Magnetic powder methods allow the detection of defects on the surface or just below the surface of non-ferrous metals in ferromagnetic materials. They are especially suitable for the detection of non-cellular features – cracks, cold joints, slag, material relocation, etc. Not suitable for internal defects.
Principle behind method
The principle behind magnetic powder methods is based on the detection of scattering magnetic flux. If the surface magnetism is perpendicular to the magnetic fields in the magnetized object, the magnetic lines of gravity rise to the surface, creating so-called dispersion magnetic flux. The lines of force on the test surface above the crack curve in an arc and can be visualized and observed by scattered iron sawdust. The iron particles attach to the magnetic fields and create a magnetic indication above the crack. Magnification of the test item is done by a pole or current magnet. Depending on the type of detector used and the method of evaluation of defect indications, the methods are divided into color and fluorescence, which have a higher sensitivity.