Advancements in Mold Feeding System. (Aluminum).
In his presentation, "Theoretical Basis for a Continuous, Pressurized, Mold Filling and Feeding System," (03-138) D. Herron, Herron Casting Services, discussed his apparatus, which bottom fills (intermittently or continuously moving) green sand molds by applied steady pressure. It then feeds the solidification shrinkage at a higher pressure, while the molds continue moving. This allows for high production rates of modern green sand molding with independent, high quality, slow filling and feeding techniques.
To start the process, a fiberglass filter cloth is inserted between the first and second molds so that the completed mold line does not slide across the cloth. The molds then are pushed across the filling device to form the tightly booked line of molds and seal the chamber by their own weight.
Vacuum then is released from the space in the furnace. The height of the metal in the furnace falls and the metal flows through the connecting channel and the height of the metal in the chamber rises to an equal level of that in the furnace column. If an additional sufficiency of metal is in the furnace, the metal rises through the filter cloth, flows up the gating system and fills the casting cavities that are currently bridging the filling/feeding chamber.
P. Enright, N-TEC, Ltd., gave his presentation, "Characterization of Molten Metal Quality Using a PrefilFootprinter" (03-086), which he coauthored with I. Huges and J. Pickering, N-TEC, Ltd., and A. Simard and J. Proulx, ABB Bomen, Inc. In his presentation, Enright characterized the molten metal quality in terms of consistency, sensitivity to metal disturbance, in-line metal treatment and additions practice using pressure filtration technique.
The pressure filtration test used the flow-rate of molten metal through a porous filter disc at constant temperature and pressure to measure the quality of the metal. Throughout the test, the system continuously weighted the metal in the weigh ladle and displayed a curve of the accumulated weight versus the elapsed time. The cleaner the metal, the higher the curve would appear. The slope and overall shape of the weight filtered versus time curve indicated the level of inclusions present in the metal.
After the pressure filtration technique was used to carry out an audit of an automotive foundry, Enright had several conclusions, including:
* under steady state casting conditions, the instrument has excellent reproducibility and measures consistently clean metal;
* the instrument is sensitive to small changes in metal sampling practice and can resolve time dependent metal quality fluctuations, such as the drossing off a degassing well;
* issues related to strontium and grain refiner additions were characterized and the effectiveness of the filter was demonstrated;
* all data was compared to the World Class Benchmark for A356 and shows that the automotive foundry studied meets the criteria for world class production.
The presentation, "A Novel Algorithm for the Calculation of Latent Heat of Solidification for Multi-Component Aluminum Alloys," (03-094) authored by M.B. Djurdjevic, J. Chen and J. Sokolowski, Univ. of Windsor, presented a novel methodology involving the application of a silicon equivalent algorithm for the calculation of the latent heat released during the solidifcation process of the aluminum 3XX series of alloys.
In order to analyze the latent heat of solidification of these alloys, four different levels of silicon and three different levels of copper were taken into consideration. The solidification path of these alloys was monitored and the corresponding latent heat released during solidification was measured using the Differential Scanning Calorimeter. The results of the calculations were found to be highly accurate in comparison to the experimental data.
According to the measured and calculated latent heat values for the 3XX series of aluminum alloys, the latent heat of solidification is strongly dependent on the silicon content and only slightly dependent on the copper content. The model to rapidly calculate the latent heat of solidifcation is based on the assumption that the latent heat of the alloy is released at the rate proportional to the formation of fraction solid during solidification.
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|Date:||Jun 1, 2003|
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