Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here


PMI vs Ferrite Testing

PMI vs Ferrite Testing

PMI vs Ferrite Testing

Hi everyone,

What is the purpose of conducting Ferrite Testing if we already conduct PMI? I know Ferrite Testing is used to measured the ferrite in the material and it based on FN, but I thought PMI will also display the Fe composition. Why we cannot use the PMI data to analyse the appropriate FN should a material have, for example DSS.

Sorry for asking, but im totally new in this field and I have been reading about PMI and Ferrite Testing, just confuse what is the exact purpose of each for the industry.

Thank you for reading

Kind regards,

RE: PMI vs Ferrite Testing

No, PMI is used as a sorting tool for material composition, ferrite testing determines the ferrite phase content in material, two totally different measurements with different outcomes.

RE: PMI vs Ferrite Testing

If let say, I conducted PMI on certain pipe and it says it is DSS, and then I conduct ferrite testing on the same pipe? Is it reasonable to conduct the same test on the same pipe?

Thank you for reply Metengr

RE: PMI vs Ferrite Testing

Ferrite testing is not to confirm composition, just to confirm that the delta-ferrite levels in the metal (usually in the weld) meet target levels.

Too little ferrite, and you could run the risk of hot cracking, too much, and you'll decrease the ductility of the weld, increase susceptibility to sigmatization (not that you'd be using DSS in services that hot), and establish galvanic couples between the base metal and the weld. I'm sure there are other reasons for ferrite testing, but that's what comes to my mind...

Since ferrite levels are impacted by things other than composition, such as cooling rates, heat input, etc. PMI is not an adequate measure to ensure correct ferrite levels (not that PMI is particularly accurate anyhow)

RE: PMI vs Ferrite Testing

Appropriate ferrite/austenite ratios in the weld are paramount for DSS to provide corrosion resistance; hence, the need to determine ferrite content. PMI simply indicates that you have purchased or installed the right material.

RE: PMI vs Ferrite Testing

Ok, I think I understand now. Ferrite testing is important especially in weldment area is that correct? Do you guys know what standard to refer if that's the correct FN number for DSS?

RE: PMI vs Ferrite Testing

It depends on the alloy to be welded but generally it is 40% to 60% ferrite.

RE: PMI vs Ferrite Testing

"but I thought PMI will also display the Fe composition"

Fe refers to the element iron in this context, it does not mean ferrite.

RE: PMI vs Ferrite Testing

Ohh, I don't know the difference between two. Ok I now I know where to start searching.

Thank you everyone for the valuable information. I really appreciate it

RE: PMI vs Ferrite Testing

Thank you all for your help.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close