Inputs
How it is calculated
- Arc energy E = U · I · 60 / (v · 1000), in kJ/mm, with v in mm/min. Effective heat input Q = k · E.
- Thermal efficiency k (EN 1011-1, after TWI and SSAB): SAW 1.0; MMA, MAG, MIG and flux-cored 0.8; TIG and plasma 0.6. The Dillinger tool uses different values for MIG (0.7), flux-cored (0.9) and TIG (0.7): you can change k at any time.
- t8/5 in 3D: (6700 − 5·T₀) · Q · (1/(500−T₀) − 1/(800−T₀)) · F₃. In 2D: (4300 − 4.3·T₀) · 10⁵ · Q²/d² · (1/(500−T₀)² − 1/(800−T₀)²) · F₂. The valid one is the larger of the two (EN 1011-2, annex D, after Dillinger).
- The geometry factors F₂ and F₃ are those in the table published by Dillinger. For fillets, F₂ varies with the Q/d ratio; here the 2D-end value is used (0.9 for corner, 0.45 for T), and in 3D flow F₃ counts.
- The 10–25 s window is the one Dillinger gives for the filling and covering layers of fine-grain steels; other steels and qualified procedures may require other values, which is why the limits are editable.
An informative tool, not a WPS. A welding procedure is specified, qualified and approved according to the standards in force, by competent personnel. The calculations here are engineering estimates made with published formulas; they do not replace the manufacturer data sheet, the material certificate, the qualified procedure or the design check.
Frequently asked questions
What is t8/5?
The time in which the weld and the heat-affected zone cool from 800 °C to 500 °C. A short t8/5 means fast cooling and hard structures, with a risk of cold cracking; a long one means coarse structures, with lower strength and toughness.
Why are there two values, 2D and 3D?
In thin plates the heat flows through the thickness (2D), in thick ones it spreads in all directions (3D). The valid result is the larger one; at the transition thickness the two coincide.
How accurate is it?
The formulas are those of EN 1011-2, published by Dillinger, who warn that results can differ from the real ones by up to 10 %. My calculations match an independent calculation of the same formulas; they do not replace temperature measurement.
Sources and method
The formulas, tables and verification examples come from public sources, listed below. The standards themselves are paid documents and are not reproduced: I cite the formulas and values published by these sources and, where sources differ, I say so.
- Dillinger: Help welding calculation (CET, CE, CEN, Pcm, EN 1011-2 method B, t8/5, F2 and F3 factors)
- TWI: Heat input versus arc energy
- SSAB: Welding heat input