Ferrite Number (FN) & Feritscope Testing
Engineering definition, metallurgical mechanisms, standard testing specifications, and manufacturing guidelines for closed-die forgings up to 50 kg.
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An internationally recognized arbitrary standardized scale measuring the delta-ferrite content in austenitic and duplex stainless steel welds and forgings.
Technical Explanation & Metallurgical Principles
In austenitic stainless steels (304L, 316L), a small amount of delta-ferrite (typically 3 to 8 FN) is required during solidification to prevent hot tearing and micro-fissuring. In duplex stainless steels, a balanced Ferrite Number (typically 35 to 65 FN, or 40–60% ferrite volume) is mandatory to guarantee high yield strength and stress corrosion cracking immunity.
Key Engineering Specifications & Parameters
| Technical Parameter / Metric | Engineering Benchmark / Value |
|---|---|
| Measurement Tool | Electromagnetic Feritscope or WRC-1992 constitutional diagram |
| Austenitic Stainless FN | 3 to 10 FN (prevents hot cracking during welding) |
| Duplex 2205 FN Range | 35 to 65 FN (40% – 60% ferrite volume balance) |
Application at Jayesh Forge (Rajkot Plant)
100% digital Feritscope verification on all duplex, super duplex, and austenitic stainless forgings up to 50 kg at our Rajkot facility.
Related Materials, Standards & Products
Related Metallurgical & Testing Terms
Ferrite (Alpha-Iron Phase)
The body-centered cubic (BCC) crystalline form of iron, stable at room temperature in unalloyed steels, exhibiting magnetic behavior and low carbon solubility.
Austenite (Gamma-Iron Phase)
The face-centered cubic (FCC) solid solution of carbon in gamma-iron, stable in unalloyed steels between 912°C and 1394°C, and stabilized at room temperature in 300-series stainless steels.
Duplex Stainless Steel (2205 / F51 / S31803)
A dual-phase stainless steel possessing an approximate 50% austenitic and 50% ferritic microstructure, combining twice the yield strength of 316L with supreme chloride pitting resistance.
Questions Regarding Ferrite Number (FN) & Feritscope Testing
Excessive ferrite reduces impact toughness, lowers ductility, and increases susceptibility to chromium nitride precipitation along grain boundaries.
Request a Forging Quote with Ferrite Number (FN) & Feritscope Testing Compliance
Our Rajkot metallurgy desk is ready to review your technical drawings, testing protocols, and delivery schedules for custom closed-die forgings strictly up to 50 kg.