Each of us encounters stainless steel products almost every day — and for good reason. This material has a wide range of impressive advantages and properties. One of the most intriguing characteristics of stainless steel is its magnetic behavior. How does it work in practice, what causes it, and should stainless steel even be magnetic at all? INOX Polska explains.
Magnetic Properties of Stainless Steels
Whether stainless steel is magnetic depends on its crystalline structure. Stainless steels with ferritic, ferritic-austenitic (duplex), or martensitic structures are magnetic. In contrast, austenitic structures are non-magnetic. Austenitic steels can be divided into two groups:
- Austenitic – this group includes, for example, AISI 304, commonly used in the food industry.
- Austenitic-ferritic – in this type of steel, chromium and nickel are the main alloying elements, while titanium, molybdenum, and copper may also be added. Such steels are characterized by high strength.
However, there are certain conditions under which austenitic stainless steel may begin to exhibit magnetic properties. What exactly are these situations?
Causes of Magnetism in Austenitic Stainless Steels
Austenitic stainless steel can acquire magnetic properties in several ways. One of the main causes is cold working, during which magnetic martensite may form in the structure, increasing magnetic permeability. This type of processing includes stretching, deep drawing, pipe bending, or machining bars. Another reason for magnetism may be the form of the product itself — magnetic properties can increase due to strain hardening, which occurs during processes such as extrusion or wire drawing.
Manufacturing technology and welding processes also play an important role, as they can enhance magnetic properties in the weld area.
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