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Mississippi State University, Mississippi State, MS, USA

R. Cuesta, A. Rivas and M. Estibaliz Alcalde Boecillo Technology Park, Valladolid, Spain

Copyright © 2012 American Foundry Society Abstract

This work examines the quality aspects of multiple gated castings in aluminum A356 alloys. During the casting of parts in which multiple ingates are used to distribute the liquid melt throughout the mold, oxidation of the surface may prevent the adherence of the opposing fronts upon rejoining, thus producing sites prone to defect formation referred to as confluence welds. This phenomenon is inves- tigated by the production of thin vertically sand-cast plates via the Electromagnetic Pump Green Sand (EPGS) process developed by the Foundation for the Research and Devel- opment in Transport and Energy (CIDAUT), Valladolid, Spain. For this research, three multiple-gated designs and one single-gated design were used to research an optimal configuration for melt delivery throughout the mold cavity. A series of numerical simulations were developed for each


The process of metalcasting often involves significant movement of the liquid medium throughout the mold cavity, which can negatively impact the mechanical properties of the melt, resulting in a final product of reduced quality from various defects or inclusion entrainment.1-3

It is known that

aluminum alloys are highly reactive with the atmosphere, leading to oxidation of the melt surface. The thin film-like structures that form as a result of this reaction are referred to as oxide films and can play a vital role in the overall sound- ness of the casting, as opposing metallic streams throughout the mold must adhere successfully to prevent sites prone to crack formation leading to premature failure of the product.1 Such interfaces at which streams remain separate are re- ferred to as confluence welds and are the motivation behind this research.1

This work is focused on the occurrence of the above phe- nomenon and examines the mechanical properties in three multiple-ingated designs (A1, A2, B) and one single-in- gated design (B0). These plates were produced by Alea- ciones Ligeras Aplicadas S.L. (Applied Light Alloys) in Valladolid, Spain, using the electromagnetic pump green sand EPGS process. Results of casting process modeling

International Journal of Metalcasting/Spring 2012

of the gating designs in order to compare modeling results with plates cast in the overseas counterpart’s foundry. Four-point bend testing was used to obtain information about the mechanical properties of the castings, and from this data, a Weibull statistical analysis was performed in order to quantify specimen failure rate for each of the con- figurations. Metallographic analysis was carried out using optical microscopy and fractography using a field emis- sion gun scanning electron microscope (FEG-SEM). The numerical and experimental studies provided interesting insights on the formation of defects associated with the confluence of flow fronts.

Keywords: aluminum A356, Weibull, four-point bend, elec- tromagnetic pump

were related to the quality aspects of the real castings. The EPGS process was developed by CIDAUT and utilizes an electromagnetic pump for the controlled dosing of the liq- uid alloy into vertically parted green sand molds produced by a DISAMATIC. The inlet is located at one side of the mold near its bottom. This system results in the quiescent filling of the counter-gravity molds while minimizing the introduction of oxide films.4

Cuesta and Moroto’s work5

gives more detailed information on the development and application of the EPGS process.

Description of Work

Two sets of aluminum A356 castings were produced for this research. The main elements of the alloy used were in the following percentages (average values are given): silicon 7%, magnesium 0.35%, and iron 0.12%. The melt was submitted to a degassing treatment before mold filling. For Set 1, several 10 mm thick plates were cast from the B configuration using both a slow and fast fill designation with average melt rising speeds along the plate of 45 mm/ second and 65 mm/second, as well as several plates from the A1 configuration at slow fill. For Set 2, a total of eight plates of the same thickness were cast (two from each gat- ing configuration). The filling temperatures for the sets 1


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