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Austenitic Stainless Steel: Is It Magnetic or Not?
Austenitic stainless steel is one of the most common and general stainless steels owing to its popularity as far as the resistance to corrosion, formability, and strength are concerned. But when it comes to magnetism, the question that most people currently using austenitic stainless steels usually ask is: can austenitic stainless steels become magnetic? Simplifying what this alloy entails, this alloy is capable of comparing to the likes of some other types, such as ferritic stainless steel or whether it can ever be made magnetic at all.
Table of Contents
What is an austenitic stainless steel?
Austenitic stainless steel may be characterised as a type of alloy-stainless steel with high levels of chromium and nickel, and in some cases, very low percentages of molybdenum and even nitrogen. These additives stabilise the austenitic micro pattern to provide the steel with corrosion resistance and outstanding vigour.
The austenitic stainless steel grades can vary depending on their type. They cannot be hardened using heat treatment, making them an excellent choice for surfaces that require smoothness and extreme corrosion resistance, such as in construction, food processing, the chemical industry, and marine applications.
Standard grades of austenitic stainless steel include, among others:
304: The most widely employed grade, which is very versatile.
316: Provides better resistance to corrosion as it is combined with molybdenum.
321: Stabilised titanium, high temperature strength.
The architectural applications and finish of these grades can be read at the official site of Topson Stainless Steel, which is a reliable source of stainless steel cladding, decorative sheets and manufactured metal products.
Do Austenitic Stainless Steels have magnetism? Is it permanently non-magnetic?
Inherently, austenitic stainless steels are non-magnetic because they belong to the face-centred cubic (FCC) crystal structure. This framework fails to give support to the arrangement of magnetic domains, which is a cause of magnetism.
But, one question that may be asked is:
● Could austenitic stainless steel be made magnetic?
● The answer is yes, and this is only in the case of certain conditions.
Under the conditions of cold working (bending, machining or deep drawing), a part of the structure of the austenitic stainless steel can be converted into a martensitic phase that is magnetic. It implies that though the steel could initially be non-magnetic, it can become partially magnetic due to some mechanical processes, particularly in lower nickel grades such as 304.
Now you must be clear whether austenitic stainless steels are magnetic or not!
Correlation between Austenitic and Ferritic stainless steel
To have a proper perception of the magnetic behaviour of stainless steel, it would be helpful to examine its mirror opposite, ferritic stainless steel.
Austenitic vs ferritic stainless steel
The ferritic stainless steels have a greater amount of chromium with minimal or zero nickel. Their structure is body-centred cubic (or BCC), and it is intrinsically magnetic. However, ferritic grades are non-phase transforming consistently with cold working, as compared to austenitic grades, which are strong in phase transformation after cold working- they always remain magnetic.
This difference points to one of the most important relationships between stainless steel types, austenitic and ferritic:
Austenitic
Non-magnetic when in the annealed state, and then may acquire magnetism when deformed.
Ferritic
Ferritic is permanently magnetic since it has a ferritic crystal structure.
When you want stainless steel that will still be non-magnetic when the fabrication is completed, you are advised to use higher nickel content austenitic varieties, i.e., 316 or 310.
Can austenite be derived from ferrite?
Yes, austenite can be transformed from ferrite. Ferritic steel can be converted into austenitic stainless steel through heat treatment, requiring a temperature up to 727℃. It can’t be obtained directly through mechanical processing.
Visit Topson Stainless Steel Products to browse high-grade architectural quality stainless steel austenitic and ferritic finishes. Topson Metal Solutions offers a comprehensive range of products suitable for interior, exterior, and artistic metal design.
Conclusion
Austenitic stainless steel is a material of choice where there is a need for high levels of corrosion resistance and sanitary appearance. It is usual to be non-magnetic, but it will transform to magnetic in some conditions, like cold working. Knowing the distinction between austenitic and ferritic stainless steel assists in making the right choice of using the best material to suit your purpose.
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