Effect of liquid nitrogen die cooling on extrusion process conditions

In the paper, a die for the production of a complex hollow profile made by AA6060 alloy
on an industrial 2500 ton press has been manufactured and tested under strict monitored conditions.
In particular 5 thermocouples were placed in proximity of interesting positions inside the die: 3 next
to the bearings and two near the welding chambers. A self-calibrated pyrometer was used for the
temperature monitoring of profile. Press loads, ram speeds and container temperatures were
continuously recorded directly from the press system. Six billets were initially extruded in order to
reach a steady state condition being the last three used as industrial benchmark for the 2011 edition
of the ICEB conference. Then the nitrogen was completely and partially opened and the evolution
of the temperature in the die and in the profile recorded together with the process load. The effect
on bearing temperature was extreme, in particular in proximity of nitrogen inlet, while almost no
change in welding chamber thermocouples and in the process load was revealed.