Titanium4.2
Simulation of Titanium and Ni-Based Superalloy Extrusions
Mahender P. Reddy, Ravisankar Mayavaram, Narendra Singh
Altair Engineering, 7800 Shoal Creek Blvd, Ste. 200N, Austin, TX 78757
Titanium alloys and Ni-based superalloys have excellent mechanical strength at high temperatures and resistance to corrosion and oxidation. These properties make them suitable for aerospace, nuclear, and defense applications. Extrusion is a cost-effective method to manufacture components such as seamless tubes, high-strength structural parts, and complex profiles in engines. In the extrusion process, heated billet is pushed through a die to produce desired shape. Unlike extrusion of other metals (such as aluminum), in the case of titanium and Ni-based alloys, the extrusion speeds and extrusion pressures are high. Glass lubrication is commonly used to reduce frictional resistance between the workpiece and tool surfaces. Here a glass wool pad is placed in-between the die and billet. In addition, glass powder coating is applied on the billet external surfaces. During extrusion, the glass pad melts and forms a thin glass film at the interface, which acts as a lubricant. This glass film appears as a glass coating on the extruded profile.
A good understanding of the melting and erosion of glass pad is essential in determining optimum extrusion process conditions and in avoiding production stoppage due to lubrication failure. In this paper we present a numerical method to predict erosion of glass pad and the thickness of glass film. This method uses finite element method to compute the flow of metal during extrusion. The erosion of glass pad depends on its thermal properties and granularity, the temperature the interface, and extrusion pressure. We also present a stability criterion to determine the change of glass film thickness in the bearing region and container surface. The accuracy of the numerical method is verified by comparing the predicted results with experimental data.