How It Works
The *sensory portion of the system consists of a superconducting, high Q, radio frequency LC resonator inductively coupled to moving ferritic strip. The quality factor (Q) of this resonator is determined to obtain a measure of energy dissipated in the coupled steel alloys. Dissipative energy in the sample results from two sources, hysteresis and eddy currents. Eddy current loss is relatively microstructure insensitive and is mainly related to chemical composition and temperature while hysteresis loss is determined predominately by microstructural factors. As an example, if microstructural variables other than grain size, and the factors determining eddy current loss are held constant, grain size will become the dominant factor in differential energy loss with grain size being inversely related to hysteresis loss. Under these conditions grain size is inversely related to total energy dissipation and thus the measured Q of the resonant circuit.
The MicroCert Surface Volume Imaging System use two or more different r.f. frequencies, and hence imaging at different depths in the surface microstructure, to produce a volume image of the strip surface. Also, the processing portion of the system can be coupled to other sensor technologies to provide an even greater cross-sectional view.
*PATENTS
Schafer, K. L. A sensor and method for the in-situ monitoring and control
of microstructure during rapid metal forming processes. U.S. patent
#5,420,518, May 30, 1995.