Chromium equivalent
Chromium equivalent is a parameter that measures the ferrite-stabilizing influence of alloying elements in steels relative to chromium. It helps predict the microstructure and mechanical properties.
Physical-Chemical Mechanism of Action
The chromium equivalent (Cr-Eq) calculates the total ferrite stabilization of all alloying elements in a steel by converting the content of ferrite stabilizers such as nickel, molybdenum, niobium, etc., into a chromium equivalent. This allows a unified view of the ferrite-stabilizing effect of all elements.
Metallurgical Relevance & Risks in Welding
A too high chromium equivalent can lead to ferrite formation, which coarsens the microstructure and reduces the toughness of the steel. This increases susceptibility to cracking and negatively affects mechanical properties. In welding, it is important to consider the Cr-Eq to ensure a homogeneous microstructure and optimal mechanical properties.
Workshop Practice & Action Guidelines
When welding high-alloy steels with a high chromium equivalent, careful control of the cooling steps is essential. Use controlled cooling (CA) or slow cooling to minimize ferrite formation. For steels with Cr-Eq > 10%, special welding procedure planning is required to ensure microstructural homogeneity and mechanical properties.