Chill casting in its present form has been practiced in the copper base alloy field for over 50 years and is principally applicable to the tin bronzes, namely phosphor bronze, gunmetal, leaded bronze and leaded gunmetal.
This process, as its name implies, speeds up the process of solidification and, with the tin bronzes, this increases the proportion of the hard delta constituent in the casting. In the case of the leaded bronzes it also assists in obtaining a finer distribution of the insoluble lead throughout the matrix. With the possible exception of elongation and reduction of area, all mechanical properties are increased by chill casting. The greatest improvement of all, however, is to be found in hardness figures, which may be on average as much as 50% higher than sand castings.
Chill casting is used both for the production of chill cast stick and rods, and also for individual chill castings of irregular shape. Both methods employ the use of permanent (metal) moulds, usually similar to those used for die-casting but of different metal, and castings can be produced weighing from a few ounces up to hundredweights by this method. The same remarks apply as for die-casting in respect of design of the casting for this process.