Pulsed GMAW is the modern standard for high-quality, all-position structural welding. The pulse waveform produces spray-like droplet detachment at a lower average current, which extends spray transfer to vertical and overhead positions and reduces heat input for thinner sections.
Documenting pulsed GMAW on a WPS is more involved than documenting spray, because the pulse waveform itself is the procedure. Here is how to do it cleanly.
Why "set amps and volts" isn't enough
A spray-transfer WPS specifies average amperage and average voltage and that's effectively the procedure. The arc behaves the same way every time at those settings.
A pulsed WPS does NOT work that way. The same average current can be produced by infinitely many different pulse waveforms — and the waveforms produce different weld characteristics. A 250 A average at 200 Hz with 25% duty cycle behaves very differently from 250 A average at 100 Hz with 50% duty cycle.
The WPS has to identify the waveform.
What goes on a pulsed GMAW WPS
The electrical block expands:
Electrical characteristics:
Current: DC
Polarity: DCEP
Transfer mode: PULSED
Power supply: Lincoln PowerWave R450 (or equivalent)
Synergic program: Pulse-GMAW-StSt-MMW-9
Software version: 5.40 or later
Peak current: 380 A ± 10 A
Background current: 80 A ± 10 A
Frequency: 150 Hz ± 20 Hz
Duty cycle: 35% ± 5%
Average amperage range: 220–280 A
Average voltage range: 22–26 V
Wire feed speed range: 200–280 IPM
The synergic program identification is the single most important addition. Most modern pulsed power supplies have a program library — each program is a tuned waveform for a specific wire, gas, and application. The program name (and version) pins the waveform.
If your power supply doesn't use synergic programs (manual pulse setup), document the individual pulse parameters in full.
Filler and gas
Pulsed GMAW is a transfer mode, not a filler type. Use any matched-classification wire:
- Carbon steel: A5.18 E70S-3 or E70S-6
- Low-alloy: A5.28 E80S-X variants
- Stainless: A5.9 ER308L, ER316L, etc. (note: under D1.6, not D1.1)
- Aluminum: A5.10 ER4043, ER5356 (note: under D1.2, not D1.1)
Gas blends for pulsed carbon-steel work:
- 90% Ar / 10% CO2
- 85% Ar / 15% CO2
- 80% Ar / 20% CO2 (C20)
- Pure Argon is NOT used for carbon-steel pulsed GMAW (causes erratic transfer)
Position capability
Pulsed GMAW's strength: all positions, including vertical-up. The pulse modulation prevents the puddle from sagging that limits standard spray transfer to flat and horizontal.
The supporting PQR must qualify the positions claimed. A 1G PQR doesn't authorize 3G or 4G production WPSs without supplementary qualification.
Common pitfalls
- WPS says "GMAW spray" but the power supply is set to pulse program. Mismatch between WPS and reality.
- No synergic program identification. The auditor can't verify the waveform.
- Software version omitted. Some manufacturers tweak waveforms between firmware releases.
- Position claimed without PQR coverage. "3G pulsed" without supporting PQR data is unqualified.
- Pure Argon listed for carbon-steel pulsed. Wrong gas; arc won't behave.
CVN considerations
Pulsed GMAW typically produces lower heat input than spray for the same average current, which helps toughness. For AISC 341 demand-critical work, pulsed is often the preferred transfer mode. The supporting PQR must include CVN data per Table 6.8, and the WPS must invoke supplementary essentials.
The audit reality
Pulsed GMAW WPSs are often the cleanest in a shop because the engineering effort to set them up is high — by the time you have a working pulsed procedure, you've already worked through the waveform documentation. The trap is the implicit pulsed WPS: a procedure that's been pulsed all along on the floor but documented as "GMAW" in the QC binder.
A rule engine that requires transfer-mode declaration on every GMAW WPS prevents this.