What Are Welding Transfer Modes?
In GMAW (MIG welding), the way molten metal moves from the Elettrodo wire to the Saldatura pool is called the transfer mode. The mode depends on welding current, Tensione, shielding gas composition, and electrode diameter. Each mode produces different penetration profiles, Spruzzi levels, and positional capabilities.
D1.1:2025 treats transfer modes as distinct processes with different prequalification status. Understanding which modes D1.1 permits under prequalified WPSs and which require qualification Prova per Clause 6 is essential for fabrication shops writing procedures.
The four modes, from lowest to highest energy, are: short circuit, globular, spray, and pulsed spray.
Short Circuit Transfer (GMAW-S)
In short circuit transfer, the electrode wire physically touches the weld pool and short-circuits, transferring metal through repeated contact rather than across the arc. This happens at a rate of 50 to 200 times per second per AWS A5.18 A6.4. The process uses small diameter electrodes (0.030 to 0.045 in) at low voltage and Amperaggio.
Short circuit transfer produces the lowest heat input of any GMAW mode. This makes it suitable for thin material, root passes, and all-position welding including vertical and overhead. The low energy also means lower penetration, which creates a risk of incomplete fusion on thicker sections.
D1.1 prequalification status: GMAW-S is not prequalified. Clause 5.5.1 explicitly lists prequalified processes as "SMAW, SAW, GMAW (except GMAW-S), and FCAW." To use GMAW-S under D1.1, you must qualify the WPS by testing per Clause 6. D1.1 treats GMAW-S as a separate process per Table 6.6.
As an alternative to in-house qualification, you may adopt an AWS Norma Specifica di Procedura di Saldatura (SWPS) from the B2.1 series per Clause 6.2.1.2.
Spray Transfer
Spray transfer produces a directed stream of fine molten droplets, approximately 250 per second per AWS A5.18 A6.2.2, that cross the arc without short-circuiting. This mode activates above a critical transition current that depends on electrode diameter, composition, and shielding gas. For 1/16 in (1.6 mm) carbon steel electrodes, the transition current is approximately 270 amperes.
Spray transfer delivers high deposition rates, excellent fusion, minimal spatter, and a smooth bead profile. The high Apporto Termico produces deep penetration.
Position limitation: Spray transfer is limited to flat (1G/1F) and horizontal (2G/2F) positions in practice. The high heat input creates a large, fluid weld pool that cannot be controlled against gravity. D1.1 Clause 10 excludes spray transfer from prequalified tubular joint details.
Typical Spray Transition Currents
Values are approximate and vary by electrode composition, surface condition, and contact tip-to-work distance. Consult your electrode manufacturer's data sheet for exact values.
| Wire Diameter | Shielding Gas | Transition Current (A) |
|---|---|---|
| 0.023 in (0.6 mm) | 98% Ar / 2% O2 | ~135 |
| 0.030 in (0.8 mm) | 98% Ar / 2% O2 | ~150 |
| 0.035 in (0.9 mm) | 98% Ar / 2% O2 | ~165 |
| 0.035 in (0.9 mm) | 95% Ar / 5% O2 | ~155 |
| 0.035 in (0.9 mm) | 85% Ar / 15% CO2 | ~180 |
| 0.035 in (0.9 mm) | 80% Ar / 20% CO2 | ~195 |
| 0.045 in (1.1 mm) | 98% Ar / 2% O2 | ~220 |
| 0.045 in (1.1 mm) | 85% Ar / 15% CO2 | ~240 |
| 0.045 in (1.1 mm) | 80% Ar / 20% CO2 | ~255 |
| 0.062 in (1.6 mm) | 98% Ar / 2% O2 | ~270 |
| 0.062 in (1.6 mm) | 80% Ar / 20% CO2 | ~345 |
Source: AWS A5.18 A6.2.2 (270 A anchor for 1/16 in wire) and electrode manufacturer data.
The D1.1 Prequalification Trap
This is the most common D1.1 audit finding related to GMAW: a shop writes "GMAW" on their prequalified WPS without specifying the transfer mode, then uses spray transfer in flat position and short circuit in vertical. Under D1.1, that is two separate processes.
D1.1 Clause 5 commentary is explicit: "if the Processo di Saldatura on the prequalified WPS is GMAW with variables that Risultato in spray transfer, it would not be acceptable to add to the prequalified WPS variables that would result in short circuit transfer." The short circuit portion requires its own WPS qualified by testing per Clause 6.
The practical consequence: a fabrication shop that uses spray transfer in flat and horizontal, and switches to short circuit for vertical and overhead, needs two separate WPSs. The spray WPS can be prequalified per Clause 5. The short circuit WPS must be qualified by testing per Clause 6, or adopted from an AWS SWPS per Clause 6.2.1.2.
D1.1 also requires constant voltage (CV) power supplies for prequalified GMAW and FCAW per Clause 5.5.4.
Globular Transfer
Globular transfer occurs at current levels between short circuit and spray, typically with 100% CO2 shielding gas per AWS A5.18 A6.3. Large, irregularly shaped droplets, larger than the electrode diameter, detach from the wire tip and transfer under gravity. Electrodes of 0.045 to 1/16 in diameter are normally used at 275 to 400 amperes.
Globular transfer produces the most spatter of any GMAW mode and is limited to flat and horizontal positions because the large droplets are difficult to control against gravity. With a buried arc technique (low voltage, arc submerged in the weld pool), spatter can be reduced significantly.
Globular transfer is rarely specified intentionally on a WPS. It typically occurs as a transitional state when parameters are set between short circuit and spray ranges, or when using 100% CO2 shielding. Stainless steel electrodes are generally not used in this mode because the high CO2 content can degrade corrosion resistance.
Pulsed Spray Transfer
In pulsed spray transfer, the power source cycles between a high peak current (where spray transfer occurs) and a low background current (where the arc is maintained but no metal transfers). This cycle occurs at 60 to 120 pulses per second per AWS A5.18 A6.2.3. Each peak pulse detaches one droplet from the electrode in spray mode, while the background current allows the weld pool to partially solidify.
The result is spray-quality welds in all positions, including vertical and overhead. Pulsed spray combines the deposition efficiency and bead quality of spray transfer with the positional flexibility of short circuit.
D1.1 prequalification: D1.1 does not explicitly exclude pulsed spray (GMAW-P) from prequalification the way it excludes GMAW-S. However, pulsed spray uses waveform-controlled power sources per Clause C-6.8.5.1, which require different heat input calculations using Clause 6.8.5.1 equations 2 and 3 instead of the conventional equation 1. Since Clause 5.5.4 requires CV power supplies for prequalified GMAW, and pulsed machines operate differently from conventional CV sources, the prequalification pathway has practical barriers. Consult the Engineer for your specific application.
Position Limitations by Transfer Mode
| Transfer Mode | Positions | D1.1 Prequalified? | Typical Use |
|---|---|---|---|
| Short Circuit (GMAW-S) | All positions | No — requires Clause 6 qualification | Thin material, root passes, out-of-position |
| Globular | Flat, horizontal | Generally avoided; 100% CO2 | Thick sections, deep penetration (buried arc) |
| Spray | Flat, horizontal | Yes — prequalified per Clause 5 | High deposition, structural flat/horizontal |
| Pulsed Spray (GMAW-P) | All positions | Practical barriers (CV requirement per Cl. 5.5.4) | All-position spray quality |