Novelis sets the standard for the global industry with our unmatched aluminum rolling operations to produce the highest quality hot- and cold-rolled products custom-tailored to achieve the specific properties required for premium applications. Our dedication to manufacturing excellence means that Novelis teams are uncompromising in their attention to every step of the rolling process.
Thanks to years of Novelis research and engineering expertise, our teams are able to work directly with customers to select the best alloy choices, and schedule deformation and thermal treatments with optimum controls for properties such as strength, formability, corrosion resistance, toughness, surface finish, flatness and gauge uniformity.
Hot Rolling Aluminum
The hot rolling process is used to convert sheet ingots into coils with a gauge suitable for the cold rolling process. Precision-controlled hot rolling enables Novelis to create the properties that will result in a final product that meets the Novelis standard of manufacturing excellence.
- Aluminum ingots are moved from direct chill (DC) casting and cooled down to room temperature.
Stages in Hot Rolling
Novelis uses precise milling procedures to provide the ingots with the optimum surface for rolling.
- First the ingots move to a slab saw, which removes the ends of the ingots to increase its surface quality.
- A scalper then removes the surface layer of the entire ingot to eliminate surface oxides, ensuring a uniform, high-quality surface finish.
- Next, we send the ingot to a pusher furnace, which pre-heats it to a point above its re-crystallization temperature (around 500°C) in order to prepare it for hot rolling. This process is called annealing, and it allows the various alloy constituents in the ingots to distribute themselves, evening out differences in microstructure and ensuring a homogeneous structure within the ingot.
- Finally, we pass the sheet ingot back and forth between the rolls of a breakdown hot mill, which reduces the ingot’s gauge until it approaches that of a strip with the desired thickness for cold rolling.
The tandem hot mills Novelis uses for hot rolling guarantee that our coils are uniform, precisely cut and have a high-quality surface finish. From the hot rolling process, Novelis sends the coils to cold rolling, where they are milled to the final gauge and their mechanical properties adjusted to suit our customers’ precise needs for premium applications.
Novelis operates a variety of types and sizes of cold roll mills at locations around the world, including some that run at exit speeds as high as 3,000 meters per minute.
Stages in Cold Rolling
- Hot-rolled aluminum strip is cooled to room temperature and fed into the cold roll mill line.
- The strip is then passed several times between a series of rollers until it is gradually reduced to the desired gauge and wound into a coil.
- The resulting coil can be rolled to a thickness of 0.05 millimeters (mm). Novelis automatic gauge and flatness control systems ensure coils of precise dimensions.
Intermediate heat treatments may be used, depending on the degree of rolling and final thickness desired for particular applications, to modify mechanical features of the cold-rolled coils. For example, by heating and maintaining the aluminum at precise pre-defined temperatures, Novelis transforms the final product to fit the customers’ exacting needs for tensile strength, yield strength and elongation. This process is also called annealing.
Rolled products are categorized by foil (less than 0.2 mm thick), sheet (between 0.2 and 6.0 mm in thickness) and plate (greater than 6.0 mm in thickness). When cold rolling is complete, Novelis puts the coils through a number of finishing processes to ensure that the end product matches our standards for “best in class.” From there the product goes to finishing.
At Novelis, we use a number of finishing processes to ensure that the aluminum products we deliver lead the industry in consistent quality and reliability of properties for customer applications. For instance:
- Cold-rolled aluminum coils are flattened to a precise thickness by running them through a series of leveling rollers, in a process called tension leveling.
- Slitters are used in order to achieve a precise width to the coil.
A protective film can be applied to Novelis rolled products. The films differ in composition depending upon the particular product application, and often carry additional information such as a guide to coating direction and Novelis brand details. In keeping with our corporation-wide sustainability goals, these films are easy to recycle.
Novelis creates functional surfaces for high-value products. For example, when a new polymer coating has been developed and manufactured, its application to the surface of the aluminum product must also be developed. During the new product‘s development phase, our Innovation teams use commercial testing and pilot coil-to-coil (CTC) surface treatment line capability to ensure a smooth transfer from laboratory-scale research to full-scale production. Novelis deploys a full suite of state-of-the-art laboratory testing and analytical equipment. Pre-painted sheet and shaped blanks are used for a diverse range of architectural, consumer and transportation applications.
Aesthetics + Durability = Novelis Surface Solutions
When it comes to combining durability and elegant design, aluminum surface finishing solutions developed by Novelis are leading the industry for a wide range of consumer and industrial applications.
Our specialty finishes merge color and texture like brushed finishes along with the basic benefits of aluminum to create a cost-efficient, versatile and durable material for both interior and exterior building and architectural applications.
For example, applications for Novelis Anodized Quality (AQ) sheet range from building exteriors and appliances to interior décor and lighting fixtures. Anodizing is an electrolytic passivation process used to increase the thickness of the natural oxide layer on the surface of aluminum; the end result is a range of options for the decoration and protection of the product’s surface. Novelis AQ sheet is well suited to batch anodizing to give customers the color uniformity, surface appearance and reflectivity they need for high-value designs. The added benefit of this Novelis surface innovation is that it provides end users with a cost-effective material with long life and easy maintenance.