Carbon Equivalent Calculator

Carbon Equivalent Value (CEV) is a calculated index that expresses the combined effect of all alloying elements in steel as an equivalent carbon content. It is critical for determining weldability — steels with CEV above 0.45 typically require preheating before welding to prevent hydrogen-induced cold cracking.

Generally, a CEV below 0.35 indicates excellent weldability with no preheat required. CEV between 0.35 and 0.45 indicates fair weldability where preheating may be beneficial. CEV above 0.45 requires preheating, and above 0.55 requires strict welding procedures with controlled heat input and hydrogen control.

CEV (IIW formula) is the most common standard from the International Institute of Welding: CEV = C + Mn/6 + (Cr+Mo+V)/5 + (Ni+Cu)/15. CET (Carbon Equivalent for Thermal cracking) is used for higher-strength steels. PCM (Parameter Cracking Measurement) is a Japanese standard better for low-carbon steels. Each formula weights elements differently based on their contribution to hardenability.

Carbon itself has the strongest effect on CEV, followed by manganese (divided by 6), then chromium, molybdenum, and vanadium (divided by 5). Nickel and copper have a milder effect (divided by 15). Keeping carbon below 0.22% and controlling manganese levels is the most effective way to maintain low CEV for good weldability.