Preheat temperature calculator
Pick a material and plate thickness to get the minimum preheat temperature. Carbon and low-alloy steels are calculated with EN 1011-2 Annex C method B using the CET carbon equivalent, hydrogen level and heat input; outside its validity limits the Seferian method is used. Stainless steels and aluminium show established guide values.
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What it calculates
- Minimum preheat Tp in °C, and a table of preheat against thickness
- Carbon equivalents CE(IIW), CET and Pcm from the chemical composition
- Built-in typical analyses for S235JR to S960QL, Hardox 400–600, Strenx 700–1100, P265GH, 16Mo3, 13CrMo4-5, C45, 42CrMo4, 4340, stainless grades and EN AW aluminium alloys
- Your own composition from a 3.1 material certificate
Formulas
CE(IIW) = C + Mn/6 + (Cr+Mo+V)/5 + (Ni+Cu)/15 CET = C + (Mn+Mo)/10 + (Cr+Cu)/20 + Ni/40 Pcm = C + Si/30 + (Mn+Cu+Cr)/20 + Ni/60 + Mo/15 + V/10 + 5B EN 1011-2 Annex C, method B: Tp [°C] = 697·CET + 160·tanh(d/35) + 62·HD^0.35 + (53·CET − 32)·Q − 328 [d in mm, HD in ml/100 g, Q in kJ/mm] Seferian (outside method B limits): Ceq = (360C + 40(Mn+Cr) + 20Ni + 28Mo)/360 · (1 + 0.005·d) Tp [°C] = 350 · √(Ceq − 0.25)
Worked example
S355J2 at 25 mm plate thickness with low-hydrogen consumables needs a preheat of roughly 85–90 °C by method B; the same steel at 10 mm needs about 35 °C.
How to use it
- Create a free account with Google or e-mail.
- Open the calculator and enter your values; units can be metric or imperial.
- Read the result with its formula and source, and export to PDF, DXF or CSV where available.
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Frequently asked questions
When is EN 1011-2 method B valid?
For CET 0.20–0.50, plate thickness 10–90 mm, hydrogen 1–20 ml/100 g, heat input 0.5–4.0 kJ/mm and carbon 0.05–0.32 %. Outside these limits BenchMaths falls back to Seferian and says so.
Does a higher heat input reduce the preheat?
Yes. In method B the term (53·CET − 32)·Q is negative for usual steels, so more heat input lowers the required preheat.
Can I enter my own chemical composition?
Yes. Choose ‘Custom steel’ and enter C, Mn, Si, Cr, Mo, V, Ni, Cu and B from your material certificate.
Guides
- How to weld Hardox wear plateHardox is a quenched and tempered wear-resistant steel.
- S355 preheat temperature by thicknessS355 needs no preheat in thin plate, but from around 10–15 mm upwards a minimum preheat is required to avoid hydrogen cracking.
- When to use 309L filler metal309L is the standard filler metal for joining carbon or low-alloy steel to austenitic stainless steel such as 304L or 316L.
- Carbon equivalent: CE, CET and PcmA carbon equivalent turns a steel's chemical analysis into a single number that indicates how hard the heat-affected zone gets and how sensitive it is to hydrogen cracking.
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Results are engineering estimates for planning. They do not replace the applicable standard, a qualified procedure or a check by a qualified engineer.