Chilled Cast Iron: Quick cooling is called Chilling, hence chilled cast iron is a white cast iron produced by quick cooling of molten iron. All castings are chilled at their outer surface by coming in contact with the cool sand in the mould.
But on most castings this hardness penetrates to a very small depth (1 to 2 mm). Some times a casting is chilled intentionally and sometimes becomes chilled accidently to a small depth.
Chills are used on the faces of the castings which are required to be hard to withstand wear and friction. The process of chilling is used in the casting of rolls for crushing grains and jaw crusher plates. The running surface of rail carriage wheels is also chilled.