Abstract
The present work investigates the residual stress formation and the evolution of phase fractions during the quenching process of cylindrical specimens of different sizes. The cylinders are made of hot-work tool steel grade X36CrMoV5-1. A phase transformation kinetic model in combination with a thermomechanical model is used to describe the quenching process. Two phase transformations are considered for developing a modelling scheme: the austenite-to-martensite transformation and the austenite-to-bainite transformation. The focus lies on the complex austenite-to-bainite transformation which can be observed at low cooling rates. For an appropriate description of the phase transformation behaviour nucleation and growth of bainite are taken into account. The thermomechanical model contains thermophysical data and flow curves for each phase. Transformation induced plasticity (TRIP) is modelled by considering phase dependent Greenwood-Johnson parameters for martensite and bainite, respectively. The influence of component size on residual stress formation is investigated by the finite element package Abaqus. Finally, for one cylinder size the simulation results are validated by X-ray stress measurements.
Highlights
Residual stresses are mechanical stresses in solid materials assuming that no external forces are present
When the bainitic phase transformation starts in the large cylinder at approximately 400∘C, the small cylinder has already reached the compressive regime whereas the large cylinder remains still in the tensile stress regime
In this work a multiphase transformation model is introduced which takes into account bainitic and martensitic phase transformations during the quenching process
Summary
Residual stresses are mechanical stresses in solid materials assuming that no external forces are present. The fact that transformation induced plasticity (TRIP) is highly dependent on the local stress state [14], which is in turn dependent on the temperature gradients in the component, gives rise to a strong size dependence of the residual stress state. It is not clear at first sight whether compressive or tensile residual stresses are obtained on the surface. The goal of this work is to study the phase fractions and the formation of residual stresses near the surface of cylindrical bodies of different sizes considering the influence of transformation kinetics and transformation induced plasticity using suitable modelling tools
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