Abstract
As a part of a research into new techniques for purifying recycled aluminium alloys, a novel electromagnetic apparatus had been developed for investigating in real-time the separation mechanisms of detrimental inclusions in aluminium alloy melts under alternating magnetic fields. The magnetic coil was designed based on the Helmholtz coil design. A viewing gap was designed for in-situ imaging studies using synchrotron X-rays. The gap was designed to maintain a uniform magnetic field in the central region where a sample is positioned. The current setup for the magnetic coil pair is able to produce a peak magnetic flux density of ~10 mT at a frequency of 25kHz. A separate electrical resistance furnace, designed to concentrically fit within the magnetic coils, was used to control the heating (up to ~850°C) and cooling of the samples. After a series of systematic tests and commissioning, the apparatus was used in a number of in-situ and ex-situ experiments.
Highlights
As a part of a research into new techniques for purifying recycled aluminium alloys, a novel electromagnetic apparatus had been developed for investigating in real-time the separation mechanisms of detrimental inclusions in aluminium alloy melts under alternating magnetic fields
The Printed circuit board (PCB) physical dimensions were driven by the requirement to have sufficient creepage and clearances for the high voltages that would be present across each PCB
It was essential that the windings were connected in series, otherwise the two individual furnace windings wound in different directions will independently be affected by the alternating magnetic field, similar to the coupling effect of a conventional-wound furnace, which was undesirable
Summary
A recent report commissioned by the European Aluminium Association [1] predicted that the global demand for primary aluminium would reach ~107.8 million tonnes (Mt) by 2050, an increase of ~50% from the current level (~70 Mt). Iron and silicon (apart from the Al-Si casting alloys) are the main elements that form irregular-shaped brittle phases that are detrimental to mechanical properties, especially ductility. Such detrimental phases prevent recycled aluminium from being used in high performance, high value structural applications such as the aerospace and the automotive industry. Guo et al [11,12] used a 9-turn induction coil, operating at a frequency of 20 kHz, for the separation of alumina inclusions and primary silicon crystals within a pure aluminium and an aluminium alloy melt, respectively
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