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# Equivalent carbon content

The equivalent carbon content of a steel alloy refers to method of measuring the maximum hardness and the weldability of the alloy based on the chemical composition of the alloy. Higher concentrations of carbon and other alloying elements such as manganese, chromium, silicon, molybdenum, vanadium, copper, and nickel tend to increase the hardness and decrease the weldability of the material. Each of these materials tends to influence the hardness and weldability of the steel to different magnitudes, however, making a method of comparison necessary to judge the difference in hardness between two alloys made of different alloying elements. The equivalent carbon content is the most common such standard, but others exist, such as the equivalent nickel content and the equivalent chromium content (usually used together and in conjunction with the Schaeffler-Delong diagram and considered more accurate for measuring weldability). A commonly used formula for calculating the equivalent carbon content is:

$E_c = \%C + \left(\frac{\%Mn+\%Si}{6} \right) + \left(\frac{\%Cr+%Mo+\%V}{5} \right) + \left(\frac{\%Cu+\%Ni}{15} \right)$