In this work, Ck85 carbon steel was subjected to cyclic heat
treatment.
Process that consisted of cyclic short-duration (3.4 minutes)
holding at 800 C (above Ac3 temperature) followed by forced air
cooling. After 8 cycles (about a total 1 hour du
ration of heating and cooling cyclic), the microstructure mostly contained fine ferrite
grains and spheroidzed cementite. This microstructure possessed
an excellent combination of strength and ductility. The disintegration of lamellar pearlite through dissolution of cementite
at boundaries lamellar during short-duration holding above Ac3
temperature, and the generation of lamellar defects during nonequilibrium forced air cooling were the main reasons of
accelerated spheroidization. The strength initially increased mainly
due to the presence of finer microconstituents (ferrite and pearlite)
and then marginally decreased with the elimination of lamellar
pearlite and appearance of spheroid cementite in the microstructure.
