Demagnetization
Demagnetization is the process of reducing the residual magnetic field in a part after magnetic particle testing, performed by passing the part through a decaying AC field or by AC current with reducing amplitude.
Definition
Demagnetization is required when residual magnetism could interfere with subsequent machining, welding, instruments, or service performance. Acceptance is typically less than 3 Gauss as measured by a Hall-effect or flux meter.
Related terms
- Residual Magnetism — Residual magnetism is the magnetization remaining in a ferromagnetic part after the magnetizing current is removed, dependent on the material's magnetic hysteresis behavior and coercive force.
- Magnetic Permeability — Magnetic permeability (μ) is a material property describing how easily it can be magnetized, equal to the ratio of magnetic flux density (B) to magnetizing force (H), and is a primary factor in MT current selection.
- Magnetic Particle Testing (MT) — Magnetic Particle Testing (MT) is a surface and near-surface NDT method for ferromagnetic materials that detects discontinuities by applying a magnetic field and observing the leakage flux attract magnetic particles to the flaw indication.
More procedure terms
Contact Coupling · Immersion Testing · Source-to-Film Distance · Exposure Chart · Wet Particle Method · Dry Particle Method · Fluorescent Particles · Visible Particles · Multi-Directional Magnetization · Solvent-Removable Penetrant
Where this comes up in practice
Terms like this one appear in three places that matter commercially: the written practice that governs how your personnel are qualified, the procedures and technique sheets that define how an examination is actually performed, and the evidence an auditor or client asks for when they want to know why an inspection was accepted. Getting the terminology right is the easy part; being able to produce the qualification record, the calibration traceability and the procedure revision that applied on the day of the inspection is the part that decides audits.
Atlantis NDT provides NDT training and certification against ASNT SNT-TC-1A and ISO 9712, ASNT Level III consulting for written practices and procedure approval, inspection management software that holds qualification, calibration and procedure-revision evidence in recoverable form, and an asset integrity platform that binds inspection results to the asset they describe. Browse the full NDT glossary or ask a Level III directly.