Separating and recovering stainless steel is an issue faced by many companies processing material, from the Recycling industry (where the focus is recovery or removal) to Food manufacturing (where the aim is purely removal). So how can you do it?
Firstly, the assumption is that stainless steel is non-magnetic? But is that actually the case?
In fact, the answer is, unfortunately, a little complicated.
As for whether they are magnetic, the answer is that it depends. There are several families of stainless steels with different physical properties. A basic stainless steel has a ‘ferritic’ structure and is magnetic. These are formed from the addition of chromium and can be hardened through the addition of carbon (making them ‘martensitic’) and are often used in cutlery. However, the most common stainless steels are ‘austenitic’ – these have a higher chromium content and nickel is also added. It is the nickel which modifies the physical structure of the steel and makes it non-magnetic.
So the answer is yes, the magnetic properties of stainless steel are very dependent on the elements added into the alloy, and specifically the addition of nickel can change the structure from magnetic to non-magnetic. Also, it is possible for the magnetic permeability of austenitic steels to be changed during processing. For example, cold work, welding and abrasion are liable to increase the amount of martensite and ferrite respectively in the steel.
In industry, whether that is in recycling or food processing, the stainless steel has been ‘worked’ and the vast majority has a recognizable albeit low magnetic attraction. Then it is a case of using the right technology to enable separation.
This can be achieved with:
The most recent technological development in Magnetic Separation is the High Intensity Separation Conveyor, which is shown to separate stainless steel items such as razor blades.
So to answer the question, yes it is possible to separate stainless steel and the type of technology needed is very much dependent on the application. Further information can be obtained by speaking with one of Bunting’s technical engineers.