Solidification process and characterisation of a mass–gravity foundry ingot

Abstract

The first step in the processing of metals is often a liquid moulding operation. Numerous defects can appear, which depend on the material, the process conditions and the thermal parameters and it is very important to know how they can evolve in order to obtain finally more homogeneous and defect-free ingot. In this study, the authors have looked at a special alloy of uranium, containing 6% of niobium. The casting operation is made up of different steps: melting of the metals; homogenisation of the liquid through stirring; and finally pouring into a graphite mould in order to obtain an ingot. In this case, the authors want to be able to validate a model that will be created after this study with the aim at minimising both the segregation that can occur in this kind of alloy, the porosities which are very common in the foundry process. To be presented are: (i) the conditions, the material and the parameters used in this case; (ii) some parameters concerning the alloy (phase diagram, inclusions and their morphologies, thermal properties); (iii) the location of the thermocouples in the ingot and in the mould which were used in order to see how the solidification evolves; (iv) the temperature recordings; and (v) the results of the characterisation of this ingot, through metallography and chemistry analysis; so that it is possible to obtain a full chart of the niobium content in this ingot. This set of experimental measurements constitutes a complete collection of data that can be used on one hand as input for the numerical model and on the other hand as results for comparison with the numerical simulations.