Sulfur segregation
Sulfur segregation is the enrichment of sulfur at grain boundaries and in residual melts during solidification. This leads to low-melting eutectics and increased hot shortness.
Physico-Chemical Mechanism of Action
Sulfur segregation occurs when sulfur concentrates at grain boundaries during cooling of metals. This can be caused by chemical bonding of sulfur with other elements or by diffusion processes.
Metallurgical Relevance & Welding Risks
Sulfur segregation can lead to the formation of low-melting eutectics that are liquid at low temperatures. This increases the hot shortness of the weld and raises the risk of hot cracking. Furthermore, it can cause poor toughness and increased stress buildup, contributing to crack formation.
Workshop Practice & Action Guidelines
To avoid sulfur segregation, stick to the correct melting temperatures. A temperature that's too high can concentrate sulfur at grain boundaries. Also, make sure the cooling rate is fast enough to prevent the eutectic from forming. For steels with high sulfur content, minimize the melting time and carefully remove the residual melt.