INVESTIGATION OF METAL FLOW AND TEMPERATURES BY FEM IN THE EXTRUSION OF TI-6AL-4V TUBES

In the extrusion of tubes from titanium alloys surface defects are often observed. These defects are related to process variables such as tool geometry and temperature, initial billet temperature, characteristics of the extrusion press and lubrication. Often it is difficult to establish optimum process variables for extruding defect-free tubes through experimentation, because this is costly and time consuming. The application of FEM to study metal flow in extrusion is also difficult because large deformations are present and the FEM mesh distorts very rapidly, requiring numerous remeshings. To overcome this problem and to improve the efficiency of applying FEM to investigate tube extrusion, an automated remeshing procedure was developed. Through this procedure the FEM mesh was automatically updated and the FEM code ALPID, version 2.3, was used successfully to simulate metal flow under three different extrusion conditions. The results of these simulations helped to understand the formation of surface defects in the internal surface of extruded tubes. This information is expected to assist in improving tube extrusion operations.