Scholarlink

The development of third generation advanced high-strength steels (AHSS) has provided automotive manufacturers with a material that is both formable and high-strength. Laser welding is already a widely used joining process for welding of AHSS. However, problems with delayed hydrogen-assisted cracking (HAC) occurring minutes or hours after laser welding have been observed in AHSS. This work examines several different strategies for mitigation of HAC. In the first stage of the work, laser-welded specimens based on a modified K2 geometry (two welds placed on a two sheet stackup with a small gap in between) from the SEP standard 1220-3 were performed to establish baseline cracking behavior of the dual-phase DP1000 and third generation DH1000 AHSS grades of interest. Crack length was measured at different time intervals for up to 2 weeks after welding. Variations in pitch distance (distance between weld stops) and weld length were implemented to observe the effect of cracking susceptibility. Increasing the weld length from 25 mm to 35 mm was found to reduce the tendency to HAC. Next, simultaneous ramping down of both the laser power and travel speed near the weld stop in the modified K2 weld configuration was employed. All ramping parameter sets were observed to significantly reduce the occurrence of HAC, likely as a combination of changes in the end crater shape and interruption of solidification cracking in the end crater. Finally, strategies involving relieving residual stress via changes in weld configuration were tested. Removing clamping from one side of the joint, pre-drilling holes near the weld stop, and moving the weld closer to the unclamped edge together while changing the angle of the weld with respect to the unclamped edge were all tested. These strategies could potentially be implemented at various stages during production (e.g., during blanking or during fixturing before laser welding). Having one free edge alone was found to not mitigate HAC, but both moving the weld close to the free edge and pre-drilling holes strategies were seen to significantly reduce delayed cracking susceptibility.

错误：搜索内容不能为空，请输入英文关键词
错误：关键词超出字数限制，请精简
高级检索

Mitigation Strategies for Delayed Cracking in Laser Welding of Advanced High-Strength Steel

  • 会议论文

  • 发表日期：

    2026年

查看全文
  • Ethan Sullivan,
  • Pia Borg,
  • Jukka Siltanen,
  • Kürşat Durmaz,
  • Peter Nerman,
  • Sergej Mozgovoy

摘要

The development of third generation advanced high-strength steels (AHSS) has provided automotive manufacturers with a material that is both formable and high-strength. Laser welding is already a widely used joining process for welding of AHSS. However, problems with delayed hydrogen-assisted cracking (HAC) occurring minutes or hours after laser welding have been observed in AHSS. This work examines several different strategies for mitigation of HAC. In the first stage of the work, laser-welded specimens based on a modified K2 geometry (two welds placed on a two sheet stackup with a small gap in between) from the SEP standard 1220-3 were performed to establish baseline cracking behavior of the dual-phase DP1000 and third generation DH1000 AHSS grades of interest. Crack length was measured at different time intervals for up to 2 weeks after welding. Variations in pitch distance (distance between weld stops) and weld length were implemented to observe the effect of cracking susceptibility. Increasing the weld length from 25 mm to 35 mm was found to reduce the tendency to HAC. Next, simultaneous ramping down of both the laser power and travel speed near the weld stop in the modified K2 weld configuration was employed. All ramping parameter sets were observed to significantly reduce the occurrence of HAC, likely as a combination of changes in the end crater shape and interruption of solidification cracking in the end crater. Finally, strategies involving relieving residual stress via changes in weld configuration were tested. Removing clamping from one side of the joint, pre-drilling holes near the weld stop, and moving the weld closer to the unclamped edge together while changing the angle of the weld with respect to the unclamped edge were all tested. These strategies could potentially be implemented at various stages during production (e.g., during blanking or during fixturing before laser welding). Having one free edge alone was found to not mitigate HAC, but both moving the weld close to the free edge and pre-drilling holes strategies were seen to significantly reduce delayed cracking susceptibility.