Ferrite testing & PWHT

[novice123]

When performing ferrite testing, API 582 recommends to perform before PWHT.
Why is this so? Why not after PWHT, ready to put in-service?

[mechcolor]

Ferrite testing is required before PWHT because ferrite control is primarily about solidification-related cracking during welding — not about the final, in-service condition.

[novice123]

Honestly, I still did not get the logic.
Do PWHT impact FN, if yes, then we need to have an FN measured after that.
It does not impact, then anyway measure once PWHT is over.

[arcpro]

I will try to explain you this, API 582 requires ferrite testing before PWHT because PWHT destroys ferrite by transforming it into brittle intermetallic phases — so testing afterward would no longer represent the true welding metallurgy that controls cracking resistance and weld quality. That is the objective we need to achieve (during welding).

[novice123]

thanks arc.

I will try to explain you this, API 582 requires ferrite testing before PWHT because PWHT destroys ferrite by transforming it into brittle intermetallic phases — so testing afterward would no longer represent the true welding metallurgy that controls cracking resistance and weld quality. That is the objective we need to achieve (during welding).