Method and device for the in situ detection of the degree of conversion of a non-magnetic phase in a ferromagnetic phase of a metallic work piece

A method for detection in situ of transformation of a nonmagnetic phase into a ferromagnetic phase of a metallic workpiece after a thermomechanical treatment and degree of said transformation, comprising positioning a measuring device in close proximity to the workpiece, wherein the detection occurs as the result (a) of eddy currents of the nonmagnetic phase, caused by an electromagnetic excitation field applied to the workpiece, and (b) response fields generated by the ferromagnetic phase, at least one electromagnetic excitation field being generated by means of at least one excitation coil, and the resulting response field being measured by means of at least one detector measurement coil, the measurement signal from which, being dependent on the distance from the measuring device to the workpiece, and said signal being used to detect the degree of transformation, further comprising, measuring a response field which results from the application of the excitation field by means of two distance-measuring coils, which are located at different distances from the workpiece, for receiving two measurement signals, said signals having a level which is dependent on the said distances, and which are used to determine a distance-dependent calculation value, and detecting of the degree of transformation on the basis of the measurement signal and the calculation value.