Ferrite Number
Ferrite percent = vol% ferrite
(Fe) = wt% of Fe
FN = (vol% ferrite) x [-0.025813 (Fe)2 + 5.408679 (Fe) - 102.3902]/100
Please check ASME II part C, SFA 5.4/SFA 5.4M, Annex A, section A6 "Ferrite in Weld Metals" (page 92 in the 2007 edition.
The weld metal composition and microstructure are predicted based on the "ferrite stabilizer" and the "austenite stabilizer" content of the base metal, the nickel equivalent and chromium equivalent of the filler metal, and the level of dilution. The microstructure will be predicted as martensitic, ferritic, or austenitic, and the level of ferrite in the weldment will be estimated. In these welds, ferrite numbers below 4 indicate microstructures in which low-meltingpoint compounds may be formed at the grain boundaries, and the welds can be prone to hot cracking. Conversely, welds with ferrite numbers above 10 have reduced corrosion resistance and can be susceptible to the formation of phase at high temperatures (Ref 13). The Schaeffler diagram has been revised many times for adaptation to different alloy modifications. An example is the inclusion of nitrogen in the nickel equivalent. Many stainless steels often contain small amounts of nitrogen, and in fact some stainless steels are deliberately strengthened with nitrogen additions. Other modifications include copper in the nickel equivalent and vanadium and aluminum in the chromium equivalent (Ref 14).
This is consistent with the findings of several investigators that the minimum ferrite content necessary to avoid hot cracking is different for different weld metal compositions
Thank & Best Regards,
M Veera SAMY- Bureau Veritas.
Coimbatore
Date: Tue, 21 Aug 2012 17:24:48 +0530
Subject: Re: [MW:15102] Ferrite Number
From: vnjoshi.leo@gmail.com
To: materials-welding@googlegroups.com
Dear,
Dear Experts,Can any one explain me difference between %ferrite, Delta ferrite and FN(Ferrite Number).My requirement in job was 5 to 10 delta ferrite. I procured consumable of 5.4 FN. And I am actually getting value 14 by ferritoscope.Can anyone explain reason.?
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With Best Regards
Mohammed Raza Rajani
Engineer - Q.C
Email ; rezarajani@gmail.com
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