Hydrogen embrittlement characteristics of the hot- and cold-stamped 22MnB5 steel

The hydrogen embrittlement (HE) characteristics of hot-stamped (HS) 22MnB5 steels were investigated experimentally with and without low-temperature heating. The HS process was carried out on a 22MnB5 plate that was heated to the temperature of its austenite region above the A3 line before die quenching. Because of the varying degrees of work hardening and quenchability, the material properties of the HS samples differed depending on the area. Due to the variety of hydrogen-trapping sites, HE occurred significantly more with different systems. HE occurred with intergranular failure in the prior austenite grain and lath boundaries of the martensite phase in the HS samples without low-temperature heating. Moreover, the resistance of HE increased because of the creation of the ε-carbide trapping site in the HS samples after low-temperature heating. However, Ti-base precipitates were created during the heating process acceleration of HE. Specifically, the trapping sites obtained in this study play different HE roles: ε-carbide improves HE resistance, while the grain boundary of prior austenite and Ti-base precipitates led to HE. Furthermore, this study explored the HE mechanisms in detail.