Resistivity of Fe–Mn–C Melts

The resistivity of liquid Fe–Mn–C alloys containing from 5 to 25 wt % manganese and from 0.4 to 2.2 wt % carbon has been measured by the rotating magnetic field method. The measurements have been made during heating from 1340 to 1810°C and subsequent cooling of the samples. The resistivity of the melts during heating was considerably lower than that during subsequent cooling, which was accompanied by a decrease in the temperature coefficient of resistivity. The temperature dependence of resistivity for some of the alloys has been found to have an anomaly in the form of a break during heating to temperatures in the range 1550–1680°C. The addition of manganese and carbon has been shown to influence the resistivity of the melts and its temperature coefficient. We have calculated the effective resistivity of a liquid alloy with the composition (wt %) Fe–10Mn–1C as a heterogeneous system using analytical relations for conductivity of inhomogeneous media, a unit-cell method, and geometric models of isolated and interpenetrating inclusions. The temperature t* = 1730°C thus obtained for the transition from isolated to interpenetrating inclusions in the Fe–10Mn–1C melt agrees with the experimentally determined temperature t* = 1680°C of the beginning of the portion common to the temperature dependences of resistivity obtained during heating and cooling. The temperature 1540°C of the transition from isolated to interpenetrating inclusions agrees with the experimentally determined temperature 1550°C corresponding to the break in the temperature dependence of resistivity.