Advantages of Pouring Compacted Graphite Iron Using the Lost Foam Casting Process

An investigation into the production of compacted graphite iron cylinder blocks using the lost foam casting process was performed in a production foundry with excellent results. This breakthrough could provide an entirely new production market for the casting industry. Current automotive compacted graphite iron production is approximately 950,000 engine equivalents per year. It is currently used for more than nineteen diesel engine blocks in vehicles produced by over eleven car and truck manufacturers. It is also the material of choice for NASCAR, NHRA and Pro Truck race engines due to higher strength, higher stiffness and reduced cylinder bore distortion compared to both gray cast iron and cast aluminum. However, none of these production cylinder blocks is produced using the lost foam casting process. A gray iron skin, which can significantly reduce strength and ductility, may form when compacted graphite iron is cast in green sand molds due to the reaction of the molten metal with the water and sulfur in the molding material. A "skin" has also been reported to form on castings produced in bonded sand molds. The lost foam casting process uses a thin refractory coating that prevents the molten metal from contacting the supporting media, typically sand or synthetic mullite. Since the metal does not contact the molding media, the detrimental "skin" is minimized.