Magnetite ore-coal composite pellets with about 10, 15 and 20 mm diameter were rapidly smelted to produce pig iron by microwave heating in N 2 gas. A microwave generator with 5 kW maximum power at 2.45 GHz was employed. Carbon content in pig iron was about 2 mass% near the liquidus line in the Fe-C system. Slag was easily separated from pig iron. By XRD analysis it is realized that the reduction of magnetite started at about 800°C and was completed to be pig iron at about 1 350°C. The heating rate of pellets was independent of their mass but dependent on applied power because of self heating. According to the increase of heating rate, the level of impurities in pig iron decreased less than blast furnace.

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Microwave thermal processing of metal powders has recently been a topic of a substantial interest; however, experimental data on the physical properties of mixtures involving metal particles are often unavailable. In this paper, we perform a systematic analysis of classical and contemporary models of complex permittivity of mixtures and discuss the use of these models for determining effective permittivity of dielectric matrices with metal inclusions. Results from various mixture and core-shell mixture models are compared to experimental data for a titanium/stearic acid mixture and a boron nitride/graphite mixture (both obtained through the original measurements), and for a tungsten/Teflon mixture (from literature). We find that for certain experiments, the average error in determining the effective complex permittivity using Lichtenecker's, Maxwell Garnett's, Bruggeman's, Buchelnikov's, and Ignatenko's models is about 10%. This suggests that, for multiphysics computer models describing the processing of metal powder in the full temperature range, input data on effective complex permittivity obtained from direct measurement has, up to now, no substitute.