In this investigation we studied the relationships between the design of dies for aluminium hot extrusion, the contact pressures on the die's bearing surface, the length of the bearing surface, the ...quality of the nitrided layer and the service lifetimes of the dies. Four nitrided dies for Al hot extrusion with a specific die design were selected to outline the approach for increasing their service lifetimes. The different die designs resulted in different contact-pressure distributions on the die's bearing surface and, consequently, in different service lifetimes. The relative values of the contact pressures, i.e., their higher or lower values with respect to the reference die, were assessed in terms of the observed wear patterns on the nitrided samples previously obtained during laboratory wear testing. The proposed approach makes it possible to optimize the geometry of the extrusion dies, which can, together with the optimization of other technological parameters, result in a prolongation of the service lifetimes of the dies.
•Obtained results explain important aspects for decreased service time of dies.•Considerable reserve for increasing of service times for Al hot extrusion dies exist.•Initial wear should be concentrated on central part of bearing surface length.•From wear patterns and time of their occurrence contact pressure on bearing surfaces can be assessed.
The thermodynamic and tribological relationships during extrusion of aluminum are presented. Frictional behavior at the interface between die bearing and flowing material through the die has been ...proposed for numerical thermodynamics analysis. The thermodynamics model predicts the influence of principal extrusion variables on maximum temperature rise at the die entry. A series of temperature measurements were also conducted to study the exit temperature of a thin walled hollow extrusion shape under three different experimental scenarios. The wear process on the die bearing is dependent on the thermodynamics of extrusion which is very much influenced by the effects of extrusion variables. The tribology in aluminum extrusion has direct influence on the accuracy of shape and the surface finish of extrusion. This paper will also explore the study of die wear and performance based upon the temperature distribution in the billet as well as in extrusion, resulting in the temperature rise in the die bearing surface.
