A Homogeneous Flow Model for nitrogen cooling in the aluminum-alloy extrusion process

Extrusion of aluminum alloys has become extensively employed as a process to manufacture a variety of products. However, heat generated by the high deformation energy and the high friction forces imposed during the process may cause defects in the extrudate, as well as reduce tool life. So, effective die cooling is key in achieving high product quality and production rate. Nitrogen has recently been identified as a promising coolant; however, current modeling does not take the presence of two phases into account, only including either the liquid or the gas phase within cooling channels, which often results in poorly designed cooling systems. The present research was aimed at exploring the homogenous flow approach as a simple, yet representative method to account for the liquid and the gas phase, as they both occur during the cooling subprocess. Ten AA6060 billets were extruded in an industrial production line, varying nitrogen flow rate and monitoring temperature trend at various locations of interest. A Finite Element model was then developed in a multiphysics environment, into which the simulation of both the extrusion process and the nitrogen flow were integrated, with the latter being represented as a homogeneous flow. Validation was performed against the experimental dataset through steady-state and transient analysis. This work proved the homogeneous-flow approach remarkably successful in capturing the involved physics and assessing the provided cooling effect quantitatively.