Magnetic Particle Testing (MT)
Magnetic particle testing can only be performed on ferromagnetic materials. This method magnetizes the test piece and sprays the test medium (colored or fluorescent) with iron particles. The resulting field lines are interrupted or deflected e.g. by a pore or crack and lead to a visual indication.
Detecting even the finest cracks
With the magnetic particle testing (MT) method, the finest hairline cracks can be detected. This testing method – also known as magnetic particle crack detection, flux testing or simply fluxing – is suitable for ferromagnetic materials. Samples are magnetized for testing. During this process, the parts are sprayed with a liquid or immersed in a bath, which is enriched with powdery oxides (usually iron oxides). Large samples cannot be magnetized in their entirety and are therefore examined in partial areas.
Application limitations:
- Only near-surface defects can be detected
- Only ferromagnetic materials with sufficiently high relative permeability can be tested
- sham indications due to rough surface or impurities possible
- No conclusion on the depth of the error possible
Application
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Non-destructive testing method (NDT) for ferromagnetic materials
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Hardening cracks after quenching and tempering
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Localization of defects open towards the surface, partially closed as well
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Test methods, e.g. for welding seams and cast parts
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Cracks in bearing shells before or during use
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Material separation by segregation lines