Cold-Rolled Aluminum Foil

I. Definition and Classification

Cold-rolled aluminum foil is a super-thin aluminum product (thickness range: 0.01–0.2mm) produced through processes including melting, casting, hot rolling, cold rolling, and finishing. It is classified by alloy composition:

• 1XXX Series (e.g., 1060/1100): Pure aluminum with high conductivity and ductility, used in electronics.

• 3XXX Series (e.g., 3003/3105): Corrosion-resistant, applied in food packaging and pharmaceuticals.

• 5XXX Series (e.g., 5005/5705): Balanced strength and processability, dominant in construction and home appliances.

• 6XXX Series (e.g., 6061/6063): High-strength alloy for aerospace and precision instruments.

II. Production Process Flow

1. Melting and Casting

• Aluminum ingots with purity ≥99.5% are melted at 750–780°C and cast with controlled cooling rates ≤15°C/min to prevent grain coarsening.

• Hot Rolling

• Ingots heated to 470–530°C are rolled to thicknesses of 2–5mm to eliminate casting defects and optimize grain structure.

• Cold Rolling

• Rolling temperature: 0–30°C (low-temperature rolling enhances strength)

• Rolling speed: 0.1–3m/s (cooling lubrication required for high speeds)

• Thickness tolerance: ±0.005mm (precision foil requirements)

• Key Parameters:

• Multi-pass rolling (8–20 passes) reduces thickness by up to 90%, achieving ultra-thin foils (down to 0.01mm).

• Finishing Process

• Bright Finish: Electrolytic polishing (current density 10–20A/dm²) yields surface roughness Ra ≤0.1μm.

• Coating Treatment: Fluorocarbon spraying (PVDF film thickness ≥20μm) for enhanced weatherability.

• Annealing: Stress relief and plasticity restoration at 300–450°C for 1–5 hours.

• Surface Treatment:

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III. Core Technical Properties

1. Mechanical Performance

• Tensile Strength: 100–300MPa (5XXX series up to 270MPa)

• Elongation: ≥15% (1XXX series up to 50%)

• Hardness: HV 30–80 (dependent on alloy and annealing state)

• Bright foil: Mirror reflectivity ≥85%

• Heat-seal foil: Roughness Ra 0.5–3μm (compatible with heat-sealing processes)

• Surface State:

• Contamination Control: Metal impurities <10ppm, oxygen content ≤0.15%.

• Natural Oxidation: Dense oxide film (10–20nm) with salt spray resistance >96 hours.

• Anodized Coating: Corrosion resistance enhanced 5–10x (e.g., black oxide film withstands Cl⁻ ion penetration >5000h).

IV. Typical Applications

1. Packaging Industry

• Food Packaging: 3003-series foil (0.03mm thickness) acts as oxygen/light barrier.

• Pharmaceutical Packaging: 1060-series sterile foil (FDA-compliant).

• Tobacco Packaging: 5005-series foil for fine pattern printing.

• Capacitor Electrode Foil: 1100-series ultra-thin foil (0.01mm thickness, dielectric constant >100).

• Electromagnetic Shielding: 6061-series foil (copper-plated) with shielding效能＞40dB.

• Insulation Materials: Aluminum foil composites (0.05mm thickness) reflect infrared radiation, improving energy efficiency by 30%.

• Automotive Air Conditioning: 5XXX-series foil (thermal conductivity 237W/m·K) for efficient heat dissipation.

• Lithium-Ion Battery Current Collectors: 6063-series foil with microstructured surfaces to reduce interface resistance.

• Fuel Cell Catalyst Supports: Platinum-coated foil (0.1mm thickness).

V. Technical Standards and Testing

1. International Standards

• ASTM B221: Specifies foil thickness, mechanical properties, and dimensional tolerances.

• ISO 5725: Classifies surface defects (e.g., pinholes, scratches).

• GB/T 3198: Aluminum foil thickness tolerance (±3%).

• GB/T 1629: Anodized film thickness measurement (ellipsometry method).

VI. Future Development Trends

1. Ultra-Thinning: Development of nanoscale foil (<0.005mm) for flexible electronic devices.

2. Functionalization:

• Conductive Coatings: Graphene composite foil (conductivity >10⁶ S/cm).

• Self-Healing Coatings: Microcapsule technology for scratch repair.

• Recycled Aluminum Foil: Recovery rate >95%, carbon emissions reduced by 40%.

• Acid-Free Rolling: Environmentally friendly lubricants replacing mineral oils.

Cold-rolled aluminum foil remains an indispensable material in high-end manufacturing due to its superior properties, driving innovation in packaging, electronics, and renewable energy sectors through continuous technological advancements.