Minimum Weld Preheat (CET Method)
The minimum preheat to keep hydrogen cracking out of a carbon or low-alloy steel weld, from the chemistry.
Example
You enter
- Carbon C (wt %) 0.18
- Manganese Mn (wt %) 1.4
- Molybdenum Mo (wt %) 0
- Chromium Cr (wt %) 0
- Copper Cu (wt %) 0.2
- Nickel Ni (wt %) 0.1
- Plate thickness (in) 1.25
- Diffusible hydrogen (ml/100 g; 5 low-hydrogen SMAW, 3 GMAW) 5
- Arc energy (kJ/in) 40
- Arc efficiency (EN 1011-1: 0.8 SMAW/GMAW, 0.6 GTAW, 1.0 SAW) 0.8
You get
- CET 0.332%
- Preheat c 109.7
No published worked example is on file for this calculation. It is checked against a hand-worked derivation of its method and an independent reference test.
Details, formula, and sources
ScopePlate thickness, consumable hydrogen, and heat input: CET = C + (Mn + Mo)/10 + (Cr + Cu)/20 + Ni/40, then Tp = 697 CET + 160 tanh(d/35) + 62 HD^0.35 + (53 CET - 32) Q - 328 (degC, the EN 1011-2 Method B equation as the steel maker Dillinger publishes it). A 0.18 C, 1.4 Mn plate 1-1/4 in thick welded at 40 kJ/in with low-hydrogen SMAW needs about 229 F. More heat input lowers it; wetter rod raises it. The European method; the WPS governs.
Formula or tableCET = C + (Mn + Mo)/10 + (Cr + Cu)/20 + Ni/40; d = t x 25.4 mm; Q = arc energy x efficiency / 25.4 kJ/mm; Tp = 697 CET + 160 tanh(d/35) + 62 HD^0.35 + (53 CET - 32) Q - 328 degC; valid CET 0.20-0.50, d 10-90 mm, HD 1-20 ml/100 g, Q 0.5-4.0 kJ/mm.
Source and editionEN 1011-2:2001 Annex C, Method B (the CET method of Uwer and Hohne), by name, as published by AG der Dillinger Huttenwerke in its welding e-service.
Free accessThe CET and preheat equations and their validity ranges are published free by Dillinger (service.dillinger.de, e-service welding help); the chemistry, thickness, hydrogen, and heat input are the user's inputs.
What governsEstimate. AHJ and licensed professional govern.
API field namesc, mn, mo, cr, cu, ni, thickness_in, hydrogen_ml_100g, arc_energy_kj_in, arc_efficiency, cet, preheat_c
- CET C + (Mn + Mo)/10 + (Cr + Cu)/20 + Ni/40, weight percentEN 1011-2 Annex C; Dillinger
- Preheat equation Tp = 697 CET + 160 tanh(d/35) + 62 HD^0.35 + (53 CET - 32) Q - 328 degCEN 1011-2 Annex C Method B; Dillinger
- Heat input Q = arc energy x efficiency, EN 1011-1 efficienciesEN 1011-1