Interlamellar cementite
Interlamellar cementite forms between ferrite lamellae in pearlite and increases the strength and hardness of the steel. However, too much cementite can lead to more crack-susceptible weld areas.
Physical-Chemical Mechanism of Action
Interlamellar cementite forms through rapid cooling of pearlite, where ferrite and carbide settle in different phases. The cementite forms a harder phase between the softening ferrite lamellae.
Metallurgical Relevance & Risks in Welding
An excessively high cementite content can increase mechanical strength but also leads to more crack-susceptible weld areas. This can cause problems especially under high stresses and thermal loads.
Workshop Practice & Instructions
To achieve a good balance between strength and ductility, the cooling rate of the steel should be controlled. For pearlite with high cementite content, slow cooling (e.g., over 10-20 minutes) is recommended to stabilize the structure and avoid cracking.