Phosphorus segregation zone
Phosphorus segregation fringe is a region of increased phosphorus concentration in the metal, caused by incomplete concentration equalization during solidification. These zones are less tough and cause weak points.
Physicochemical Mechanism of Action
The phosphorus segregation seam forms when the phosphorus concentration rises locally during cooling of the weld. This happens through incomplete exchange of atoms between the different phases in the structure. That leads to a local over-concentration of phosphorus.
Metallurgical Relevance & Welding Risks
These zones are less tough and create weak spots in the weld, which hurts the mechanical strength. They can lead to hot cracks or stress concentrations, especially when the metal is under load.
Workshop Practice & Instructions
To avoid the phosphorus segregation seam, make sure the weld cools down properly. This can be done with a controlled cooling technique. The cooling time should be long enough to allow full atom exchange, but not so long that the structure gets too coarse. Recommended cooling time: 10-20 seconds per cm of steel thickness.