Microsegregation and inclusion development during the casting of steel

The enrichment of composition in the residual liquid during solidification is of itself an important parameter regarding the fitness for purpose of the alloy and, furthermore, will have a major influence on the precipitates and oxide inclusions that can nucleate and/or grow in the mushy zone. Corus sought a relatively simple, rapid model for this microsegregation and its associated inclusion type and size, for predictions across the thickness of continuously cast steels, suitable for use in conjunction with macro-models but demonstrably superior to the use of analytical equations. Notably, the analytical equations employ constant temperature equilibrium and diffusivity data for a process that can cover a very wide temperature range, and the assumed growth laws coupled with these data have an implied thermal history at odds with the environment of the macroscopic model within which the algorithm is to be used. The development and use of this model are described, along with its validation against a proven but time-consuming Finite Difference program for this purpose.