Time for one last look at this idea again which
@RitSim first identified on his prop shaft and separate the wheat from the chaff.
@dLj was good enough to supply a document from the Australian Stainless Steel Development Asociation (ASSDA) which seems a reputable association so I think it safe to go by their figures. After all, we're not getting paid for this and no children are going to die at the end of the day if we're wrong.
The one chart from the ASSDA which interested me was the following:
This indicates cold working does in fact cause austenite (non magnetic) to transform into ferrite (magnetic) as it is plastically deformed. This is indicated by the increase in permeability. Linear, funtionally related, who cares, it increases. But I'm from Missouri so I've got to see for myself.
Not having a lab to work in, it's down to the workshop and way back to basics.
I managed to find a 1/8" dia. SS stud which showed no signs of magnetic attraction as measured by my little retrieval magnet which has an amazing amount of pull for such a small magnet:
The next move was to start work hardening the 1/8" stud and keep an eye on it as I beat on it mercilessly with a ball peen hammer on the top of an anvil. Very little happened initially (when checked by the magnet) until it was really getting deformed:
At the above amount of plastic deformation, it was quite magnetic:
As shown above, I was then able to hang the relatively heavy magnetic device from the cold worked SS stud. The other end of the stud still showed no attraction to the magnet. I'm now satisfies that work hardening does in fact alter the austenite.
So what's the magnetic attraction (permeability) of SS items on a sailboat ? So off to the marina to check a few things. Randomly held out my little magnet to the pulpits of several sail boats as I passed and not a trace of attraction there.
Once on our boat, I checked every SS object I could find and found only two items which had some attraction: the 15 kg. SS claw anchor:
................... and the assorted forged SS fittings on the SS pushpit and pulpit.
Everything else on the boat: railings, hand holds, sheet SS covers, shroud wires, AND the
propeller shaft showed no sign of magnetic attraction. Only the deep drawn SS sink showed minuscule attraction at the tightly bent corners, but none on the flat surfaces of the sink.
From this pleasant little passtime on a rainy, miserable afternoon, I think it safe to say that
@RitSim 's prop shaft permeability is not due to previous work hardening but some other cause, which may include the fact that the shaft is a piece of CRAP. Any way you look at it, if it's got pitting under the cutlass bearing, I wouldn't risk doing the job all over again in the near future. High quality shafts don't pit from oxygen starvation.