Instrument and Control. Induction Heating Inspection for Non-magnetic Square Billet.

When the surface of steel billets is heated up by RF induction, the surface defects detour the induced current and then develop the temperature disruption around them. It is the induction heating inspection to detect the surface defects by marking such spots with infrared sensing devices. Authors applied this induction heating inspection to non-magnetic and square billets and optimized the procedures to improve the sensitivity and the accuracy. The results are as follows. (1) The sensors should be placed at the exit of the induction coil to scan the billet surface. (2) The defect detectability is enhanced as the billet travels at the higher speed. (3) The minimum defect depth is 0.5mm to be detected by this system.