This project will identify the age-strengthening mechanism in gray cast iron, quantify the parameters which control the process, measure properties and develop a predictive model, and quality the relationship between aging and machinability.
This research is the third phase of a program investigating the age strengthening of gray cast iron. Previous research that was sponsored by the AFS and industry partners has proven the capability of some gray cast irons to increase strength up to 10% of the ultimate tensile strength. The mechanism and control of this phenomenon has not been conclusively quantified. Current research from Phases I and II has indicated that dissolved nitrogen may be the control mechanism There are also indications that these aging phenomena may favorably affect the machinability of gray cast iron. The ability to initiate and control this phenomenon could result in a significant improvement in casting mold yield, casting weight reduction, and possibly improved machining productivity. A 10% increase in strength would allow the production of higher carbon equivalent irons and a corresponding improvement in mold yield along with improved machinability. There is also the potential to reduce casting weight by producing higher strength iron.
The scope of work includes four main tasks. The time and temperature effect studies will be done in laboratory environment with irons cast at production foundries. The composition will be varied so that the effect of nitrogen activity and activity coefficient can be evaluated as well as the influence of substitutional elements on the process. This will require about five test-bar casting runs per year in participating foundries. This data will allow us to control and design with the process, but will also contribute to the understanding of the process.