In magnetic particle testing, what type of particles is commonly used?

In magnetic particle testing, the method relies on materials that can be magnetized to detect surface and near-surface flaws in ferromagnetic materials. The particles used are typically iron filings or specially formulated magnetic powders. These particles are effective because they can readily be magnetized and will gather at the locations of magnetic flux leakage, which occurs when there is a flaw or discontinuity in the material being inspected.

Iron filings and magnetic powders are designed to be attracted to magnetic fields, which allows for clear visibility of the indications when the magnetic field is applied. When a magnet is introduced, these particles will cluster at flaws like cracks, enabling the inspector to identify issues that might compromise the integrity of the structure.

On the other hand, plastic beads and water droplets do not possess the magnetic properties needed for this inspection technique, and while metal shavings could theoretically be conductive, they are not specifically designed to be used in this testing method where the characteristics and behavior of magnetic particles are crucial. Therefore, the use of iron filings or magnetic powders is standard practice in magnetic particle testing to ensure accurate and effective detection of defects.