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Information on Thermal Analysis for Foundries

Dual Cup Analysis for Iron – October 2010
The dual cup analysis system was pioneered by MeltLab in the early 1990’s as a way of getting chemistry, chill, and inoculation information in a single step. The method was to simply pour both a tellurium cup and a plain cup from the same spoon of iron in quick succession. Besides the extensive analysis of both kinds of cup (chemistry and microstructure) we were also able to compare the “distance” separating the grey and white eutectics (stable and metastable). The greater the distance between the two in terms of temperature, the softer the iron was. We published a paper with AFS on comparing chill wedges to the separation between curves back in 1996. There is a lot of human variation that goes into chill wedge readings that can be removed by DualCup. The concept of chill measurement by thermal analysis is documented in my paper “Chill measurement by Thermal Analysis”, AFS Transactions, 1996, page 969. The separation between the graphitic eutectic and the white/metastable eutectic is both a measure of the grade of iron, and the chill potential of the iron. A G25 iron will have a large separation, while a G45 iron will have a much smaller separation. But rather than just specifying the grade, we can draw a finer distinction between the different heats to the point of actually predicting the chill by using the metastable eutectic and the eutectic undercooling temperature. Since the degree of undercooling is directly affected by the inoculation, this factors in both the overall chemistry and the inoculation into the chill calculation. Calculated Chill = (k1 * C.E.) + (k2 * (TEU – TCE) + k3 Calculated Chill = (k4 * Liquidus) + (k5 * (TEU – TCE) + k6

or

C.E. = Carbon Equilivant derived from the Liquidus temperature TEU = Temperature of Eutectic under cooling TCE = Temperature of Carbidic Eutectic (metastable or white eutectic)

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