Journal de recherche et d'applications en physique

Corrosion of steels in environments containing hydrogen sulfide

Ohyubi N

By utilizing the inhomogeneity of temperature and stress state during heavy plate rolling, with controlled cooling, polygonal ferrite and quasi-polygonal ferrite with two grain sizes for each were obtained, and their precipitation state varied with different microstructures. GLEEBLE 3500 was used to study the influence of microstructure and precipitation state during high-temperature tensile deformation. The results revealed that the microstructure of ferrite matrix and the nucleation of precipitates were determined by the overall cooling process, while the final precipitation state was mainly determined by the cooling rate in the precipitation temperature range during the subsequent isothermal process [1]. In addition, dislocations and subboundaries acting as containers facilitated the growth of precipitates along some particular directions. Pre-existing substructures, such as low-angle boundaries and statistically stored dislocations, as well as small precipitates, influenced the formation of subgrains and dislocation cells during high-temperature deformation. These newly generated substructures involved rotation or rearrangement of dislocations, and finally resulted in recrystallized grains. In addition, the grain size was closely related to the interaction probability of subboundaries. Although the polygonal ferrite matrix showed a more stable stress state, the quasi-polygonal ferrite matrix with fine precipitates and small grains exhibited better mechanical properties.