Ledeburite II
Ledeburite II is the transformed eutectic microstructure of cast iron below the eutectoid temperature, consisting of pearlite and cementite. It occurs after full heating and transformation at room temperature.
Physical-Chemical Mechanism of Action
Ledeburite II forms from the cooling of cast iron below the eutectoid temperature. It consists of a mixture of pearlite and cementite, where the pearlite has crystal cells with a content of ferrite and austenite, while the cementite consists of pure ferrite.
Metallurgical Relevance & Welding Risks
Ledeburite II is a more stable structure than ledeburite I and has higher strength and toughness. However, cooling too fast can lead to glass-hard martensite, increasing cracks and hot cracks. Cooling too slowly can enlarge the grain size, reducing toughness.
Workshop Practice & Instructions
To achieve the desired ledeburite II structure, the cast iron should cool at room temperature. Rapid cooling can be prevented by using cooling water or coolants. The cementite unit should be between 0.2% and 1.5% to ensure sufficient strength.