SMAW vs GMAW — Process Comparison for Structural Welding
SMAW (stick welding) uses flux-coated electrodes and deposits 1 to 5 lbs/hr. GMAW (MIG) uses continuous solid wire with external shielding gas and deposits 5 to 12 lbs/hr. Both are prequalified under D1.1:2025 Table 5.1. The process choice changes your preheat category, equipment requirements, and wind tolerance.
Side-by-Side Comparison
| Property | SMAW (Stick) | GMAW (MIG) |
|---|---|---|
| AWS process designation | SMAW | GMAW |
| Deposition rate | 1–5 lbs/hr | 5–12 lbs/hr |
| Filler metal form | Flux-coated stick electrodes | Continuous solid wire |
| Shielding method | Flux coating decomposition | External gas (Ar/CO₂ mix) |
| Common classifications | E7018, E6010, E6013 | ER70S-6, ER70S-3 |
| D1.1 preheat category | A (non-LH) or B (LH like E7018) | B (inherently low hydrogen) |
| D1.1 prequalified? | Yes (Table 5.1) | Yes, except short-circuit (Table 5.1) |
| All-position capable | Yes (with correct electrode) | Yes (spray limited to flat/horizontal) |
| Wind tolerance | Good — flux provides shielding | Poor — gas disperses above 5 mph |
| Equipment cost | Lower — simpler power source | Higher — wire feeder + gas system |
| Operator skill ceiling | Higher — electrode manipulation | Lower — faster to learn |
| Duty cycle | Low — electrode changes | High — continuous wire feed |
How Each Process Works
SMAW (Shielded Metal Arc Welding) uses a consumable electrode coated with flux. An arc forms between the electrode tip and the workpiece, melting both the electrode core wire and the base metal. The flux coating decomposes to produce shielding gas and slag that protects the molten weld pool from atmospheric contamination.
After each electrode is consumed (typically 12 to 18 inches of electrode per stick), the welder replaces it. This start-stop cycle limits deposition rate to typically 1 to 5 lbs/hr and reduces duty cycle.
GMAW (Gas Metal Arc Welding) feeds a continuous solid wire electrode through a welding gun. An external shielding gas (typically 75% Ar / 25% CO₂ for structural steel, or 100% CO₂) flows through the gun nozzle to protect the weld pool. Because the wire feeds continuously, the welder does not stop to change electrodes, resulting in deposition rates of 5 to 12 lbs/hr — a 3 to 5x productivity advantage over SMAW that directly reduces labor cost per joint.
Hydrogen Control and Preheat Impact
D1.1:2025 Table 5.11 assigns preheat categories based on hydrogen risk. GMAW inherently deposits low hydrogen because the solid wire contains no flux compounds that introduce hydrogen. All GMAW welding falls under Category B (low hydrogen processes).
SMAW preheat category depends on the electrode classification. Low-hydrogen electrodes like E7018 fall under Category B. Non-low-hydrogen electrodes like E6010 and E6013 fall under Category A, which requires higher preheat temperatures above 3/4 inch thickness. This means GMAW always matches or beats SMAW on preheat requirements.
For A36 steel at 1 inch thickness: GMAW requires 50°F preheat (Category B). SMAW with E7018 also requires 50°F (Category B). But SMAW with E6013 requires 150°F (Category A). The process and electrode combination together determine your preheat.
When to Use SMAW
Outdoor and field welding: SMAW excels where wind makes gas-shielded processes impractical. The flux coating provides its own shielding, so SMAW works in wind, rain, and remote locations without gas cylinders. Pipeline welding, structural erection, and field repairs are traditional SMAW applications.
All-position work on heavier plate: SMAW with E7018 runs well in all positions on thick material. Vertical-up and overhead welding with E7018 produces consistent, code-compliant welds. GMAW spray transfer is limited to flat and horizontal positions; short-circuit transfer works in all positions but is not prequalified under D1.1.
Equipment portability: SMAW requires only a power source and electrode holder. No wire feeder, no gas cylinder, no gas lines. For field work where equipment must be carried to the joint, SMAW is lighter and simpler.
Dirty or rusty material: E6010 and E6011 electrodes are designed to penetrate through mill scale, rust, and contamination. GMAW is more sensitive to surface conditions and requires cleaner base metal preparation.
When to Use GMAW
High-volume shop fabrication: GMAW deposition rates of 5 to 12 lbs/hr versus 1 to 5 lbs/hr for SMAW translate directly into faster completion times. On a 100-joint project with 3/8 inch fillet welds, GMAW can cut welding time by 50% to 70%. The continuous wire feed eliminates electrode change downtime.
Consistent quality on repetitive joints: GMAW produces uniform weld profiles with less operator-dependent variation. Wire feed speed and voltage settings produce repeatable results. For production welding where consistency matters, GMAW provides tighter quality control with lower rejection rates.
Lower-skill operators: GMAW has a shorter learning curve than SMAW. The continuous wire feed and visible arc make it easier to teach, especially for flat and horizontal fillet welds that constitute most shop production.
Thin material: GMAW short-circuit transfer (GMAW-S) provides precise heat input control on thin material, reducing burn-through risk. Note that GMAW-S requires Clause 6 qualification under D1.1 because it is not prequalified.
Frequently Asked Questions
Weld strength depends on the filler metal classification, not the process. ER70S-6 (GMAW) and E7018 (SMAW) both provide 70 ksi minimum tensile strength. Both produce welds that meet D1.1 acceptance criteria when applied per a qualified or prequalified WPS. The process affects deposition rate, hydrogen content, and operator skill requirements, not the final weld strength.
Yes, for most structural applications. Both SMAW and GMAW are prequalified under D1.1 Table 5.1. GMAW provides higher deposition rates (5-12 lbs/hr vs 1-5 lbs/hr), inherently low hydrogen deposits, and lower preheat requirements (Category B). However, GMAW requires wind protection because the external shielding gas disperses in wind above 5 mph, making SMAW the better choice for outdoor field welding.
Both SMAW and GMAW are prequalified under D1.1:2025 Table 5.1 for structural steel welding. SMAW is prequalified with all electrode classifications listed in Table 5.7. GMAW is prequalified except for short-circuit transfer mode (GMAW-S), which requires qualification by testing per Clause 6. Spray transfer and globular transfer GMAW are prequalified.
FCAW (flux-cored arc welding) combines advantages of both processes. FCAW-G (gas-shielded) provides high deposition rates similar to GMAW with better out-of-position performance. FCAW-S (self-shielded) eliminates the external gas requirement, making it suitable for outdoor and windy conditions. Both FCAW variants are prequalified under D1.1 Table 5.1. E71T-1 (FCAW-G) and E71T-8 (FCAW-S) are among the most common structural welding consumables.