Ferrite count procedure

[lusitano8]

Hello!
I am a QC in welding. I have 321 stainless steel that requires ferrite count at fabrication. Ferritescope instruments are available. However, how can I be sure that testing by third parties has been done correctely. Is there any special metal preparation to extract a very close count by a Ferritescope of between 3% and 8% ferrite content?

Please advise.

Thanking you in advance

Lusitano

 

[arunmrao]

Ferrite testing
thread330-196616


Some interesting discussions here. Also place a search for Ferrite Number in Metallurgy forum and a few more links come up for your reference.

 

[enmax]

You ask how do you ensure the testing has been done correctly by a third party. The way I tackle this situation is to ask for a written procedure from the third party carrying out the test. This should be approved by a suitably qualified person - a metallurgist is a good start, particularly if he has experience of the Ferritescope instrument. If your client is overseeing the work, he may also be approached for approval of the procedure. The procedure should cover calibration of the instrument, the frequency of testing, the qualifications of the individual doing the tests, etc. Having got the approval, the test then needs to be witnessed by an inspector or other suitably qualified individual, to ensure the test is carried out to the agreed procedure.

 

[weldtek]

lusitano8,
Verify your 3rd party inspector is using a calibrated instrument and that he has with him, certified ferrite calibration samples within the applicable range. Although there's not a huge difference in the numbers between % ferrite and ferrite number, verify he's checking in the mode you requested.
Be sure the surfaces being tested are clean but other than that we don't typically do a lot of surface prep prior to testing.
If you have a lot of this to do, I'd recommend your company purchase its own instrument. Many third party inspectors don't do a lot of ferrite testing so you'll need to decide how comfortable you are in turning this inspection over to them.

 

[Guest102023]

The Fischer FerritScope is accurate, fairly idiot-proof, and cheaper/faster than metallographic methods. It just requires a nominal amount of surface preparation.

 

[unclesyd]

A meter definately beats a microstructural analysis even with the new microscopic procedures.
I also like the idea of purchasing your own instrument and a set of calibration standards.
You can use your calibration standards to verify practically any instrument used the NDT group.
The present day intrinsically safe meter of today sure beat the mechanical lift off instruments.