Columnar Solidification
Columnar crystallization is the directional growth of long crystal needles against the direction of heat removal during the solidification process. This results in a fine, smooth structure and increases toughness and hardness.
Physicochemical mechanism of action
Columnar crystallization occurs when a metal shows slow grain growth during cooling. The crystals grow in the direction toward the heat source (against the heat removal direction), leading to thin, elongated needles.
Metallurgical relevance & risks during welding
Columnar crystallization can lead to increased toughness and hardness of the material, which is helpful for certain applications such as in the machine building industry. However, it can also lead to a fine structure that can cause difficulties during welding, because the crystals are hard to exchange and the weld can become weaker.
Workshop practice & instructions for action
To control columnar crystallization, it is important to ensure careful cooling of the metal. This can be achieved by using cooling water or special cooling dies. When welding columnar crystallized steels, it is advisable to ensure slow, controlled cooling to keep the structure undamaged.