2024-11-22
Stainless steel-Why isn't stainless steel magnetic?
Magnetic knife racks might be good for hanging up your knives, just don't try throwing your kitchen sink at one.Although knives and kitchen sinks are both made of stainless steel, they're made of different combinations of alloys so they have different magnetic properties.Stainless steels are alloyed steels, says materials engineer Professor Veena Sahajwalla from the University of New South Wales.As well as containing iron and carbon, like plain carbon steel, they also contain other components which give the stainless steels superior properties for different applications.For example, knives are most likely from the 400 series says Sahajwalla, a family of stainless steels that also contains the metal chromium, which makes the knives more resistant to rust than if they were made out of plain steel.Whereas the kitchen sink is more likely to be from the 300 series. These stainless steels have had both chromium and nickel added, and are easier to form and weld. Some of the 300 series steels also contain molybdenum, which further increases their corrosion resistance, and is why they're often used in marine environments.But unlike other grades of stainless steel, the 300 series is not magnetic.The reasons for this come down to their structure.At the atomic level in a material like iron, which has strong magnetic properties, all the iron atoms are acting as mini magnets aligned in the same direction.So cumulatively they are all adding to the overall magnetisation of the material, this is known as ferromagnetism.But once you start adding other components to the iron, things get a little trickier.