超高强度热冲压用钢中H的扩散与氢致滞后开裂行为

Hydrogen Diffusion and Hydrogen-Induced Delayed Cracking of Ultra-High Strength Steels for Hot Stamping

采用阴极充H、恒载荷拉伸和电化学H渗透等试验方法,研究了超高强度钢22MnB5Nb的H扩散行为及氢致滞后开裂性能,并与常用热冲压钢22MnB5进行了对比。结果表明,H在22MnB5Nb钢中的扩散系数为3.02×10-7 cm2/s,显著低于22MnB5钢;与22MnB5钢相比,22MnB5Nb钢具有较好的耐氢致滞后开裂性能;这是由于22MnB5Nb钢晶粒较细小,增加了晶界的有效面积,使H陷阱分布更均匀,进而抑制H向裂纹尖端扩展,避免了局部H的富集。

Cathodic charging hydrogen, constant load tensile test and electrochemical hydrogen permeation method were used to study the hydrogen permeation and hydroggn-induced delayed cracking of ultra-high strength steels 22MnBSNb, which were also compared with commercial hot stamping steels 22MnBS. The results show that the diffusion coefficient of hydrogen in 22MnB5Nb is 3.02 × 10^-7 cm^2/s and evidently lower than that in 22MnBS, delayed fracture resistance of 22MnBSNb is superior to 22MnBS. The reason for this is that the effective area of grain boundary is increased for the refined grain, which lead to more homogeneous distribution of hydrogen trap sites in the sample. Then the permeation of hydrogen to crack tip is hindered and the local enrichment of hydrogen is avoided.