This paper describes the development and validation of a Lagrangian-based finite element model for the aluminum extrusion process used to produce thin sections which are characteristic of tubing used in automotive air conditioners. Due to the large reduction involved in producing such tubing, extrusion ratios are between 500 and 2000. In order to study metal flow and establish baseline strains and strain rates in the process, a finite element model based on non-isothermal plane strain deformation was developed. Effective strain rates were predicted to be as high as 1500 s-1 in the weld chamber with effective strains reaching 4.0 in each wall. Billet cooling on the order of 20 °C occurs in the container and portholes of the die while significant adiabatic heating occurs as a result of deformation in the weld chamber. Surface velocities and temperatures were compared to process data collected on-line from an instrumented extrusion press and were found to be in excellent agreement with the model.