Hydrogen permeation tests were conducted in 1.2 MPa H₂ on welding thermal simulated specimens to determine the hydrogen permeation parameters in each subzone of the girth welded joints. Optical microscope, electron back-scattered diffraction, and X-ray diffraction were applied to analyze the corresponding microstructure changes. The results show that the hydrogen diffusion coefficient D is mainly determined by the final heat-treated peak temperature, and the key microstructural affecting factors of hydrogen permeation will change with this temperature. The order of D from high to low is acicular ferrite, granular bainite, lath bainite, polygonal ferrite, and M-A constituent.

氢渗透试验在1.2 MPa H ₂焊接热模拟试样上进行，以确定环焊缝每个分区的氢渗透参数。应用光学显微镜、电子背散射衍射和X射线衍射分析相应的微观结构变化。结果表明，氢扩散系数D主要由最终热处理峰值温度决定，影响氢渗透的关键微观组织因素会随该温度发生变化。D从高到低的顺序是针状铁素体、粒状贝氏体、板条贝氏体、多边形铁素体和MA成分。