According to the Steel Recycling Institute, 73 million tons of steel were recycled or exported in the United States in 2006--more than aluminum, paper, glass and plastic combined. The act of recycling steel involves a long factory process, but much of it can be collected and used again. The Steel Recycling Institute found that about half of the steel produced in the United States today has been recycled already.
Significance
Steel is one of the easiest materials to recycle. It's taken from roadside collections, drop-off sites or multi-material buyback centers. However, most of the steel suitable to be recycled is mixed in with other materials. Reusing steel is a simple matter, since it is a material that can be used over and over, but first it must be separated. This is the part that requires the most effort. Each material-recovery facility may have its own unique methods, so treat each on a case-by-case basis.
Types
The scraps initially collected include three main types: ferrous metal, which is defined as metal that contains iron; non-ferrous metal; and non-metallic materials, such as plastic and foam. The ferrous metal is the type that recycling facilities want to collect and ship to steel mills. The other two materials are also worth collecting for different purposes.
Delivery
Schnitzer Steel Industries--a Portland, Oregon company that is one of the nation's largest recyclers of scrap metal--states that scraps arrive in a facility by train, barge, truck, car or foot. If radiation is detected, the supplier cannot unload the contents. Otherwise, the scraps are unloaded into a large pile. Once they are placed onto a conveyor, the scraps go through a double-feed roller, which crushes the material and controls the flow into the mill, and a hammer mill, which continues to cut through scraps until they are small enough to fit through the grates below.
Separation
Small pieces of shredded scraps fall through the grates and onto a shaker table and conveyor. The pieces again are scanned for radiation to ensure that none of the dangerous substance has leaked from sealed containers during the process. Magnetic drums automatically separate the metallic materials. Any remaining non-metallic materials are sucked up into a container like a vacuum.
Collection
Workers stationed along the conveyor recover recyclable materials like copper, which would reduce the purity of steel, and non-recyclable materials that couldn't previously be extracted from the ferrous metal. Ferrous materials are then collected and shipped back to steel mills to be reused for new products. The rest of the non-ferrous metals, such as stainless steel and aluminum, are separated again and shipped to foundries for use in metal products.
Steel Mills
Steel is shipped in large crushed bales to steel mills. There, the bales are combined with other steel scraps and melted in a furnace to make new steel. From this point, recycled steel is treated just like steel made from virgin materials.
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