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 Jo and DI and among DI, Da 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.

Application of, and precautions for the use of, the Rule of additivity in phase transformation

“…[11] and [15] into Eq. [9] yields firmed that the rule of additivity does not work well with the incubation time for nucleation.…”

“…The rule of additivity has been widely used to calculate d g dt ϭ h g (T) g g () [11] CCT diagrams from corresponding TTT diagrams. There have been several attempts to define the conditions under which the rule of additivity is valid.…”

“…Determination of the equilibrium phase-transformation temperature from those measured under continuous heating or fraction at time t under an isothermal temperature T. The term i (T, t) can be described with a generalized Avrami cooling was also briefly discussed. equation, [1,11,18] i (T, t) ϭ 1 Ϫ exp [ϪK(T)t n(T) ]…”

“…[1,2,[6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23] The principle obtained under isothermal conditions. It is our hope that this assumption of the rule of additivity is that the transformation article will serve as guidance for the application of the rule behavior during continuous cooling can be described as the of additivity.…”

A Pure Implicit Finite Difference-Based Modeling Approach for Prediction of the Hardenability of Eutectoid Steel

“…However, in these studies, the definition and measurements of hardenability have been limited to hardness, and the details of the solid-state transformations in steel are completely ignored. Thus, it is considered that the Grossmann's method would have its own limit in accuracy [11]. Accordingly, in last few decades, significant mathematical modeling approaches have been proposed [11][12][13][14][15][16][17] for the prediction of hardenability in view of ascertaining hardening behavior of steels; these typically involve integration of theoretically generated cooling curves and solid-state transformation in steels.…”