1. Weld Porosity (Small Holes in Weld Metal)
Causes:
Contaminants on the base metal (oil, grease, rust, or mill scale) that vaporize during welding and get trapped in the weld pool.
Damp welding consumables (e.g., E8018-G electrodes not dried properly) releasing moisture when heated.
Insufficient shielding (e.g., incorrect arc length, drafty work environments) letting air (oxygen/nitrogen) enter the weld pool.
Prevention:
Clean the base metal with stainless steel brushes + acetone (25mm width on both sides of the joint) to remove all contaminants.
Dry electrodes per manufacturer specs (E8018-G typically requires 350°C for 1–2 hours, stored in a heated rod oven).
Maintain a short arc length (1–1.5× electrode diameter) and shield the weld pool from drafts with wind screens.
2. Heat-Affected Zone (HAZ) Softening
Causes:
Excessive heat input (above 35 kJ/cm) or high interpass temperature (over 250°C), which coarsens the HAZ microstructure and breaks down strengthening phases.
Slow cooling of thick plates (≥30mm) without post-weld heat treatment (PWHT) to refine grains.
Prevention:
Control heat input within 15–35 kJ/cm (adjust current/voltage based on plate thickness; e.g., 3.2mm electrodes use 120–150A).
Keep interpass temperature below 250°C (monitor with a temperature gun between passes).
For plates >30mm, use multi-pass welding with small bead sizes and forced air cooling (if needed) to speed up cooling.
3. Weld Corrosion Mismatch (Weld Rusts Faster Than Base Metal)
Causes:
Using non-weathering consumables (e.g., E7018, ER70S-6) that lack SMA570W's Cu/Cr alloying elements.
Over-grinding the weld (removes Cu/Cr-rich surface layers, exposing low-alloy inner metal).
Slag/spatter residues blocking patina formation on the weld.
Prevention:
Use only weathering-grade consumables (E8018-G for SMAW, ER80S-G for GMAW) and verify Cu/Cr content via material certificates.
Avoid unnecessary grinding; only grind to repair defects (use ≥120 grit abrasive to blend smoothly).
Remove slag/spatter immediately after welding with a stainless steel brush.
4. Undercut (Grooves Along Weld Edges)
Causes:
Excessive current (e.g., 180A for 3.2mm electrodes) melting too much base metal along the weld edge.
Incorrect electrode angle (holding the electrode too flat, directing arc heat to the base metal instead of the weld pool).
Fast travel speed leaving insufficient filler metal to fill the edge.
Prevention:
Match current to electrode size (follow manufacturer recommendations: e.g., 3.2mm E8018-G uses 120–150A).
Maintain a 20–30° electrode angle (drag angle for SMAW) to focus arc heat on the weld pool.
Adjust travel speed to ensure filler metal fully fills the weld edge (no visible grooves).
5. Cold Cracks (Delayed Cracks in Weld/HAZ)
Causes:
High hydrogen content in the weld (from damp electrodes, oily base metal, or humid air).
High residual stress (from rapid cooling or restrained joints).
Low toughness in the HAZ (due to excessive heat input or coarse grains).
Prevention:
Use low-hydrogen electrodes (E8018-G is low-hydrogen) and dry them properly.
Preheat thin plates (≤10mm: 50–100°C; 10–20mm: 100–150°C) to slow cooling and reduce residual stress.
Perform post-weld heat treatment (PWHT) for thick plates (>20mm): hold at 550–600°C for 1–2 hours to release hydrogen and refine grains.
