Ultrasonic Degassing in Molten Aluminium, Zinc, Magnesium, Copper, Glass and steel
Grain refinement, micro-alloying up to 1,800 Celsius
Ultrasonic treatment of metal melts can substantially improve the properties of castings, in particular, their microstructure and mechanical properties. Recently, new refinements to the technique using proprietary ultrasound technology provide significant benefits to industrial continuous casting, offering an alternative to argon degassing, replacement of standard master alloy additives, and substantial improvements to microstructure.
Here we will look at the mechanisms that underlie ultrasonic liquid metal interactions, in particular how they apply to ultrasonic degassing and grain refinement. Finally, we will look briefly at our ultrasonic technology as applied to industrial continuous casting.
Various techniques are available for enhancing the microstructure of aluminium alloys, for instance, there is a strong correlation between grain size and casting temperature; however, significant improvements can be achieved using ultrasonic treatment. Two mechanisms contribute to this process.
During the high-pressure cycle of the cavitation process, collapsing bubbles result in localised high temperatures and pressures. Temperatures can exceed 1000 K while pressures can exceed 400 MPa; rapid cooling rates also occur. The effects of this are twofold: many nucleation sites are formed inducing finer grain sizes, and the energies generated destroy dendritic structures that would otherwise form.