Pearlite Transformation during Continuous Cooling and Its Relation to Isothermal Transformation

抄録

An attempt was made to predict the cooling transformation over the entire range of pearlite reaction, from the isothermal transformation kinetic data. A kinetic equation of pearlite transformation during cooling was derived by applying an additivity rule to the transformed fractions. A good agreement was observed between the measured and calculated cooling transformation curves although the pearlite reaction would not precisely satisfy any one of the additive conditions. A possible deviation of a cooling transformation kinetics from that estimated with the additivity rule was considered based on the nucleation and growth process. It was found that the transformed fractions of pearlite appeared to be additive firstly because the change in the ratio of the nucleation to the growth rate as a function of supercooling was small, and secondly because the cooling transformation occurred either nearly isokinetically when the cooling rate was slow or almost in the condition of site saturation when the cooling rate was fast.