Phosphorus Edge Embrittlement
Phosphorus edge embrittlement is brittle fracture at the edges of thick-walled components, caused by phosphorus enrichment and slow cooling. This requires controlled cooling and high cleanliness of the base steel.
Physico-chemical mechanism of action
Phosphorus edge embrittlement occurs when thick-walled components are cooled slowly. The phosphorus in the steel reacts with carbon to form carbon phosphide (Fe3(CO)12), which makes the edge more brittle.
Metallurgical relevance & risks in welding
This embrittlement leads to increased susceptibility to brittle fracture and cracks at the edge of the components. It can result in incomplete weld formation and lower mechanical strength, which affects the service life of the components.
Workshop practice & instructions
To avoid phosphorus edge embrittlement, cooling of the steel should be accelerated. The maximum cooling flow rate should be maintained to rapidly cool the temperature in the weld zone. Additionally, it is important that the raw steel has high purity and the phosphorus content stays below 0.1 %.