Lamellar phosphide eutectic

A hard, brittle microstructural constituent in grey cast iron, also known as steadite, consisting of phosphorus segregations and Fe3P-rich phases. It forms in the final residual melts, increasing hardness while impairing machinability.

Phosphorus can segregate in the last residual melt during solidification and form a brittle, lamellar structure there. This makes the material hard but also prone to cracking, especially when the weld cools rapidly. When welding gray cast iron or steels with higher phosphorus content, you need to be careful. Keep the heat input controlled and let the part cool slowly, otherwise the weld or the heat-affected zone will crack. If you're unsure, preheat the part or use a suitable backing layer.

MetallurgieSchweißtechnik