Describes work that saw too much temperature or time: grain has grown coarse, retained austenite is high, and in the worst case grain boundaries have started to melt or oxidize, which metallurgists call burning. Cooked parts break with a coarse, glittering fracture and often crack in the quench. Mild overheating can be corrected by normalizing and rehardening; burned steel is scrap.
Controller stuck at 1,800 overnight and cooked the whole load, fracture face looks like rock candy.
Also heard as
- overheated
- burnt
- fried
Related terms
Grain size
The average size of the crystals in a metal, usually reported as an ASTM number where higher means finer.
Quench crack
A crack that forms during or soon after quenching from thermal and transformation stress in hardened steel.
Rehard
To harden a part again after it misses hardness, usually after normalizing or annealing it first.
Normalizing
Heating steel above its upper critical temperature and cooling it in still air to refine and even out grain.