Measurement of Ferrite Number and Ferrite Percentage in stainless steel
Industrial processing and chemical plants work at high temperatures and pressures, often with aggressive media; stainless steel is often the material of choice for these applications. If the ferrite content of the steel steel is too low, then welding of stainless material may crack at elevated temperature or with high stress or vibration. If the ferrite content is too high, the weld may be weaker and corrode.
To address the need to measure the amount of ferrite in a sample the Welding Research Council introduced the Ferrite Number (FN) as standardised value which related to the ferrite content of an equivalently magnetic weld metal. The volume percentage of ferrite is estimated using a piecewise linear model for typical steels. The relationship depends upon the type and origin of the stainless steel used and the measurement technique.
The Diverse Ferrite meter MF300Fm+ measures the Ferrite number (FN) of austenitic and duplex stainless steel weld material. There are 4 probe options: P46 with an active area of 4x6mm; P46R right angled probe; P10 that is sensitive to ferrite content in a 10 mm diameter; P10AC is an air cooled version of P10 for use with hot samples.  Depth sensitivity of approximately 1 mm. MF300Fm+ can be supplied with up to 5 probes as follows: P10 (1 or 2), P46, P46R and P10AC.
The instrument is calibrated using NIST secondary weld standards. All 16 standards are used in the calibration giving an instrument with a measurement range from 0 to 115 FN. Transfer standards are supplied with the instrument allowing performance to be verified at any time.
Features of MF300Fm+ Ferrite Meter
- NDT of the ferrite content in a range of 0.1 to 115FN equivalent to 0.1 to 83% Fe in austenitic & duplex steel.
- Robust and portable
- Standard or peak measurement of Ferrite Number
- Piecewise estimate of ferrite percentage
- Automatic zero on demand
- Supplied with 5 transfer standards allowing veracity of instrument to be checked
- Storage of 1000 measurements, downloaded to PC with RS232/USB option
- 10mm diameter (P10) and 4x6mm (P46) probe options
- Right angled probe for use where access is restricted (P46R)
- Use with high temperature samples (air-cooled probe option)
- Up to 5 probes per instrument
- Simple measurement with small sample area.
- Units selectable between WRC-FN and %Fe.
- Calibration with standards traceable to NIST standards
- Large character display mode
- Backlit display
- Supplied in carry case
