Thermo-Fluid-Dynamics Quenching Model: Effect on Material Properties

Abstract

Abstract.A fully-coupled model of quenching by submerging for steel workpieces is presented. The model includes cooling of the piece due to piece-to-bath heat transfer calculations by solving the multiphase problem of an evaporable fluid, as well as the corresponding metallurgical transformations, the generation of residual stresses and associated geometrical distortions. The heat transfer model takes into account different boiling stages, from film boiling at very high workpiece surface temperatures, to single-phase convection at surface temperatures below saturation. The evolution and activation of each heat transfer mechanism depend on the dynamics of the vapor-liquid multiphase system of the quenching bath. The multiphase flow was modeled using the drift-flux mixture model, including an equation of conservation of energy of the liquid phase. Metallurgical transformations, geometrical distortions and residual stresses at the end of the process, are obtained based on the different cooling rates along the piece. The final distribution of metallurgical phases is obtained by the integration of the thermal evolution and using information of the CCT diagrams of studied steels. The analysis of deformations and residual stresses takes into account elasto-plasticity (without viscosity effects), transformation induced plasticity and hardening restoring phenomena. Comparison of results considering the approach presented here versus a simplified heat transfer model indicates that the level of induced residual stresses are noticeable different implying the necessity of developing a more precise heat transfer quenching model.

An Efficient Fluid-Dynamic Analysis to Improve Industrial Quenching Systems

“…Of course, the same will be true for q w . Equation 16together with Equations (17) and (18) represent a relationship between the computed isothermal wall shear stress and the expected heat flux. Application of this equation to the production tank requires that the laboratory heat flux curve should also be corrected for the Taylor wavelength according with Equation (13).…”

“…The success of fluid flow simulations was further boosted by more powerful and available computer facilities. In the present decade, new contributions appeared that solved, simultaneously with CFD equations, the transient heat conduction equation to determine the temperature evolution of a solid body within the computational domain [10][11][12][13][14][15][16][17][18]. References [13,14,18] also solved the corresponding solid-phase transformation kinetic equations, and in [13,18], the residual stress and deformation were additionally computed.…”

“…In this way, the authors could obtain a heat transfer coefficient that changed with both the position on a solid surface and time. References [11][12][13][16][17][18]] moved a step forward by simulating boiling heat transfer using the mixed fluids approach. This method considers two intermixed or interpenetrated fluids (vapor and liquid) with the space-dependent void fraction of every phase.…”

Numerical Model of Simultaneous Multi-Regime Boiling Quenching of Metals

“…However, the authors did not present a model validation by comparing their numerical results against experimental measurements. Passarella et al [7] developed another multiphase mixed model to simulate the quenching of a low-carbon steel cylinder using mineral oil flowing in a vertical tube at 1 m/s. The momentum equation was solved under turbulent conditions using the k-e model implemented in the Comsol ® Multiphysics code.…”

Numerical Modeling for the Prediction of Microstructure and Mechanical Properties of Quenched Automotive Steel Pieces

“…The implementation of a complete model implies, on the one hand, solving physics problems (such as the generation, departure, and condensation of vapor bubbles) that occur at characteristic lengths of the order of microns and, on the other hand, solving turbulent fluid flow and heat transfer problems up to lengths of the order of the piece size. Only a few attempts at solving the multi-phase problem under very simplified assumptions have been made, most of them not specifically aimed at the analysis of industrial quenching of steel pieces but at the nuclear engineering industry conditions ( [7][8][9][10]). Despite the great simplifications introduced by these multi-phase models, the computational effort and time required to be implemented correctly make them ineligible to simulate the quenching of complex industrial pieces.…”