Entwicklung einer optimierten Vormaterialherstellung für den Einsatz verlorener Kerne beim Druckgießen teilerstarrter Metallsuspensionen

摘要

High pressure die casting is one of the most cost-effective methods for mass producing aluminium components. Thus, for example, die casting is used to currently manufacture a large volume of all aluminium engines. However, besides the undisputed advantages, the restricted freedom in mould design largely limits the applications of high pressure die casting. Although in the past it was possible to significantly improve this situation by means of sliding core technologies, it is however still not possible to represent complex internal geometries. This can only be achieved by using lost cores. Conventional core systems made of sand, i.e. for low pressure die casting, only partially endure the high mechanical loading. However, continuously increasing component and material requirements necessitate constructions having internal contours. An example are crankcases which can currently be high pressure die cast using mass production technology only in an open-deck construction. By using an operational coring system, the motors could also be cast as a single piece in a closed-deck. In relation to this, there are commercial endeavours to implement suitable sand and salt coring systems. Another application which is considered in this work is a combination of lost cores for die casting partially liquid metal suspensions. Rheocast processes are a particularly cost-effective alternative to conventional high pressure die casting and provide, moreover, advantages intrinsic to the process such as, for example, lower shrinkage, pressure tightness, near-net shapes as well as the possibility of carrying out heat treatments or welding thick-walled components. A decisive advantage for implementing lost cores is a significantly slower and, in the ideal case, a non-turbulent flow. By using the cooling channel process, which was developed at the Foundry Institute of RWTH Aachen, different coring systems based on sand, salt, zinc and plastic are well proven in tests with respect to their suitability for rheocasting. Furthermore, the parameters influencing the material and the process are determined and thoroughly investigated for the cooling channel process. Here, the aim is both to provide a reproducible input material, which is as homogeneous as possible, for subsequently high pressure die casting using lost cores as well as to assess the suitability of the cores and the cooling channel process for possible industrial applications. Moreover, the knowledge gained about both rheocasting as well as highly reactive alloys, which can be employed due to the lower processing temperatures, is firstly verified by means of the alloy AlLi2.1Mg5.5. Secondly, the influences of processing the partial-liquid in the Rheo-Container-Process on the morphology and phase formation are analysed in detail.