Casting Porosity Elimination in CGI Cylinder Head 2009-01-0219
Compacted Graphite Iron (CGI) has been used for many of recently developed cylinder heads and engine blocks. CGI has been the choice for most of the automotive and truck manufacturers since it is combining the useful properties of both grey and nodular cast irons in one material.
Although its superior mechanical properties, the production process of CGI makes the engineers to pay more attention to the microstructural and design-related issues. In the case of heavy duty cylinder head, X-Ray examination results showed that significant amount of porosity was present at the guide hole area. MagmaSoft casting simulation of the cylinder head revealed that some hot spot areas were formed during solidification, due to the insufficient feeder capacity, the location of the feeder and complex design of the water galleries.
The aim of the project is to eliminate the casting porosity by improving the feeding system design to allow the excess liquid metal to feed the part properly while shrinking during solidification. Modifications such as changing the head molding design and the location of new feeders are given in detail in this paper. Redesign of the feeding system prevented the formation of hot spots, thus delivering a robust end-product.