Z120 Galvanized Steel Sheet: Precision Protection for Industrial and Architectural Applications
Z120 Galvanized Sheet Product Overview
The Z120 galvanized steel sheet is a hot-dip coated material engineered for balanced corrosion resistance and formability. With a zinc coating weight of 120g/m² (three-point test) or 36g/m² (single-point test) per surface, this product delivers 400–600 hours of salt spray resistance (ISO 9227) while maintaining exceptional cold-forming capabilities. Compliant with ASTM A653, EN 10346, and JIS G3302 standards, Z120 sheets are ideal for roofing systems, HVAC components, and agricultural equipment exposed to moderate environmental stress.
Technical Specifications
1. Material Composition
- Base Steel: Cold-rolled low-carbon steel (C ≤0.15%)
- Zinc Coating:
- Total Weight: 120g/m² (±10%)
- Thickness: 16.8µm per side (calculated at 7.14g/m² = 1µm)
- Surface Structure: Zinc-iron alloy layer (Fe-Zn phases) with pure zinc outer layer
2. Dimensional Tolerances
| Parameter | Range | Tolerance |
|---|---|---|
| Thickness | 0.12mm–6.00mm | ±0.03mm (≤3mm) |
| Width | 600mm–1,500mm | ±2mm |
| Coating Uniformity | – | ≤±15% deviation |
3. Mechanical Properties
| Grade | Yield Strength (MPa) | Tensile Strength (MPa) | Elongation (A80%) |
|---|---|---|---|
| DX51D+Z120 | 240–380 | 270–500 | ≥22% |
| S220GD+Z120 | ≥220 | ≥300 | ≥20% |
Manufacturing Process
- Continuous Hot-Dip Galvanizing:
- Steel coils are cleaned in alkaline solutions (pH 12.5) at 75°C
- Annealed at 720°C in hydrogen-nitrogen atmosphere
- Dipped in 455°C zinc bath with 0.18–0.22% aluminum content
- Air-knife calibrated to achieve ±5g/m² coating accuracy
- Post-Treatment Options:
- Chromate Passivation (Code C): 0.3–0.8µm layer for enhanced paint adhesion
- Phosphate + Oiling (Code Q): 1.2–2.5g/m² oil film for storage protection
Environmental Performance Guide
| Exposure Condition | Recommended Solution | Service Life* |
|---|---|---|
| Indoor dry environments | Z120 + Chromate (C) | 12–15 years |
| Automotive interiors | Z120 + Phosphating (Q) | 8–10 years |
| Agricultural machinery | Z120 + 50µm polyester coating | 15–18 years |
Based on ISO 12944-2 corrosion categories C2–C3
Forming & Fabrication Properties
- Bending Performance:
- Minimum bend radius: 1× thickness for 90° bends (0.5mm sheet: R0.5mm)
- No cracking observed in 180° hemming tests
- Welding Compatibility:
- MIG welding parameters:
- Voltage: 18–22V
- Wire feed: 4–6m/min (1.2mm ER70S-6 wire)
- MIG welding parameters:
- Surface Finishes:
- Regular Spangle: Gloss level 60–70 GU (20° measurement)
- Zero Spangle: Ra 0.4µm for Class A painted surfaces
Chemical Composition
| Element | C | Mn | P | S | Al |
|---|---|---|---|---|---|
| Content | ≤0.15% | ≤1.70% | ≤0.025% | ≤0.025% | 0.02–0.20% |
The controlled aluminum content (0.02–0.20%) ensures optimal zinc adhesion while minimizing dross formation during galvanizing.
Comparative Advantages
- Versus Electro-Galvanized: 300% higher zinc coating durability
- Versus Galvalume: 40% lower material cost with comparable C3 corrosion resistance
- Versus Z275: 25% weight reduction for equivalent structural applications
Industry Applications
- Construction:
- Standing seam roofing (0.7mm Z120 withstands 150km/h winds)
- Perforated acoustic panels (0.5mm sheets with ±0.1mm hole precision)
- Manufacturing:
- Electrical enclosure stamping (Z120 + Q treatment, 500k+ cycles)
- Conveyor system components (Z120 + 30µm epoxy coating)
- Agriculture:
- Grain silo roofs (Z120 + SMP coating, 20-year warranty)
- Livestock watering troughs (Z120 + polymer lining)
Sustainability Features
- 85% recycled content in steel substrate
- Zinc recovery rate ≥98% through closed-loop galvanizing
- Water-based pretreatment systems (VOC emissions <25g/m²)
Key Purchase Considerations:
- Specify coating treatment (C/Q/S) based on painting requirements
- Request mill test certificates for mechanical properties
- Confirm packaging standards (VCI paper for marine transport)
For projects requiring enhanced corrosion protection without compromising formability, Z120 galvanized sheets provide an optimal balance of performance and cost-efficiency across multiple industries.
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