Why is the magnetization step critical in magnetic particle inspection?

The magnetization step is crucial in magnetic particle inspection because it establishes a magnetic field that is necessary for the detection of surface and near-surface discontinuities in ferromagnetic materials. During this process, the object being inspected is magnetized, creating an electromagnetic field that permeates the material. If there are any defects, such as cracks or voids, they disrupt the flow of the magnetic field and lead to leakage fields.

The magnetic particles, which are applied afterward, will align along these leakage fields, indicating the presence and location of the defects. This step is foundational to the entire inspection process, as without it, there would be no magnetic field and, hence, no way to attract the particles to the areas where defects are present. The effectiveness of the magnetic particle inspection method hinges on how well the magnetization step is conducted, as it directly impacts the visibility and clarity of the indications that arise from any discontinuities within the test material.