PURPOSE: To detect the flaws of a steel material, by deciding the signal given from a detecting coil of a unidirectional linear winding structure when the signal of a detecting coil of a circular winding structure is less than a certain level.
CONSTITUTION: The 1st detecting coil of a unidirectional linear winding structure and the 2nd detecting coil 2 of a circular winding structure are set on a surface opposite to a steel material M to be detected with a certain distance (l) secured between them. The material M is shifted while varying the temperature of the material M to perform the detection of flaws. In this case, the signals generated from both coils 1 and 2 have a large change respectively when the temperature of the material M is within a magnetic transformation region. Accordingly the detection is avoided for the signal given from the coil 1 in consideration of the time difference of the distance (l) and in case whe the preceding coil 2 detects that the temperature at the area to be detected is within the magnetic transformation region. In such way, the detection of flaws is carried out with no confusion between the signals in the magnetic transformation region and the flaw signals.
SUGIMOTO TAKAO
OOTA MITSUHIRO
