Lamellar graphite
Lamellar graphite consists of fine, sharp-edged carbon flakes in the gray cast iron structure and acts as notches. It improves vibration damping but drastically reduces tensile strength and ductility.
Physical-Chemical Mechanism of Action
Lamellar graphite forms through the arrangement of fine carbon lamellae in the metal matrix. These lamellae are sharp-edged and can expand in the direction of stress, leading to local deformations.
Metallurgical Relevance & Risks in Welding
The presence of lamellar graphite in the microstructure can greatly impair the mechanical properties of steel. It promotes high vibration damping, which can be advantageous in machine components. However, it drastically reduces tensile strength and ductility, which can lead to premature failure or cracking. During welding, it is important to adjust temperature and time conditions so that no new lamellar graphite structure forms.
Workshop Practice & Instructions
To minimize the risk of lamellar graphite, the following measures should be taken during welding:
• Use a shielded charge and avoid high voltage peaks.
• Keep the cooling time after welding as short as possible to reduce the growth of carbon lamellae.
• For steels with high carbon content and lower chromium content, careful selection of the welding process should be made to avoid the formation of lamellar graphite.