Super duplex sigma phase avoidance
Avoids the occurrence of brittle sigma phases in super duplex steels through optimized cooling and hot forming to maintain toughness.
Physical-Chemical Mechanism of Action
Sigma phases are brittle intermetallic phases that form in superduplex steels under uneven cooling conditions. These phases can develop from cooling that is too fast or too irregular and lead to loss of toughness.
Metallurgical Relevance & Welding Risks
The formation of sigma phases can significantly reduce the toughness of the material, severely impairing mechanical properties. This increases the risk of cracks and fractures in the welded joint.
Shop Practice & Action Guidelines
To avoid sigma phases, it is essential to ensure controlled cooling and proper hot forming. This can be achieved by using welding processes with slow cooling (e.g., austenitic welding). The maximum thermal cycle temperature should be kept below 10 mm to ensure uniform cooling.