Welding
Carbon equivalent calculator
In short
The carbon equivalent is worked out from the steel composition: CE = C + Mn/6 + (Cr+Mo+V)/5 + (Ni+Cu)/15 (IIW) and CET = C + (Mn+Mo)/10 + (Cr+Cu)/20 + Ni/40. With the plate thickness d, the hydrogen HD and the heat input Q, EN 1011-2 method B gives a minimum preheat Tp.
Calculation
Example calculated with the tool’s default values.
Inputs
- C (carbon)
- 0.16%
- Mn (manganese)
- 1.4%
- Cr (chromium)
- 0.05%
- Mo (molybdenum)
- 0%
- V (vanadium)
- 0%
- Ni (nickel)
- 0.1%
- Cu (copper)
- 0.1%
- Si (silicon, range check)
- 0.3%
- Joint
- Butt
- Thickest plate
- 15 mm
- Diffusible hydrogen in weld metal
- 5
- Heat input Q
- 1 kJ/mm
- Base metal yield strength
- 355
Results
- Carbon equivalent CE (IIW)
- 0.417
Worked example
Every value in this section belongs to the example, calculated with the tool’s default values.
Other results of the example
- CET (EN 1011-2)
- 0.310
- Indicative preheat Tp
- 46 °Cmethod B, minimum
- Plate thickness d
- 15 mm
- Indicative values: they do not replace the qualified WPS or the table of the applicable code (AWS D1.1, ASME B31.3, EN 1011-2 method A…).
- EN 1011-2 method B: minimum temperature against hydrogen cold cracking of plain and low-alloy steels; it does not apply to stainless, aluminium or cast iron.
- Measure the temperature at 4 t or 75 mm from the joint and keep it through the whole joint; for unequal thicknesses the thicker plate governs. Single-run fillet: the method gives up to 60 °C too much.
- The base metal CET must exceed that of the weld metal by at least 0.03 %; otherwise start from the weld metal CET + 0.03 %.
Step-by-step calculation
IIW carbon equivalent
CE = C + Mn/6 + (Cr+Mo+V)/5 + (Ni+Cu)/15
0.160 + 1.400/6 + (0.050+0.000+0.000)/5 + (0.100+0.100)/15 = 0.417
CET (EN 1011-2, eq. C.2)
CET = C + (Mn+Mo)/10 + (Cr+Cu)/20 + Ni/40
0.160 + (1.400+0.000)/10 + (0.050+0.100)/20 + 0.100/40 = 0.310
Plate thickness (method B)
d = t (thickest part)
15.0 mm
Preheat (EN 1011-2, eq. C.8)
Tp = 697·CET + 160·tanh(d/35) + 62·HD^0.35 + (53·CET − 32)·Q − 328
697 × 0.310 + 160 × tanh(0.429) + 62 × 5.0^0.35 + (53 × 0.310 − 32) × 1.00 − 328 = 46.1 °C
How to use it
- Enter the steel composition in %: C, Mn, Cr, Mo, V, Ni, Cu, and Si for the range check.
- Pick the joint (butt, T or fillet) and enter the thickest plate, or enter the plate thickness d directly.
- Enter the diffusible hydrogen in weld metal (ml/100 g) and the heat input Q in kJ/mm.
- Enter the base metal yield strength if needed, for the range check.
- Read the carbon equivalent CE (IIW).
Frequently asked questions
What is the carbon equivalent formula for welding?
The IIW carbon equivalent is CE = C + Mn/6 + (Cr+Mo+V)/5 + (Ni+Cu)/15, with contents in mass %. The EN 1011-2 CET (annex C, eq. C.2) is CET = C + (Mn+Mo)/10 + (Cr+Cu)/20 + Ni/40: it is the one used for the method B preheat calculation.
How do I calculate the carbon equivalent of a steel?
Example with C 0.16 %, Mn 1.4 %, Cr 0.05 %, Ni 0.1 % and Cu 0.1 %: CE = 0.160 + 1.400/6 + (0.050+0.000+0.000)/5 + (0.100+0.100)/15 = 0.417, and CET = 0.160 + (1.400+0.000)/10 + (0.050+0.100)/20 + 0.100/40 = 0.310.
How is the preheat temperature calculated to EN 1011-2?
Method B (annex C.3, eq. C.8) gives Tp = 697·CET + 160·tanh(d/35) + 62·HD^0.35 + (53·CET − 32)·Q − 328, with d the plate thickness in mm (that of the thickest part, not the method A combined thickness), HD the diffusible hydrogen in ml/100 g and Q the heat input in kJ/mm. With a CET of 0.310, two 15 mm plates butt welded (d = 15 mm), HD = 5 and Q = 1.0 kJ/mm, the result is Tp = 46.1 °C.
What is the validity range of method B?
The calculation flags a result as out of range if the CET is outside 0.20 to 0.50 %, the plate thickness outside 10 to 90 mm, the hydrogen outside 1 to 20 ml/100 g, the heat input outside 0.5 to 4.0 kJ/mm, if the yield strength exceeds 1000 N/mm², or if a content is outside its limits (for example C 0.05 to 0.32 %, Mn 0.5 to 1.9 %).
Does the carbon equivalent tell me if a steel is weldable?
The calculation gives no weldability rating. It uses the CET for a minimum temperature against hydrogen cold cracking, valid for plain and low-alloy steels, not for stainless, aluminium or cast iron. The CE (IIW) feeds method A (charts) of EN 1011-2, which the calculation does not cover.
Limits
Indicative results: they replace neither the qualified WPS nor the table of the applicable code (AWS D1.1, ASME B31.3, EN 1011-2 method A). Only EN 1011-2 method B is calculated, from public sources quoting the standard. Measure the temperature at 4 t or 75 mm from the joint; on a single-run fillet, the method gives up to 60 °C too much. The base metal CET must exceed that of the weld metal by at least 0.03 %.
Sources
- EN 1011-2:2001+A1:2003 Soudage : recommandations, soudage à l’arc des aciers ferritiques : Annexe C.3, méthode B : éq. C.2 (CET) et C.8 (Tp), domaine de validité (link)
- BS EN 1011-2:2001+A1:2003 (texte intégral) : méthode B, d = épaisseur de tôle : § 16 b, § C.3.2.2 éq. C.4, § C.3.3 éq. C.8 (link)
- CE (IIW) : IIW Doc IX-535-67, repris par EN 10025 et API 5L ; CET : EN 1011-2 annexe C : Formules de carbone équivalent (link)
- Limites de composition de la méthode B (C 0,05–0,32 ; Mn 0,5–1,9 …) : ISO/TR 17671-2 / EN 1011-2 annexe C.3 (link)