Development of an Instrumented Test Tool for the Determination of Heat Transfer Coefficients for Die Casting Applications

Abstract

In the case of casting processes with permanent molds, there is still a relatively pronounced lack of knowledge regarding the locally prevailing heat transfer between casts and mold. This in turn results in an insufficient knowledge of the microstructure and the associated material properties in the areas of the casting component close to the surface. Therefore, this work deals with the design and evaluation of a test tool with an integrated sensor system for temperature measurements, which was applied to obtain a time-dependent heat transfer coefficient (HTC) during casting solidification. For this purpose, the setup, design and computational approach are described first. Special attention is paid to the qualification of the multi-depth sensor and the calculation method. For the calculations, an inverse estimation method (nonlinear sequential function) was used to obtain the HTC profiles from the collected data. The developed sensor technology was used in a test mold to verify the usability of the sensor technology and the plausibility of the obtained calculation results under real casting conditions and associated temperature loads. Both the experimental temperature profiles and the HTC profiles showed that, in the evaluated casting series, the peak values determined were close to each other and reached values between 6000 W/(m2·K) and 8000 W/(m2·K) during solidification.

Advances in Metal Casting Technology: A Review of State of the Art, Challenges and Trends—Part II: Technologies New and Revived

“…Here, the correct representation of heat transfer coefficients over time, including effects like the formation of gaps between the casting and the die, remains an area of research [281]. This is illustrated by the fact that two contributions to the present Special Issue are related to the topic [282,283].…”

“…The studies by Wolff et al [283] and Kouki et al [282] are linked to virtual casting and simulation approaches, as they both consider the heat transfer coefficient (HTC), a crucial though difficult to determine parameter in casting. Kouki et al propose and evaluate a tool for measuring time-dependent HTCs in permanent mold casting.…”

“…With the general approach justified, future work will be oriented toward transferring the measurement principle first to closed models then to HPDC molds. The expectations are that results from the coming experiments will improve the predictability of cast part properties [282].…”