Heat Input / Arc Energy

Calculates arc energy (nominal heat input) and, optionally, net/effective heat input for an arc welding pass from voltage, current, and travel speed.

Engineering calculator — results require technical review before production use.

Voltage (V)

Current (A)

Travel speed (mm/min)

Net travel speed along the weld joint. Used when speed is provided directly (speed.mode: "direct").

Run-out length (mm)

Length of weld deposited per electrode (SMAW / process 111). Used together with burn-off time to derive travel speed (speed.mode: "runOutLength") instead of measuring it directly.

Burn-off time (s)

Arc time to consume one electrode (SMAW / process 111). Used together with run-out length to derive travel speed.

Thermal efficiency factor (k)

Optional process efficiency factor. Allowed: left blank (undefined/null), or a value with 0 < k <= 1 — 0 and values above 1 are rejected. When provided, net/effective heat input (k x Q) is also computed; when omitted, only the arc energy / nominal heat input (Q) is reported. Typical values: SMAW/GMAW/FCAW ≈ 0.8, SAW ≈ 1.0, GTAW ≈ 0.6 — confirm against the applicable WPS/code.

Source & assumptions

IWE Module 2 – Materials and Their Behavior during Welding, Chapter 5, Section 2 (Heat Input)

Assumptions

Arc Energy / Nominal Heat Input: Q (kJ/mm) = (U x I) / (v x 1000), where U is arc voltage (V), I is welding current (A), and v is travel speed in mm/s.
Net/effective heat input = k x Q, where k is a process-dependent thermal efficiency factor. This is only calculated when an efficiency factor is supplied (0 < k <= 1); otherwise only Q (nominal heat input) is reported.
For SMAW (process 111), travel speed can alternatively be derived as run-out length / burn-off time (speed.mode: "runOutLength") instead of measuring travel speed directly.
Voltage and current are steady, representative values for the pass (not instantaneous/oscillating values from pulsed or AC waveforms).
This formula, as given in IWE Module 2, Ch. 5.2, applies to steel; it is not directly applicable to aluminium and other high-thermal-conductivity alloys without further correction.