Incremental Formulation for the Prediction of Microstructural Change in Multi-pass Hot Forming.

Abstract

A new mathematical formulation for static microstructural changes in hot forming is proposed. This formulation can be easily coupled with incremental modei for dynamic microstructural changes as it is formulated in an incremental form using the dislocation density as a representative variable with the simplification of recrystallized structure.Coupling incremental formulations for dynamic and static microstructural changes, microstructural changesunder multi-pass hot forming are computedand discussed.As these formulations are formulated in an incremental form, we will be able to predict microstructural evolution incl uding partial dynamic/static recrystal lization causedby any deformation history and temperature history computedby FEM and/or FDM.

Three-dimensional Numerical Analysis of Microstructural Evolution in and after Bar and Shape Rolling Processes.

“…The analytical accuracy of currently used method had been validated earlier, 13,15,16) and it was concluded that this model was accurate enough for predicting the evolution in microstructure in and after hot forming. Table 1 shows the changes of process parameters for the rolling of 127ϫ127 mm square billet down to 12 mm diameter bar, 19) which was given by Maccagno et al Table 1 demonstrates the averages of temperature and strain rate, neglecting their distribution in cross-section and transition in rolling direction.…”

“…Figure 1 shows the schematic illustration of integrated analysis. Change in distribution of dislocation density and grain size during hot rolling were analyzed by incremental formulations for microstructure evolution, 12,13) temperature transition and strain rate along each stream line was used as 'process oriented' boundary conditions. Material parameters, embedded in recrystallization kinetics, recoveries etc.…”

“…It was the purpose of current research by implying the incremental formulation proposed [12][13][14][15][16] to demonstrate an integrated numerical model of predicting microstructural evolution, three-dimensional plastic deformation and temperature changes applied to the industrial hot bar rolling and Hbeam rolling. Their characteristics of microstructural evolution in industrial rolling processes will be the topic of examination and discussion based on the information obtained from numerical analysis.…”

“…For this reason, authors had proposed the incremental formulation for the prediction of microstructural changes in austenite state and phase transformation state. [12][13][14][15][16] In the model, authors used dislocation density and grain size as representatives to trace the microstructural evolution procedure. By this model, the microstructural changes in austenite state has been evaluated continuously, and the effect of plastic deformation on phase transformation prior to cooling can described by the resid-ual dislocation.…”

Rolling Technology and Theory for the Last 100 Years: The Contribution of Theory to Innovation in Strip Rolling Technology

“…Therefore, the technique to calculate the change of the internal micro structure depending on the history of stain velocity and rolling temperature was necessary and some techniques were suggested in the 1990s. [124][125][126] In addition, the internal micro structure of material after hot rolling changes while cooling down. The model to analyze the incremental phase transformation for the purpose of the nucleation mechanism in the grain boundary was formulated by Yanagimoto and others, based on the models 127,128) targeted at the plain carbon steel for ferrite, pearlite, and bainite transformation.…”