Lamellar structure of alternating ferrite and iron carbide plates, formed when austenite transforms between roughly 550 and 727 °C. A 0.77 percent carbon steel cooled slowly becomes fully pearlitic. Fine pearlite from faster cooling is harder and stronger than coarse pearlite from a furnace cool, which is why normalizing gives more strength than full annealing. In a part that should have hardened, pearlite is the signature of a slack quench.
Met lab found pearlite at the root of the tooth, so the quench didn't keep up with that section.
Also heard as
- fine pearlite
- coarse pearlite
Related terms
Ferrite
The soft, low-carbon, body-centered cubic phase of iron that makes up most of an annealed low-carbon steel.
Cementite
Iron carbide, Fe3C: the hard, brittle compound that carries most of the carbon in slowly cooled steel.
Normalizing
Heating steel above its upper critical temperature and cooling it in still air to refine and even out grain.
Slack quench
A quench too slow to make full martensite, leaving pearlite, bainite or ferrite and low hardness.
TTT diagram
Time-temperature-transformation chart showing how long austenite takes to transform when held at a fixed temperature.