The principle of the Magnetical Particle Testing (MT) exploits the property of some materials, known as ferromagnetic, of attracting other materials or themselves. Through special equipment an intense magnetic field is applied to the test piece. If there are surface or subsurface discontinuities, they disrupt the magnetic flux lines and create a localized flux escape, detectable by the application of pigmented ferromagnetic particles.
- Imperfections can be detected on the surface or just under it;
- Complex geometries can be easily examined;
- The surface precleaning is less critical than other methods (for example, PT);
- The technique is quick, and the indications are detectable directly on the test surface;
- Costs are altogether reduced;
- The portable equipment allows high onsite inspection flexibility.
- The method is inapplicable on non-ferromagnetic materials (several stainless steels, Al, Mg, Ti, Cu, Ni alloys and others);
- Tests performed in non-horizontal plane need suitable detectors;
- In some cases it may be necessary to remove paint or surface protective coatings to achieve the desired testing sensitivity;
- The ability to detect subsurface discontinuities is limited;
- The orientation between the plane of discontinuity and the direction of the magnetic field plays a pivotal role.
Metalprove S.r.l. performs magnetical particle testing by using dry or liquid (in suspension) detection media, with the possibility of varying the magnetization techniques and under photopic or scotopic viewing conditions.
The adopted reference standards may have European (EN ISO 17638, EN ISO 23278, EN ISO 9934-1, EN 1369, EN 10228-1, EN 10246-12, etc.) or American origins (ASME Sec. V, ASME Sec. VIII, ASTM E709, ASTM E1444, etc.).