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| CSIRO | SOLVE | Issue 6 Feb 06 | |
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ARTICLE
LIGHT METALS:
Coming On Light and Strong By David Adams
The worldwide push for fuel-conserving, lighter cars has been aided by a new heat treatment. Driven by the worldwide need to lower vehicle gas emissions, a growing demand in the automotive industry for lighter cars has meant researchers have been looking for a heat-treatment process that can deliver lighter, stronger aluminium for car parts. Although heat treatment is commonly used to strengthen wrought and cast aluminium parts, it cannot be used on high-pressure die castings because air bubbles trapped during casting can blistering and distort the parts, making them unusable. A new heat-treatment technique developed at CSIRO has overcome the problem, allowing high-pressure die cast parts to be strengthened without running the risk of these metal defects.
Therefore a strengthening treatment that fits with this existing process is an important development. "Most of the aluminium parts you see when you open the bonnet of your car are aluminium high-pressure die castings,” says Dr Lumley. The process allows parts to be made quickly – up to 20 small parts a minute. CSIRO has overcome this manufacturing hurdle by developing a process where die casts can be heat treated. Dr Lumley says this results in quite large improvements in the strength of the part with an excellent surface finish. Trials at CSIRO’s Clayton laboratories have shown the new process can at least double the strength of high-pressure die cast parts. This means they can be lighter and still do the same task – a factor that is particularly important in the automotive industry where lighter cars use less fuel and have lower greenhouse gas emissions. “A lot of these parts are designed for their loads and basically the stronger the material, the lighter you can make the part,” says Dr Lumley. “We would like to think that we could see a 30 per cent weight reduction. “The die casting industry is very, very cost-sensitive, and if you can use less metal per car part, you also save money. “We’ve done trials on large batches of parts purchased from industry and have developed treatments for those parts. That has gone really well. The trials show very few rejects due to heat treatment – in a recent batch of 575 parts, only one per cent of the parts blistered.” Details of the new process will remain under wraps until the Australian Die Casting Association meeting in February, where the results of the project will be presented to industry. Sam Tartaglia, business development manager at CMIT, says the industry has sought such a technique for many years. “This is a major advance,” says Mr Tartaglia, who until recently was a senior executive at US-based company Teksid Aluminum, a world leader in the production of aluminium castings. “While the new techniques will improve existing parts, it will be in new product design that the benefit will be the greatest. The big advantages will come when products are designed taking into account these new material properties. “The process also allows high-stress parts, which previously could only be made by expensive processes, to be die cast, at least halving the cost.” Dr Lumley says that while aluminium die casting worldwide is dominated by the automotive industry, other industries can use the new process. Examples include builders’ nail-gun casings and even door handles. “Basically anything that requires a fairly complex and strong part to be produced quite cheaply can be made using this process,” Dr Lumley says. APPLICATION Tests show a new heat-treatment process can double the strength of high-pressure die cast vehicle parts For further information contact: |
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Dr Roger Lumley, leader of a Light Metals Flagship research team at CSIRO Manufacturing and Infrastructure Technology (CMIT), says high-pressure die casting is commonly used as a high-volume production process in a range of sectors, particularly the automotive industry, where it is used to manufacture parts such as engine blocks, transmission housings and many small parts.
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