Effect of Microstructural Features on Magnetic Properties of High-Carbon Steel

Industrially produced high-carbon steel has been heat treated in order to obtain various microstructures of the single phase of martensite, bainite, pearlite, and retained austenite or their combinations. Magnetic properties and the fraction of retained austenite were determined in a magnetometer. Thermomagnetic measurements were also used to record the magnetic response of selected microstructures upon controlled cooling from 300 K to 10 K. Optical metallography, electron scanning microscopy, and electron backscatter diffraction techniques were used to identify selected microstructural features. In general, complex microstructures have higher coercivity and lower remanence. Pearlitic microstructures, obtained through isothermally transformed austenite, showed an increase in coercivity and remanence and a decrease in saturation magnetization with an increase in interlamellar spacing. In martensitic structures, the coercive force decreased by an increase in tempering temperature. The findings that microstructural features have a significant effect on the magnetic properties of the high-carbon steels are important since they reveal that the magnetic measurements have the potential to be used as a reliable non-destructive method to detect and monitor microstructural features in high-carbon steel.