Softening Behavior and Hardness Prediction of H13 Hot‐Work Die Steel during Isothermal Tempering

Abstract

In this study, the microstructural evolution of H13 hot‐work die steel during isothermal tempering at 500∽650 °C was evaluated, and kinetic equations and a neural network were constructed to describe the softening behavior. The results showed that the softening behavior appeared as a loss of hardness with increasing isothermal tempering temperature and time. The softening mechanism was ascribed to the decomposition of martensitic laths, annihilation and rearrangement of dislocations, formation of sub‐grains and precipitation and coarsening of secondary carbides. The evolution of secondary carbides included the coarsening of V‐rich MC nanoprecipitates, and the precipitation and coarsening of secondary phases (Cr‐rich M23C6 and Mo‐rich M6C carbides) during long‐term isothermal tempering. Regarding the applicability of the model in precipitation evolution and hardness prediction, the Johnson‐Mehl‐Avrami (JMA) model was considered to be more suitable than the Hollomon‐Jaffe (H‐J), Lifshitz‐Slyozov‐Wagner (LSW) and back‐propagation neural network (BPNN) models.This article is protected by copyright. All rights reserved.