Predictive Tools for in-Line Isothermal Extrusion of 6xxx Aluminum Alloys

During the last fifty years, the metal forming of aluminum alloys advanced significantly, leading to a more competitive market on which production rate and overall quality are kept as high as possible. Within the aluminum industries, extrusion plays an important role, since many industrial products with structural or even aesthetic functions are realized with this technology. Especially in the automotive industry, the use of aluminum alloys is growing very fast, since it permits a considerable weight loss and thus a reduction of the emission. Nevertheless, the stringent quality standards required don’t allow the use of extruded aluminum alloys produced for common building applications. An important parameter that can be used as an index of the quality of the extruded product is the emergent temperature: if the temperature at the exit of the press is kept constant within a certain limit, products with homogeneous properties and high-quality surface are obtained and the so called “isothermal extrusion” is achieved. As extrusion industries are spread all over the world with different levels of automation and control, a universal but simple on-line tool for determining the best process condition to achieve isothermal extrusion is of particular interest. The aim of this work is to implement this model, which allows evaluation of the thermal gradient which has to be imposed on the billet. Several experiments have been carried out on an industrial extrusion press, and the outer temperature was recorded and compared with the simulated one to demonstrate the model consistency.

Isothermal extrusion of thicknesses and flanges on axisymmetrical workpieces

Technological scheme and ratios for calculating of the extrusion modes of thickenings and flanges on pipe workpieces are proposed. The viscous-plasticity state of the deformable material is accepted. The kinematics and power mode of the process are established using the extreme upper-boundary plasticity theorem with the involvement of the discontinuous fi eld of displacement velocities. Estimate of the continuity loss of the workpiece material is given. The diagram of the die tooling and sample of product are presented.

Influence of Die Surface Topography and Lubrication on the Product Quality during Indirect Extrusion of Copper-Clad Aluminum Rods

Copper-clad aluminum rods are usually fabricated using hydrostatic extrusion, since during direct and indirect extrusion fracture of the copper sleeve is difficult to avoid. In this study, different die surface topographies and lubrication conditions were applied to improve the material flow during indirect extrusion of copper-clad aluminum rods. Thus, conic dies with different roughness (polished and sandblasted) and surfaces shapes (fine and coarse grooves) were tested. Additionally, the effects of a wax-graphite-based lubricant as well as a graphite-like carbon (GLC) coating of the die conic surfaces were investigated. The composite billets were made of aluminum EN AW-1080A cores and copper CW004A sleeves with an equivalent copper cross section of 0.24 of the total billet cross section. For all trials, an extrusion ratio of 14.8:1 and a conic die angle of 2α = 90° were chosen. Non-isothermal extrusion trials were carried out using a container at 330 °C and billet and tools at room temperature to reduce the flow stress ratio σCu/σAl. The extruded composite rods’ integrity, surface quality, interface integrity, and equivalent copper cross section were analyzed. In addition, a visual inspection of the sleeve-die contact surface was performed. The results showed that the GLC coating proved to be unsuitable due to a lack of lubrication, which causes accumulated sleeve fractures and longitudinal grooves on the extruded rods. The best results were achieved with the combination of the sandblasted die surface and the wax-graphite-based lubricant, observing a uniform material flow without sleeve fractures.

Theoretical substantiation of reverse isothermal extrusion scheme of pipe billet with active friction and drawing of its edge part

Method consisting in the implementation of the reverse extrusion process of tube billet in isothermal сondition of stamping with active friction is considered. Feature of the method is the simultaneous use of friction forces and pushing of the formed thickened edge part of the workpiece and its further straightening. The force conditions and stress state in the product are estimated. Comparison of this method with the classical extrusion scheme is given.

Isothermal extrusion of ribs on plate

Technological schemes and relationships are given for calculating of operating modes during isothermal heating of workpieces. The conditions of viscoplastic non-stationary deformation are accepted. The energy form equilibrium equation as applied to the discontinuous displacement velocity fi eld and material damage kinetics equations are used. The calculation results and product samples are presented.

Dynamic Recrystallization Microstructure Grain Size Prediction of 7075 Aluminum Alloy Piston Prepared by Isothermal Extrusion

According to the structure features of the piston, the method of combining application of finite element simulation and theoretical analysis was explored to determine the extrusion process program and the extrusion process parameters. Theoretical calculation shows that a longitudinal extrusion and a lateral extrusion can form piston. The result comparing simulative prediction with theoretical calculation demonstrates that there is a good fit between the two and the theoretical calculation is right. The result of simulative prediction demonstrates that the grain size of piston after extrusion is about 17.8 μm and the refining rate reaches 55%. The grain size on both sides of the piston skirt and piston internal floor place is about 27 μm, so the refining effect is less obvious than other parts. However, the grain refinement in the piston pin holes is more obvious, the grain is refined to 13 μm and the refining rate is about 67.5%.The result comparing simulative prediction with the experimental analysis demonstrates that there is a good fit in grain refinement between the two.