Phosphorus Segregation Bands
Phosphorus segregation bands are microscopic concentration differences of phosphorus in rolled structures, leading to anisotropic mechanical properties and local toughness drops.
Physical-Chemical Mechanism
Phosphorus segregation bands form due to uneven phosphorus distribution during rolling. These concentration differences cause local deformation phenomena that affect the crystal lattice and lead to anisotropic mechanical properties.
Metallurgical Relevance & Welding Risks
The anisotropic properties of phosphorus segregation bands can cause uneven stresses and strains, leading to cracks or fractures in the weld. Additionally, they can reduce the toughness of the rolled structure, increasing the risk of hot cracking.
Shop Practice & Guidelines
To minimize phosphorus segregation bands, the rolling process must be carefully controlled. This includes optimal temperature control and a uniform pressure profile. When welding rolled steels with phosphorus segregation bands, it's important to cool the weld slowly (t8/5 > 25 s) to stabilize the structure and avoid cracks.