Evolution Of Steel Research Articles

Simulation of Precipitates Evolution in Steels

The model describing the behavior of precipitates of variable composition at heat treatment is suggested. The specific feature of this model is that it enables to take into account the effect of diffusion inside the particles on the kinetics of the process. The application of this model is demonstrated by the example of vanadium carbonitrides V(C,N) evolution in austenite at heat treatment of vanadium-containing steels. The necessity to take into account the diffusion modification of carbonitride composition is considered. Examples of particles composition evolution at heat treatment are demonstrated.

Computer Simulation of Microstructure Evolution in Low Carbon Sheet Steels

Models of microstructure evolution in steels are reviewed. The emphasis of the review is on low carbon sheet steels both hot-rolled and cold-rolled and annealed. First the state-of-the-art on industrial microstructure process models is presented. The individual model concepts for grain growth, recrystallization, precipitation and phase transformations are briefly discussed. The development from empirically-based models to physically-based models is identified as a key issue to have increased predictive capabilities for these models over a wider range of steel grades and operational conditions. The challenges in the development of the next generation of models are delineated. In particular, new aspects of microstructure evolution associated with novel processing routes and advanced high strength steels are evaluated. Further, the majority of the currently employed models are on the macro-scale but future microstructure models will increasingly be meso-scale models that predict actual microstructures rather than a number of average parameters (e.g. grain size, fraction transformed) to describe microstructure evolution.

Simulation of VC precipitate evolution in steels with consideration for the formation of new nuclei

A numerical method of simulation of precipitate ensemble evolution is suggested, accounting for the formation of new centres of nucleation. This method is based on the mean field approximation for the description of evolution of the particles present and on the classical theory of nucleation for calculation of the formation rate of new nuclei. It may be used for simulation of evolution of constant composition precipitates in multicomponent alloys at different stages of the process. The method is used for simulation of VC precipitate evolution in steels, and the results of these calculations are compared with the available experimental data.

Analysis of temperature and microstructure in the quenching of steel cylinders

A finite-element procedure has been developed for temperature and microstructural analyses of quenching problems involving nonisothermal phase transformations. The finite-element analysis incorporates temperature-dependent material properties, time-temperature-transformation (TTT) diagrams to describe the microstructural evolution in steels, and the latent heat released during a phase change. The procedure is applied to calculate temperature, microstructure, and hardness distributions in 1080 steel cylinders quenched in water and in two polymeric quenchants. The calculated values for the three quantities are found to be in good agreement with corresponding measurements made in quenched 1080 steel cylinders. The effect of latent heat released during a phase change on the temperature and microstructural evolution is studied computationally. It is found that, when the latent heat is not included in the calculations, the resulting volume fractions of pearlite and matensite present in the quenched steel are nearly one order of magnitude different from the corresponding values calculated by including the latent heat in the formulation. Finally, the quenching of a large-diameter 1080 steel cylinder in water is analyzed to show the nonlinear effect of cylinder diameter on the temperatures and microstructures.

Hydrogen embrittlement of ferrite-pearlite steels during drawing

Methods of transmission electron microscopy are used to establish the influence of preliminary surface decontamination on the microstructures of 20G2R and 30G1R steels after drawing and stamping. We explain how surface hydrogenation during decontamination by acid media leads to penetration of hydrogen into the metal and leads to an increase in long-range stress fields and formation of micropores and microcracks. We analyze the effect of the quantitative statistical characteristics of substructure evolution of steels with different contents of carbon and alloying elements. We consider possible mechanisms for hydrogen hardening of steel.