Experimental Determination of the Electrical Conductivity and Magnetic Permeability of Different Steels and its Application to the Prevention of Steel Mixings in a Pipe Mill

Eddy currents based equipments can be used to detect differences in electrical conductivity or magnetic permeability of metallic samples. In this work we deal with the problem of detecting eventual steel mixings in a steel pipe production line. The starting point of the analysis is the development of a technique to measure the electrical conductivity and the magnetic permeability of steel samples which allows to characterize completely the expected coil impedance at low excitation currents. At higher excitation currents the nonlinear/hysteretic behavior of the steel cannot be disregarded. We present some preliminary measurements of hysteresis curves together with a numerical analysis of its influence on the anharmonicity of the coil output.