Effect of Discontinuous Change in Cooling Rate During Continuous Cooling on Pearlitic Transformation Behaviors of Steel

Abstract

In this investigation, the pearlitic transformation behaviour of steel with the cooling rate discontinuously altered during continious cooling was studied in relation to the CCT diagram of the steel. The main results are as follows:
(1) The pea litic transformation behaviour with the cooling rate discontinuously altered during continuous cooling was diffe-ent from the transformation behaviour illustrated by usual CCT diagram.
(2) The pearlitic transformation behaviour and the critical cooling rate with the cooling rate altered at a point during continuous cooling were observed to be related to the incubation period consumed before changing the cooling rate.
(3) Including the degree of consumed incubation period in usual CCT diagram as a parameter, the transformation behaviour and the critical cooling rate can be estimated from a conventional CCT diagram.
(4) If the same amount of the incubation period was consumed by either continuous cooling or isothermal holding, the transformation behaviour was virtually the same in subsequent cooling when the cooling started from the same temperature.