What Is a Magnaflux Test?

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When metal parts are manufactured, especially those parts that involve the transportation industry, they must withstand a through testing of integrity. These types of tests must not destroy the parts that have been manufactured. A systematic examination called nondestructive testing was developed. Included in these series of checks is the magnaflux or magnetic dye test.


Metal parts when they are machined and/or welded can become stressed during those processes. Those stresses can reveal themselves in the from of small fissures or cracks in the metal joints. These stress fractures at times may be difficult to see with the human eye. A method of employing small magnetic particles and a fluorescent dye was implemented to highlight any abnormalities of the machining and joining those metal parts.


Magnaflux testing can be used only on metal parts that can be magnetized. The size of the part can range from small ball bearings to entire aircraft frames. As long as the material can be coated with the dye solution that contains the small magnetic particles and that particular test piece can withstand a small magnetic field, the part can be magnafluxed.


After the part is sprayed with the magnetic particle dye solution, a handheld electro magnet is passed over the part. The magnetic field causes the small particles in the solution to align themselves with that magnetic field. Generally if the part being tested has no small fissures or cracks, the magnetic particles simply lay on the surface.


A testing part that does contain a crack or fracture will hold the solution in that small fissure, and once the magnetic field is passed over the area, a “line” of particles will form. This identification line will fill into the fissure and the particles will remain in place due to the magnetic field that was induced.


Some fissures are so small that it may be difficult to identify the abnormality with the human eye. The dye that is employed in the testing solution is a fluorescent base. This liquid fluorescent base is readily seen under a black light illumination source. Typically the magnaflux light test is performed in a darkened area so the black light illumination can be seen.

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