Carbon equivalent
A calculated value used to evaluate the weldability of steels based on their carbon and other alloying element contents. It helps estimate the steel's susceptibility to hardening and cracking during cooling.
The carbon equivalent (CEV) converts the influence of alloying elements on hardenability into a fictitious carbon content. The higher the value, the harder and more brittle the heat-affected zone becomes during rapid cooling, and the greater the risk of hydrogen-induced cracking, which often only appears hours later. You have to calculate the CEV from the mill certificate before you start. If the value is high, it means for you: preheat, use low-hydrogen consumables, and let the weld cool slowly, for example with an insulating blanket. For very critical values, you must stress-relieve the component immediately after welding.