1. Shielded Metal Arc Welding (SMAW) – Most Widely Used
Principle: Uses a coated electrode to create an arc between the electrode and workpiece; the coating melts to form slag and shielding gas, protecting the weld pool from air contamination.
Advantages: Simple equipment, flexible operation, suitable for on-site welding (e.g., outdoor signs, guardrails, steel structures). Works for all thicknesses (from thin plates to heavy sections).
Key Notes: Choose low-hydrogen electrodes (e.g., E7018-G for SPA-H) to avoid cold cracking; bake electrodes at 300–350°C for 1–2 hours before use to remove moisture.
Typical Applications: On-site repair of weathering steel components, small-batch production, and welding of complex joints.
2. Gas Metal Arc Welding (GMAW/MIG/MAG) – High-Efficiency Option
Principle: Uses a continuous wire electrode and shielding gas (MIG: argon; MAG: argon + CO₂) to protect the weld pool; high deposition rate and stable arc.
Advantages: Fast welding speed, smooth weld surface, low spatter. Suitable for medium-thickness plates (3–20 mm) and large-scale production (e.g., container manufacturing, structural frames).
Key Notes: Use argon + 2–5% CO₂ mixed gas for better weld strength and corrosion resistance; match the wire grade to the base metal (e.g., ER70S-6 for SPA-H).
Typical Applications: Mass production of weathering steel planters, guide signs, and prefabricated structural parts.
3. Flux-Cored Arc Welding (FCAW) – Ideal for Thick Plates
Principle: Uses a tubular wire filled with flux; the flux melts to form slag and shielding gas (self-shielded or gas-shielded versions available).
Advantages: High penetration, suitable for thick plates (>16 mm) and outdoor windy environments (self-shielded FCAW does not require external gas). High deposition efficiency for heavy-duty components.
Key Notes: For weathering steel, use low-hydrogen flux-cored wires to reduce cracking risk; remove slag thoroughly between multi-pass welds.
Typical Applications: Welding of thick weathering steel bridge components, heavy machinery frames, and large storage tanks.
4. Submerged Arc Welding (SAW) – High-Volume Production
Principle: The arc is submerged under a layer of granular flux, which protects the weld pool and reduces spatter and arc light.
Advantages: Extremely high deposition rate, deep penetration, and excellent weld quality consistency. Suitable for long straight seams or circular seams of thick plates (>20 mm).
Key Notes: Limited to flat or horizontal welding positions; not suitable for complex or on-site welding. Match flux and wire combinations to ensure weathering resistance of the weld metal.
Typical Applications: Large-scale production of weathering steel ship hulls, pressure vessels, and structural steel beams.
5. Gas Tungsten Arc Welding (GTAW/TIG) – Precision Welding
Principle: Uses a non-consumable tungsten electrode and shielding gas (argon) to create an arc; filler wire is added manually if needed.
Advantages: High weld precision, clean and aesthetic weld surface, minimal heat input (reduces HAZ size). Suitable for thin plates (≤3 mm) and root pass welding of critical joints.
Key Notes: Slow welding speed, high skill requirement for operators. Ideal for decorative weathering steel components (e.g., art installations, thin-walled signs).
Typical Applications: Welding of thin cold-rolled weathering steel strips, precision components, and root passes of high-integrity joints.
