Off-line measurement of decarburization of steels using a multifrequency electromagnetic sensor

A multifrequency electromagnetic sensor was used to measure decarburization in steel. Decarburization samples were generated by heat treating Fe–0.8 wt.% C steel rods for various times in air at 1000 °C. The inductance value of the sensor at different frequencies varied as a function of decarburization depth due to the difference in magnetic permeability between ferrite and pearlite. The relationship between sensor output and decarburized layer thickness was modelled using finite element software.