Structure and mechanism of the formation of granular bainite in steel 20Kh2NACh

At the present time the structure of granular bainite is widely used in heat treatment. The novel technologies include spheroidizing treatment of rolled stock from steel 20Kh2NACh. The composition of the steel provides a structure of granular bainite in rolled strips up to 10 mm wide with their cooling in still air from the temperature attained at the end of hot rolling. After a high-temperature tempering of the strips for 4 h the granular bainite transforms into granular pearlite which is optimum for cold forging. The available published data on the structure of granular bainite are insufficient for explaining the causes of the accelerated transformation. In this connection, it is interesting to investigate the phase composition, the microstructure, and the transformation mechanism of granular bainite.