Effects of annular electromagnetic stirring processing parameter...
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Effects of annular electromagnetic stirring processing parameters on
semi-solid slurry production
CHEN Xing-run(陈兴润), ZHANG Zhi-feng(张志峰), XU Jun(徐 骏)
National Engineering & Technology Research Center for Non-ferrous Metal Matrix Composites,
General Research Institute for Non-ferrous Metals, Beijing 100088, China
Received 13 May 2010; accepted 25 June 2010
Abstract: A computational model coupling an electromagnetic model with a macroscopic heat and fluid flow model in semi-solid
aluminum alloy slurry preparation by annular electromagnetic stirring (A-EMS) was developed. Effects of A-EMS processing
parameters, such as stirring current, stirring frequency and stirring gap width, on macroscopic transport phenomena during the
solidification were analyzed by commercial software ANSYS 10.0 with corresponding experimental verification. The results show
that the magnetic flux density and the melt velocity increase and the temperature difference decreases as stirring gap width and
stirring frequency decrease or the stirring current increases. The slurry with the fine and uniform globular grain structure can be
gained by adjusting gap width, electromagnetic frequency and current, such as under the conditions of 10 mm of gap width,10 Hz of
electromagnetic frequency and 50 A of current. The calculated results are in reasonably good agreement with the measured ones.
Key words: electromagnetic stirring; semi-solid slurry; numerical simulation; microstructure
1 Introduction
To obtain Al alloys semi-solid slurry or billet with
high quality, an annular electromagnetic stirring (A-EMS)
process has been developed, where intensively forced
shearing could be achieved under higher shear rate inside
the annular chamber at the commercial frequency by
means of innovatively combining non-contact
electromagnetic stirring and an annular chamber with
specially designed profiles, and thereby more uniformly
fine microstructures of Al alloys slurry were produced in
comparison with normal EMS[1-4]. Although a
computational model coupling an electromagnetic model
with a macroscopic heat and fluid flow model in
semi-solid Al alloy slurry preparation by A-EMS has been
developed[5-6], much research work is needed to disclose
effects of A-EMS processing parameters on macroscopic
transport phenomena in slurry-making process, which is
important to optimize processing variables. In this study,
based on the developed models, effects of A-EMS
processing parameters, such as stirring current, stirring
frequency and stirring gap width, on macroscopic
transport phenomena during the solidification were
investigated with corresponding experimental verification.
2 Experimental
A schematic diagram of semi-solid Al alloys slurry
preparation by A-EMS is illustrated in Fig.1, which
contains melt, air, cooler, crucible and electromagnetic
stirrer consisting of yokes, cores and coils. The stirrer
design entails the placement of the coils around the
crucible to generate a rotational motion along the
horizontal direction[7]. The stirring intensity and rate are
changed by the adjustment of the AC voltage input
employed in a range of 0-200 V, and frequency input
employed in a range of 0-50 Hz, respectively. An
annular chamber is designed by controlling the gap space
between the crucible and the cooler, and thus an
intensively forced shearing could be achieved.
In the experiments, as A357 melt was poured into the
austenitic stainless steel crucible preheated to a given
temperature, a cooler was inserted in the center of the
crucible, and then EMS started. The lids are made of
insulation kaowool, ensuring that thermal exchange
during solidification mainly occurs in the radial direction.
The crucible filled with semi-solid slurry was quenched
Foundation item: Project(2006CB605203) supported by National Basic Research Program of China; Project(2009AA03Z534) supported by the National
Hi-tech Research and Development Program of China
Corresponding author: ZHANG Zhi-feng; Tel: +86-10-82241229; E-mail: [email protected]
Trans. Nonferrous Met. Soc. China 20(2010) s873-s877
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