On-line nondestructive evaluation of carbon content of steel using surface temperature during induction heating

A novel method was put forward to on-line evaluate the carbon content of low alloys and carbon steels nondestructively by measuring surface temperature of billet. The practical induction heating process for steel bar was simulated by finite element method. The regression equation for determining carbon content was derived from simulated data. The carbon content and temperature dependence of physical properties, electrical resistivity and thermal conductivity etc., were taken into account in simulation. The result indicated that a 1°C perturbation in the surface temperature of workpiece may attribute to nearly 0.01 wt.% changes in the carbon content of steel below Curie temperature. However, surface temperature of billet was uncorrelated with carbon content above Curie point. In addition, the phenomenon of surface temperature of billet is depended on carbon content of PC steel bar had been proved by experimental data from existing line.