Researchers at Brunel University London report that an ultrasound treatment could be a much cheaper and more environmentally friendly way to remove hydrogen from aluminum alloys than conventional methods. Treating molten metal with ultrasound is a cleaner, greener and more efficient route to produce high quality castings. The most widely- used method of hydrogen removal – argon rotary degassing – is energy intensive and requires costly components.
Molten aluminum alloys at 700°C naturally contain a high percentage of dissolved hydrogen. Left untreated, the resulting solid metal is highly porous. In pilot scale trials funded by EU Framework Seven Programme, the team found that ultrasound was just as efficient as the standard method, but produced far less waste material (dross). The price of argon gas continues to rise because making it requires producers to liquefy air, which takes a lot of energy.
Research with quantities of up to 150 kg confirmed earlier laboratory tests that a moving ultrasound probe could achieve results similar to those of the argon process, but with the advantages of not relying on expensive and fragile graphite rods and expensive gas which cannot be captured and recycled. The five-fold reduction of the amount of dross created is another benefit.
