1.What is the role of zinc content on weld defects?
Pore formation
Intensified spatter
Brittle phase formation
Fe-Zn intermetallic compounds: Formation of ζ phase (FeZn₁₃) and δ phase (FeZn₇) at high temperature
When zinc content is >80g/m², the thickness of brittle phase in heat affected zone (HAZ) is >5μm
2.What are the zinc content tolerance limits for different welding processes?
Laser welding
Advantages: Low heat input → 50% reduction in zinc volatilization
Zinc content window: GI galvanized sheet (zinc layer 60-80g/m²): weldable
ZM coating (zinc layer 100-150g/m²): 0.2mm gap must be reserved for pressure relief
3.What are the zinc content grading solutions?
Low zinc layer
Applicable processes: all arc welding, laser welding
Welding parameter optimization: increase arc voltage 2-3V (extend the existence time of molten pool to help zinc volatilization)
Use double pulse mode (low frequency pulse to clean zinc vapor)
Medium to high zinc layer
Porosity control: laser-arc hybrid welding
Spatter suppression: activator
Electrode wear: dispersed copper electrode
Ultra-high zinc layer
Required measures: Laser cleaning before welding (remove zinc layer in weld area, width > 5mm)
Use cold metal transfer (CMT) technology (reducing heat input by 40%)
Fill with rare earth wire (La/Y refines grains and neutralizes Zn brittleness)
4.How to choose different parts for industrial applications?
Body welding
Process selection: Top cover/side panel: laser welding (gap 0.1mm)
Chassis structure: pulse MAG
Transmission tower
Key steps: Flame preheating (200℃ to slow down zinc volatilization)
Use E6010 welding rod (cellulose type, strong arc blowing force)
Household appliance thin plates
High-efficiency solution: resistance spot welding + local passivation treatment of coating
5.What is the core influence of zinc content on weldability?
Low zinc layer (＜70g/m²): Adjust arc parameters and weld directly
Medium to high zinc layer (80-150g/m²): Laser-arc hybrid welding + activator
Ultra-high zinc layer (＞150g/m²): Laser cleaning + CMT + rare earth welding wire