Multi-Scale Full-Process Prediction and Performance Analysis of Carburizing and Quenching Heat Treatment

This study focuses on FZG gears made of carburizing steel 20MnCrS5, considering the effects of carburizing hardening. A modified phase transformation kinetics formula and constitutive equation are introduced. Based on the ‘phase − thermal − mechanical’ coupling theory and multi-scale simulation methods, a diffusion − temperature − phase − stress − strain − hardness multi-field coupling model is established. The multi-scale and full-process "visualization" prediction of carburizing and quenching heat treatment under phenomenological phase transformation kinetics has been carried out. The results show that, under the H2 process, the surface carbon content is 0.763%, the residual austenite volume at the surface is 7.7%, the residual compressive stress is 513 MPa, the maximum deformation is 40 μm, the surface hardness is 696 HV, and the carburized layer depth is 1.02 mm. The prediction errors are 1.7%, 9%, 2.1%, 7.5%, 0.14%, and 2.9%, respectively. This confirms the feasibility of the multi-field coupling model. The study analyzes the mechanisms of carburizing diffusion kinetics, iron − carbon phase transformation, and carbide precipitation, revealing the effect of process parameters on microstructure and distortion. It also discusses the impact of surface integrity on gear fatigue contact life, offering new insights for optimizing carburizing heat treatment processes and enhancing macroscopic mechanical properties.