ABSTRACT We have developed a technique for observing the weld cracking behaviour in laser welds of high strength steel sheets, using an X-ray transmission in-situ observation system. Weld cracking in the lap joints of this type of steel could be clearly seen, demonstrating that this was, in fact, delayed cracking initiated from the solidification crack at the weld end. It was also discovered that the delayed cracking behaviour such as cracking modes, incubation periods and crack growth rates, varied according to the carbon content in the steel and welding length. The former influenced the hardness of the weld bead, while the latter affected solidification cracking sizes and residual stress. The results of this crack propagation are useful not only for developing laser welding methods of high strength steel but also for additive manufacturing, aimed at mass production.

中文翻译：

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使用 X 射线透射原位观察系统研究高强度钢板激光焊缝中的延迟开裂行为

摘要 我们开发了一种使用 X 射线透射原位观察系统观察高强度钢板激光焊缝中焊缝开裂行为的技术。可以清楚地看到这种钢搭接接头处的焊缝开裂，这表明这实际上是由焊缝端部的凝固裂纹引发的延迟开裂。还发现延迟开裂行为，如开裂模式、潜伏期和裂纹扩展速率，根据钢中的碳含量和焊接长度而变化。前者影响焊道硬度，后者影响凝固裂纹尺寸和残余应力。这种裂纹扩展的结果不仅可用于开发高强度钢的激光焊接方法，还可用于增材制造，