Abstract In this study, the susceptibility of API X70 weld joints to hydrogen gas was investigated using slow strain rate tensile (SSRT) tests. The microstructure of the subregion of the actual heat-affected zone (HAZ) weld joint was reproduced by weld thermal-cycle simulation techniques. The SSRT results showed that the weld and cross-weld specimens had the highest hydrogen embrittlement (HE) susceptibility, followed by the subregions of the fine-grained heat-affected zone (FGHAZ) and coarse-grained heat-affected zone (CGHAZ) specimens and the base metal. The HE index ranking of the samples was as follows (in increasing sequence): weld, cross-weld, simulated FGHAZ, simulated CGHAZ, and base metal specimens. The rupture location of the cross-weld specimen in ambient air is different to that tested in 10 MPa H2. The higher susceptibility of the weld and cross-weld specimens was primarily attributed to synergic effects between the microstructural characteristics, stress localization, and microhardness distribution – particularly, microhardness plays an important role in the nucleation of microcracks and the hydrogen diffusion rate induced by stress/strain localization.

中文翻译：

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高压氢气下X70焊接热影响区氢环境辅助开裂

摘要 在这项研究中，使用慢应变速率拉伸 (SSRT) 试验研究了 API X70 焊接接头对氢气的敏感性。实际热影响区 (HAZ) 焊接接头的子区域的微观结构是通过焊接热循环模拟技术再现的。SSRT 结果表明，焊缝和交叉焊缝试样的氢脆 (HE) 敏感性最高，其次是细晶热影响区 (FGHAZ) 和粗晶热影响区 (CGHAZ) 试样的子区域和贱金属。样品的HE指数排序如下（按递增顺序）：焊缝、交叉焊缝、模拟FGHAZ、模拟CGHAZ和母材试样。交叉焊接试样在环境空气中的破裂位置与在 10 MPa H2 中测试的不同。