Chromium Equivalent for Microstructure Prediction
The chromium equivalent is the sum of weighted ferrite stabilizers like Ni, Mo, and Cr in an alloy. It helps predict the microstructure after cooling.
Physico-Chemical Mechanism of Action
The chromium equivalent is calculated by adding weighted amounts of ferrite stabilizers like nickel (Ni), molybdenum (Mo), and chromium (Cr). These elements prevent the steel from transforming into glass-hard phases like martensite on cooling.
Metallurgical Significance & Risks in Welding
A too high chromium equivalent can lead to an excessive ferrite content, reducing hardness and toughness of the steel. This increases the risk of cracking and reduces the mechanical properties of the weld.
Workshop Practice & Action Guidelines
To predict the microstructure, calculate the chromium equivalent using the formula: Cr_eq = 0.5 * Cr + Mo + Ni. For optimum hardness and toughness, the chromium equivalent should be between 1.5 and 3.