Carbon Equivalence

Carbon is usually considered to be the most important contributor to the hardness and strength of ferrous steels. Even when other alloying elements are not present, high carbon content can result in high local hardness. The effect of carbon contain to hardness have write on the early article about chemical composition, to review again about this please click Chemical Compositions.

However, other alloying elements also contribute to the overall harden ability of the steel. This effect can be generally quantified by the determination of the carbon equivalence (CE) of the steel.

CE is defined by several formulas, and it is important that close attention be paid to the formula being used. The following formula is used in most ASME applications:

CE = C + (Mn + Si)/6 + (Cr + Mo + V)/5 + (Ni + Cu)/15

It is important that any CE determination be calculated using the actual chemical analysis rather than the maximums specified in materials specifications. If this is not done, the calculation will result in an unrealistically high CE.

The CE can be specified at certain maximum values (for example, SA-537 Class 1; see Appendix A) and can be applied to a variety of fabrication variables. These are covered within the discussion of those variables.