Isothermal annealing is the process used for uniform pearlitic and austenitic microstructures. The reason for this is that the center and surface both have different cooling rates. Normally, this causes variation in grain size of the material as in center cooling rate is slow and pearlite will have large grain size while, on the surface of the material, the cooling rate is fast giving finer pearlite. Homogenous pearlitic transformation helps obtain uniform properties throughout the structure in comparison to conventional annealing.