Conventional NDT
Ferrite content testing
The ferrite content of a stainless-steel weld decides how it behaves in service. Too little ferrite in austenitic weld metal risks hot cracking; too much or too little in duplex and super duplex risks loss of toughness and corrosion resistance. Field ferrite measurement confirms the welding procedure delivered the balance the specification requires.
How ferrite is measured
A magnetic-induction gauge measures how magnetic the weld metal is, which depends on the ferrite present. Instruments are calibrated to report ferrite number (FN) against secondary standards, and results for duplex steels may be reported as ferrite number or percentage as the specification requires. Readings are taken on the cap, root where accessible, and the heat-affected zone, at the number of points the specification sets.
Where it is required
- Duplex and super duplex piping and vessels in oil and gas, desalination and chemical service.
- Austenitic stainless welds where hot cracking is a concern.
- Welding procedure qualification and production weld checks.
How we deliver it
Ferrite content testing is carried out to a written procedure approved for the scope, naming the code and edition, the equipment and calibration, the coverage and the acceptance criteria. The procedure and each technician’s certification are submitted for the client’s review before mobilisation.
Work is planned and supervised by ASNT Level III personnel; our founder holds ASNT NDT Level III in UT, RT, MT, PT and VT. Reports state the coverage achieved and any limitations, so the engineer reading them knows what was examined and what was not, and any reportable finding is raised the same day.
Governing codes and standards
- AWS A4.2 and ISO 8249 (calibration and determination of ferrite number)
- Owner and project specifications for duplex welds (for example NORSOK M-601 where adopted)
- ASME Section IX welding procedure qualification records
What you receive
- Ferrite readings per weld location with the instrument calibration reference
- Comparison with the specified range and a pass/fail statement
Industries served
- Oil and gas (duplex piping)
- Chemical and pharmaceutical
- Desalination and water
- Fabrication shops
Frequently asked questions
What is ferrite number?
Ferrite number (FN) is a standardised scale for the ferrite content of stainless weld metal, measured with a calibrated magnetic instrument to AWS A4.2 or ISO 8249.
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Or email the same details to info@atlantisndt.com. Mobilisation: North America; confirm your location in your RFQ.
Speak to an ASNT NDT Level III
Atlantis NDT provides ASNT Level III consulting, NDT training to ASNT SNT-TC-1A, inspection management software and independent report validation. Request a free consultation and we will return a tailored quote — affordable, accessible and fully customizable to your programme.