Dendritic fragmentation
Dendritic grain refinement is the process in which rigid crystal structures in a metal split into smaller, finer grains through forming or heat. This leads to improved toughness and formability.
Physical-Chemical Mechanism of Action
Dendritic crystals form during the melting process in metals, growing in a tree-like pattern. During forming or thermal changes, these rigid crystal structures can break down into smaller grains.
Metallurgical Relevance & Risks in Welding
A finer grain structure improves the toughness and formability of the material, leading to better mechanical properties. However, uncontrolled grain refinement can lead to increased growth of phases such as martensite, causing hardness problems and possible cracks in the material.
Workshop Practice & Instructions
To achieve controlled dendritic grain refinement, it is important to precisely regulate welding temperatures and times. For steels with high carbon content, a slow cooling (t8/5 > 25 s) is recommended to obtain a fine grain structure. Avoid too rapid cooling, as this can lead to martensite formation and hardness.