C-276 Shaft Straightening

[StoneCold]

Greetings all
I have a 2.375" diameter x 120" solid C276 shaft. The shaft is for an agitator that spins 155 RPM. The shaft has a coupling at one end, goes through a double mechanical seal and then extends down into the vessel about 9ft. The shaft was bent in process, almost an inch, overall end to end runout.
We tried to have the shaft straightened by spot heating, now the runout is considerably better but still .008 between the coupling and the seal (about a 8 inch distance). I am wondering if we could anneal the shaft while it was hanging upright if that would reduce the stress in it enough that it would straighten out, or then could be straightend by spot heating. Any thoughts on this?
Thanks
StoneCold

 

[EdStainless]

How did you spot heat? You may have cause serious damage to the local corrosion resistance.

You would be better off having someone straighten this in a press. The guys that hone (Scot Ind) can do this.

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Plymouth Tube

 

[StoneCold]

I wondered about that issue as well, It was not my call
I believe the spot heating is done with a small tipped acetylene torch. The spots are blue/black opon return, about 5/16" in diameter.
Pressing may be an option. I am not sure if it will stay straight though. I really need about .002" TRO between the coupling point and the seal when it is not under load. Mixing causes the shaft to flex and the numbers get worse obviously.

 

[arunmrao]

stonecold,appreciate your concern in salvaging a C276 shaft,which cannot be easily discard for economic reasons.

I agree with ed,that cold press to straighten would have been effective. Localised heating might have caused now damage to the shaft. The alloy has 40% min elongation and about 28kg/mm2 min yield strength,.

 

[StoneCold]

ARUNMRAO

What were you implying by saying "The alloy has 40% min elongation and about 28 kg/mm2 min yield strenght"?

Thanks

StoneCold

 

[metengr]

Is this for an FGD? I would consider re-solution treatment of this shaft to remove the effects of spot heating. I believe you may have compromised the corrosion resistance of this alloy.

Re-solution treatment should be done by a qualified heat treatment company. You can discuss the specifics with them to re-estbalish the corrosion resistance, and to minimize distortion during the rapid quench operation.

 

[MikeMet]

I think you will have trouble with any of the methods discussed. We have had luck with and interative process of cold straightening and re-solution anneal. It will likely take more than two times, the key is to be patient.