Chilled Cast Iron:

Understanding chilled cast-iron is as important as understanding the rolls themselves. To make chilled cast-iron, iron and other elements are melted in the furnaces to obtain the required chemical composition. In a casting pit, circular chills are stacked one on top of the other to obtain the required roll length. Then, with very large ladles, the cast-iron is poured into the pouring basin. The molten iron runs down a “runner” to the “gate” and enters the chills from the bottom. This tangential entry point causes centrifugal forces which push the heavier materials to the outside of the roll. The chills cause the outer layer to cool quickly, forming carbides on the outside of the roll. As the roll cools or chills, the difference in the rate of solidification causes principally two layers on the roll. White iron, which is also known as the chill layer, forms on the outside and grey iron on the inside. A week or two after pouring, the casting will be removed from the pit after cooling completely.