TOOLS / WELDING

Carbon equivalent & preheat screening calculator

Screen weldability from mill chemistry using the IIW carbon equivalent. Screening only: this page gives no preheat temperature and is not a WPS.

IIW carbon equivalent0.44

Middle screening band: take extra care; preheat and hydrogen control are commonly required. Confirm from the applicable standard and WPS.

Safety-critical screening only. This is NOT a welding procedure specification (WPS) and gives no preheat temperature. Preheat tables differ between standards (for example AWS D1.1 and EN 1011-2 Method B), and Method B has its own validity ranges and inputs. A qualified person must set preheat, interpass temperature and hydrogen controls; never use this page to waive a specified preheat.

Formula

IIW carbon equivalent CE = C + Mn/6 + (Cr + Mo + V)/5 + (Ni + Cu)/15, with all elements in weight percent. Higher CE means higher hardenability and higher hydrogen-cracking risk.

Standard / source

IIW carbon equivalent formula and EN 1011-2 Method B, cited by reference only in the MetalCalz tool-expansion research (2026-10-27). Method B uses its own carbon-equivalent variant (CET) and validity ranges and is not computed here. Preheat tables differ between standards, so no single preheat temperature is published on this page.

Worked example

C 0.18, Mn 1.20, Cr 0.20, Mo 0.05, V 0, Ni 0.10, Cu 0.10: CE = 0.18 + 1.20/6 + (0.20 + 0.05 + 0)/5 + (0.10 + 0.10)/15 = 0.18 + 0.20 + 0.05 + 0.0133 = 0.44. These are the calculator defaults, so the page loads showing CE 0.44, in the middle screening band.

Safety note

Safety-critical screening only: qualified-person gate. This is NOT a welding procedure specification and must never be used to waive a specified preheat. A qualified person must set preheat, interpass temperature and hydrogen controls from the applicable standard and WPS, considering thickness, restraint, heat input and hydrogen level. This result is not an approval or compliance statement.