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THE PROCESS

 

Magnetic powder testing (also magnetic powder crack testing , flux testing or fluxing) is a method for identifying cracks in or near the surface of ferromagnetic work materials.

 

The workpiece must be magnetised for the test. In the case of large workpieces, which cannot be completely magnetised, only the section to be tested will be magnetised. The flux lines produced by the magnetisation run parallel to the surface. Cracks near the surface, which run perpendicular to the flux lines, create a stray magnetic field. This means that the flux lines on one side of the crack emerge from the ferromagnetic material and go back in on the other side. This produces the magnetic poles. If iron powder is sprinkled over this stray field, it collects at the crack because it is attracted by the magnetic effect. Cracks that run parallel to the flux lines do not produce a stray field and can therefore not be identified. Pores and cracks beneath the surface can only be located up to a certain depth.