Eddy current testing for case depth determination
Eddy current testing measures the case depth of steel through the penetration depth of electromagnetic fields. Different microstructural conditions influence the measurement, thus showing the actual hardness.
Physical-Chemical Mechanism of Action
Eddy current testing uses electromagnetic fields whose penetration depth depends on the material's electrical conductivity. In a hard-laid steel, the penetration depth is less than in soft steel, because the hard area has higher resistance.
Metallurgical Relevance & Welding Risks
Hardening depth affects mechanical properties and material behavior under load. Too high a hardening depth can lead to cracks and fractures, while too low a hardening depth reduces strength. Eddy current testing helps control these properties and thus prevents potential defects.
Workshop Practice & Action Instructions
To perform eddy current testing correctly, the material should be dry and free of dirt before the test. A test coil is moved over the area to be examined while a constant current is applied. The field's penetration depth is measured and compared with reference values. If results are unclear, further tests should be run.