Ferrite Content
The percentage of ferrite in a duplex microstructure or a weld, normally required to sit between 35% and 55% for the grade to behave as intended.
Why it is measured
Too little ferrite and the strength and chloride stress corrosion resistance drop toward austenitic levels. Too much and toughness falls away. Welding is where the balance moves, which is why duplex weld procedures are qualified on ferrite number as well as mechanicals.
How
Magnetic (Feritscope) measurement for a quick production check, point counting per ASTM E562 for qualification work.
Related terms
Where this applies
Duplex & Super Duplex Plate
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