What Does Hot Cracking Mean?
Hot cracking is the formation of shrinkage cracks during the solidification of weld metal. This phenomenon occurs in almost all metals.
Hot cracking is also known as hot shortness, hot fissuring, solidification cracking and liquation cracking.
Corrosionpedia Explains Hot Cracking
These cracks are known as hot cracks because they occur immediately after welds are completed and sometimes while the welds are in progress, when the weld metal tends to solidify from the corners of the base metal to which it is joined. As the solidification proceeds, the low melting eutectics are concentrated in the center and remain liquid, which is then torn apart by the stress associated with the welding, resulting in a center line crack.
Hot cracking occurs when the available supply of liquid weld metal is insufficient to fill the spaces between solidifying weld metal, which are opened by shrinkage strains.
Thus, hot cracking occurs when:
- Strain on the weld pool is too high
- Liquid cannot reach the regions where it is needed due to inadequate supply or blockage/narrow channels between solidifying grains
- Temperature is > 1200°C
- Impurities such as carbon (C), sulfur (S) or phosphorus (P) are present
To control hot cracking, the following principal factors need to be manipulated:
- Weld metal composition
- Weld solidification pattern
- Strain on the solidifying weld metal
- Adding manganese, chromium, or molybdenum