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Magnesium Production
| Through improved process design and alloying
technology, assist agnesium casthouses to reliably produce magnesium
product of the specified quality. |
The use of the light metal
magnesium in manufacturing can be problematic because of magnesium's
unique physical and chemical properties. Molten magnesium burns
in air, making it more difficult to work with in comparison to aluminium.
However, other properties of magnesium make it attractive to manufacturers,
for example, it is extremely light weight, is readily castable and
it responds uniquely to deformation. As safe handling techniques
for magnesium manufacturing continue to be improved, the widespread
application of magnesium in the light metals industry is gaining
more acceptance due to magnesium's advantages over other metals
for certain applications. Research in the Magnesium Production Sector
aims to improve the efficiency of production and reduce the cost
of products from Australian magnesium smelters. The scope of work
covers metal handling, melt protection, refining, quality measurement,
alloy production and casting of metal products.
An important factor in encouraging
industries to substitute magnesium in the manufacture of major components
is the demonstrated success of magnesium production to create world
class quality products at an internationally competitive price.
The Magnesium Production Sector, like all metal production industries,
must also keep in mind their responsibility to the environment in
the form of environmental accountability. To achieve acceptance
of magnesium as a component in a wide range of applications, particularly
the automotive industry, magnesium production processes must be
competitive with other metals in terms of not only cost, but also
environmental impact. CAST's research tackles all of these issues
facing magnesium producers and CAST researchers work in close contact
with our industry partners to find solutions to all aspects of magnesium
production.
Projects
Melt Protection
To replace sulfur hexafluoride gas with a low
cost, low global warming gas for the protection of magnesium melts.
The use of CAST's new cover
gas technology as an alternative to sulfur hexafluoride SF6 for
magnesium melt protection has been successfully tested at Australian
Magnesium Corporation's Gladstone Demonstration Plant and for a
range of applications at a magnesium recycling facility operated
by Magnesium Elektron in the UK. CAST is now in discussions on a
licence agreement with Magnesium Elektron for them to introduce
CAST's cover gas into their operations. CAST has also developed
a commercialisation strategy with AMC for use in their Stanwell
Magnesium Smelter and to take the development into the global market
place.
Research has shown that judicious
use of diluent gas can dramatically lower the level of HF produced
as a thermal decomposition product. Environmental monitoring in
the laboratory and the AMC Demonstration Plant has confirmed that
HF levels can be managed so that they are below accepted exposure
levels. A medical specialist has confirmed that the gas can be safely
used in an industrial environment. The project is now leaving a
research phase and entering a commercialisation phase. AMC plans
to use the cover gas in the magnesium plant that is being built
at Stanwell in Central Queensland. Beta test sites have been selected
for testing in full-scale application in Europe and North America.
As HFC-134a is still a moderate greenhouse gas, a program of work
will be undertaken to capture the majority of the unreacted gas,
particularly in die casting applications.
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Magnesium Alloy Production
To reduce the operating and capital costs associated
with addition of alloying elements and additives in the production
of magnesium alloys.
Reducing the costs of sand
casting alloys relies on the ability to minimise the amount of zirconium
added. CAST, with the support of AMC, have examined a number of
methods for adding zirconium to grain refine magnesium alloys and
have developed a method which looks promising at laboratory scale.
It would appear that effective grain refining requires both dissolved
and particulate zirconium to achieve the best results. The dissolution
rates of various rare earth elements have been determined and most
appear to dissolve into magnesium easily, although some dissolve
faster than others.
It is intended to use all of
the knowledge gained in zirconium and rare earth additions to make
batches of AMC-SC1 alloy at 400 kg scale to confirm the flow sheet
for a production process for commercial quantities of this alloy.
Work is also progressing on using less pure grades of rare earth
elements and what effect this will have upon alloy properties.
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Intense Refining
To develop methods for measurement of the level
of non-metallic impurities in liquid magnesium and procedures for
their removal.
The project has identified
a scanning ultrasound method as a promising tool for detection of
inclusions in magnesium. The method appears to supply far more detail
than x-ray radiographs. It is intended to conduct cleanliness analysis
on ingot slices and cast plates of magnesium with the aim of correlating
the results to fast neutron activation analysis and mechanical properties.
There also appears to be scope for more detailed numerical analysis
of the ultrasound signals. Successful filtration trials have been
conducted at rates of up to one tonne/hour. A range of filter materials
has been tested and one commercially available filter appears to
be particularly promising. Filtration would appear to be technically
feasible as a method to increase the refining rate of molten magnesium.
Filtration trials will continue with the aim of quantifying the
results using ultrasound analysis. A range of new filter materials
for magnesium is due for commercial release and these will be tested
over the next year.
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Life Cycle Assessment
To conduct life cycle assessment of the production
and use of magnesium products.
A report has been prepared
that examines the life cycle analysis of magnesium ingots produced
in Australia. This report covers the first stage of the project,
examining the cradle to casthouse gate system. The analysis has
been very thorough and the methodology used has been consistent
with approved international standards. The project will now focus
on cradle to manufacturing gate and will also examine environmental
emissions from Chinese magnesium producers.
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Magnesium Ingot Surface
Quality
To determine the effect of humidity, temperature
and salt-spray on the storage life of magnesium ingot in terms of
the appearance of the ingot surface.
To determine the appropriate environment, specifically humidity
and temperature, that will enable long-term storage of magnesium
ingot while retaining the original appearance of the ingot.
As expected, humidity is the
main factor affecting the rate of surface degradation through oxidation
of magnesium ingot. Trials with the support of AMC conducted to
date have shown the importance of covering bundles of magnesium
ingots to reduce humidity below a critical level and to prevent
degradation of the surface of ingots. In the next stage of the project,
research will focus on determining how ingots should be stored during
transport in shipping containers. Both the temperature and humidity
inside the container will fluctuate during transportation, and trials
to date have only examined the effect on surface quality at static
temperature and humidity levels. Future trials will involve exposing
ingot surfaces to a cycle of temperature and humidity to model the
effect of transporting ingots across oceans. A range of covering
bag materials will be tested.
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