Modeling of charge welds evolution through Cahn-Hilliard equation for interaction between different Fluids: Experimental-numerical comparison with industrial case studies

In the hot extrusion process for metals, the interaction between the old and new billet materials during each cycle contaminates a specific length of the extruded profile. Experimental analysis of defect evolution is both time-intensive and costly, while empirical industrial methods and analytical formulas lack the precision required in scenarios where minimizing scrap is critical. To address this, a numerical model was developed using COMSOL Multiphysics® software, coupling the Navier-Stokes equations with the Cahn-Hilliard equation to investigate the interaction between two immiscible fluids with very high viscosities—representing the old and new billet materials. The model’s accuracy was validated through four industrial case studies, that varied in terms of profile-shape complexity and material extruded.