3. Pearlitic steels

3.1 Hardening of lamellar perlite

When steel containing around 0.8% carbon cools, pearlite forms the majority component. The yield strength of pearlite is much higher than that of granular ferrite. Plastic deformation is initiated only in the ferrite lamellae, and their width governs the yield strength through an effect analogous to that of grain size in granular microstructures. The main contribution to the hardening of perlite is thus linked to the interlamellar spacing S. The lower the transformation temperature, the smaller the spacing (figure 13 ). In industrial practice, the interlamellar spacing is set between 0.1 and 1 µm,...