10 Questions You Should to Know about Forged Step Shaft

tgmcg;
I can give you one possibility having gone through a recent technical audit because we are purchasing a forging, not just a cast ingot, for a large turbine generator. The volumetric nondestructive testing for a large forging is usually conducted after forging and rough machining and is performed in zones.

For most reputable mills that supply rotor forgings for turbine or generator rotors, the UT is normally done using an automatic process. Some still use manual scans. The zones I referred to above are evaluated based on how critical the locations are relative to stress levels in service. My point to this is that there may have been different acceptance criteria depending on location in the rotor. I would review the procedure used by the foundry and their acceptance criteria for the entire rotor.
The turbine vendor is a well known name. The forge is located in Canada. Unfortunately the turbine vendor does not provide much source inspection anymore. We need to investigate the whole process but this will wait till after we formulate a recovery plan.

I've been reading of late about phased array UT and eddy current techniques. Do you have any suggestions as to the best NDE method for detecting core defects on rotor forgings? In this case the raw A470 Class 4 forging had a diameter of 9" in the bearing and seal areas and a finished diameter of 4". Today we are performing FPI to assess how many of the defects penetrate the surface.

Is there a good reference for acceptance criteria for rotor forgings? ASTM A470 limits linear defects to 0.125". In our case a few indications exceed this, but the entire shaft end is peppered with smaller defects. A photographic guide would be helpful.

Thank you for your suggestions. Thank you all for the great suggestions.

According to our inspector who witnessed the FPI inspection of the two rotors, "the shaft journal and seal areas looked like the Milky Way". In several areas, the FPI results lined up with the MPI results. Some surface indications exceed 0.500" in length. Despite this, the vendor continues to advocate a fracture mechanics analysis of the shaft as a possible means for determining shaft suitability for service...wishful thinking I suspect. The vendor would love to ship these rotors, and the customer would very much like to take posession of the machine prior to the scheduled shutdown.

In view of the unusually large number of confirmed surface defects, I have to wonder at what concentration of subcritical defects does fracture mechanics analysis cease to be a valid method for determining shaft integrity? I am far from convinced that fracture mechanics analysis is an appropriate tool for this situation. Any thoughts/comments?



Best regards,

Tom McGuinness, PE
Turbosystems Engineering
Thank you all for the great suggestions.

According to our inspector who witnessed the FPI inspection of the two rotors, "the shaft journal and seal areas looked like the Milky Way". In several areas, the FPI results lined up with the MPI results. Some surface indications exceed 0.500" in length. Despite this, the vendor continues to advocate a fracture mechanics analysis of the shaft as a means for determining shaft suitability for service...wishful thinking I suspect. The vendor is desperate to ship, and the customer is desperate to take posession of the machine prior to the scheduled shutdown.

In view of the unusually large number of confirmed surface defects, I have to wonder at what concentration of subcritical defects does fracture mechanics analysis cease to be a valid method for determining shaft integrity? I am far from convinced that FMA is an appropriate tool for this situation. Any thoughts/comments?

I ❤❤❤ my forged 923s. I am reluctant to own another set of cast irons. Even my S23 wedge has such a different feel from the SM9s. Will be replacing them as soon as I beat a little more life out of their grooves.

I bought a brand new set of Mizuno JPX 850's about 5-6 years back. They remain the only OMG irons I've ever bought new. They were a tremendous upgrade to the Adams irons I had. I tried both the cast and the forged when I was doing the fitting. Even though they shared the same JPX 850 model name, they were two different club head designs. The cast had a bigger top line and wider sole. I remember wanting the forged because they looked so much nicer. Since I hit the SGI cast version better I went with those and that was probably a wise decision.

The one thing I remember from the fitting is that I needed the lie adjusted 2º but the fitter was reluctant to bend the cast heads that much - even though Mizuno claimed it was ok. He ended up trimming the shafts a little longer which brought the toe up. He told me the forged would have been no problem to bend.

The forged heads I'm looking at are considered SGI (they are D2C clubs... ridicule gladly accepted). I'm going to build a 7i before buying the rest and will compare it to the 7i from my current set which is a design. I have a (lower end) launch monitor now so I can at least compare both in a more controlled environment. Both will have the same shaft.

I don't pretend to know much about golf clubs and even less about physics and engineering. Plus, I'm a bit cynical about marketing and take everything I read with a grain of salt. But here's the description of the model I'm looking at...

"...feature a diminutive but modern profile preferred by a wide range of player types. Smooth lines and a moderate top line provide the looks of a "players" club head in the playing position but provides Super Game Improvement playability.

"True Forged using a Precision 5 Step Forging process for unparalleled specification tolerances, the TS3 Forged head design features a forged C carbon steel body with an internal tungsten weight co-forged low and towards the toe inside the club head. The co-forged tungsten centers the vertical center of gravity location for a more stable and playable head design.

"To further enhance playability, the TS3 Forged irons feature a progressive cavity design that moves more mass low and towards the toe in the long irons and progresses to a more neutral position in the more lofted scoring irons and wedges."

While I still really like my current irons, I'm just looking for newer tech and am not obsessed with forged or clubs designed for better players. These have slightly stronger lofts - 32º 7i compared to 33º of my current 7i. If the newer 7i doesn't put up better numbers, I'll continue to search.

My goodness it's amazing how many attributes people ascribe to the label "cast" versus "forged". That label simply describes one set of steps in the preparation of the clubhead, or in some cases just one insert and not even the entire head.

I swear you could find the same mis-attributions being made on rec.sport.golf circa . Some things never change.

Do the different processes produce the same results? Or are there attributes that are slightly different? Can forged clubs still be bent easier than cast? Is one type of club more prone to faster wear or oxidation than the other?
These are serious questions not a disagreement with your post @Et Tu Brute?. I really don’t know what has changed over the years. Some of the answers indicate forged can be every bit as forgiving - which was my primary concern and seems to back up the manufacturer claims.