Arc and beam (laser/EBW) welding heat input, in SI units. Pick a process (and, for laser, a material) to load a suggested efficiency, then use it as-is or overwrite it with your own value.
Arc efficiencies are typical values consistent with AWS-style process references (process-dependent, not material-dependent). Laser efficiencies represent typical stable keyhole-mode absorption for a fiber/Nd:YAG (~1 μm) source and vary meaningfully with surface condition, power density, and shielding. EBW efficiency is largely material-independent since it's a charged-particle beam, not a reflectivity-driven process.
Heat input is the energy delivered per unit length of weld. It sets the cooling rate, which controls HAZ hardness, toughness, distortion, and hydrogen-cracking risk.
With η = 1.0, as ASME calculates it: 1.06 kJ/mm.
ASME Section IX (QW-409.1) and AWS D1.1 calculate heat input as V × I × 60 / travel speed, with no efficiency factor. EN 1011-1 calls that value arc energy and multiplies it by a thermal efficiency factor to get heat input.
To match an ASME value, set η to 1.0. For waveform-controlled power sources such as pulsed GMAW, ASME requires instantaneous energy or power instead of average volts × amps.
| Process | Efficiency |
|---|---|
| SAW | 0.95 |
| FCAW | 0.85 |
| SMAW, GMAW | 0.80 |
| GTAW, PAW (DCEN) | 0.65 |
| GTAW (AC) | 0.55 |
| Electron beam | 0.90 |
| Laser, 1 µm keyhole | 0.45 (Cu) to 0.85 (steel) |
Laser efficiency depends on the material because absorption depends on reflectivity. Treat all values as starting points.
Too little heat input cools the weld fast, which raises HAZ hardness and hydrogen-cracking risk in hardenable steels and leaves too little austenite in duplex stainless. Too much coarsens grains and lowers toughness, sensitizes austenitic stainless, softens heat-treatable aluminum, and increases distortion. That's why ASME IX treats an increase in heat input as a supplementary essential variable when toughness is required.
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