Weld Metal Microsegregation
Microsegregation is a local enrichment of alloying elements and impurities in the weld. It increases susceptibility to hot cracking.
Physical-chemical mechanism of action
Microsegregation occurs when certain chemical elements or impurities are concentrated in the molten weld pool and accumulate during cooling in the last solidified areas of the weld volume. This can be caused by uneven distribution of gases, chemical reactions, or mechanical influences.
Metallurgical relevance & risks in welding
Microsegregation leads to an increased susceptibility to hot cracks and porosity in the weld. The concentrated enrichment can alter the structure, affecting the mechanical strength and toughness of the material. This can lead to significant quality problems, especially at high temperatures and under rapid cooling.
Workshop practice & instructions
To minimize microsegregation, it is important to ensure a uniform melting input and controlled cooling. If necessary, use deoxidizing agents such as silicon or potassium fluoride to increase the oxygen binding in the weld pool. Also pay attention to correct vacuum treatment and compliance with the specific temperature profiles for the respective material.