1. Key Challenges in Welding Weathering Steel
Patina Formation Disruption: Welds may not develop matching rust appearance
Hydrogen Cracking Risk: Higher susceptibility than mild steel
Heat-Affected Zone (HAZ) Properties: Potential toughness reduction
Matching Corrosion Resistance: Ensuring weld metal weathers similarly to base metal
2. Recommended Welding Processes
| Process | Suitable For | Notes |
|---|---|---|
| SMAW (Shielded Metal Arc) | Field/Shop | Most common, use low-hydrogen electrodes |
| GMAW (MIG) | Shop/Production | Best for automation |
| FCAW (Flux-Cored) | Field/Heavy Sections | Higher deposition rates |
| SAW (Submerged Arc) | Thick Plates | Requires proper flux selection |
3. Filler Metal Selection
AWS Specifications:
SMAW: E7018-W (e.g., Lincoln LH-D78W)
GMAW/FCAW: ER70S-3W or E71T-1W
SAW: EM12K + neutral flux
Key Requirements:
Must match weathering characteristics
Low hydrogen (<5ml/100g)
Similar CTE (Coefficient of Thermal Expansion)
4. Pre-Weld Preparation
Joint Design:
60° V-groove for plates >10mm
Root face 1.5-2mm
Root gap 2-3mm
Cleaning:
Remove mill scale 25mm either side of joint
Degrease with acetone
Preheating:
<20mm thickness: 50-100°C
20-40mm: 100-150°C
>40mm: 150-200°C
5. Welding Parameters
| Thickness (mm) | Passes | Current (A) | Voltage (V) | Speed (mm/min) |
|---|---|---|---|---|
| ≤6 | 1 | 90-120 | 18-20 | 300-400 |
| 6-12 | 2-3 | 120-160 | 20-22 | 250-350 |
| 12-25 | 3-5 | 160-220 | 22-26 | 200-300 |
| >25 | Multi | 200-280 | 24-28 | 150-250 |
