Aluminum Rolling Mills
What Is An Aluminum Rolling Mill?
Aluminum rolling mills go through the process of shaping raw aluminum into finished plates, sheets, and coils for countless applications. Aluminum is incredibly popular for manufacturing across many industries, including packaging, engineering, consumer goods, and more. This metal offers naturally beneficial characteristics, including:
- Corrosion resistance & recyclable
- Highly ductile and malleable
- High tensile strength
- One-third the weight of steel
How Is Rolled Aluminum Made?
Rolling mills produce a wide array of aluminum products, from heavy plates several inches thick to paper-thin foils. Completed aluminum coils are cold-pressed to achieve a smooth surface. Plates and sheets are available in a sleek finish with the option for perforated, expanded or diamond plate patterns.
Aluminum products can be heat-treated, painted, and alloyed for added functions and features. The primary difference between plates, sheets and foil is thickness:
Foil: Up to .0079" thick
Sheets: From .0079" to 1/4" thick
Plates: 1/4" thick and up
The aluminum rolling process takes place over three steps.
1. Preparing the Aluminum Stock
Before making rolled aluminum, a rolling mill must decide if it will hot or cold work the stock. This decision largely depends on the material properties desired for a specific roll.
If the mill decides to cold work the aluminum, the material will not undergo a heating process before rolling. Cold working changes the microstructure of the aluminum to become harder and stronger. Some advantages of the cold working process include:
- The ability to maintain dimensional accuracy.
- There's no need to wait for the aluminum to reach a specific temperature.
- Oxidation does not occur during the cold working process, leading to better surface finishes.
- The strength and wear properties of the aluminum increase.
The opposite of cold working is hot working. Hot working is when the mill decides to heat the aluminum before beginning the rolling process. The exact temperature in the hot working process will vary among alloys. For example, the hot working temperature of 3004 aluminum is between 260 degrees Celsius to 483 degrees C or 500 degrees Fahrenheit to 900 degrees F. The hot rolling process prevents materials from hardening and the aluminum remains ductile. Some additional advantages of hot working include:
- The size and shape of the aluminum are easily changeable.
- Workers can minimize stresses and other defects.
- The mechanical, physical and chemical properties of aluminum can undergo improvements.
- The hot working process is economical, fast and reliable.
2. Rolling the Aluminum to the Preferred Thickness
After the aluminum slabs go through the hot or cold work process, the next step is to go through the roller mill. Each roller mill applies pressure to the upper and underside of the aluminum until the slab forms the optimal width. Aluminum with specific rolled shapes, such as roofing sheets or building siding, will also undergo shaping during the rolling process with help from specialty shaped rollers.
3. Additional Processing
If needed, a rolled aluminum product can undergo further processing, such as hot forming and blank cutting. The mill will apply any mechanical or chemical treatments to the surface of the aluminum last. Undergoing these additional treatments can alter the color and finish of the products and add texture or improve corrosion resistance.
TYPES OF ALUMINUM PRODUCTS THAT ROLLING MILLS PRODUCE
1. ALUMINUM PLATES
Rolling mills produce aluminum plates from thick slabs of aluminum which then undergo a shaping process to reach the desired size. During this process, the mill will heat large aluminum ingots to a workable temperature before machine-rolling them to measure several inches in length. Large rolling mills can produce aluminum plates of enormous size, with raw ingots exceeding 20 tons. Aluminum plates can be heat treated or cold-rolled, improving the final product.
Aluminum plates are best suited for rigorous use. Plates are common in the military, maritime, transportation and aerospace industries. Aluminum performs exceptionally well in cold temperatures, making it ideal for use in extreme conditions or with hazardous materials.
2. ALUMINUM SHEETS
Shaping an aluminum sheet begins with the same process as an aluminum plate. Aluminum plates pass through a continuous rolling mill to further reduce plate thickness. The final step for the aluminum sheet is cold rolling, where aluminum sheets compress between two rollers, reducing material thickness up to 50%. Cold rolling aluminum sheets can eliminate surface imperfections, enhance flexibility, and improve plate strength. Aluminum sheets can also undergo heat treatment.
Aluminum sheets are the most common form of rolled aluminum products and are often in products ranging in size and application, from automobile frames to household rolls of aluminum foil. The construction, automotive, packaging industries, and other manufacturers all depend on aluminum.
3. ALUMINUM COILS
Aluminum coils are continuous sheets of aluminum. Both hot and cold rolled aluminum products are available. In hot-rolled production, molten aluminum continuously moves through the roller to create a long sheet before undergoing a coiling process at completion. The cold rolling process produces coils by compressing sheets and plates of aluminum, spreading material, and reducing thickness.
Aluminum coils come in all sizes for many uses, such as keeping food fresh in the kitchen and a ship's hull watertight or for electronics manufacturing, packaging pharmaceuticals, and building automobiles.
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