Prediction of Hardenability from Isothermal Transformation Diagrams

Abstract

An analytical method for evaluation of quantitative hardenability of eutectoid steels from the corresponding TTT diagram was considered.
The isothermal transformation kinetics of pearlite and cooling curves were combined by the additivity rule, and an equation expressing continuous cooling transformation of pearlite has been derived. Based on this equation, simple algorithms for the calculation of the widely used measure of hardenability, such as the critical cooling rates, the Jominy distance and the ideal critical diameter from the corresponding TTT diagram were presented. It was shown that the derived equations give the above measures of hardenability with good accuracy.
Finally the relationships between J₀ and D_I and among D_I, D₀ and H were reexamined taking cooling transformation into account. It was found that the formerly obtained relationships based on the half temperature time require correction. New relationships based on the cooling transformation were presented.