my game still wouldn't be TOUR worthy.

Please tell me this, do forged blades offer more performance than cavity backs? Or the fact that they do minimal?

[+TourSpecGolfer]

1. Copper coating as an underlayer is generally not for feel. It is for plating efficiency. It may be that someone noticed that copper coating gave a better feel so they increased the thickness of the copper coating. But I have my doubts here. Why? Well, a tenth of a millimeter of copper just is not thick enough or dynamically active or resonant enough or dense enough to change feel substantillly. Whereas, copper undercoating is necessary to get an even distribution of chrome plating. Copper is highly conductive and plating uses electricity. So, many products are copper coated before plating to ensure uniformity of coating, and thus sheen and luster. But, yes, covering pits may be one other use; however, the condensing done by the 15 ton press should have taken the pits out in the first place. Sterling silver electroplating has a copper underlayer, for example.

2. Second, TSG reports that, "...The less pressing that is done to a forged club the better, currently only Endo does a true double press...'"

Your correct it can deal with plating efficiency but keep in mind we deal with the manufactures of the clubs you are trying to figure out and only needed to ask to get the correct answer. We have direct contact with several manufactures that have used copper underlay in their irons and none of them have mentioned your reasoning to us.

Yes the less the head is pressed the better it feels and more difficult to accomplish, also pressed design is more desired than CNC or engravings by a mile. Again I dont know where you get your opinion or information from but we consult with the largest maker of forged golf product in the world. Im talking 85% of the complicated forged irons on the planet. We also speak with competitors of that factory and we are all on the same page.

Sounds like you know far more about metallurgy than myself so we welcome your expertise in any way shape or form.

[Goshinboku]

i am gonna keep this brief and short, there is no comparison between the mr23 diamondbacks and both of the us models, the us spec (cb's) and the us blade.

the diamondbacks were nothing special, and of all 3 sets command the lowest value on the yahoo japan market. they were clunky and had a terrible feel to them.

Edited September 1, 2007 by Goshinboku