Speaker
Description
As the steel industry is tending to the autonomous line control and to improve the control of the products properties by predicting them as a function of the process variables, a model that could estimate the mechanical properties of low-carbon martensitic steels after tempering is required. Modifications to a physical-based model previously developed [1] were applied to simulate industrial short time tempering treatments (between 200 and 400ºC for 300 s maximum) for three low-carbon (0.1, 0.15 and 0.21wt%C) low-alloyed steels. The model considers classical nucleation theory, growth under paraequilibrium condition and coarsening of coexisting precipitate populations, precipitation sequences and carbide size distributions [1].
The model parameters were adjusted on the basis of in situ HEXRD analysis of microstructure evolutions, performed at DESY, Germany (PETRA-III), TEM measurements and calorimetry experiments. Dislocation densities were estimated by the Modified-Williamson-Hall method. A dislocation recovery model was considered and calibrated on the recovery kinetics determined on the single 0.21wt%C grade. The yield strength has been carefully determined and compared to experimental yield strengths. The yield strength was calculated on a physical basis with accounting of the Peierls barrier, strengthening by carbon and substitutionals in solid solutions, dislocation hardening, and precipitation strengthening/softening. The precipitation contribution was analyzed, and a linear sum was applied to consider the effect of the ε-carbide and the cementite. As the precipitates have sizes in the nanoscale, the shearing mechanism was accepted even for the cementite particles.
Good agreement was found between the simulation and the experiment.
[1] Y. Wang, S. Denis, B. Appolaire, and P. Archambault, “Modelling of precipitation of carbides during tempering of martensite,” J. Phys. IV JP, vol. 120, pp. 103–110, 2004.
| Speaker Country | France |
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