Chilled cast iron
Chilled cast iron is a cast iron in which the composition and technical casting measures ensure that the carbon remains bonded to the iron atoms as iron carbide (Fe 3 C, cementite ) during solidification , while otherwise it is usually in the form of graphite of lamellas - into which the iron structure is excreted (lamellar gray cast iron ).
If, for example, iron with a carbon content of 3.5 to 4% and a silicon content of less than 0.5% is poured into a mold that is itself made of sufficiently thick-walled iron, the direct contact between the two causes rapid cooling, which causes the graphite to precipitate prevented. After a shell has formed, the rate of further solidification in the core is slowed down to such an extent that graphite is precipitated. One casting process is used to produce a casting that consists of two completely different materials: The shell is hard, wear-resistant and has a white, shiny appearance when broken, while the core has the good machinability of gray cast iron and appears gray when broken. In between there is a more or less strong transition zone.
Chilled cast iron is used, for example, in the manufacture of calender rolls for smoothing and calendering paper. The mold consists of thick-walled cylinders (molds) that are precisely stacked on top of each other and is coated with a coating on the inside to prevent welding. The roller bodies are ground on the outside with high precision and smoothness and are often machined inside by turning, drilling and honing .