The Influence of Warm abc-Pressing on the Structure and Mechanical Properties of Stable Chromium-Nickel-Molybdenum Steel

Resumo

The structure and properties of the 17Cr13Ni3Mo0.01C stable austenitic steel subjected to high-temperature plastic deformation by the abc-pressing (multiaxial forging) are investigated in the temperature range from 800 to 600°С. The results of investigations demonstrate that after the abc-pressing the steel has a single-phase austenitic ultrafine-grained structure with the size of its elements (grains and subgrains) of (200 ± 140) nm. The formation of the ultrafine-grained state increases the strength properties (0.2 proof stress increases threefold) and decreases the elongation value of the steel at room temperature compared to the coarse-grained specimens. An analysis of the contributions from hardening during abc-pressing evidences in favor of the strength improvement being primarily due to the grain refinement; it is well described by the Hall–Petch relationship. In this case steel with ultrafine-grained austenitic structure exhibits an effect of structural superplasticity at the temperatures T > 750°С: the elongation value at Т = 800°С is found to be 180%.