The carbon equivalent (Cekv) is used to determine how well common carbon steel can be welded and whether preheating of the welded steel is necessary.
If the result is Cekv ≤ 0.45 and at the same time the carbon content is ≤0.2%, the steel is well weldable without the need for preheating.
Otherwise, the steel must be preheated.
Formula proposed by the International Welding Institute.