Pearlite Start

Pearlite is a lamellar steel microstructure composed of alternating plates of soft ferrite and hard cementite (Fe3C). It forms during the eutectoid transformation when austenite cools through the critical range. In commercial heat-treatment practice, the cycle that produces this lamellar-pearlite structure is often called an LP anneal or lamellar pearlite anneal.

In a CNC cell, pearlitic steels usually arrive as as-received bar stock, normalized plate, gears, shafts, or fixture hardware. Lamellar pearlite forms after controlled cooling from austenite, and finer interlamellar spacing raises strength and hardness. The tool cuts through alternating soft ferrite and hard cementite plates, so the edge experiences cyclic loading that increases flank wear, promotes chipping, and roughens the surface compared with spheroidized material. When incoming stock is normalized or partially transformed with lamellar pearlite, standard feeds and speeds can cause poor chip control and unstable offsets. A full annealing or spheroidizing anneal before machining reduces cutting forces and extends tool life. Incoming inspection verifies hardness by lot and segregates overly abrasive heats. Aggressive machining can also transiently dissolve pearlite near the cut zone, creating a white layer and altered surface integrity.