Carbon content is the main factor determining the strength and weldability of carbon steel. In addition to carbon, alloy steel (mainly low alloy steel) also plays an important role in the strength and weldability of steel. In order to express the strength and weldability of these materials conveniently, the statistical data of a large number of test data are simply expressed by carbon equivalent. There are many carbon equivalent indicators, such as tensile strength carbon equivalent, yield strength carbon equivalent, welding carbon equivalent and crack sensitivity index (basically carbon equivalent).


The conceptual origin and theoretical application of carbon equivalence are closely related to iron-carbon phase diagrams. By comparing the carbon content of CE with the eutectic point, the direction and degree of specific composite cast iron deviating from the eutectic point can be determined. It is easy to judge whether the composition is hypereutectic, hypoeutectic or eutectic.