A new casting technology, Low Pressure Casting (LPC), for aluminium extrusion billet casting has been developed by Hydro Aluminium and Hycast. The new technology produce billets with improved surface appearance and sub-surface microstructure. The technology is validated trough production in two casthouses in regular production. The technology is verified for the dimension range Ø152–405mm (6–16”).The new technology uses siphon feeding of liquid metal to the casting moulds, and has thus eliminated the metallostatic pressure in the liquid metal inside the moulds. The sub-surface microstructure is improved compared to billets cast with conventional technologies since exudation of enriched residual melt on the billet surface is eliminated. The surface segregation is significantly lower in depth and in alloying element enrichment compared to billets produced with conventional gas-assisted graphite wall moulds. The surface appearance is improved due to the elimination of the pulsing nature of the meniscus in conventional casting technologies and the elimination of exudation.The improved surface quality has the potential of giving increased yield and productivity in the extrusion process. For hard alloys the machining of the billet surface may be reduced or even eliminated.
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- A New DC Casting Technology for Extrusion Billets with Improved Surface Quality
John Erik Hafsås
- Springer International Publishing
in-adhesives, MKVS, Hellmich GmbH/© Hellmich GmbH, Zühlke/© Zühlke