Magnetic particle testing of ferromagnetic material workpieces, if there is a defect in the shallow surface or surface, there is a discontinuity of the matrix material. After being magnetized, the magnetic lines of the surface and the near surface will be locally distorted to generate a leakage magnetic field, and the adsorption is applied. The magnetic powder on the surface of the workpiece, under suitable illumination, the magnetic powder being adsorbed forms a visible magnetic powder trace. The position, scale and shape of the trace show discontinuity, that is, the position, size, shape and severity of the defect.
Magnetic particle testing can be used for: (1) inspection during the manufacture of pressure vessels, such as inspection of welding bevels; inspection during welding; quality inspection of weld surface; inspection of forged steel parts of pressure vessels.
(2) Detection of pressure vessel in use The magnetic particle detection method can detect defects such as fatigue cracks and stress corrosion which occur during use of the pressure vessel.
The advantages of magnetic particle detection: visually display the shape, position and size of the defect, and can roughly determine the nature of the defect; the detection sensitivity is high, and the surface crack with a width of only 0.1 μm can be detected; the application range is wide, and the workpiece is almost undetected Size and shape restrictions; simple operation, fast detection and low cost.
Disadvantages of magnetic particle detection: It can only be used to detect surface and near-surface defects of workpieces made of ferromagnetic materials (Fe, Co, Ni and their alloys) that can be significantly magnetized, and cannot be used for non-magnetic materials (such as Cu, Al). The detection of etc.).
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