Phosphorus segregation
Localized accumulation of phosphorus at grain boundaries during melt solidification. This increases cold shortness susceptibility and promotes temper embrittlement in the material.
Phosphorus is undesirable in steel. During solidification, it migrates to the grain boundaries and makes the structure brittle there. This leads to cold shortness, especially at low temperatures, and can cause cracks in the weld and in the heat-affected zone during welding. Phosphorus can also embrittle the steel during tempering. Therefore, pay attention to the phosphorus content in the base material and use filler materials with low phosphorus content. For old, unknown steels, an analysis is worthwhile, and if the value is too high, only preheating and controlled cooling help.