Primary Dendrite Arm Spacing
The primary dendrite arm spacing is the distance between adjacent main stems of solidifying crystallites and influences the microhardness as well as the segregation distribution.
Physicochemical Mechanism of Action
During the melting process, the metal grows into crystallites that spread as primary arms (dendrites). The spacing between these primary arms determines how well oxygen and other additives can distribute within the crystals.
Metallurgical Relevance & Welding Risks
Too large a primary dendrite arm spacing can lead to uneven distribution of additives, causing segregation and possibly cracks or loss of toughness. Too small a spacing can increase microhardness but also coarsen the structure and impair weld integrity.
Workshop Practice & Action Instructions
To optimize primary dendrite arm spacing, pay attention to proper melting temperature and an appropriate cooling step. For steels with high carbon content (e.g., HSS), the dendrite arm spacing should be between 100 and 200 µm to ensure good segregation distribution.