Effects of die land on the cold extrusion of lead alloy

In the present investigation, the effects of die land, an uncommonly investigated die extrusion parameter, on the extrusion pressures are experimentally and theoretically evaluated. The analyses of the extrusion pressure determination by the upper bound method have been extended to include the power due to the ironing effect, resulting from frictional forces within the die land region. The extrusion pressure contributions due to the die land evaluated theoretically and practically are found to increase with die land length for any given percentage reduction and also increase with increasing percentage die reductions at any given die land length. There is a good agreement between theory and experiment on the extrusion pressures evaluated. For the purpose of designing for suitable extrusion die to extrude lead material, it is recommended that the die land length should be chosen equal to or greater than 0.6 of the billet diameter for small work pieces and with die exit clearance angle less than 10°, so as to extrude lead products with negligible bend or curvature.