Hot Extrusion Process Grain Size Prediction and Effects of Friction Models and Hydraulic Press Applications

Abstract

This study focuses on realistic modeling of forming load and microstructural evolution during hot metal extrusion, emphasizing the effects of friction models and hydraulic press behavior. Rather than merely predicting load magnitudes, the objective is to replicate actual press operation by integrating a load limit response into finite element modeling (FEM). By applying Coulomb and shear friction models under both constant and hydraulically controlled press conditions, the resulting impact on grain size evolution during deformation is examined. The hydraulic press simulation features a maximum load threshold that dynamically reduces die velocity once the limit is reached, unlike constant presses that sustain velocity regardless of load. P91 steel is used as the material system, and the predicted grain size is validated against experimentally measured data. Incorporating hydraulic control into FEM improves the representativeness of simulation results for industrial-scale extrusion, enhancing microstructural prediction accuracy, and ensuring forming process reliability.