A new approach to the determination of the liquidus and solidus points associated with the melting curve of the eutectic Co–C, taking into account the thermal inertia of the furnace

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In the case of metal–carbon eutectics, with transition temperatures above 1000 °C, the liquidus-point temperature, associated with melting, serves as a prime reference temperature. Factors influencing the shape of the melting curve and how to deal with them when specifying the liquidus temperature are the main subject of this paper. Influence factors investigated are the impurity factor, the furnace-temperature gradient, and a factor not considered before: the thermal inertia of the furnace and the associated transient in furnace temperature during melting. These investigations resulted in an improved method for determining the liquidus point, demonstrated for Co–C, which implicitly corrects for the post-melting effect, if any. In addition, a new method, the step-shift method, is proposed for the determination of the solidus point by direct observation. As shown, there is a clear justification for establishing reference methods to determining the solidus and liquidus points of M–C eutectics along the lines set out in this paper.