Unveiling the mechanism behind irregular inclusions triggering no HIC cracks in steels

This research investigates a specific type of irregularly shaped inclusions in steel, which are typically considered detrimental. A comparative study of two steels, treated with different inclusion modification methods by oxide metallurgy technology, reveals that spherical inclusions with complex structures can provide beneficial multipoint trap sites for hydrogen, thereby reducing the risk of hydrogen-induced cracking (HIC). Notably, irregular stripe-shaped silicate-oxide inclusions with sharp tips, due to their hot-soft characteristics during the process of hot-rolling, do not exacerbate cracks but instead mitigate local stresses. Conversely, large single-phase hard inclusions are detrimental to HIC resistance. This investigation provides insights into the mechanisms behind why certain irregular inclusions do not trigger HIC crack after the NACE TM 0284-2016 standard test.