Cast Plate
Metals of all types have the unique quality of being recyclable and infinitely recyclable. No matter how many times they’re melted down, the reprocessed metal is just as good as when it was smelted from ore dug out of the ground.
This advantage means that metals are among the most sustainable materials humans use. This is especially true of aluminum, whose lightweight strength makes it cost-effective to move around and thus to use as packaging. Hence, aluminum is widely used and continues to be used as a food container, including aluminum cans and aluminum baking trays.
The aluminum recycling process is vital to maintaining a sustainable industry. It is estimated that some seventy-five percent of all aluminum produced is still in use in the aluminum material market.
With sustainability becoming a growing concern, lightweight aluminum will play an even greater role, and while existing recycling practices are outstanding, there is always room for improvement in the aluminum recycling process.
The Aluminum Scrap Recycling Process
At the surface level, the process of aluminum recycling is very simple. The aluminum needs to be gathered, it needs to be cleaned, and then it can be remelted. This is true in the broadest sense. In the details, it is a little more complicated. Aluminum is used in a variety of different roles, and it does need to be processed to remove potential contaminants before it can be reprocessed into a fresh aluminum product. Examples of these contaminants are:
| Non-Aluminum Metals | Non-aluminum metals, like iron, can cause problems during aluminum recycling. These metals can be introduced in aluminum turnings—chips left over from machining—after being scraped from tooling. Magnetic processes can remove iron from the aluminum recycling process, and sink-float tanks can separate non-magnetic metals |
| Paints and Lacquers | Paints, coatings, lacquers, and other organic materials are commonly applied to aluminum beverage cans. These must be removed before recycling in order to avoid contaminating the metal and producing fumes. This removal is usually accomplished through mechanical means. |
| Water and Moisture | Water and moisture can create hydrogen gas, which can lead to porosity and other defects in recycled aluminum. Typically metal is heated and dried to remove any chance of moisture. |
| Grease and Oils | Oils and coolants are part of the machining process, and these can be introduced into aluminum turnings that are sent for recycling. A combination of heat treatments and mechanical processes can remove these oils before recycling. |
In addition to processing to remove these potential contaminants, recycled aluminum can also be processed differently depending on its source, its quality, and its composition. Alloys that are heavily mixed with other raw materials besides aluminum may be melted in furnaces with heavy fluxing and filtration to separate other metals from the aluminum. Higher grade metals, like turnings from machine shops whose composition is known, are recycled in high-heat, rapid-mixing furnaces that minimize oxidation during the remelt.
Although aluminum recycling is a little more complicated than the sort, shred, and melt that it is usually made out to be, it is, in fact, vastly more energy efficient than making aluminum from virgin ore. However, direct reuse of metals as they are is even more energy efficient. It is also an option that is underutilized by many metal workers in the industry.
Productions of Virgin Aluminum and the Importance of Recycling
In nature, aluminum is most typically found in the form of aluminum oxide. Sapphire gemstones are aluminum oxides and are, in effect, transparent aluminum, but metallic aluminum is refined from an aluminum oxide ore called bauxite. Bauxite isn’t pure aluminum oxide but also contains iron, silicates, magnesium, titanium, and other metals. Separating the aluminum from the ore isn’t simply a matter of crushing and heating the ore until the aluminum melts out but a multistage process—called the Bayer process—where the ore is first dissolved into a series of chemical solutions:
- Digestion: Crushed bauxite ore is mixed with caustic soda (sodium hydroxide) and heated to 300°F to 400 °F in large tanks. This creates sodium aluminate while impurities like silicates settle to the bottom of the tank, where they are removed.
- Clarification: The slurry is then passed through a series of settling tanks, where the sodium aluminate decomposes into aluminum hydroxide and sodium hydroxide. The aluminum hydroxide settles to the bottom of the tank, where it can be removed.
- Calcination: The aluminum hydroxide is heated in a kiln at high temperatures (~1,160°F) to remove hydrates and convert them to pure aluminum oxide powder.
This final aluminum oxide powder can then be smelted to create metallic aluminum.
This aluminum oxide powder is then subjected to an additional and separate high-heat chemical process—the Hall-Heroult Process—where aluminum oxide is dissolved into molten cryolite, a sodium-aluminum salt. Then through electrolysis, or a direct current-induced chemical reaction, nearly pure metallic aluminum is formed and allowed to cool into an ingot.
This metallic aluminum ingot can then be sent to a foundry where an electric-arc furnace can melt it alongside trace percentages of other metals into aluminum alloys like the 3000 series aluminum used in drink cans, 6061 or 6063 structural and architectural aluminum, or 5000 series aluminum alloys used to cast tooling plate.
The production of virgin aluminum from ore is a three-step process, with every step being energy-intensive.
Additionally, many parts of the process offer a double carbon emission penalty both from the electrical production required for the process and as part of the chemical action needed for production.
Recycling aluminum is vastly less energy-intensive. Existing aluminum can simply be melted down and used to make a new aluminum product without repeated chemical reactions.
Direct Reuse Is the Best Aluminum Recycling
Reduce, reuse, and recycle is an old saying in environmentalism. Of the three, reuse is the most preferred but most underutilized. Aluminum comes from the foundries in standard shapes and sizes.
Typically, at least some of this isn’t used and sent to be recycled. While this is a worthy use, directly reusing the metal would be worthwhile since the metal is still in use.
The remnant aluminum left after cutting or machining has removed parts is the same as new metal for all intents and purposes.
This metal can be directly reused as it is. The only difference between remnant aluminum and new aluminum is that it is a nonstandard size and possibly cosmetic issues like scratches.
Direct reuse of this metal means energy savings and a reduction of carbon emissions, which improves even the process of recycling aluminum into new aluminum products.
All that is to ensure that this reclaimed remnant aluminum is the alloy needed for the job. Ensuring the use of 6061 instead of 7075 or vice versa where needed, or 6061 aluminum vs. 6063 or Alca 5 vs. 6061, and many other examples besides.
So long as you use aluminum where the alloy can be verified, there should be no issue with the use of remnant aluminum.
Enhancing the Aluminum Recycling Process
The aluminum recycling process is essential for maintaining sustainability in the modern world. As the demand for aluminum products increases, so does the importance of recycling. Not only does this process reduce the need for raw materials, but it also significantly lowers carbon dioxide emissions compared to producing virgin aluminum from ore. The recycling process for aluminum is remarkably efficient, with over seventy-five percent of all the aluminum ever produced still in use today—a testament to the effectiveness of recycling practices.
Recycled aluminum plays a critical role in the industry, as it is used to create new aluminum products such as aluminum cans, aluminum sheets, and aluminum foil. These items are staples in both consumer and industrial applications, and their continued production relies heavily on the availability of recycled aluminum.
The process begins with the collection of aluminum scrap, which includes everything from used aluminum cans to industrial aluminum sheets. This scrap aluminum is then cleaned and processed to remove contaminants, such as other metals and aluminum oxide, before being melted down. During melting, molten aluminum is formed, which can be molded into new products.
One of the most critical stages in this recycling process is ensuring that the aluminum scrap is free from impurities. Contaminants such as aluminum oxide and other metals can affect the quality of the final product, making it essential to thoroughly clean and sort the scrap before melting. By doing so, the industry can produce new aluminum products that are of the same high quality as those made from virgin materials.
Aluminum recycling is not just about reducing waste; it’s about creating a more sustainable and efficient system for producing the materials we rely on every day. As recycling technologies continue to improve, so too will the recycling rates for aluminum, ensuring that this valuable metal remains in use for generations to come.
Industrial Metal Service is a long time metal recycler that offers collection and scrap metal pick-up services to industrial firms.
In addition to these services, IMS also offers cut-to-order sawing of new and remnant aluminum. An XRF scanner verifies the remnant aluminum’s contents, so you know what type of aluminum you’re getting.
Our cutting service also allows you to buy precision-cut and process-ready aluminum that can be worked on directly after delivery. It is the ultimate in time, energy, cost, and carbon saving for metal workshops nationwide.