Shrinkage crack
Shrinkage cracks occur during cooling when the weld metal and the structure are not uniformly expanded. This leads to uneven stresses and cracks in rigid construction joints.
Physical-Chemical Mechanism of Action
During welding, the metal expands significantly due to laser or plasma energy. Upon cooling, it contracts again, but if the weld metal and adjacent structure cool at different rates, stresses arise. These stresses can cause cracks, especially in highly stressed structural joints.
Metallurgical Relevance & Welding Risks
Shrinkage cracks seriously impair component integrity. They can lead to collapse or fracture, especially under high loads. Cracks can also significantly shorten component lifespan.
Shop Practice & Action Guidelines
To avoid shrinkage cracks, ensuring uniform cooling is critical. This can be achieved by using cooling water or special shielding gases. The cooling rate should be adjusted so that the weld and base material cool simultaneously. Too rapid cooling can lead to martensite formation, increasing hardness and promoting cracking.