Minimizing the Distortion of Steel Profiles by Controlled Cooling

Abstract

A complex thermomechanical model is introduced for the simulation of the transient fields of temperature and stresses during the quenching of steel products. The material behaviour is an extension of the classical J 2-plasticity theory with the extension of temperature and phase fraction dependent yield criteria. The coupling effects, i.e., dissipation of mechanical energy, transformation induced plasticity (TRIP), and phase transformation enthalpy, are considered. The model is used for the determination of the optimal cooling or quenching for reducing the distortion in the long steel profiles. The simulation results are presented in order to investigate the effects of material properties, boundary conditions, profile size and geometry. In the simulations, L-, T-and U-profiles made of steel C45 and steel CaD are considered. It is demonstrated that with a higher cooling rate in the mass lumped regions of the profiles, the distortion can be reduced. Basic Equationswhere k is the heat conduction coefficient, q is heat flux vector, and T is the temperature. The heat treatment process is a transient heat conduction problem where the tempera-sufficient to estimate the behaviour of the prismatic profile under such conditions with much fiever degrees of freedom. In addition, the dimensional reduction of the problem from three-dimension to two-dimension substantially simplifies not only the visualisation of the field variables but also the determination of optimal cooling strategy.Temperature field. The microstructure and mechanical properties are strongly temperature dependent. Hence the temperature field must be determined correctly for an accurate simulation. The latent heat of the phase transformation has to be taken into account. The heat conduction is governed by the Fourier law, after which the heat flux vector is parallel to the temperature gradient,The mathematical model of the heat treatment is described by a thermoelastoplastic theory which also covers the phase transformation effects. The temperature field has a great influence on the microstructure and mechanical properties. Hence the temperature field must be simulated accurately. The latent heat of phase transformation is considered as an additional heat source or heat sink. The microstructural evolution is obtained by using the isothermal time-temperature-transformation (TTT-) diagrams charts. The diffusion controlled phase transformations are computed according to the Johnson-Mehl-Avrami equation and the displacive phase transformation is calculated from the Koistinen-Marburger equation [2]. For the determination of stress/strain field, a constitutive relation is established, which depends on temperature and phase fraction. The total strain tensor is additively decomposed into several parts, as usual. The introduced model is applicable to 2D-and 3Dproblems. steel research int. 76 (2005) No.5

Minimizing Stress and Distortion for Shafts and Discs by Controlled Quenching in a Field of Nozzles

“…This method contains a linearization [12] and sometimes requires a conversion of the reference temperatures. An alternative method is based on the temperature dependency of the density [13]. The transformation induced plasticity (TRIP) is an additional irreversible deformation, which occurs during phase transformation.…”

Integrated fluid-thermal-structural numerical analysis for the quenching of metallic components

“…Due to the studies on the theory and the numerical simulation of the individual events that occur during quenching and the computational method for fast and accurate prediction of the multi-physical phenomenon in the last three decades, the simulation of quenching process became realistic and several commercial software packages had been developed to be capable of simulating quenching process, such as DANTE, DEFORM-HT, FORGE, HEARTS, SYSWELD and Quench Simulator. However, most studies consider the quenching process as a thermalmicrostructural-mechanical problem [1][2] and these software are incapable of coupling with dynamic characteristics of fluid in quenching tank, which determines the local cooling rate at part surfaces.Coupling quenching simulations with computational fluid dynamics (CFD) is a major interest [8][9] . However, fluid-thermal simulation in most of the research is focused on single phase liquid or gas quenching.…”

“…Coupling quenching simulations with computational fluid dynamics (CFD) is a major interest [8][9] . However, fluid-thermal simulation in most of the research is focused on single phase liquid or gas quenching.…”

Distortion and Residual Stresses during Metal Quenching Process

“…The complex mechanism behind the residual stress evolution during the quenching process is well explained by Todinov [3]. References [4][5][6][7][8] give more information about the distortion and residual stress calculation during metal quenching. This article is arranged in the following manner: Section 2 presents the mathematical formulation of the three physical fields.…”

“…As the phase transition penetrates through the legs, the distortion again changes its direction and the profile bends toward the legs one more time (2-3-4). Finally, the phase transition is completed throughout the profile and the distortion gradually decreases as the temperature becomes uniform (4)(5). However, a permanent deformation remains due to the mechanical yielding and transformation induced plasticity.…”