Development of an A356 die casting setup for determining the heat transfer coefficient depending on cooling conditions, gap size, and contact pressure

Abstract

In this paper, the development of an experimental die casting setup to perform simultaneous in-situ measurements of temperatures, air-gap formation and contact pressures is presented. The derivation of the resulting heat transfer coefficients between mold and melt is also included. To take the influence of different cooling rates into account, an active die tempering is applied. For the implementation of this experimental setup, a special mold for a rotationally symmetrical test specimen is developed which incorporates the necessary measuring technique and can be adapted to different cooling conditions by means of exchangeable die inserts. Concluding, first results and the corresponding heat transfer coefficients are presented.Keywords: Heat transfer coefficient / air-gap formation / contact pressure / mold tempering / permanent mold casting Es wird die Entwicklung eines Kokillenguss-Versuchssaufbaus vorgestellt, um gleichzeitige in-situ Messungen von Temperaturen, Spaltbildung und Kontaktdrücken zu ermö glichen, genauso wie die Ermittlung der sich daraus ableitenden Wä rmeü bergangskoeffizienten zwischen Form und Gussteil. Dabei wird der Einfluss von verschiedenen Abkü hlraten durch aktive Formtemperierung berü cksichtigt. Hierfü r wird eine spezielle Form fü r ein rotationssymmetrisches Gussteil entwickelt, die die nö tige Messtechnik aufnehmen sowie durch wechselbare Formeinsä tze an verschiedene Abkü hlbedingungen angepasst werden kann. Es werden erste Ergebnisse inklusive der zugehö rigen Wä rmeü bergangskoeffizienten vorgestellt.Schlü sselwö rter: Wä rmeü bergangskoeffizient / Spaltbildung / Kontaktdruck / Formtemperierung / Dauerformguss Figure 6. Values of the air-gap related heat transfer coefficient for different die temperatures versus the corresponding cast interface temperature. On the right side for the complete solidification process and on the left side a cut out with a smaller temperature range. N. Wolff et al.

Development of an Experimental Setup to Investigate Influences on Component Distortion in Gravity Die Casting and a First Variation of Temperature Control Strategy

“…The use of two oil temperature control units (type 1502/12 by Thermobiel Apparatebau GmbH, Gladbeck, Germany) with a total of four circuits, that can be set up independently from ambient up to 350 • C medium temperature and with a flow rate of 16 l/min each, enables full thermal control. The die coating was selected to be KS-81 (by Hüttenes-Albertus, Düsseldorf, Germany) from the previous works [1][2][3]. The measuring devices to measure the relative movement of the part and the contact pressure were also adopted from these previous test setups, with which the gap and contact pressure dependent heat transfer coefficients were determined.…”

“…The long-term goal of this sub-project, on which the work presented here is based on, is to improve component precision in permanent mold casting by creating a knowledge base in the areas of distortion and hot cracking, and furthermore, the development of corresponding concepts for their prediction, influencing, and minimization. The heat transfer coefficient (HTC) between mold and component, which has already been considered as a possible major influencing factor, was analyzed in this project in several separate studies [1][2][3]. In addition to these primarily experimental studies, in closely related subprojects, the working group is developing numerical methods to advance the coupled thermomechanical simulation on both the macroscale and the microscale [4,5].…”

Heat Transfer Coefficient Determination in a Gravity Die Casting Process with Local Air Gap Formation and Contact Pressure Using Experimental Evaluation and Numerical Simulation

“…The investigations performed are based on the experimental setup shown in Figure 1. 14 Here a ''bowl'', i.e. a cylindrical and thus rotationally symmetric part, is casted on an inner core.…”

“…Experimental setup for the casting of a ''bowl'' geometry with measuring instrumentation for temperature, gap width and contact pressure. 14 Three quantities are measured by the applied instrumentation (cf. Figure 2 left): Type K thermocouples (''TCs'') measure the temperature development inside of the die walls as well as inside the melt.…”

“…Especially the heat transfer through an air gap represents a rather high thermal resistance, as the heat conductivity of air is significantly smaller than those of metal-to-metal contacts. A suggestion for a comprehensive HTC model considering these phenomena was proposed by Laschet et al 9 The experimental evaluation is based on previous research activities 10,11 and utilizes temperature, gap size and pressure measurements to reconstruct the heat fluxes between casting and die to deduce the HTC development. The numerical simulations apply an inverse and manually parametrized model for the local HTC using thermal simulation in Magmasoft and thermomechanical simulation via the software Abaqus.…”