Steel and preheat
Carbon equivalent CET (BS EN 1011-2 method B)
- where
- carbon equivalent, CET (%)
- carbon (%)
- manganese (%)
- molybdenum (%)
- chromium (%)
- copper (%)
- nickel (%)
Explain this equation
Works out the CET carbon equivalent, used in the BS EN 1011-2 method B to calculate preheat for structural, fine-grained and low-alloy steels.
Like the IIW figure, it weights each element by how much it raises the hardenability compared with carbon, but with different weightings fitted to cold-cracking tests: manganese and molybdenum count a tenth, chromium and copper a twentieth, nickel a fortieth. The result is used directly in the preheat equation.
An empirical weighted sum; CET values are smaller than IIW CE for the same steel.
Sense check: the same S355 analysis that gives CE about 0.44 gives CET about 0.33.
Watch out: the method B preheat equation is only valid for CET between 0.20 and 0.50%.
The carbon equivalent used by the BS EN 1011-2 method B (CET) preheat equation. Feed the result into the CET preheat calculator.
Enter your values to see the result.
Good to know
CET gives carbon more weight than CE(IIW) and leaves vanadium out. Values for structural steels typically sit around 0.2–0.4 %.
Common mistake
Mixing up CET and CE(IIW). They are on different scales and must only be used with their own preheat method.
Limits
The method B equations are validated for CET 0.20–0.50 % and for unalloyed and low-alloy steels within the composition limits given in BS EN 1011-2 Annex C.
Sources
- BS EN 1011-2:2001 Welding – Recommendations for welding of metallic materials – Part 2: Arc welding of ferritic steels (Annex C: CE and CET preheat methods; Annex D: cooling time t8/5)
- TWI FAQ: What is the difference between the various carbon equivalent formulae used in relation to hydrogen cracking? (CE(IIW), Pcm, CET in EN 1011-2)
- Dillinger welding calculator help: CET, EN 1011-2 preheat formula and validity range (CET 0.2–0.5 %, d 10–90 mm, HD 1–20 ml/100 g, Q 0.5–4.0 kJ/mm), t8/5 2D/3D equations, transition thickness and shape factors F2/F3
Results are calculations from the published methods and figures shown, and depend on the data you enter. Follow the welding procedure specification (WPS), BS EN ISO 15614/9606, BS EN 1090, BS EN 1993 and manufacturers’ data. Structural welds need qualified welders and engineered designs.