METHOD AND DEVICE FOR ELECTROMAGNETIC INDUCTION FLAW DETECTION

PURPOSE:To achieve high-precision flaw detection for a hot steel material, by cooling the steel material, including its surface, to prescribed depth down to magnetic transformation temperature and below sequentially and temporarily. CONSTITUTION:A signal generation part 10 outputs a temperature signal for the surface of a billet 1 measured by a temperature sensor 54. A flaw detection control part 11 compares the signal from the signal generation part 10 with a predetermined constant level to generate a flaw-detection start signal (a) and an end signal (b), thus controlling the energizing power source part of an inspecting coil 57. A cooling control 12 averages the signal from the generation part 10 at constant intevals of time, and discriminates the result by preset levels to output the result, thereby inputting a cooling control signal to the selection part 13 for cooling means. The input is classified by predetermined levels at the selection part 13 to send a release signal to a solenoid valve 56a corresponding to the level or to send a signal, operating a water feed pump 55, to a water feed pump control part 14, thereby performing cooling by compressed air and cooling water for proper use.