Managing and remaking metals
Recycling basics
The steel industry, together with the scrap-processing industry, laid the groundwork for the recycling infrastructure for automobiles that exists today. In an effort to provide more steel scrap to the steel industry and reduce the automobile's impact on the environment, the two industries worked together in the early 1960s to develop the first automotive shredders.
Old cars are typically hauled to one of North America's estimated 12,000 automobile dismantlers, where reusable parts are removed before the stripped hulk is recycled. Selected items such as engines, transmissions, and other auto parts are resold to the public or auto repair garages and body shops.
After removing reusable components and other items such as batteries, tires, and fluids, the hulks are usually flattened and shipped by truck to ferrous scrap processors, where they are weighed for payment and unloaded. At a scrap yard, a crane lifts the crushed automobiles and loads them into the automobile shredder. The shredding process, which handles one car every 45 s, generates three streams: iron and steel, nonferrous metal, and fluff (fabric, rubber, glass, etc.). The iron and steel are magnetically separated from the other materials, and the steel shred is magnetically loaded into a railcar or truck, or stockpiled for future shipment to end markets or steel mills, where it is recycled to produce new steel.
The North American shredding industry consists of more than 200 shredders. Most shredders are located in the heavily populated states east of the Mississippi River. In Canada, most shredding operations are found in Ontario and Quebec, the nation's most populated provinces.
Environmental controls
Hand-in-hand with the technological advances in the steel-making process have come controls that minimize its environmental impact. Mills are now equipped with stack cleaners, which keep the dust out of the atmosphere. Among the dust-collection processes are bag houses that use cloth bags (like a vacuum cleaner).
North American steel mills have reduced their overall energy consumption by 43% in the past 20 years, while increasing productivity 94% since 1980 in terms of employee hours per ton of steel produced, according to the Steel Recycling Institute. In the future, increased attention will be paid to the total environmental picture, including resource consumption.
Several environmental benefits are realized from the steel industry's need for automotive scrap. Recycling a single car conserves more than 1130 kg (2500 lb) of iron ore, 635 kg (1400 lb) of coal, and 55 kg (120 lb) of limestone.
Aluminum on the rise
American Metal Market (AMM), a metals trade journal, reported late last year that aluminum would surpass plastic in the 2001 model year to become the third most-used material in light vehicles, with an average content of 115 kg (257 lb) per vehicle. "Steel and iron are the only materials still ahead of aluminum on the content scale, and iron interests have a lot to be concerned about in the competition from aluminum," AMM reported. According to AMM, high-performance aluminum is the fastest-growing class of major materials in the domestic auto market.
 After the removal of reusable components and other items such as batteries, tires, and fluids, the hulks of automobiles are usually flattened and shipped to ferrous scrap processors. |
"Automakers are responding to consumer demands for cleaner, more efficient, and safer cars and trucks. Hybrid-electric technologies get lots of attention, but cost and complexity are preventing their immediate, widespread use," said Richard Klimisch, Vice President of The Aluminum Association. "Engineers know that aggressive weight reduction is the best way to improve fuel economy, emissions, and performance. For these reasons, as well as improved corrosion resistance and recycl-ability, automakers are more and more turning to lightweight, high-strength aluminum."
Automakers in the past have applied aluminum mostly to specialty vehicles or very high-performance models. Examples include Acura's NSX, Audi's flagship A8 luxury sedan, and the civilian Hummer. As manufacturing methods have advanced, aluminum has become increasingly affordable. Several production vehicles prove the feasibility of affordable and environmentally friendly aluminum-bodied vehicles. For example, equipped with a lightweight aluminum frame, the Honda Insight achieves 30 km/L (70 mpg) on the highway.
According to AMM, examples of parts being converted from iron and steel to aluminum for 2001 models include:
- Front fenders and hoods on Ford's redesigned four-door Explorer and Mountaineer SUVs.
- Trunk lids, bumper beams, hoods, and wheels on the redesigned Oldsmobile Aurora. V6 models use aluminum-intensive suspensions. The Aurora contains an estimated 220 kg (480 lb) of aluminum.
- Aluminum engines will replace heavy iron units in GM's Duramax 6600 turbo-diesel V8 in GMC and Chevrolet 2500 and 3500 pickup trucks, crew cabs, and other vehicles.
 The shredding process, which handles one car every 45 s, generates three streams: iron and steel; nonferrous metal; and fluff such as fabric, rubber, and glass. |
According to The Aluminum Association, another reason for the increasing use of aluminum is "the superior strength of aluminum." On a per pound basis, aluminum is twice as strong as steel, which allows the designer to provide strong, yet lightweight, crumple zones. These help protect vehicle occupants from injury in all kinds of collisions. In addition, the use of aluminum in light trucks reduces the weight differential between cars and trucks, thereby reducing the risk of serious injuries to car passengers.
Aluminum has also found its way into light-duty trucks in places other than the body. A team of engineers from GM, Dana Corp., and Alcoa Inc. were challenged to develop "the world's longest one-piece light-truck propshaft." The engineers replaced the two-piece steel design with a one-piece aluminum driveline in an effort to improve NVH on the Chevrolet Silverado and GMC Sierra Heavy-Duty extended cab longbox pickups. The team's original challenge was to develop a one-piece aluminum propshaft with a length of 2032 mm (80 in) and a diameter of 146 mm (5.75 in), specifications previously unattainable in the light-truck industry.
To meet the stringent GM balance specification the new design required, Alcoa decreased the variation of the tube wall thickness by 50%, while Dana instituted rigid assembly and precision balance requirements. According to the team, the new one-piece propshaft not only provides improved vehicle NVH, but also "significant" cost reductions, a mass reduction of 8.5 kg (18.7 lb), and a simplified installation process.
