UK university proposes new aluminum casting technique

Scientists at Brunel University in London have confirmed that treating molten aluminum with ultrasound is what they call “a cleaner, greener and more efficient route to produce high-quality castings.”

 

Molten aluminum alloys at 1,292 °F (700 °C) naturally contain a high percentage of dissolved hydrogen and, left untreated, the resulting solid metal is highly porous. The most widely used method of hydrogen removal is argon rotary degassing, which can be energy intensive and may require costly components, say the Brunel researchers.

 

In pilot scale trials funded by the EU Framework Seven Programme, a team at Brunel, led by Professor Dmitry Eskin of the Brunel Centre for Advanced Solidification Technology, found that ultrasound was just as efficient as the standard method but produced far less scrap material (dross).

 

“We know from industry that the price of argon gas continues to rise because making it requires producers to liquefy air, which takes a lot of energy,” says Eskin. “There are also issues with the graphite impellers used. If they break in use the entire batch of alloy [can be] contaminated and useless.”

 

He continues, “Our pilot scale research with quantities of up to 150 kg (330 pounds) confirmed earlier laboratory tests that a moving ultrasound probe could achieve the similar end results (in terms of the resulting casting quality) to using argon, but with the advantages of not relying on expensive and fragile graphite rods and expensive gas that cannot be captured and recycled.”

 

Adds Eskin, “The five-fold reduction of the amount of dross created is another benefit. Recovering useable metal from dross is also an expensive and energy-intensive process that involves electrolysis.”

 

The next aim of Eskin’s team is to scale up the trials to a level of one half metric ton. The research team says the eventual aim is to introduce cost-effective ultrasound de-gassing earlier in the production cycle.

 

“Economic drivers like producing lighter engines and lighter car bodies are pushing process improvements in producing higher quality alloys much further back in the production cycle to where alloys are first smelted,” states Eskin. “Ultrasound treatment holds out the promise of being able to de-gas effectively and continuously, and we have already made some steps towards achieving this on the pilot level.”

 

Those seeking more information about the Brunel project can contact Mark Howard in the Brunel Press Office at mark.howard@brunel.ac.uk.