Effect of Inclusions and Precipitates on Hydrogen Embrittlement of Mn‐Alloyed Austenitic Stainless Steels

Abstract

The aim of this study was to characterize the inclusions and precipitates of the six austenitic stainless steel test materials by the INCA analysis program as well as to examine the capability of inclusions and precipitates to act as hydrogen traps by utilizing the thermal desorption spectroscopy (TDS). Especially, the hydrogen trapping capability of nano‐sized Nb‐precipitates of the steel 204Cu/Nb was of interest. On the INCA results it was noticed that the average sizes of the inclusions as well as the distribution and the amount of the oxide inclusions were about the same in all test materials. In comparison to the other grades, the distribution of inclusions and precipitates was significantly different in the niobium‐alloyed 204Cu/Nb steel containing a large number of small micro‐ and nano‐sized niobium precipitates. In the TDS study, it was observed that the TDS spectra of 201B, 204Cu, and 204Cu/Nb were similar, although the inclusion and precipitation distribution of these steels differs considerably between the materials. Thus, it was assumed that the nano‐sized Nb‐precipitates or other inclusions were not able to trap sufficiently hydrogen to their interface, which would result in a better resistance against delayed cracking.

Compositional Evolution of Oxide Inclusions in Austenitic Stainless Steel during Continuous Casting

“…Nozzle clogging at submerged entry nozzle (SEN), degradation of mechanical properties, surface defects, initiation of corrosion‐fatigue cracks, hydrogen embrittlement, etc. are some of typical detrimental effects that non‐metallic inclusions can cause . In steelmaking process of plain carbon steel, most of inclusions are formed through deoxidation of the liquid steel during tapping of the liquid steel into a ladle.…”

Effect of Nb Microalloying on Reversion and Grain Growth in a High-Mn 204Cu Austenitic Stainless Steel

“…1, Nb(C,N) precipitates will be an equilibrium phase in the austenite at very high temperatures, right up to the liquidus temperature, and indeed they were observed by Pulkkinen et al 25) in a 204Cu steel containing 0.45% Nb. Figure 2 shows that coarse precipitates also exist in the present Nb microalloyed materials after cold rolling before the reversion treatment.…”

“…Hence, these particles might tend to grow and possibly partly dissolve at high reversion annealing temperatures. Pulkkinen et al 25) observed that the NbC and Nb(C,N) precipitation structure did not change in the 0.45Nb steel even during annealing up to 10 h at 1 173-1 273 K. Anyhow, the number and size of the particles at 1 373 K were examined here by extraction replicas in TEM. As an example, Fig.…”

Pitting Corrosion Resistance of Mn‐Alloyed Austenitic Stainless Steels

“…In 201B, 201Cu and 304 steels the amount of MnS inclusions was considerably less in comparison to the other steel grades. The inclusion and precipitate analyses made by the automatic INCA feature analysis program are presented in detail in the earlier study …”