Effects of Extrusion Process Conditions on `Die Pick-Up`

In this research AA6060 alloy was used and was extruded at 25m/min, 30m/min, 35m/min, 40m/min and 45m/min for a particular profile. The highest exit temperature increased from 542 C to 567 C when the extrusion speed was increased from 25m/min to 45m/min. Three types of die pick-up were identified. They were named as normal pick-up, die line pick-up and lump pick-up. Normal pick-up occurred regardless of the extrusion speed and exit temperature; however the amount of normal pick-up did not increase when the extrusion speed was increased. Die line pick-up occurred when the extrusion speed was 45m/min and appeared only on the die lines. Lump pick-up is not significant since it was very rare. AA6060 (0.4%Mg and 0.5%Si) alloy has about 0.27% excess silicon and therefore at 555 C, Mg2Si particles react with aluminium and excess silicon to form liquid. However normal pick-up and die line pick-up still occurred at temperatures lower and higher than 555 C and therefore it confirms that eutectic reactions do not influence formation of pickup. Therefore die pick-up is most likely to be caused due to a mechanical process rather than a metallurgical process.