Novel billet design for co-extrusion of ferrous material tubes

Novel billet design using a shortened core was explored in an effort to control material flow during the co-extrusion of plain carbon/stainless steel tubes. In order to minimize the amount of material that is extruded “out of geometrical tolerance” as a result of non-concurrent material flow, the core length in the initial billet is shortened. Extrusion was simulated using DEFORM 2D™ finite element modeling (FEM) software and compared to actual extrusion experiments. FEM and industrial scale extrusion results are presented and compared for two different extrusion ratios. There is a strong agreement between the FEM and actual results when investigating the core material distribution throughout the extrudate. It is shown that by reducing the core length in the initial billet approximately 10–20%, concurrent material flow is promoted during the early stage of extrusion and the amount of out of tolerance material is minimized.