The use of ceramic foam filters in ductile iron foundries to reduce the number of inclusions that reach the casting has been widely accepted. However, the exact mechanisms contributing to foam filter effectiveness are not yet known; this limits the ability to maximize filter performance and inclusion reduction. The objective of this work is to qualify and quantify the effects of the foam filter structure on inclusion retention. This has been accomplished through the development of a three-dimensional (3-D) mathematical model, based on physical water modeling and mathematical simulations. It was found that the casting rate and inclusion density play minor roles in the capture ratio, while inclusion size is the most influent variable. One mechanism for capturing inclusions involves the direct impact of an inclusion on the web wall and its adhesion after crossing over the liquid film. Two additional mechanisms involve the entrainment of inclusions by buoyancy-lift forces into low-velocity fields and the ulterior adhesion through buoyancy effects. The second mechanism is the entrainment of inclusions into microrecirculating flows; the inclusions remain in these flows for times that exceed the mold filling time. The latter mechanism has limited intensity for inclusions approximately 30 to 100 lm in size. In order to enhance the effects of this mechanism in this range of sizes, the vorticity magnitude in the microfree shear flows in the filter's pores must be increased, through changes in the structure geometry of this device.

Slag entrainment during steel teeming-drain operations from a steel ladle impacts negatively steel cleanliness and quality. In the present work water modeling and mathematical simulations using a multiphase model for momentum and heat transfer were employed to understand the mechanisms of vortex funnel drain and sink drain flows. The critical bath height for vortex development increases with steel throughput and valve gate opening. Six stages during vortex development are identified, passing from a dimple formation on the bath surface until sink drain which begins when the bath level has the same magnitude as the nozzle diameter. This later drain pattern is independent from any other teeming-draining variable being only a function of the bath height and nozzle diameter; when they are about the same the metal-interface collapses. The temperature gradients originated by the heat losses of the ladle to the surroundings provide buoyancy forces that are large enough to influence liquid motion in the ladle. At large bath levels steel observes long-vertical recirculating flows and at low bath levels these flows change to horizontalcircular recirculating flows that become a seed for later vortex development. These buoyancy forces increase the critical height for vortex development and slag entrainment.

The interfacial instability in the development of core‐annular flow by the influence of the inlet nozzle in a horizontal pipe was investigated by computational fluid dynamics (CFD). The two‐phase flow has been simulated using Volume‐Of‐Fluid model (VOF) and k‐ϵ turbulence model for the core (viscous oil) and the annular phase (water). The simulation results showed that by increasing the water input fraction, the interfacial instability appeared when the eccentricity of the core with an upward position and an oscillating position were generated by the input pressure, turbulent kinetic, and buoyancy force. In the development of the perfect core‐annular flow an input concentric core changes to eccentric position with negligible turbulence. The onset of entrainment is formed by a reverse flow at the junction of the two‐phase at the nozzle exit. The interfacial formation was analyzed using a proposed two‐phase Froude number and modified Eötvos number involving the water input fraction.

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Simulation of the grain growth process, as a function of steel heat transfer conditions, is helpful for predicting grain structures of continuous cast steel products. Many authors have developed models based on numerical methods to simulate grain growth during metal solidification. Nevertheless, the anisotropic nature of grain structures makes necessary the employment of new mathematical methods such as chaos theory, fractals, and probabilistic and stochastic theories of simulation. The problem is significant for steelmakers to avoid defects in products and to control the steel microstructure during the continuous casting process. This work discusses the influence of nodal solidification times and computer algorithms on the dynamic formation of the chill, columnar, and equiaxed zones including physical phenomena such as nucleation and grain growth. Moreover, the model incorporates pre-nucleation and pre-growth routines in the original algorithm. There is a description of the influence of the mathematical parameter criteria and probabilities over the grain morphology obtained after solidification. Finally, an analysis of these algorithms elucidates the differences between these structures and those obtained from models considering only the solidification.