Equivalent Nickel Ratio
The Equivalent Nickel Ratio is a mathematical index that quantifies the effectiveness of austenite-forming alloying elements relative to nickel. It is used to determine phase stability in high-alloy steels.
Physicochemical Mechanism of Action
The Equivalent Nickel Ratio (EN) is an index that indicates the effectiveness of austenite-forming elements like cobalt, molybdenum, and chromium relative to nickel. It is calculated by summing the amounts of these elements with their respective weight factors to a reference value (in this case nickel).
Metallurgical Relevance & Risks in Welding
The EN influences phase stability and the steel's microstructure. A high EN value leads to greater austenite formation, increasing durability and toughness but reducing hardness. A low EN value can lead to the formation of ferrite and martensite, increasing hardness but reducing toughness and formability.
Workshop Practice & Procedural Guidelines
When welding high-alloy steels with a high EN, it is important to ensure a slow cooling time (t8/5 > 25 s) to promote austenite formation. For lower EN values, the cooling time should be shortened (t8/5 < 5 s) to achieve sufficient hardness. The exact cooling time depends on the specific alloy and desired properties.