Aluminum Coil: Types, Grades, Applications & Advantages

Aluminum Coil

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Introduction

This article will provide a comprehensive overview of aluminum coils.

By the end of this article, readers should have a clearer understanding of:

• What Aluminum Coils Are, Their Characteristics, and Important Considerations When Choosing Them
• The Manufacturing Process of Aluminum Coils
• Different Types and Grades of Aluminum Coils
• The Applications, Advantages, and Disadvantages of Aluminum Coils
• And much more…

Chapter One: What is Aluminum Coil? What are the Characteristics of Aluminum Coil? What are Some Considerations in Choosing Aluminum Coil?

An "aluminum coil" refers to aluminum that has been flattened into sheets, significantly wider than their thickness, and then coiled into rolls. Storing individual aluminum sheets can be cumbersome due to their inconsistent sizes and the difficulty in retrieval. In contrast, aluminum coils are easier to store and transport.

Once at a metalworking facility, aluminum coils can undergo different processing steps such as cutting, welding, bending, stamping, engraving, and attaching to other metal items. These coils are supplied to production facilities and metal fabricators for the creation of numerous everyday objects, from automotive parts to food cans.

Characteristics of Aluminum Coil

Non-corrosive

Aluminum is highly resistant to weathering and corrosion, even in industrial environments. Several acids won't corrode aluminum due to its natural oxide layer, which provides exceptional corrosion resistance, almost making it impermeable to many corrosive substances.

Easily machined and cast

Aluminum coil melts more readily than steel, making it pliable and easier to mold. Aluminum castings are less rigid and simpler to work with, which significantly reduces machining time.

Lightweight yet durable

With its low density, aluminum coil is light and portable, ideal for airplane construction. Its recyclability further enhances its durability.

Non-magnetic and non-sparking

Aluminum's crystalline structure makes it non-magnetic. It forms an oxide layer quickly after a scratch, rendering it non-sparking.

Good thermal and electrical conductor

The free electrons in aluminum coils ensure good electrical and thermal conductivity.

Soft

Aluminum's softness is due to the availability of free electrons for bonding.

Non-toxic

Exposure to aluminum is not harmful to the body.

Malleable

Aluminum is easier to shape than most other metals. This increased flexibility allows for effective designs, such as microchannel coils which enhance heat transfer, decrease leaks, and offer higher corrosion resistance.

Ductile

Aluminum's low density, non-toxicity, high thermal conductivity, and excellent corrosion resistance contribute to its high ductility, making it ideal for wire transformation.

Common internal diameters of aluminum coils are 508 mm, 406 mm, and 610 mm. The external diameter is determined by the recoiler machine's capacity and geometric features. Coil thickness and width significantly impact the precision of design calculations, as even a difference of 0.06 mm can be critical.

The weight of an aluminum coil can be roughly estimated as (Coil Diameter*1/2*3.142 - Inner Diameter*1/2*3.142)*Coil Width*2.7(Density of Aluminum). Keep in mind that different alloys have varied densities and there are always measurement errors. The manufacturer's feeding frame capacity also affects the coil weight.

The thickness of aluminum coils ranges from 0.2 to 8mm, with most between 0.2mm and 2mm thick. Different thicknesses determine specific applications. For example, insulation aluminum coils are typically 0.75mm thick, while coated aluminum roof coils are only 0.6 to 1.0mm thick. Special-purpose aluminum rolls can be thicker, and customers can request any thickness within these ranges.

Considerations in Choosing Aluminum Coil

Aluminum is one of the most popular and widely used metals today. Before purchasing aluminum from a coil supplier, there are several factors to consider.

Supplier History

Choosing the right aluminum coil supplier can be challenging. The supplier's experience should be the primary consideration. Working with a supplier with a proven track record is preferable, as inexperienced suppliers may offer limited information about the quality and types of materials they sell. A credible supplier should have an established history and a solid online presence.

Machining

The ease of machining is essential when choosing aluminum coils to integrate with other metals. The machining process should consider whether it is compatible with the selected aluminum coils. Weldability should also be factored in, as some aluminum grades can be welded easily while others cannot. A good supplier will provide this information.

Price vs. Value of Aluminum Grades

Various grades of aluminum exist. If one only has a basic understanding, it would be best to deal with a knowledgeable supplier who can clarify things. Lower-grade coils may be less expensive but might not match the material’s intended use. A reputable supplier should know the various grades and their suitable applications.

Formability

Formability refers to the degree of deformation achieved during the metal-forming process without causing undesirable states like cracking, necking, buckling, or developing folds and defects. Note the different aluminum coils' formability levels when selecting one.

Supplier Reliability

Unless it's a one-off purchase, choose a supplier with a significant stock of the selected material. This way, you won't need to restart the vetting process if you change suppliers.

Typical End-Use Applications

Different coil grades may be available and cheaper, but may not be suitable for all applications. This should be an important consideration in selecting the proper aluminum coil.

Price

A competitive, fair price should guarantee the material's quality. Different manufacturers offer various price ranges based on the grade and other factors. Some firms may cut costs by thinning the coating, so finding the best value without compromising quality is essential.

Chapter Two: How Aluminum Coils are Manufactured

Step One: Smelting

Smelting is used in extractive metallurgy to create metal from its ore. Smelting involves using heat and a chemical reduction agent to break down the ore, removing other components as gases or slag and leaving only the metal. The Hall-Heroult process and the Bayer process are typically used to separate aluminum from its oxide, alumina.

Bauxite rock contains alumina, water atoms, and other minerals. The Bayer process dissolves the particle's components to extract alumina, refined through filtration. After separating alumina from bauxite, the smelter discards the remaining components. Each chemical in bauxite requires a different extraction technique, though the overall process remains similar. After isolation, the gibbsite (a mineral form of aluminum hydroxide) is cooled and seeded.

The Hall-Heroult process lowers the melting point for electrolysis by dissolving alumina in molten synthetic cryolite, a crystalline powder. This process generates liquid aluminum at the cathode while forming carbon dioxide from carbon and oxygen.

Aluminum smelters require a lot of energy, often located near major power plants. Any increase in power costs or refining energy requirements raises aluminum coil prices. Dissolved aluminum separates and collects, consuming considerable energy and impacting market prices.

Step Two: Hot Rolling

Hot rolling is commonly used to thin aluminum slabs. Metal is heated above recrystallization temperatures and passed through rolls to reduce thickness, make it uniform, and achieve desired mechanical qualities. An aluminum coil is produced by processing the sheet at 1700 degrees Fahrenheit.

This method produces shapes with appropriate geometrical parameters and material characteristics while maintaining metal volume. Semi-finished and finished items like plates and sheets are created through hot rolling. Finished rolled products differ from cold-rolled coils in that they have less uniform thickness due to surface debris.

Step Three: Cold Rolling

Cold rolling involves putting aluminum through rollers at temperatures below recrystallization levels, which increases yield strength and hardness. It occurs at the work-hardening temperature, whereas hot rolling happens above this temperature.

Cold rolling produces strip and sheet metal with desired final gauges. Rolls are heated to make aluminum more workable, and lubrication prevents sticking. Aluminum strips undergo repeated passes through rolls, progressively reducing thickness while maintaining lattice planes offset and disrupted, resulting in harder, stronger final products.

Cold rolling is popular for hardening aluminum. It can reduce an aluminum coil's thickness by up to 0.15mm.

Step Four: Annealing

Annealing is a heat treatment process that makes materials more malleable. It changes the crystalline grain structure, improving flexibility and reducing hardness. An aluminum alloy must be heated between 570°F and 770°F for a set duration, depending on the part's size and alloy.

Annealing stabilizes dimensions, reduces internal stresses, and prevents brittle failure. Thermally-stable non-heat-treatable aluminum can also be easily annealed.

Material formability improves with annealing, avoiding fractures. It also enhances machinability by decreasing hardness, reducing tool wear, and eliminating residual stresses that could cause cracks and mechanical issues.

Annealing Stages

Stress Reduction

This procedure minimizes internal mechanical loads from hard work, casting, or welding at low temperatures.

Recrystallization

It changes the metal's crystalline structure by generating new grains from cold-deformed metal, absorbing flaws and reverting the alloy's strength and flexibility to pre-cold-work levels.

Grain Growth

This stage involves new grains growing at the expense of their neighbors, creating coarser grain structures and occurs above the recrystallization temperature.

Step Five: Slitting and Cutting

Aluminum coils are manufactured in continuous rolls and sliced into smaller rolls using slitting equipment with sharp blades. This operation requires significant force, cutting the roll into smaller pieces once the applied force exceeds aluminum's tensile strength.

The slitting process starts by placing aluminum in an uncoiler, passing it through rotary knives set for desired width and clearance, then feeding it through separators to the recoiler. The aluminum is wrapped into a coil for shipping.

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Chapter Three: Types and Grades of Aluminum Coil

Aluminum coils come in grades like the 6000, 7000, 8011, and 3000 series, varying in composition and applications. Each grade's properties suit different industries, such as pliability or hardness. Selecting an appropriate grade depends on fabrication and welding suitability for the specific application area.

1000 Series Aluminum Coil

1000 series aluminum is commercially pure, containing at least 99.5% aluminum. It has outstanding workability, corrosion resistance, and electrical and thermal conductivity, though not heat-treatable. Welding it requires specific precautions, and its look remains unchanged upon heating. 1050, 1100, and 1060 series are common, used to create cookware, curtain wall plates, and building decorations.

2000 Series Aluminum Coil

Containing copper, 2000 series aluminum coils achieve steel-like strengths through precipitation hardening, with copper content ranging from 2% to 10%. Used primarily in aviation for building airplanes, offering lightness and availability.

2024 Aluminum

2024 aluminum alloy, with copper as the main element, is used in applications requiring high strength-to-weight ratios and superior fatigue resistance, such as aircraft structural components, truck wheels, and hydraulic manifolds. It has fair machinability and can only be joined by friction welding.

3000 Series Aluminum Coil

3000 series aluminum uses manganese as the primary alloying element, making it non-heat treatable and more brittle than pure aluminum. Alloy 3003 and 3004 are commonly used due to their strength, corrosion resistance, formability, and ease of sheet metal forming processes. Applications include beverage cans, chemical apparatus, storage containers, and lamp bases.

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Additional reading:
The Evolution of Coil Coatings and Paint Systems for Metal

4000 Series Aluminum Coil

4000 series aluminum alloys have high silicon concentrations, making them suitable for sheets, forgings, welding, and brazing. Silicon lowers aluminum's melting temperature and increases its flexibility, ideal for die casting.

5000 Series Aluminum Coil

5000 series aluminum offers a smooth surface and exceptional deep-drawability, making it suitable for heat sinks and equipment casings. With excellent corrosion resistance, it's used in mobile homes, residential wall panels, and marine applications. Aluminum magnesium alloys in this series include 5052, 5005, and 5A05.

The 5000 series aluminum is favored for marine applications due to its weight savings and resistance to acid and alkali corrosion, making it ideal for marine use.

5754 Aluminum Coil

Aluminum alloy 5754 contains magnesium and chromium, used in rolling, extrusion, and forging rather than casting. It exhibits excellent corrosion resistance, particularly in seawater and polluted air, for applications like automotive body panels, flooring, shipbuilding, and food processing.

6000 Series Aluminum Coil

6000 series aluminum alloy coil, represented by 6061, contains silicon and magnesium, offering high oxidation and corrosion resistance, good workability, and ease of coating. Its applications include aircraft joints and low-pressure armaments. Occasionally, small amounts of copper or zinc increase strength without significantly reducing corrosion resistance.

Aluminum 6062, with magnesium silicide, responds to heat treatment for age-hardening and can be used in submarine manufacturing due to its corrosion resistance in fresh and saltwater.

7000 Series Aluminum Coil

7000 series aluminum coils, primarily Al-Zn-Mg-Cu, offer maximum strength and are favored in aerospace and high-demand industries. Their high hardness, corrosion resistance, and compatibility with various manufacturing applications make them suitable for radiators, aircraft parts, and more.

7075 Series Aluminum Coil

Zinc is the main alloying element in the 7075 aluminum alloy, offering exceptional ductility, high strength, toughness, fatigue resistance, and good mechanical properties. Frequently used in airplane part production, its strength and light weight advantage industries like rock climbing and bicycle part manufacturing.

8000 Series Aluminum Alloy Coil

The 8000 series aluminum coils contain lithium and tin, with additional metals to enhance stiffness and properties. These coils offer high strength and formability, corrosion resistance, electrical conductivity, and bending ability, suitable for electrical applications like cable wires.

Chapter Four: Applications, Advantages, and Disadvantages of Aluminum Coil

Applications of Aluminum Coil

Due to its characteristics, aluminum is used in many industries for various applications. Here are some specific applications:

The Automotive Sector

Aluminum coil is widely used in the automotive sector for components like engine parts, air conditioners, radiators, wheel hubs, and automobile doors. This is due to its durability, light weight, and corrosion resistance.

Protective Covering for Exposed Wooden Home Trim

A trim coil is a thin sheet of aluminum coated with polyester, used to cover and protect exposed wood trim from heat and moisture.

Architectural Construction and Decoration

Due to its strength, corrosion resistance, and processing performance, aluminum coil is used for architectural ornamentation, creating structures, doors, windows, ceilings, curtain wall profiles, pressure plates, and color coating sheets.

Components for Electronic Appliances

Although not as electrically conductive as some metals, aluminum coils are used in electronics for wiring, ensuring long-lasting wires in hostile environments. Items like power cables and air conditioners benefit from aluminum’s corrosion resistance.

Food Containers

Aluminum's malleability and resistance to rust and corrosion make it ideal for food cans, ensuring freshness. It's also used for other containers like metal bottles and lid caps.

License Plates

In some countries, aluminum coils make flexible, easy-to-machine license plates.

Interior Ceilings

Aluminum coils are used for decorative home ceilings.

Partitioning Walls

Offices use aluminum coils for partitioning walls.

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