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As industrial modernization surges forward, the heat treatment industry strives for lower pollution, reduced oxidation and defects, minimized waste, and automatization. This paper reviews the mechanisms, processes, equipment, and simulations of the vacuum gas quenching technology, presenting a comprehensive account of the structure and working principle of a typical vacuum gas quenching furnace. Firstly, the mechanism of the heat transfer process, flow process, and flow–heat transfer–phase transition coupling were summarized. Then, the influences of process parameters on the mechanical properties and distortion of vacuum gas quenched workpieces, as well as the process optimization methods, were discussed. Finally, the advantages of vacuum gas quenching in energy saving, low pollution, and high efficiency were introduced, with the future development directions figured out. [ABSTRACT FROM AUTHOR]

Abstract: In order to find a simple and efficient simulation for plasma spray process, an attempt of modeling was made to calculate velocity and temperature field of the plasma jet by hexagonal 7-bit lattice Boltzmann method (LBM) in this paper. Utilizing the methods of Chapman–Enskog expansion and multi-scale expansion, the authors derived the macro equations of the plasma jet from the lattice Boltzmann evolution equations on the basis of selecting two opportune equilibrium distribution functions. The present model proved to be valid when the predictions of the current model were compared with both experimental and previous model results. It is found that the LBM is simpler and more efficient than the finite difference method (FDM). There is no big variation of the flow characteristics, and the isotherm distribution of the turbulent plasma jet is compared with the changed quantity of the inlet velocity. Compared with the velocity at the inlet, the temperature at the inlet has a less influence on the characteristics of plasma jet. [Copyright &y& Elsevier]

Abstract: When plasma is used to spray coatings on a mould surface, the states of the plasma jet and powder particles have great influence on the quality of the spray layer. In order to find a simple and efficient simulation for the states of the plasma jet and powder particles, an attempt of modeling was made by hexagonal 7-bit Lattice Boltzmann method (LBM) and a probabilistic algorithm in this paper. The velocity and temperature field of the plasma jet and particles are calculated and compared with those obtained by previous models and measurements. The dynamic moving process, accelerating course, maximal speed and distribution of powder particles are calculated by the present model. The optimal spraying distance and deposition efficiency under different spraying conditions are also acquired. It can be concluded that the combined model is competent for numerical simulation of the atmospheric plasma spraying. Simulation by LBM is simpler and faster than that by traditional methods. LBM is also a computational method that offers flexibility and outstanding capacity of parallel computation. [Copyright &y& Elsevier]

A constitutive equation has been established based on the dislocation theory, the work hardening and dynamic recovery theory. The stress–strain curves of bainite steel have been measured by a hot compression experiment at temperatures of 1173, 1273, 1373, and 1473 K with strain rates of 0.01, 0.1, 1, and 10 s −1 on a thermo-mechanical simulator Gleeble-1500. The material constants involved in the constitutive equation have been optimized by an inverse analysis of the stress–strain curves. This information is used to determine the materials models of work hardening and dynamic recovery, and the strain–stress relationship of the investigated steel in high temperature deformation. The results are in agreement with those obtained from experimental measurements. They demonstrate that the material constants determined by the stress–strain curves can capture the underlying materials science of high temperature deformation. On this basis, the evolution law of dislocation density has been obtained in work hardening and dynamic recovery. A relationship function between the critical dislocation density for dynamic recrystallization and deformation parameters has been established. And an equation for recovery kinetics has been proposed with reference referring to the Avrami equation. [ABSTRACT FROM AUTHOR]

Abstract: A set of integrated mathematical models for predicting microstructures evolution during hot rolling and controlled cooling of high carbon wire rods has been developed through laboratory research work and industrial validation experiments. It consists of many sub-models such as critical strain, static and dynamic recrystallization of austenite, fraction of transformed austenite, interlamellar spacing of pearlite, microstructure–property relations. Based on the models, a simulating software is programmed which can run on PC computers. The physical metallurgy process during hot rolling and controlled cooling including the temperature distribution, the evolution of austenite grains, fraction of transformation austenite, final microstructure and mechanical properties were predicted. The predicted results are agree well with measured of the industrial tests. [Copyright &y& Elsevier]