The Influence of Filling System Design on Quality Performance in Gray Iron

Abstract

Significant evidence now supports the quality improvement seen in castings that employ naturally pressurized filling systems in their production. However, despite the documented evidence for improvement, these systems have not become ubiquitous. Gray iron, the industry’s most prominent alloy, has been particularly slow to accept the shift in system design. The suggested tolerability of gray iron to turbulence, the market’s price sensitivity, and the perceived economics of naturally pressurized systems are potential factors that have hindered adoption. However, if, through improved quality, the economic justification for these systems can be made in this adverse setting, there is a merit in their application to all alloys and processes. A sample gray iron part, currently being produced in a foundry environment with known porosity issues, was selected, to which a new system and several basin designs were applied. A mixed method analysis of casting simulations, production trials, and economic and environmental modeling was used to evaluate system performance. The results show a strong association between filling system design and sub-surface porosity. However, no association was found between basin design and porosity occurrence at lower porosity levels. Nevertheless, the economic and environmental modeling highlights that quality-orientated systems yield significant financial and environmental savings for the organization due to reduced scrap levels. These findings imply that quality-orientated system designs should be employed even when cost is the most critical measure.