Spheroidisation

This treatment involves subjecting steel to a selected temperature cycle usually within or near the transformation range in order to produce a suitable globular form of carbides for such purposes as:
(a) Improved machinability
(b) Facilitating subsequent cold working
(c) Obtaining a desired structure for hardening the steel

These treatments are frequently used on hypereutectoid steels to overcome grain boundary carbide networks, which are brittle and unsuitable for subsequent hardening of these high carbon steels (i.e. hypereutectoid steels contain more than 0.80% carbon.