Dry Magnetic Particle Testing
Dry magnetic particle testing is a method for ferromagnetic materials where magnetic flux leakage at surface flaws is made visible by dusted iron particles. It is especially suitable for rough surfaces or thick plate.
Physical-Chemical Mechanism of Action
Dry magnetic particle testing uses the property of iron and similar materials to influence magnetic fields. A layer of iron powder is applied to the surface to be tested. When magnetic flux leaks at defects such as cracks or splits, it attracts the powder particles, making them visible.
Metallurgical Relevance & Welding Risks
This test is especially important for workpieces with high surface quality requirements, such as machine parts or components in the chemical industry. Missing or poor surface defects can lead to cracks, corrosion, or other defects that make the material unusable. This method is particularly useful for rough surfaces or heavy plate, where other test methods are difficult.
Workshop Practice & Instructions
1. Preparation: The surface to be tested must be clean and dry. Rough spots should be polished.
2. Applying the Powder: A thin layer of iron powder is sprinkled onto the surface to ensure there are no liquids or oils underneath.
3. Creating Magnetic Fields: The workpiece is placed in a magnetic field, or a magnet is moved over the surface to create leakage fields.
4. Observation and Interpretation: The visible attraction of powder on the surface is observed. Missing or irregular attraction indicates defects.
5. Documentation: All results are documented, including photos or sketches of the visible flux.