Effect of Nitrogen Content on Hot Deformation Behavior and Grain Growth in Nuclear Grade 316LN Stainless Steel

Abstract

316LN stainless steel with 0.08%N (08N) and 0.17%N (17N) was compressed at 1073–1473 K and 0.001–10 s−1. The hot deformation behavior was investigated using stress-strain curve analysis, processing maps, and so forth. The microstructure was analyzed through electron backscatter diffraction analysis. Under most conditions, the deformation resistance of 17N was higher than that of 08N. This difference became more pronounced at lower temperatures. The strain rate sensitivity increased with increasing temperature for types of steel. In addition, the higher the N content, the higher the strain rate sensitivity. Hot deformation activation energy increased from 487 kJ/mol to 549 kJ/mol as N concentration was increased from 0.08% to 0.17%. The critical strain for initiation of dynamic recrystallization was lowered with increasing N content. In the processing maps, both power dissipation ratio and unstable region increased with increasing N concentration. In terms of microstructure evolution, N promoted dynamic recrystallization kinetic and decreased dynamic recrystallization grain size. The grain growth rate was lower in 17N than in 08N during heat treatment. Finally, it was found that N favored twin boundary formation.

Dynamic Recrystallization and Hot Workability of 316LN Stainless Steel

“…Guo [15] constructed the power dissipation map of 316LN stainless steel without a clear description on its applications. He [16], Guo [17], and Liu [18] investigated the hot workability of 316LN and constructed the hot processing map, but the characteristics of different regions on the conventional processing map should be further detailed. Sun [19] also constructed the hot processing map with metallographic analysis.…”

Microstructure Evolution and Surface Cracking Behavior of Superheavy Forgings during Hot Forging

“…is strain rate is far below that used, in general, in hot forging [5]. Typically, strain rates that , including those for ultra-supercritical rotors [6,7], main pipes in nuclear plants [8,9], and rollers [10,11]. Deformation at very low strain rates features varied and complex recrystallization mechanisms [12,13] and cracking behaviors [14].…”