Quenching crack
Quench cracking is a separating structural failure caused by extreme thermal stresses and martensite formation during cooling.
Physical-Chemical Mechanism of Action
During cooling of high-carbon steels, extreme thermal stresses arise. These lead to martensitic transformation, which greatly enlarges the grain and causes porosity and cracking.
Metallurgical Relevance & Risks in Welding
Quench cracking can lead to severe material failure, especially in highly stressed components. It can greatly affect the toughness and stress level of the material, leading to fractures or failure in service.
Workshop Practice & Action Instructions
To avoid quench cracking, it is crucial to ensure controlled cooling. This involves using cooling water or cooling gases with a small temperature difference to the weld. The cooling rate should not be too fast (t8/5 > 25 s) to ensure homogeneous martensite formation and avoid porosity.