Magnetic particle (MP) testing is widely used in industry to detect surface and subsurface discontinuities in ferromagnetic materials. This method combines the magnetization of the material with the application of magnetic particles to identify flaws visually and precisely, and stands out for its ability to detect flaws accurately and efficiently.

The basic principle of magnetic particle testing is the formation of a magnetic field in the material under inspection. When a discontinuity, such as a crack or non-magnetic inclusion, interrupts this magnetic field, a leakage field is created. This leakage field attracts the magnetic particles applied to the surface, forming a visible indication of the flaw. This mechanism allows the method to be widely recognized for its efficiency and precision in identifying discontinuities.

Inspection process

1. Surface preparation: The surface of the material must be clean and free of contaminants such as oil, grease and other residues that could hinder detection.
2. Magnetization: A magnetic field is applied to the material using one of the following techniques:

• Direct electric current (DC or AC).
• Magnetization by coils or electromagnets
• Magnetization by contact with Yokes magnetic.

 

3. Application of Magnetic Particles: The particles can be applied as a dry powder or liquid suspension (water or oil-based). The fluorescent particles, visible under UV light, are ideal for highly sensitive inspections.

4. Observation and interpretation: The surface is inspected for accumulations of particles that indicate the presence of flaws. In the case of fluorescent particles, a UV lamp with the appropriate intensity is used, such as those complying with ASTM E3022. This step is essential to ensure that faults are detected accurately and efficiently.

5. Demagnetization and Cleaning: After the test, the material must be demagnetized to avoid future interference in its use, and cleaned to remove the applied particles.

Advantages and limitations

The advantages of magnetic particle testing include the detection of both surface and subsurface discontinuities, simplicity and speed of application, high sensitivity, especially with fluorescent particles, and a relatively low cost compared to other non-destructive testing (NDT) techniques. The method's limitations include the fact that it is restricted to ferromagnetic materials, the need for direct access to the surface to be inspected and the possibility of false positive results due to the accumulation of particles in complex geometric regions.

With all this, we know that magnetic particle testing is currently an essential tool for guaranteeing the integrity and safety of critical components in a wide range of industries. Its proper use, combined with advanced technologies such as high-intensity UV lamps, contributes to precision and reliability in fault detection. And Metal-Chek ensures that these results are always guaranteed with maximum efficiency.