Depending on their location and mode of occurrence, hot cracks can be:

1. Solidification cracks: occur in the weld metal (usually along the centreline of the weld) as a result of the solidification process.
2. Liquation cracks: occur in the coarse grain HAZ, in the near vicinity of the fusion line as a result of heating the material to an elevated temperature, high enough to produce liquation of the low melting point constituents placed on grain boundaries.