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Magnetic Field Control of the Mould Filling Process of Aluminum Investment Casting
Galindo, V.; Gerbeth, G.; Eckert, S.; Witke, W.; Gerke-Cantow, H.; Nicolai, H.; Steinrücken, U.
The mould filling process of aluminum investment casting consists basically of the flow in a U-bend showing a high pouring velocity at the beginning and decreasing velocity values during the course of the process. The high velocities during the starting phase are supposed to cause distinct problems like bubble or inclusion entrapment. Several types of filters are already in use for the purpose of inclusion filtering but velocity reduction, too.
We present results on the design and application of a DC magnetic field to control the pouring velocity. Numerical calculations were performed to simulate the filling process and the effect of the magnetic field. The free surface problem which occurs in the riser of the casting unit was taken into account by a Volume-of-Fluids Method. 3d transient calculations using the commercial finite- element code FIDAP (FLUENT Inc.) were carried out for a simplified model system as well as for the real aluminum casting unit. The term for the electromagnetic force was implemented into the code via a user defined subroutine, and an additional equation for the electrical potential was solved. End effects due to the limited size of the magnet poles were taken into account. In that way, results from three-dimensional transient simulations of the filling process were obtained.
Parallel to the simulations model experiments have been performed using the low melting eutectic InGaSn. The casting unit was modelled by a plexiglas model [1]. The ultrasonic Doppler velocimetry was applied to carry out detailed velocity measurements in the model [2]. Such measurements delivered the basis to validate the numerical calculations. A comparison between numerical and experimental results showed an excellent agreement, allowing scaling up the simulations to the realistic aluminium casting process.
Real tests have been performed at an industrial investment caster with molten aluminium. The primary action of the magnetic field, i.e. the reduction of the velocity peaks at the beginning of the process, was clearly shown. In a second set of experiments the amplitude of the DC field was tuned during the process. At the beginning the maximum braking force was applied, whereas the field strength was reduced with increasing fluid level in the casting unit. In this regime, a clear reduction of the peak velocities is obtained without a significant prolongation of the overall filling time.

REFERENCES

[1] S. Eckert, G. Gerbeth, A. Cramer, B. Willers, W. Witke, V. Galindo, Liquid metal model experiments on casting and solidification processes, Proc. Int. Symposium on liquid metal processing and casting, Eds.: P.D. Lee, A. Mitchell, J.-P. Bellot, A. Jardy, (2003), 333-343.
[2] S. Eckert, G. Gerbeth, T. Gundrum, F. Stefani, W. Witke, New approaches to determine the velocity field in metallic melts, EPM 2003, Lyon, Proceedings PL13 (2003).
  • Contribution to proceedings
    Computational Mechanics, WCCM VI in conjunction with APCOM`04, 05.-10.09.2004, Beijing, China, paper No. 677
  • Invited lecture (Conferences)
    6th World Congress on Computational Mechanics, 05.-10.09.2004, Beijing, China

Publ.-Id: 6129 - Permalink