Studies of Porthole Extrusion through Die with Different Sizes of Portholes

Aluminium extrusion industry produces hollow profiles that have different wall thickness in the cross section. Production of such profiles requires billet extrusion through porthole die with different sizes of the portholes and this result in variation of material flow velocity through the different portholes. Experiments are reported here in which a grid pattern technique was used to characterize the metal flow through two porthole channels of unequal size. The design of laboratory die that represents the industrial case of porthole extrusion has been modified to get variation in size of portholes. The technique has successfully mapped the non-symmetric material flow i.e. similar to the extrusion of industrial profiles having different wall thickness across the section. One of the channels delivers more material into the extrusion weld zone behind the die bridge than does the other channel. The applied technique is described and the mapped flow of metal are provided as new information regarding flow velocity variations through the two ports. The encountering of two metal streams behind die bridge and deformation characteristics within the welding chamber have been studied. Metal flow achieved from the finite element model of the experimental set up is compared with experimental results. The boundary conditions of the model provide information about the real conditions in the experimental set up.