Electromagnetic Properties Inspection during Heat Treatment Cooling Process Using Pulsed Eddy Current Testing

Monitoring variations in the electromagnetic properties of steel during thermomechanical processing is essential for ensuring consistent mechanical performance and quality control. Conventional post-process inspections, such as hardness testing and microscopy, are offline and cannot capture through-thickness property evolution in real time under insulation and high lift-off. This paper presents a pulsed eddy current (PEC) approach for in-situ monitoring of electromagnetic properties during the air-cooling stage of normalising heat treatment. A portable PEC system with a U-core ferrite probe and integrated water cooling was developed for non-contact measurements in high-temperature environments. Experiments on two low-carbon steel specimens with different magnetic hardness under identical thermal protocols demonstrated consistent PEC responses during cooling, clearly capturing the Curie-related magnetic transition. The results validate PEC as a robust tool for real-time tracking of electromagnetic-property evolution, providing contactless, lift-off-tolerant, multi-depth sensing for high-temperature heat-treatment monitoring.