Flow behaviour of phosphorus-deoxidised copper in plane-strain hot extrusion

Jin, L.Z.1, Ssemakula, H.2, Sandström, R.1
1 Department of Materials Science and Engineering, Royal Institute of Technology, Sweden
2 Department of Production Engineering, Royal Institute of Technology, Sweden

Flow behaviour of phosphorus-deoxidised copper in plane-strain hot extrusion with an insertion in the die has been studied through a finite-element model consisting of fluid dynamics and heat transfer approaches.

The billet material is considered as rigid-visco-plastic and rate-sensitive. A dynamic viscosity, which is strain-rate and temperature dependent, has been integrated into the model. It has been found that the hydrostatic stress is compressive everywhere in the interior of extrusion die and change of stress state from compressive to tensile can be used a criterion for void or crack formation.

A parallel study has been performed using a work-rate model constructed by Qform-2D. Steady-state solutions from fluid dynamics model and work-rate model are compared. The work-rate model cannot reliably predict the situations where a tool is inserted into the die. The inconsistency of stress dependence on extrusion ratio and temperature dependence on stress in the work-rate model is identified.

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