Segregation crack
A segregation crack forms due to the enrichment of low-melting phases at grain boundaries during solidification. This leads to local coarsening and increases the risk of cracking.
Physikalisch-chemischer Wirkmechanismus
During welding, the metal in the weld crystallizes. With certain filler materials and temperature curves, low-melting phases can build up at the grain boundaries. These phases are less stable and lead to local grain coarsening.
Metallurgical relevance & welding risks
Segregation cracking can make the weld more prone to cracking, leading to cracks and hot cracks in the material. This hurts the mechanical properties and service life of the weld joint.
Workshop practice & action points
To avoid segregation cracking, set the right welding temperature and controlled cooling rate. Don't let the weld cool too fast (t8/5 > 25 s) to prevent coarsening. For special steels or fillers, it's a good idea to talk to a metallurgist to set the best welding parameters.