(Case study) Lightweight, heat-resistant molten metal runners made of paper to be used in the production of castings

Castings are made by melting materials such as iron scrap in a device such as an electric furnace. These materials are shaped into machine or engine parts used for various applications. A sand mold is used to create an empty space in the shape of the desired product into which high-temperature molten metal, at approximately 1400°C in the case of iron, is poured to form the desired product. The path used for pouring the molten metal is known as a runner and it requires strict functionality. Because a large amount of molten metal flows through runners in a short period of time, they need to withstand high temperatures and shocks. In addition, runners must be composed of a material that prevents the inclusion of impurities. Conventionally, ceramic tubes are commonly used for this purpose. However, to increase their strength, these tubes are generally manufactured to be thick and heavy, which thus increases the amount of waste generated at casting process and creates a heavy burden on the sand-refurbish processing equipment. By using pulp-molding technology and high-temperature materials technology, Kao has developed a runner made of paper. By adding fire-resistant material to a substrate of waste newspaper, we were able to reduce the weight to 1/16th that of the ceramic tubes. In addition, these tubes withstand the high-temperature molten metal and carbonized after use, which enabled a significant reduction in waste compared with that in conventional runner made by ceramic.