ISSN:
1662-9752
Source:
Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
Topics:
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
Notes:
Vertical direct chill (VDC) casting of aluminium alloys is a mature process that hasevolved over many decades through gradual change to both equipment design and casting practice.Today, air-pressurised, continuous lubrication, hot top mould systems with advanced stationautomation are selected as the process of choice for producing extrusion billet. Specific sets ofoperating parameters are employed on these stations for each alloy and size combination to produceoptimal billet quality. The designs and parameters are largely derived from past experience andaccumulated know-how. Recent experimental work at the University of Queensland hasconcentrated on understanding the way in which the surface properties of liquid aluminium alloys,e.g., surface tension, wetting angle and oxide skin strength, influence the size and shape of thenaturally-stable meniscus for a given alloy, temperature and atmosphere. The wide range of alloyandcondition-dependent values measured has led to the consideration of how these propertiesimpact the stability of the enforced molten metal meniscus within the hot top mould cavity. Theactual shape and position of the enforced meniscus is controlled by parameters such as the upstreamconduction distance (UCD) from sub-mould cooling and the molten metal head. The degree ofdeviation of this actual meniscus from the predicted stable meniscus is considered to be a key driverin surface defect formation. This paper reports on liquid alloy property results and proposes howthis knowledge might be used to better design VDC mould systems and casting practices
Type of Medium:
Electronic Resource
URL:
http://www.tib-hannover.de/fulltexts/2011/0528/02/13/transtech_doi~10.4028%252Fwww.scientific.net%252FMSF.519-521.1693.pdf
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