Magnetic Particle Testing (MT)
Magnetic particle testing detects cracks in magnetizable materials through leakage fields and iron particles that settle at the cracks.
Physicochemical Mechanism of Action
Magnetic particle testing uses a homogeneous magnetic field generated by a magnet. Fine iron particles are dissolved in a suspension and spread over the workpiece. These particles are attracted to the magnetic surfaces of the workpiece in the magnetic field.
Metallurgical Relevance & Welding Risks
This test is particularly useful for steel materials, as it can detect microscopic cracks and weld defects. A missing or too weak magnetic field leads to inaccurate results. The particles must be fine enough to penetrate into cracks, but not so fine that they scatter easily.
Workshop Practice & Action Instructions
• Preparation: The workpiece must be clean and dry. It is placed in the magnetic field and coated with the particle suspension.
• Duration: The test typically takes 10 to 30 seconds, depending on the size of the workpiece.
• Interpretation: A positive result is indicated by visible particles at the cracks. It is important to set the magnetic field and particle density correctly.