Degenerated pearlite
A variation of pearlite where the cementite fails to form regular lamellae and instead takes on a disrupted or globulized appearance, often caused by very slow cooling rates.
You normally get pearlite as a fine lamellar structure of ferrite and cementite. If the part cools too slowly after welding or is held hot too long, the cementite decomposes and balls up into globules. That's called granular or degenerate pearlite, and it's softer and not as strong as the lamellar structure. This mainly happens in the heat-affected zone when you put in too much heat or the cooling is too slow. Then the strength of the weld drops, and you don't want that with high-strength steels. If that happens, only normalizing again will fix the structure. When welding, you have to watch the cooling and not put in too much heat.