Widmanstätten ferrite

Widmanstätten ferrite forms when the steel cools too slowly after welding. Then needle-like microstructures develop, making the material brittle and reducing toughness. You don't want that in the component because it cracks more easily under load. To avoid this, you have to speed up cooling after welding. The thicker the material, the more critical it becomes. So don't leave the heat in too long, but ensure the area cools down quickly. If you let the weld cool normally and the structure still looks bad, you must actively support cooling.