Cut edge hardening
The local microstructural alteration at the thermally cut edge due to rapid heat dissipation into the cold base material, which can lead to the formation of brittle phases. This often requires material-appropriate preheating or post-processing.
Cut edge hardening occurs when, during flame cutting, the heat dissipates quickly into the cold base material. This forms a hard, brittle structure at the edge that tends to crack – especially in higher-strength steels. When welding over such edges, you have to be careful that the weld doesn't crack. If the material is hard and brittle, it helps to grind or mill the edge before welding to remove the hardened zone. Alternatively, you can preheat the area so that cooling is slower and no martensite forms. If you're unsure whether the edge is critical, do a hardness test or ask the foreman. When in doubt, it's safer to machine the edge – that's the most reliable way.