Magnetic particle inspection

After the ferromagnetic material workpiece is magnetized, due to the discontinuity, the magnetic field lines on the surface and near the surface of the workpiece are locally distorted to generate a leakage magnetic field, which absorbs the magnetic powder applied on the surface of the workpiece, and forms a visible magnetic field under suitable light. Marks, which show the location, size, shape, and severity of the discontinuity.

The scope of application of magnetic particle testing

1. It is suitable for detecting surface and near-surface defects of ferromagnetic materials, such as cracks with very narrow gaps between the surface and near-surface and other defects that are difficult to see with the naked eye. It is not suitable for detecting deeply buried internal defects.

2. It is suitable for testing iron-nickel-based ferromagnetic materials, such as martensitic stainless steel and precipitation hardening stainless steel materials, but not for testing non-magnetic materials, such as austenitic stainless steel materials.

3. It is suitable for detecting unprocessed raw materials (such as steel billets) and processed semi-finished products, finished parts, and in-service and used workpieces.

4. It is suitable for testing pipe, bar, plate, shape and forging steel castings and welding parts.

5. It is suitable for detecting defects where the extension direction of the surface and near surface of the workpiece is perpendicular to the direction of the magnetic field line as far as possible, but it is not suitable for detecting defects where the angle between the extension direction and the direction of the magnetic field line is less than 20 degrees.

6. It is suitable for detecting small defects on the surface and near surface of the workpiece, but not suitable for detecting shallow and wide defects.