Coring
An inhomogeneous chemical composition within a single dendritic grain resulting from incomplete diffusion during solidification. It causes local property variations and often requires homogenization annealing.
Coring occurs during solidification when alloying elements don't mix properly and distribute unevenly in the structure. This makes the material softer in some spots and more prone to cracking, especially when the weld is later heavily loaded. In practice, you often notice it by irregular hardness variations or when grinding, the material doesn't wear evenly. If you have coring, homogenization annealing helps, where the part is heated to high temperature for a long time and evenly, so the elements can redistribute. When welding itself, you can prevent it by controlling heat input and not letting the part cool too quickly.