Measurement of electrical conductivity of liquid metals using Lorentz force sigmometry

Lorentz force velocimetry (LFV) is a non-contact electromagnetic technique that can be applied to measure flow rate and/or local velocities in electrically conducting liquids like metal melts. The technique is based on the principles of magnetohydrodynamics: when the moving conductor interacts with an externally applied magnetic field, Lorentz forces are generated within the melt. During LFV, the counterforce to the Lorentz force is measured. Acting on the system that produces the external magnet field, this counterforce is proportional to the flow rate or the local velocity and the electrical conductivity of the melt. Hence, in application the knowledge of electrical conductivity is demanded. To this end we develop an electromagnetic technique for non-contact measurement of electrical conductivity of metal melts, termed Lorentz force sigmometry (LOFOS). During LOFOS, Lorentz forces are measured that are generated by a welldefined pipe flow for which mass flow rate is determined via a weighing procedure. The present paper describes the physical laws controlling LOFOS operation, shows the mathematical procedure of the evaluation of electrical conductivity and addresses the problem of calibration of a respective Lorentz force sigmometer. In detail, we present laboratory measurements at room temperature using solid metal bars and the liquid metal alloy GaInSn in eutectic composition as test melts. Here, uncertainty of measurement less than 0.5% and about 3% for solid and liquid tests, respectively. Currently, high-temperature applications of LOFOS in tin and copper melts are on the way.