FN Range for Type 347
FN Range for Type 347
(OP)
In weld deposit overlay, our specification shows limit FN 5 to FN 8 for Type 347. The limit shall be confirmed prior to PWHT.
-Is this practical in the fabrication industry to control in only 3 range as above requirement?
- What should be the specific concerns for Type 347?
The fabricators informed that they need at lest 5 range to control the ferrite number (FN 3 to FN 8) for Type 347.
I found the related thread in thread725-34135 . However, this is not answer my question about the FN range for Type 347. Please comment.
-Is this practical in the fabrication industry to control in only 3 range as above requirement?
- What should be the specific concerns for Type 347?
The fabricators informed that they need at lest 5 range to control the ferrite number (FN 3 to FN 8) for Type 347.
I found the related thread in thread725-34135 . However, this is not answer my question about the FN range for Type 347. Please comment.





RE: FN Range for Type 347
According to my reference material to prevent weld metal liquation cracking in 347, the minimum ferrite number is 6.
So, I would use a range of 6-10. The source of this information is "Welding Metallurgy and Weldability of Stainless Steel" by Lippold and Kotecki.
RE: FN Range for Type 347
RE: FN Range for Type 347
Thanks for the comment. I just check API RP 582. The acceptable range for Type 347 is FN 5 to FN 11.
I understand that the proposal FN 5 to FN 10 should be acceptable.
Please advise me if you have additional comment.