Ultrasonic grain refinement

Ultrasonic grain refinement

First industrial degassing & grain refinement technologie for aluminium melts.

Grain Refinement

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.  

Ultrasonic assisted industrial continuous twin roll casting

Twin roll casting converts the melt into aluminium strip for subsequent cold rolling operations. The process holds several challenges, in particular, coarse columnar grains, chemical segregation at the strip centre, microstructural gradients and inhomogeneity.

 

A breakthrough in industrial ultrasonic casting can address these problems. In particular the technique offers a substantial reduction in grain size, elimination of central intermetallic needle, and improved homogeneity. Furthermore, the process removes the need for argon degassing.

Results & Applications:

  • Improved metal homogenization, grain refinement and mixing of new alloys.
  • Excellent ultrasonic degassing results (defragments and wetted inclusions)
  • Excellent results after vibrating ‘in sump’ of a vertical Wagstaff DC caster.
  • Excellent results on a Bruno Presezzi continuous casting line.
  • Improved micro crystallization and alloy characteristics in casting.
  • Friction reduction between a tool (e.g. casting, drawing, extruding, molding).
  • Improved surface finish.

Conclusion

Ultrasonic degassing & grain refinement offers numerous advances over conventional methods offering substantial improvements in the properties of the final products, along with reduced costs and environmental impact.

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