Wed, 03 April, 2024
The innovation of Magnetic Particle Testing (MT) in the 1930s revolutionised the assessment of steel components on production lines. Rooted in the USA, this method magnetizes specimens to generate magnetic lines of force, or flux, within the material. When these lines encounter a flaw like a crack, secondary magnetic poles form at the crack's faces, leading to a distinctive pattern.
The revelation of these secondary magnetic fields at the metal's surface occurs through the application of magnetic particles, either as powder or in liquid suspension. These particles, drawn to flux leakage, cluster around flaws, rendering them visible. To enhance visibility, particles can be black or coated with fluorescent dye.
The efficacy of MT hinges on the alignment of magnetic flux lines perpendicular to flaws, maximising flux leakage for optimal detection. Consequently, the choice of magnetizing technique is crucial, often requiring a combination of methods for comprehensive inspection. Flaw visibility is contingent upon factors such as flaw depth, angle relative to magnetic lines, and induced magnetic field strength.
MT inspections entail a series of meticulous steps, including pre-cleaning, potential demagnetization, and application of background contrast paint. Magnetization follows, succeeded by the application of magnetic particle powders or inks, inspection for flaw indications, and subsequent demagnetization or re-magnetization. Flaws are recorded as necessary to ensure thorough scrutiny.
MT offers various inspection methods, adaptable to different settings. Portable equipment options include permanent magnets, electromagnetic yokes, current flow probes, flexible coils, and adjacent cables. Bench installations in factories encompass current flow, threading bars, magnetic flow, fixed coils, and induced current methods for specialised applications.
In conclusion, Magnetic Particle Testing (MT) stands as a cornerstone of Non-Destructive Testing (NDT), marrying the principles of magnetism with meticulous inspection techniques. As industries continue to rely on MT for flaw detection in ferromagnetic materials, its legacy of innovation and reliability persists, shaping the future of structural integrity across diverse sectors.
For more information about Magnetic Particle Testing (MT) training offered by TWI Caspian Sea, contact: enquiry@twi-cs.com