mighoser:
Yes, I believe you can do this. But you wil have to work up your own standard method, depending on your part geometry. We are learning that Biddle measurements on tube surfaces are dependent on tube diameter(!), and so we are taking care to measure on flat surfaces (tube...
Ed:
Confused by your last; can you explain?
We have the same inserts, but as I indicated the meter does not help with the 1450F and below HT material. It's only good for telling you about vry small amounts of magnetism (1900F condition. So Biddle picks up when Severn reaches its limit. And...
The Biddle meter is simply a pen-shaped device. The magnetic "point" is attached to a spring so that after contacting your test piece you pull against the spring and read off the spring extension against a scale from 1-10. Not sure what the feld strength of the magnet is. One (1) is high, 10 is...
Agreed-although I was not sure about the delta ferrite for a while!
The 1950 delta ferrite is magnetic;-a polished section reacts to a magnetized needle hung above it. But the 10% volume fraction of this phase is not enough to have any effect on a Biddle meter, when tested on the OD of a tube...
Ed/Michael:
The whole situation with this alloy is a metallurgical maze. The fact that it is a very close cousin to 304SS is what really gets me going. We have alredy started a few lab tests. So far:
1. The delta ferrite is not magnetic at any stage, and takes no part in any of the reactions...
Michael:
Thanks for the reminder that 17-7 starts life as a ferritic material. Your comments are well-taken and agreed.
The phenomenon I am struggling with is ferromagnetism in the alloy, and how to control it. Despite the residual delta ferrite after a 1950 solution anneal the material is...
Thanks for rapid response, unclesid. How can I send you pics? We have tried numerous etches already with material in various conditions and cannot correlate microstructure, etch reactions and ferromagnetism readings to anything that makes consistent metallurgical sense.
I would appreciate a...
It is not clear to me how ferrite content of 17-7PH is controlled. In the mill anneal condition, there is apparently no ferrite. As heat treatments progress to produce martensite and carbides, ferromagnetism increases from RH to TH condition. Is ferrite the residual phase after all this...
