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Proceedings Paper

Solidification process and infrared image characteristics of permanent mold castings
Author(s): Roman Viets; Markus Breuer; Heinz Haferkamp; Thomas Kruessel; Matthias Niemeyer
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Paper Abstract

Interdependence between the development of temperature gradients at the solid-liquid interface during solidification of metals and the formation of local defects demands for thermal investigation. In foundry practice thermocouples are used to control the die's overall cooling-rate, but fluctuations in product quality still occur. Capturing FIR- thermograms after opening the die visualizes the state, when most thermal throughput has already flattened the temperature gradients in the mold. Rapid dissipation of heat from liquid metal to the mold during solidification forces further approach of the process investigation by slowing down the heat flux or the use of transparent mold material. Aluminum gravity casting experiments under technical vacuum conditions lead to decelerated solidification by suppression of convection and image sequences containing explicit characteristics that could be assigned to local shrinkage of the casting. Hence relevant clusters are extracted and thermal profiles are drawn from image series, pointing out correlations between feeding performance from the sink heads and the appearance of local defects. Tracing thermal processes in vacuum casting can scarcely be transferred to image data in foundry practice, since only little analogies exist between atmospheric and vacuum casting. The diagnosis of the casting process requires detection of the still closed mold using a transparent silica- aerogel sheet as part of the die. Hereby thermograms of the initial heat input are recorded by adapting a NIR-camera in addition to the FIR-unit. Thus the entire thermal compensation at the joint face for each casting is visualized. This experimental set-up is used for image sequence analysis related to the intermediate casting phases of mold filling, body formation and solidification shrinkage.

Paper Details

Date Published: 19 March 1999
PDF: 9 pages
Proc. SPIE 3700, Thermosense XXI, (19 March 1999); doi: 10.1117/12.342280
Show Author Affiliations
Roman Viets, Univ. of Hannover (Germany)
Markus Breuer, Univ. of Hannover (Germany)
Heinz Haferkamp, Univ. of Hannover (Germany)
Thomas Kruessel, Univ. of Dortmund (Germany)
Matthias Niemeyer, Univ. of Hannover (Germany)


Published in SPIE Proceedings Vol. 3700:
Thermosense XXI
Dennis H. LeMieux; John R. Snell, Editor(s)

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