Novel billet design for co-extrusion of bi-metallic shapes and tubes

Abstract

Novel billet design was introduced in an effort to better control material flow during the co-extrusion of bi-metallic shapes and tubes. In order to minimize the amount of material that is extruded out of geometrical tolerance (measured by the interface location) 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 confirmed by actual extrusion experiments on an industrial press. Results for a specific billet geometry extruded using a selected extrusion ratio for plain carbon/stainless steel tubes are presented. It has been shown that by reducing the core length in the initial billet by approximately 10% - 20%, concurrent material flow is promoted and the amount of out of tolerance material is minimized. The presented innovation was first developed for solid bi-metallic profiles made from different aluminum alloys and then applied to bi-metallic ferrous tubes showing general application of the proposed invention.