Inverse Segregation
Inverse segregation is an unwanted enrichment of low-melting elements at the edge of the weld pool due to remaining molten metal. This leads to a finely distributed hardness and increases the risk of cracking.
Physikalisch-chemischer Wirkmechanismus
Inverse segregation occurs when low-melting elements like silicon or sulfur remain molten in capillary channels at the edge of the weld pool and concentrate. This happens due to the difference in melting points and convection currents in the liquid metal.
Metallurgical Relevance & Welding Risks
Inverse segregation leads to a finely distributed hardness at the edge of the pool, which increases the occurrence of cracks. The toughness and mechanical properties of the weld are impaired because the metal in these areas becomes too hard and is not as ductile.
Werkstattpraxis & Handlungsanweisungen
To avoid inverse segregation, the melt time should be minimized and uniform cooling ensured. A high arc voltage and low voltage drop during cooling help prevent residual melt. For difficult-to-weld steels, it is advisable to perform a short post-weld heat treatment (tempering) to homogenize hardness.