Preheat Calculator

BS EN 1011-2:2001+A1:2003, Annex C.3, Method B — composition, thickness, hydrogen and heat input in, minimum preheat temperature out.

Carbon Equivalent (CET)

Carbon (C) %

Manganese (Mn) %

Molybdenum (Mo) %

Chromium (Cr) %

Copper (Cu) %

Nickel (Ni) %

CET = — %

CET %

Joint & Welding Parameters

Combined Thickness (d) mm

Diffusible Hydrogen (HD) ml/100g

Heat Input (Q)

Heat Input (Q) kJ/mm

Current A

Voltage V

Travel Speed mm/min

Process (thermal efficiency k)

Q = — kJ/mm

Result

Minimum Preheat Temperature (Tp) — Enter composition, thickness, hydrogen and heat input

Formula: T_p = 697·CET + 160·tanh(d/35) + 62·HD^0.35 + (53·CET−32)·Q − 328 (°C), per BS EN 1011-2:2001+A1:2003, Annex C.3 (Method B). Valid for structural steels up to 1000 N/mm² yield strength, with CET 0.2–0.5%, d 10–90mm, HD 1–20 ml/100g and Q 0.5–4.0 kJ/mm. Addresses HAZ hydrogen (cold) cracking only — not weld-metal cold cracking, which can require additional preheat in restrained sections over 20mm thick with high heat-input runs. Assumes the parent metal CET exceeds the weld metal CET by at least 0.03% (otherwise base the calculation on weld metal CET + 0.03%) and moderate fabrication restraint. For steels with yield strength over 460 N/mm² and thickness over 30mm welded by SAW, consider a post-weld hydrogen soak (e.g. 2h at 250°C). This is a working estimate, not a substitute for a qualified WPS — confirm against the applicable code and procedure qualification requirements.