To detect flaws present on the surface of a canister and even internal flaws impossible to observe visually on the canister with respect to flaws like a crack or the partial irregularity of electric resistance of the canister.
The canister 2 for high frequency melting formed of conductive refractory is heated using an induction heating furnace 1 and taken out of the furnace on the way of the temperature rise of the canister. The outside surface of the canister is scanned by an infrared camera 4 as shown by Fig. 1 while rotating the canister on a rotary stand 3 and the temperature distribution thereof is measured by a thermograph to detect the flaw of the texture constituting the canister on the basis of a principle such that temperature irregularity is produced in a flaw region.
KAMEI YOSHIYUKI
Akio Najima
Fumio Yamamoto