Leakage Field Method
The stray field method is a magnetic particle testing technique where magnetic particles are attracted to surface defects. This allows detection of cracks and other discontinuities.
Physical-Chemical Mechanism of Action
The magnetic particle testing method uses the phenomenon that magnetic particles are attracted to surface defects such as cracks or damage. These particles are brought into the test area by a magnetic field and remain there when they encounter a defect.
Metallurgical Relevance & Welding Risks
This method is especially important for checking weld defects. Cracks or incomplete fusion attract magnetic particles and thus become easily visible. Misuse of the technique can lead to errors if the magnetic field is not strong enough or the particles are not applied correctly.
Shop Practice & Working Instructions
To successfully use magnetic particle testing, a strong magnetic field generator should be used. The particles should be suspended in a liquid and applied as a mixture with a carrier such as silicone oil. The test area must be clean and dry. The application time typically ranges from 1 to 2 minutes, after which the surface is washed and the particles removed. It is important that the magnetic field is correctly set to detect all possible defects.