Dendrite Tip Growth
Dendrite tip growth is the directed growth of crystal needles into the melt. A fast growth rate leads to fine microstructure, which increases toughness.
Physical-Chemical Mechanism of Action
Tip growth of dendrites describes the directional growth of crystal needles (dendrites) into the melt. This process depends on the temperature and the concentrations of chemical elements in the weld pool. A fast growth rate leads to a fine structure, while a slow rate leads to a coarse grain structure.
Metallurgical Relevance & Risks in Welding
Too fast tip growth can lead to a fine structure, which increases toughness. Too slow growth, however, can lead to a coarse grain structure and thus reduce toughness and scale resistance. Additionally, uneven tip growth can cause stresses in the structure, which can lead to cracks or wear.
Workshop Practice & Action Instructions
To achieve a fine structure, control the weld pool so that dendrite tip growth is fast. This can be achieved by selecting the right welding process and proper temperature control. For steel welding, a t8/5 value of about 10 to 20 seconds is often suitable to get a fine structure. It is important to precisely control the melt temperature and cooling time to achieve the desired structure.