Effect of Submicron‐Scale MnS Inclusions on Hydrogen Trapping and HIC Susceptibility of X70 Pipeline Steels

Abstract

In this work, the non‐metallic inclusions contained in a trial X70 pipeline steels are characterized by optical microscopy, scanning electron microscopy, energy‐dispersive X‐ray spectrum, and transmission electron microscopy. Statistical analysis is conducted to summarize the size and shape of the inclusions. The hydrogen trapping and the resulting hydrogen‐induced cracking (HIC) susceptibility of the steels are tested. Density functional theory is used to calculate the binding energy of hydrogen at MnS inclusions, and the impact of MnS inclusions on hydrogen trapping and the HIC susceptibility is evaluated. It is found that the majority of submicron scale inclusions are MnS, which serve as irreversible hydrogen traps. The content of the trapped hydrogen can be effectively decreased by controlling the size of MnS inclusions below submicron scale and distributing the inclusions uniformly in the steel. As a result, the susceptibility of the steel to HIC is reduced.

Improved Stress Corrosion Cracking Resistance of High‐Strength Low‐Alloy Steel in a Simulated Deep‐Sea Environment via Nb Microalloying

“…Hereafter, for convenience, the peaks in the spectra that fall in the range of 373-573 K are denoted as low-temperature peaks and those at temperatures higher than 573 K as high-temperature peaks. [49] It is notable that the low-temperature desorption peaks are more clear with an increase in the heating rate and when the heating rate is increased to 5 K min À1 , an apparent desorption peak appears at 447.5 K. In addition, the TDS peak temperature increased as the heating rate increased. These findings were applicable for the hydrogen desorption peaks detected in the high-temperature range; the high-temperature peaks detected at heating rates of 1.66, 3.33, and 5 K min À1 were located at 665.1, 685.6, and 703.1 K, respectively.…”

A Model for Predicting Residual Hydrogen Content in Blooms and Billets Stacked in Large Industrial Piles

“…In the ideal situation, which is characterized by the presence of a perfect lattice where hydrogen can uniformly flow, diffusivity follows the Arrenhius’ law expressing the temperature dependence of reaction rates . However, the existence of lattice defects (i.e., vacancies, substitutional and interstitial atoms, grain boundaries, precipitates, inclusions, interfaces between matrix and second phases particles, microvoids, etc.) compromises the applicability of Arrhenius’ principles.…”

Discerning phase-matrices for individual nitride inclusions within ultra-high-strength steel: experiment driven DFT investigation

“…In such experimental limitations due to complex microstructure of steel matrix and hidden inclusions within, different computational approaches including the atomic multiplet theory [9,10] and delta-self-consistent splitting and the Bethe-Salpeter Equation methods [11] have been proposed to realize the physical mechanism of inclusions formation in different systems including a few variants of steel. For instance, these approaches can be successfully utilized for the investigation of shape and morphology of inclusions in metallic materials [12], prediction of the effect of inclusions on the hydrogenation of steels [13], and differentiation of elements via their X-ray absorption (XAS) spectra simulations [14]. Despite the progress described above, investigating nitride inclusions within multi-phase carbon steel is still posing challenges.…”