Crater crack
A star- or line-shaped crack at the end of the weld bead, formed during undamped arc extinction through rapid, undirected solidification in the center. It is prevented by implementing a crater-filling program.
A crater crack forms at the end of the weld when you break the arc too abruptly and the filler metal solidifies too quickly there. That happens because the material at the crater edge is thinner and can't relieve the stress properly. In practice, you see the crack as a fine, often star-shaped hairline crack in the crater. If you don't get rid of it, it's a weak point that can tear under load. To avoid it, fill the crater cleanly at the end by holding the torch in place briefly and feeding filler until the crater is full. Or use a crater fill program if your machine has one. Then let the arc fade out slowly instead of snapping it off. If one does form, grind it out completely and reweld the spot.