Carbide Former Index
The carbide former index determines whether special carbides form instead of iron carbides in high-alloy steel. This affects tempering resistance and hot strength.
Physical-chemical mechanism of action
The carbide former index indicates how strongly a transition metal picks up carbon and reacts to form special carbides. A high index means a strong affinity for carbon.
Metallurgical relevance & risks when welding
When the carbide former index is high, special carbides such as molybdenum or vanadium carbides form instead of iron carbides. This increases the tempering resistance and hot strength of the steel, but can also lead to increased hardness and lower ductility. With incorrect welding treatment, cracks or distortion may occur.
Workshop practice & instructions
To maintain optimal steel properties, pay attention to correct welding temperatures and times. For high-alloy steels with a high carbide former index (e.g., molybdenum steels), slow cooling after welding is required to promote the formation of special carbides. Use special welding methods for such steels, such as gas welding or TIG welding with low voltage.