Globular solidification morphology
Globular solidification morphology is a fine-grained, rounded grain shape with a high nucleation rate and a low thermal gradient. It leads to high toughness and good formability.
Physicochemical Mechanism of Action
Globular solidification morphology occurs when crystallization is rapid and the thermal gradient is low. This results in small, rounded grains with a high surface area per volume.
Metallurgical Relevance & Welding Risks
This morphology increases the toughness of the material and improves its formability. However, it can also lead to increased susceptibility to hot cracking if the material is not cooled properly.
Workshop Practice & Action Guidelines
To promote globular solidification morphology, the weld should be cooled quickly and uniformly. This can be achieved through optimal cooling radiation or the use of cooling water. A typical target is a t8/5 value between 10 and 20 seconds.