Welding-metallurgy engine for welding engineers and IWE/IWTs: arc energy and heat input with process efficiency, transition thickness between 2D and 3D heat flow, t8/5 cooling time per EN 1011-2 Annex D with seam shape factors, carbon equivalents (CE-IIW, CET, Pcm), and preheat temperature per EN 1011-2 Method B from CET, combined thickness, hydrogen scale and heat input. Every report with the full audit trail.
SectorCalc SC-029 evaluates welding thermal cycles per EN 1011-2: heat input from arc parameters and process efficiency, the transition thickness that decides between two- and three-dimensional heat flow, t8/5 cooling time with seam shape factors, carbon equivalents, and the Method B preheat temperature. The t8/5 result is checked against an acceptance band because both extremes are dangerous — too fast means hard, crack-sensitive HAZ; too slow destroys toughness, especially in TMCP steels. Computed cooling times carry the standard's own ~10 % model tolerance; in critical applications, verify by measurement.
Arc energy E counts every joule the arc draws; heat input Q counts only what enters the plate. EN 1011 and most WPS forms want Q. Heat input is the single most lied-about number in fabrication — measure travel speed with a stopwatch, never trust the program value on a robot without verification.
Thick plates sink heat in three dimensions — thickness stops mattering. Thin plates conduct only in-plane — t8/5 explodes with Q²/d². The transition thickness dt tells you which regime you are in; near it, the standard's error is largest and measurement is recommended.
t8/5 is the HAZ's thermal signature: it sets hardness, microstructure and toughness. Shape factors F2/F3 (EN 1011-2 Table D.1) correct for joint geometry — a fillet weld on a T-joint sinks heat into three plates, not one. Acceptance bands come from the steel maker or WPS qualification, not from this tool.
CE(IIW) suits conventional C-Mn steels; CET is the basis of Method B preheat and behaves better for low-C TMCP grades; Pcm targets modern low-carbon HSLA. Report all three — auditors and steel makers each have their favourite.
Method B balances the four hydrogen-crack drivers: hardenability (CET), restraint (combined thickness), diffusible hydrogen (HD scale) and heat input (Q lowers the need). A computed Tp below 20 °C means no preheat; the result is the temperature AT the weld, measured on the opposite face for thick sections, and maintained through the joint plus tack welds.
Lower heat input: raise travel speed first (cheap), then reduce current/voltage. If the band cannot be met, the joint design or process must change — do not simply weld colder and accept lack of fusion.
The 800→500 °C interval sits closer to a preheated plate's temperature, so the thermal gradient driving cooling is smaller. Preheat simultaneously slows cooling (good against hydrogen cracks) and softens the HAZ (bad for some TMCP grades) — hence acceptance BANDS, not just minimums.
EN 1011-2 itself states ~10 % under fulfilled assumptions, worse near the 2D/3D transition and for surface heat loss on thin sheet. For qualification-critical work, measure with a plunged thermocouple.
No — the (6700−5T₀) and (4300−4.3T₀) coefficients are fitted to unalloyed and low-alloy steels. Austenitic stainless conducts heat ~3× slower; use the same regime logic with material-specific models (or FEM) and interpass limits of 100–150 °C instead.
