METHOD OF AND APPARATUS FOR CONTACTLESS PLANARITY MEASUREMENTS ON FERROMAGNETIC METAL STRIP

摘要

A method and apparatus for the contactless determination of planarity of a ferromagnetic metal strip during transit of the strip through a strip-processing line or cold-rolling line. Hysteresis loops are repetitively impressed in the metal strip and the tangential magnetic field strength is measured at a surface of the strip and electromagnetic parameters are determined from the time course of the tangential field strength signal. The parameters are functions of the mechanical stress which is evaluated to determine residual intrinsic stress distribution and then the planarity or nonplanarity of the strip.