Glossary
Cold shut — definition
A weak zone where two flow fronts meet without fully fusing, because the front had cooled too far.
When the melt divides around a core and meets again on the other side, the two fronts have to be hot enough to fuse. If they are not, a visible seam appears on the surface and a zone of reduced strength forms in the section.
The causes are usually too low a casting temperature, too long a flow path, locally too thin a wall, or a gate placed so the metal has to travel unnecessarily far.
Cold shuts are one of those defects that look cosmetic and are not. A cold shut in a loaded section is a crack waiting to happen.