Influence of Microalloying Elements Nb and V on Microstructure and Hydrogen Embrittlement Sensitivity of Hot Stamping Steel

Microstructure and hydrogen embrittlement sensitivity of Nb and V microalloyed hot stamping steel 22MnB5NbV and conventional non-microalloyed hot staping steel 22MnB5 were studied with optical microscopy (OM), electron back-scatter diffraction(EBSD), transmission electron microscopy (TEM) and 3D atom probe combining with the continuous bending test in 0.1 mol/L HCl solution. The results show that compared with 22MnB5, 22MnB5NbV has finer structure and better uniformity after quenching. Under the same stress level and hydrogen environment solution, the time for delayed fracture of 22MnB5NbV plate is longer than that of 22MnB5, and the critical stress level for delayed fracture is higher than that of 22MnB5. The number of small angle grain boundaries of 22MnB5NbV steel matrix is more than that of 22MnB5, and Nb, V can effectively capture H element, inhibit hydrogen diffusion and reduce the hydrogen embrittlement sensitivity of the material through the second phase particle region formed by the combination of Nb and V with C.