High-pressure Die Cast Cylinder Blocks Made of ... - KSPG AG

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1. Aluminium cylinder blocks support light weight design Castings of aluminium are making an evermore significant contribution to leveraging light construction potentials in modern passenger cars. The heaviest individual component, the cylinder block, has meanwhile taken on a key role. If we consider the enormous number of in-line engines produced, especially four-cylinder and three-cylinder engines, but increasingly also six-cylinder engines in in-line and V arrangement, the cost/benefit aspect must have absolute priority. The replacement of grey cast iron with aluminium for cylinder blocks therefore presupposes low-cost concepts. 2. Concept diversity for aluminium cylinder blocks Contrary to the cylinder blocks produced so far, mostly made from grey cast iron based on a uniform concept which already incorporates the cylinder bore surfaces when a perlitic structure configuration is chosen, there are many diverse options in the case of aluminium. These relate to the concept modules of type or cylinder block design, alloy, casting method and cylinder bore surface, in which case manifold incompatibilities have to be considered. The overriding aspect is therefore the compatibility of the concept modules. 2 Fig. 1: Highly efficient solution specifically for passenger car in-line engines A further constraint for the concepts which are viable in principle results for concrete engine development projects from the targets and general specifications with respect to the engine function, elemental engine characteristics (number and arrangement of cylinders), annual outputs, costs of castings and engine systems, optimization potential, environmental aspects and recyclability. This situation has led to a large number of marketable concepts. 3. Aluminium cylinder blocks and high-pressure die casting method 3.1 Economic aspect From the economic aspect, for mass produced engines, highpressure die casting is mainly competing with the highly automated sand core package process whose cycle time is not bound to the solidification. In the highly competitive, cost-sensitive market segment of the three-cylinder and four-cylinder engines, however, high-pressure die casting is unrivalled in cost-effectiveness thanks to outstanding productivity based on appropriate component design. Currently, worldwide large quantities of four-cylinder engine blocks of aluminium are made by this method. The aluminium highpressure die casting method is now also in the process of establishing itself in the six-cylinder engine business.
Applying the latest high-pressure die casting technology, aluminium cylinder blocks are produced whose properties are hardly inferior to high-grade low-pressure die castings or sand core castings and which boast a decisive cost benefit in bulk production. Its attractiveness is the greater the smaller the component and the higher the product output are. Innovative approaches with new die concepts to increase the tool life and further reduction of the cycle time, not least through intensive die cooling, additionally contribute to curbing production costs. 3.2 High-pressure die casting technology As far as the frequently applied conventional high-pressure die casting method is concerned, it should be mentioned that in light of today’s constantly increasing requirements it often fails to yield the necessary component quality. What is more, conventional high-pressure die cast cylinder blocks made of aluminium exhibit a relatively high degree of porosity which prohibits the application of solution annealing and of cylinder bore coating. To achieve the necessary static and dynamic strengths, however, evermore refined high-pressure die casting processes and new production processes are essential. In order to remedy this situation, KS Aluminium-Technologie employs techniques like an optimally degassed melt, an efficiently evacuated high-pressure die as well as residue-free lubricants for the shot plunger in the die filling chamber. Further improvements are achieved through innovations like optimized high-pressure die spraying technique combined with wax-free spraying agent, long-life tool coating as well as uniform, intensive cooling of the die. The basic prerequisite for high strength and its enhancement is a low degree of porosity at the quality level of low-pressure die casting. In addition, this enables the cylinder bore surfaces to be coated, in high-pressure die casting as well. 3.3 Design features For cylinder blocks, the weight reduction potential inherent in material substitution ranges from 35 %, expected of aluminium used in passenger-car diesel engines as a minimum requirement, appr. 50 %. High-pressure die casting allows for extremely reduced wall thicknesses and thus offers especially favourable conditions for light construction. In combination with its near-net-shape benefits, the weight can be reduced by eight to 15 % in comparison with low-pressure die casting where no, or only a water jacket sand core is used. For the conventional high-pressure die casting method, mouldability in steel is a must and the open-deck design is unavoidable therefore. But today, in general it is more readily accepted for aluminium cylinder blocks. Distinctly reduced water jacket depth and co-moulded cylinder bores have created an option besides the conventional open deck Fig. 2: Open-deck and closed-deck design, shown with one and the same high-pressure die cast aluminium cylinder block (left); high-pressure die casting resistant water jacket sand core made by the warm-box process with the application of a special wash (right) 3
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High-pressure Die Cast Cylinder Blocks Made of ... - KSPG AG

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