Surface Inspection of Ferromagnetic Materials
Magnetic Particle Inspection (MPI), also known as Magnetic Particle Testing (MT), is an efficient, cost effective and reliable non-destructive test method for detecting critical flaws in ferromagnetic[ii] materials.
Generally applied as a surface inspection[i] on carbon steels and other alloys that can be magnetized, magnetic particle inspection can accurately reveal flaws that normal visual inspection cannot detect including:
- cracks
- seams
- laps
- fusion discontinuities
Higher stress loads and most severe flaws are generally concentrated on the outer surfaces of components rather than in their interior volume. Therefore, enhanced surface inspection processes such as magnetic particle and liquid penetrant testing are crucial to flaw detection and failure prevention.
Quality Control Applications
Applications for magnetic particle inspection include testing welds, castings, tools, bar-stock, and other components for quality control, surface integrity, code conformance and pre-machine screening.
Magnetic Particle Inspection Process
When materials are magnetized by direct electric current or induction from magnetizing coils and hand held yoke-type solenoids, lines of magnetic force (or flux) - similar to the magnetic fields of permanent magnets and the Earth itself – are interrupted by material flaws and material changes.
Flaws on (or slightly below) metal surfaces cause a leakage in the applied magnetic field that draws very fine, sensitive, colored or fluorescent particles to the discontinuity.
Indications formed by particles attracted to these flaws can be evaluated by our trained and certified technicians for code acceptance or failure, surface integrity, and to ensure reliable service of components subjected to stress and wear.
Magnetic particle testing is often used in conjunction with, or in support of, other non-destructive test methods.
Qualified Inspection Technicians
- Large and small parts or components can be inspected in accordance with ASME, AWS, MIL-STD, AMS, ASTM codes or specifications as well as customer specific requirements.