Steel Recycling

Did you know?

• Recycling steel saves considerable energy. Making steel from recycled material uses only about a quater of the energy to make steel from raw materials
• The recycling rate for steel cans in Australia in 2003 was only around 44%
• 867 tonnes of steel cans were collected for recycling in Canberra in 2005-06

Introduction

The tin plated steel can, although widely used today as a strong container to preserve foods, was only invented by Durand in 1810, with the first cannery opening in London shortly afterwards. The first cans were all hand made, and it was not until the late nineteenth century that machines for making cans were developed.

Steel itself, unlike cast iron, is a relatively new material. Steel was first made in small quantities from iron by Huntsman in 1740, but it took until the middle of the 19th Century before processes were developed that led to the large-scale production of steel.

Manufacture

Coils of steel suitable for manufacturing tin plated steel cans are made by Integrated Steel Making techniques; Electric Arc Furnace melting followed by continuous casting of steel slabs suitable for hot strip rolling and cold reduction or rolling down to small thickness or gauge.

In Integrated Steel Making, the first step is to make molten cast iron by heating a mixture of coke, iron ore and limestone (flux) in a blast furnace. The cast iron produced is converted to steel using the Basic Oxygen Steel Making Process (BOS). In this process, the iron from the blast furnace is heated to about 1,700oC together with up to 20% scrap steel, which can be used to control furnace temperature. In the BOS furnace, oxygen is blown over the molten surface, removing a particular level of carbon from the iron. Other impurities are also removed during this process.

Steel can also be made in Electric Arc Furnaces and processed in Mini Mills. These mills use electricity to melt scrap steel, which is then cast into slabs and further processed into other steel products. Steel from the BOS is continuously cast into slabs ready for rolling at the Hot Strip Mill. After hot rolling, coils are cleaned and cold rolled to final gauges suitable for the application of tin. The product made here is called Tinplate.

Steel cans are made from Tinplate - by using sheets cut from coils of steel coated with a very thin layer of tin. The tin, which is applied by an electrolytic process, is used to prevent corrosion of the steel surface, thus making Tinplate suitable to package food and pet food, aerosols, paints, juice, cooking oils, etc.

Recycling

Steel cans from kerbside collections are taken to recycling sorting centres where they are either separated by hand or with magnets.

The cans are then baled and sent to either

1. BHP steel works at Newcastle or Whyalla, which use the cans to makes new steel
2. A detinning plant at Port Kembla in NSW, where the cans are detinned before being made into new steel in an integrated steel plant

Sources

Beverage Industry Environment Council, 1996, Recycling Audit and Garbage Bin Analysis, June - September.

BHP Steel brochures, 1993 and 1997.

Recycling and Resource Recovery Council, 1994, Recycling and Resource Recovery in Victoria, Annual Report.