Aluminum Coil: "Metal Pioneer" in the Lightweight Era

As a key basic material for modern industry, aluminum coils have set off a material revolution of "replacing steel with aluminum" in the fields of construction, automobiles, packaging, electronics, etc. with their excellent lightweight characteristics and versatility. From 0.01mm thick food packaging aluminum foil to 2600mm wide building curtain wall aluminum coils, this highly plastic metal coil continues to break through the boundaries of material performance through alloy design and process innovation, becoming a landmark material for green manufacturing in the carbon neutral era.
1. Definition and classification system of aluminum coils
Definition: Aluminum coils refer to rolled sheets made of aluminum and aluminum alloys through smelting, casting or hot rolling, cold rolling and other processes. The thickness is usually between 0.006mm-6.0mm and the width can reach 2800mm. According to the GB/T 3190-2020 standard, the alloy system of aluminum coils covers 1 series pure aluminum to 7 series high-strength aluminum alloys, and its performance is precisely controlled by the ratio of alloy elements (such as copper, magnesium, silicon, zinc, etc.) and heat treatment processes.
Precise classification by alloy system
Production process:
Cast-rolled coil: directly cast and rolled from aluminum liquid into 0.1-6.0mm aluminum coil, with high efficiency, used for packaging and construction;
Hot-rolled coil: the ingot is heated to 400-550℃ and hot-rolled into 2.0-6.0mm, and then cold-rolled to the target thickness;
Cold-rolled coil: rolled at room temperature, with a thickness accuracy of ±0.005mm, used for precision parts;
Composite aluminum coil: aluminum and plastic/paper composite, such as aluminum-plastic composite coil for building waterproofing.
Surface treatment:
Anodizing: oxide film thickness 5-25μm, corrosion-resistant and wear-resistant, used for building curtain walls;
Powder spraying: coating thickness 60-100μm, rich colors, used for door and window profiles;
Fluorocarbon spraying: PVDF coating, weather resistance for more than 20 years, used for high-end buildings;
Alu-zinc plating: aluminum-zinc alloy plating, corrosion resistance is 3 times that of galvanizing, used for roofs.
2. Production process and key technological breakthroughs
Full process analysis
Smelting and casting:
Waste regeneration: Double-chamber furnace smelting is adopted, the waste aluminum recovery rate reaches 95%, and the energy consumption is reduced by 90% compared with primary aluminum;
Melt purification: Through ceramic filter plate (pore size 20-40ppi) and online degassing, the hydrogen content is controlled at ≤0.1ml/100g Al;
Continuous casting and rolling: 1+4 casting and rolling mill produces 0.2-3.0mm aluminum coils, with a speed of 15m/min and a thickness tolerance of ±0.01mm.
Rolling and finishing:
Hot rolling stage: 2300mm four-roll reversible hot rolling mill, rolling force up to 50000kN, pass reduction rate ≤40%;
Cold rolling stage: 20-roll Sendzimir rolling mill rolling 0.01mm aluminum foil, rolling oil mist concentration ≤5mg/m³;
Heat treatment process:
Annealing: pure aluminum coil annealing at 300-350℃ for 2 hours to restore plasticity;
Aging: 7075 aluminum coil aged at 120℃ for 24 hours to precipitate η'(MgZn₂) phase and maximize strength.
Surface treatment technology:
Chromium-free passivation: Silane/titanium zirconium salt treatment, film thickness 0.1-0.5μm, salt spray test (1000 hours) without corrosion;
Nano-composite coating: Al₂O₃-TiO₂ nano-layer is deposited on the surface of aluminum coil, with a hardness of 5H and wear resistance increased by 3 times;
Laser roughening: Micron-level pits are formed on the surface of aluminum coil by femtosecond laser, the friction coefficient is reduced by 40%, and the deep drawing performance is improved.
Cutting-edge technology cases
Continuous heat treatment production line: Nanshan Aluminum has built the first continuous annealing coating line in China, with a heat treatment speed of 200m/min for aluminum coils, and energy consumption is 35% lower than that of traditional furnaces;
Digital rolling mill: The intelligent rolling mill deployed by China Aluminum Corporation adjusts rolling parameters in real time through AI algorithms, and controls the thickness tolerance of 0.5mm 6061 aluminum coils to ±0.003mm;
3D printing special aluminum coils: The AlSi10Mg aluminum coils developed by Tianjin Zhongwang use electrospark deposition technology to prepare 3D printing substrates with a density of ≥99.5%.
3. Performance advantages and engineering applications
Curtain walls and roofs:
Beijing Daxing International Airport Terminal uses 3003H24 aluminum coils (thickness 2.5mm), which are fluorocarbon sprayed (three coats and two bakes) and have a weather resistance of more than 25 years;
Shanghai Tower uses 5052H32 aluminum coils (thickness 1.5mm) to make honeycomb panels, which are 60% lighter than steel plates and have a wind pressure resistance of ≥2.4kPa.
Energy-saving doors and windows:
The broken bridge aluminum doors and windows use 6063T5 aluminum coils (thickness 1.4mm), with PA66 insulation strips, and the heat transfer coefficient K≤2.8W/(㎡・K);
The sun room uses 1060O aluminum coils (thickness 0.8mm) to make reflectors, with a reflectivity of ≥85%, to improve indoor lighting efficiency.
Automobile and transportation field
Lightweight body:
Tesla Model 3 body uses 6016T4 aluminum coil (thickness 0.8mm), which reduces the body weight by 15% and energy consumption by 8% through roll forming;
NIO ES6 battery pack shell uses 5083H111 aluminum coil (thickness 3.0mm), which is resistant to seawater corrosion and has a puncture strength of ≥500N.
Rail transportation:
CRRC Sifang high-speed rail train roof uses 5754H22 aluminum coil (thickness 1.2mm), with a density of 2.68g/cm³, which is 40% lighter than the steel roof;
Subway screen doors use 6063T5 aluminum coil (thickness 2.0mm), which is anodized (film thickness 15μm) and has been in service in underground environment for 20 years without rust.
Packaging and electronics
Food packaging:
Tetra Pak uses 8011O aluminum foil roll (thickness 0.012mm), which has excellent barrier properties and oxygen permeability ≤0.1cc/(day・m²);
Chocolate packaging uses 1235H18 aluminum foil roll (thickness 0.006mm), with a light reflectivity of ≥95%, to keep food fresh.
Electronic heat dissipation:
5G base stations use 1050A aluminum roll (thickness 1.5mm) to make heat sinks, with a thermal conductivity of 205W/m・K, 30% lower cost than copper plates;
Laptop shells use 5052H34 aluminum roll (thickness 0.5mm), which is processed by CNC, with a surface hardness of ≥120HV and a wear resistance of ≥10,000 times.
Energy and aviation fields
New energy:
1060O aluminum coil (thickness 0.1mm) is used for CATL battery soft connection. After ultrasonic welding, the resistance is ≤50μΩ, which meets the requirement of 1000 cycles;
3003H16 aluminum coil (thickness 0.3mm) is used for photovoltaic modules to make frames. There is no corrosion in the salt spray test (2000 hours), and the service life is ≥25 years.
Aerospace:
2024T3 aluminum coil (thickness 1.2mm) is used for the wing skin of C919 passenger aircraft, σb≥420MPa, and fatigue life ≥10^7 times;
7075T651 aluminum coil (thickness 2.0mm) is used for structural parts of Chang'e 5 probe, which is dimensionally stable in an environment of -196℃ to +120℃.
IV. Market dynamics and technological trends
Global industry status
Capacity distribution: In 2024, the global aluminum coil production will be about 38 million tons, of which China will account for 56% (Shandong, Henan and Zhejiang are the main production areas), followed by Europe (15%), North America (12%) and Japan (6%);
Price dynamics: The average price of 3003H14 aluminum coil (1.0mm×1200×C) in 2024 is about US$2,600/ton, which is 8% higher than that in 2023 due to the LME aluminum price (US$2,200-2,400/ton);
Import and export pattern: China exports about 6 million tons of aluminum coils annually, mainly to Southeast Asia (accounting for 40%), and imports about 1.2 million tons, mainly high-end coated aluminum coils (such as fluorocarbon coated aluminum coils imported from South Korea, which are 30% higher than domestically produced).
Technology development direction
Green and low-carbon production:
Application of hydropower aluminum: Yunnan Shenhuo uses Jinsha River hydropower to produce aluminum coils, and CO₂ emissions per ton of aluminum are reduced from 11 tons to 4.5 tons;
Short process recycling: The direct casting and rolling technology of scrap aluminum developed by Zhongwang Group reduces energy consumption by 60% compared with traditional processes, and the purity of recycled aluminum coils is ≥99.5%;
Chromium-free coating: Develop silane-graphene composite coatings with salt spray resistance of 3,000 hours, replacing traditional chromate treatment.
High-performance innovation:
7 series high-strength aluminum coil: 7050T7451 aluminum coil σb≥580MPa, used for aviation structural parts, 40% lighter than steel;
Superconducting aluminum coil: Al-Nb alloy coil with 0.5% niobium added, superconducting at 4.2K, used for maglev trains;
Bionic aluminum coil: Al-Mg-Si-Ca composite coil simulating the structure of beetle shell, with impact resistance increased by 2 times, used for automotive anti-collision beams.
Intelligent manufacturing:
AI detection of aluminum coil surface defects: using deep learning algorithm to identify defects above 0.05mm, with an accuracy rate of 99.6%;
Digital twin rolling: establish a digital twin model of aluminum coil rolling process, predict plate shape deviation ≤0.02mm, and reduce trial and error costs;
Blockchain traceability: blockchain technology is applied to aviation aluminum coils to record the full process data from ore to parts to meet AS9100 certification requirements.
Functional surface engineering:
Self-cleaning aluminum coil: Aluminum coil coated with TiO₂ photocatalytic coating, with an efficiency of ≥90% in degrading organic matter under ultraviolet light, used for building curtain walls;
Electromagnetic shielding aluminum coil: Aluminum coil with copper-nickel composite layer deposited on the surface, with shielding efficiency ≥80dB, used for electronic equipment housing;
Phase change energy storage aluminum coil: Aluminum coil embedded with paraffin phase change material, with heat storage density ≥150kJ/kg, used for building energy-saving ceiling.
V. Selection Guide and Maintenance Points
Selection Decision Factors
Lightweight Demand:
Aerospace: Select 7075T6 aluminum coil, strength-to-weight ratio ≥200MPa・cm³/g;
Automobile body: Select 6016T4 aluminum coil, with formability index FLD≥25%;
Packaging material: Select 8011O aluminum foil coil, with a thickness tolerance of ±3%, which meets the requirements of high-speed packaging machines.
Environmental adaptability:
Marine environment: select 5083H111 aluminum coil, resistant to seawater corrosion (Cl-≤5000ppm);
Industrial atmosphere: select 3004H16 aluminum coil, anodized (film thickness 20μm);
High temperature environment: select 2A12T4 aluminum coil, strength retention rate ≥80% at 150℃.
Processing requirements:
Deep drawing: select 5182H19 aluminum coil (r value ≥1.5);
Roll coating: select 1100H14 aluminum coil, surface roughness Ra≤1.6μm;
Welding connection: select 6061T6 aluminum coil, use MIG welding, welding strength ≥85% of the parent material.
Storage and maintenance technology
Rust-proof storage:
Indoor storage: overhead stacking, humidity ≤50% RH, temperature 15-30℃, avoid direct sunlight;
Open-air storage: covered with waterproof canvas, the bottom is raised more than 300mm, and drainage ditches are set around;
Sea transportation protection: the surface of the aluminum coil is coated with dry anti-rust oil, wrapped with moisture-proof paper, and calcium chloride desiccant is placed in the container (dosage 1kg/ton).
Surface maintenance:
Daily cleaning: wipe with neutral detergent (pH7-8), avoid using detergents containing chloride ions;
Coating repair: When the powder coating is damaged, electrostatic spraying can be used for local repair, and the color difference ΔE≤1.5;
Oxide film maintenance: The anodized surface can be cleaned with 5% citric acid solution (temperature 40-50℃) to remove slight rust.
Special environment maintenance:
Coastal buildings: Use high-pressure water (pressure ≥ 8MPa) to wash the surface of aluminum coils every year to remove salt spray deposition;
Photovoltaic modules: Wipe the aluminum frame with a soft cloth every quarter to avoid dust blocking the power generation efficiency;
Automobile body: Use nano-ceramic coating (thickness 5-8μm) to increase the surface hardness of aluminum coils to 9H and resist scratches.

As a model of lightweight materials, aluminum coils are playing an increasingly important role in the era of carbon neutrality and intelligence through material innovation and process innovation. From aircraft skins to mobile phone shells, from building curtain walls to photovoltaic modules, aluminum coils, with their unique performance combination, continue to promote technological progress and green transformation in various industries, and become a key basic material to support high-end manufacturing and sustainable development.