Recycling iron and steel
Steel has one outstanding characteristic: it can be endlessly recycled without its material qualities being compromised. The iron atoms are indestructible, and by melting scrap metal it is simple to get the atoms to arrange themselves in a new, regular way to form new steel with new properties.
Recycling is really nothing new for the steel industry. Ever since the 19th century, indeed, there have been processes for melting scrap metal and making new steel products. Nowadays, scrap is a strategic and sought after raw material for the steel industry.
Naturally enough, accompanying the iron atoms are all the other species of atoms, the alloying elements, which go to constitute different steels. Most often, the scrap mixture can be adjusted in order to utilise the existing alloying elements for new products.
Moreover, it is also possible to recycle steel which has been surface treated. One example that can be mentioned here is electro galvanised steel sheets from e.g. motor cars. When the galvanised steel product is sent for recycling and the steel undergoes remelting, the zinc coating ends up in the flue gas dust emissions and it is also duly handled and recycled.
On the one hand, steel plants utilise internal scrap, which derives from the companies’ own production processes. This may include, for example, steel residues from ladles and furnaces or cropped (sheared) tail-ends from continuous casting and rolling processes. On the other hand, the plants utilise merchant (external) scrap; this consists of end-of-life steel products (from scrap metal collections) and scrap from the fabrication/metalworking of steel products in workshops (prompt scrap).
For merchant scrap, there is a well-established market in operation, with scrap metals being bought and sold in accordance with agreed rules governing quality.
Scrap divided into different classes
Steel scrap comes from several different sources and it varies sharply, both in respect of physical and chemical properties. The age of a scrap consignment can vary from one day to over 100 years old! The properties depend on where the scrap comes from and when it was produced. Thousands of different kinds of steel, for literally tens of thousands of different applications, mean that one piece of scrap is seldom like another. It is therefore essential that the scrap is sorted into different categories, classes of scrap, in order for the recycling process to be as effective as possible.
Steel scrap is divided, for quality reasons, into a number of classes or categories depending on origin, dimensions and analysis. The scrap classification - together with rules covering delivery - is shown in the form of one Swedish Scrap Book for unalloyed metal scrap and one for stainless steel scrap. These result from voluntary agreements between the scrap metal trade and steel production plants. Similar scrap classes are also to be found in other countries. The scrap classification thus functions as a basic data and regulatory framework for trade with scrap, but also as a platform for joint quality development encompassing the metal recycling industry and the steel industry.
Non-alloy and low alloy scrap, certain examples:
Scrap class and designation
- 11 Prime miscellaneous scrap
- 117 Fragmented scrap
- 12 Secondary miscellaneous scrap
- 142 Prime railway scrap
- 31 Prime loose steel sheet scrap
- 32 Prime compressed (baled) thin steel sheet scrap
- 622 Miscellaneous copper alloyed scrap
Stainless steel scrap:
- Chromium-bearing stainless steel scrap (2 quality classes)
- Chromium and nickel-bearing stainless steel scrap (9 quality classes)
- Chromium, nickel and molybdenum-bearing stainless steel scrap (9 quality classes)
Film from Team Stainless on the recycling of stainless steel:
Research and development
In order for the sorting, quality assessment and – not least – the use of metal scrap to become even more effective and efficient, continuous research into scrap metals and scrap handling are undertaken. The research takes place both under the terms of Jernkontoret’s joint Nordic research and at the metal scrap recycling companies themselves.
Several projects within the context of the Steel Eco-Cycle research programme 2012-2014 (Stålkretsloppet) have dealt with metal scrap and recycling. The Steel Eco-Cycle has, among other things, provided new insights into how we can increase the yield of iron and alloying elements and how we can retain the metals in steel’s own eco-cycle.
Read more: The Steel Eco-Cycle research programme, summary and final reports.