Magnetic particle inspection
Magnetic control is used to detect defects in objects with a variety of sizes and shapes. With its help you can quickly find hair, cracks of different origin, sunsets and welds of welded joints.
The magnetic method of nondestructive testing is actively used today in the search for microdefects in various products made of ferromagnetic materials. The basis of this method is the use of the properties of magnetic particles to concentrate on the inhomogeneities of the magnetic field of the object. These heterogeneities are due to the presence of defects in the product. The process of magnetic control in general form is as follows. The test article is magnetized, after which it is covered with a magnetic powder. Then the powder settles in places of defects, thus forming their clear "traces". Being attracted to each other and guided by the magnetic lines of force of the field, the powders line up in chains and form drawings in the form of rollers, along which they judge the presence and complexity of the defects. The greatest probability of detecting defects is possible when the defect plane makes an angle of 90 degrees to the direction of the magnetic flux. As the angle decreases, the sensitivity decreases, which reduces the probability of detecting defects. Two methods of magnetic particle testing are known - using powder (dry method) and using a special magnetic suspension (wet method). Depending on the shape, size, magnetic properties of the investigated part and the presence of a non-magnetic coating on it, both remanent magnetization monitoring and control in the applied field are possible.
Magnetic particle inspection has found a very wide application in railway transport, aviation, shipbuilding, chemical engineering, automotive, oil and gas production (pipeline control). Magnetic powder control has a very high performance, sensitivity, and also a convenient visibility of the results of monitoring. With the proper use of this method, defects can be detected even in the initial stage of their appearance.