Triple junction
The triple point is the location in the microstructure where three different phases (e.g., steel, melt, and gas) meet. Here segregation processes are strong and grain boundaries migrate.
Physico-chemical mechanism of action
The triple point forms where three phases (like steel, melt, and gas) meet. At this location, there is a high concentration of chemical elements and increased segregation activity. Grain boundaries can move here and change their structure.
Metallurgical relevance & risks during welding
If cooling is too fast, the triple point can lead to strong segregation, causing uneven stresses and possible cracks in the microstructure. If cooling is too slow, it can lead to grain boundary migration and changes in the structure, affecting the toughness of the steel.
Workshop practice & instructions
To minimize the risks of the triple point, it is important to use controlled cooling steps. When welding high-performance steels (e.g., high-temperature steel), the cooling rate should be strictly maintained to avoid segregation and grain boundary migration. Recommended cooling times vary by material, but in general they should be between 5 and 20 seconds.