Magnetopowder control is applied for the detection of surface and subsurface defects in ferromagnetic materials. It is based on the ability to register their magnetic properties and changes in the interaction of the magnetic field with defects.
Essence of magnetopowder control
In magnetised materials magnetic power lines are evenly distributed in the intersection, but if the magnetic flux encounters an obstacle with a small magnetic permeability (crack, pore, etc.), it is dissipated around these defects. When these defects are on the surface of the device, at the point of the defect produces magnetic polarization. Sprinkled with magnetic powder, magnetic materials these specks about concentrating defect, due to their interaction with the magnetic field distortion. The width of the resulting from accumulated magnetic powder is much bigger than the actual width of the rift, with which it is possible to detect defects invisible to the naked eye.Through this kind of flaw detection can detect small surface and subsurface non-integrity, as cracks, cracks of operation or repair, voids, etc.
1. Does not apply to magnetic materials with relative permeability under 40.
2. Does not apply to testing on surfaces covered with non-magnetic layer thickness of 50 μm.
3. Does not apply to testing on surfaces with temperatures higher than 500 C.
This method detects defects:
1. Surface with a width of 2 µm discovery and more depth, 10 µm and more.
2. Subsurfaces, located at a depth of up to 2-3 mm.