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<p>Spot welding, a widely used process in advanced high-strength steel (AHSS) for automotive assembly, is known to induce microstructural changes that accelerate hydrogen embrittlement (HE) in AHSS, where the HE characteristics are critically important. This study investigates the HE sensitivity and H-trapping behavior of 1.5&#xa0;GPa AHSS before and after spot welding under various H-charging times, focusing on the relationship between microstructural changes and HE behavior. Spot welding significantly degrades the HE resistance of AHSS, transferring cracking region from subcritical heat-affected zone to fusion zone (FZ). This degradation is primarily attributed to microstructural factors of FZ induced by the high-temperature and rapid cooling cycles, including weld porosities, voids, grain coarsening, and residual stresses. Collectively, these factors play a critical role in accelerating HE susceptibility. Following H-charging, the pronounced crack formation was consistently observed in the FZ regardless of the charging time, particularly originating from coarse weld porosities. At low H content, transgranular cracking along {110} plane was promoted by the interaction between the high density of dislocations and H desorbed from the weld porosities and voids in the FZ. As the H content increased, intergranular fracture also occurred because of the presence of sufficient reversible H per unit grain boundary area, facilitated by the significantly coarsened PAGBs.</p> Graphical Abstract <p></p>

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Investigation of Mechanism of Hydrogen Embrittlement Susceptibility in Resistance Spot-Welded Advanced High-Strength Steels

  • 期刊论文

  • 发表日期：

    2025年6月11日

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  • Dan-Woong Choi,
  • Jisung Yoo,
  • Jin-Jong Lee,
  • Chi-Won Kim,
  • Chang-Hoon Lee,
  • Seung-Pill Jung,
  • Hyun-Yeong Jung,
  • Wan Yook,
  • Hyungkwon Park,
  • Yoon-Suk Choi

摘要

Spot welding, a widely used process in advanced high-strength steel (AHSS) for automotive assembly, is known to induce microstructural changes that accelerate hydrogen embrittlement (HE) in AHSS, where the HE characteristics are critically important. This study investigates the HE sensitivity and H-trapping behavior of 1.5 GPa AHSS before and after spot welding under various H-charging times, focusing on the relationship between microstructural changes and HE behavior. Spot welding significantly degrades the HE resistance of AHSS, transferring cracking region from subcritical heat-affected zone to fusion zone (FZ). This degradation is primarily attributed to microstructural factors of FZ induced by the high-temperature and rapid cooling cycles, including weld porosities, voids, grain coarsening, and residual stresses. Collectively, these factors play a critical role in accelerating HE susceptibility. Following H-charging, the pronounced crack formation was consistently observed in the FZ regardless of the charging time, particularly originating from coarse weld porosities. At low H content, transgranular cracking along {110} plane was promoted by the interaction between the high density of dislocations and H desorbed from the weld porosities and voids in the FZ. As the H content increased, intergranular fracture also occurred because of the presence of sufficient reversible H per unit grain boundary area, facilitated by the significantly coarsened PAGBs.

Graphical Abstract