Study on metal flow in extrusion billet is fundamental and useful to understand extrusion technology. In particular, knowing the skin behavior of extrusion billet is indispensable to maintain qualities of extrusions. In order to investigate its behavior, the FE analysis by DEFORM-2DTM was performed. The billet skin was piled up at the back end of billet in direct extrusion. The skin behavior in single layer model analysis was similar to that of 2 layer model analysis. Therefore, single layer model analysis can investigate the skin behavior. Friction between billet back end and ram affected the behavior of billet skin. High lubricant accelerated thin skin 2.1% of billet diameter entering extrusion, but it constraint thick skin 6.4% of billet diameter entering extrusion.
