Extrusion is a compressive deformation process in which a billet is ‘forced’ (extruded) through a die in order to obtain a reduction in its cross-section and convert to the desired shape. The length of the extruded part will vary, dependent upon the initial dimensions of the billet and the profile extruded. The extrusion process produces profile cross-sections that are uniform over the entire length of the product, ideally suited for fabrication of long pieces or members. Currently, the extrusion process is capable of manufacturing innumerable shapes and profiles that are widely utilized in the aerospace industry. Superior strength to weight ratio, electrochemical compatibility with graphite in graphite-reinforced organic-matrix composites, makes it convenient to employ titanium alloy extrusions for aerospace applications1).
Metal extrusion processes, in the manufacturing industry, can be broadly classified into two main categories – direct and indirect. Plymouth Engineered Shapes employs the direct or forward extrusion process, where the die and the ram are in the opposite ends and the billet travels in the same direction as the ram. Typically, the cross-section of the work billet is much larger than the cross-section of the extruded part. To relate the cross-section of the workpiece to that of the extruded product, a value commonly termed as “extrusion ratio” was established that is defined as the ratio of the area of the original billet cross-section (Ao) to that of the extruded product (Af). The extrusion ratio, or reduction ratio, can be expressed as (Ao/Af). Depending on the final geometry of the part, there exists a wide range of extrusion ratios for extruding different titanium products. As mentioned earlier, almost all titanium extrusions will require a hot straightening operation after the completion of the extrusion process.
For more information about this process, please read the technical paper Near-to-Net Shape Aerospace Extrusions.