Magnetic particle testing using remanent magnetization
Magnetic particle testing using residual magnetization inspects parts after the magnetizing current is switched off. A residual magnetic field is used to detect liquids or gas pockets.
Physicochemical Mechanism of Action
Magnetic particle testing uses the property of metals to become magnetic when placed in a magnetic field. After the current is turned off, the material remains magnetic in the remanent magnetic field for a short time. Liquids or gas pockets affect this property and can thus be detected.
Metallurgical Relevance & Welding Risks
This test is especially useful for series testing of rotationally symmetric parts, such as cylinders or wheels. It can detect liquids or gas pockets in the weld seam that result from improper degassing or lack of tightness. A faulty test can lead to inaccurate results and overlook potential defects.
Workshop Practice & Instructions
To perform magnetic particle testing, the component is first placed in a magnetic field. After the current is turned off, powder is sprayed onto the surface. The liquids or gas pockets attract the powder and appear as dark spots. It is important that the component is dry and clean to get accurate results. The test should be performed in a protected environment to minimize interference factors like electromagnetism or sheet steel.