Prediction of Thermal Conditions in Rod Extrusion by FEM-Analysis for Laboratory and Industrial Aluminum Extrusion

摘要

In this article, the thermal conditions in axisymmetric unlubricated hot extrusion of aluminum (Al) alloys are studied by means of experiment and modern Finite Element Modeling (FEM) analysis. The FEM models created are able to describe fine details regarding the heating of the billet material during extrusion, and how the main extrusion parameters affect the temperature build-up during the process, including cooling effects caused by colder tools. The work consists of three parts. In the first part, 3D FEM analysis is used to reproduce the thermal conditions as they have been determined earlier by measurements in a laboratory experiment. Thermal data were then collected from within the die and the ram, with thermocouples placed in different positions inside the used tools. The experiment has been recreated in a 3D FEM model, using the software DEFORM to calculate corresponding thermal data as those extracted in the measurements. When comparison is made between simulation and experiment, with respect to temperatures, and necessary ram force vs. stroke length, good agreement is obtained, i.e., it is confirmed that these extrusion parameters are accurately predicted by the FEM analysis. In the second part, FEM simulation is applied to an industrial-sized extrusion process to study how the temperature distribution inside the billet and the tooling is affected by the extrusion conditions in the process. Because many temperature data are collected in such a study, it is not straightforward to characterize the difference between two different cases of extrusion. Therefore, the temperature distributions are presented graphically for comparable stages of two extrusion situations run with different extrusion parameters. By the subtraction of one distribution from the other, a temperature difference distribution plot is obtained, which clearly depicts the difference between the two conditions. In the third part, a comparison is made between differently-sized extrusion processes, i.e., small size laboratory processes and a big industrial process. The methodology from part 2 is used for comparable study of how strain rates and thermal conditions in aluminum extrusion are affected by process size. The analysis shows that in the shear zones inside the extrusion material, the temperature rise will be higher in industrial rod extrusion than in a corresponding small-size, scaled-down laboratory process.