Is Stainless Steel Magnetic? Understanding the Truth Behind the Metal
by AMC
Posted on August 08, 2025 at 05:01 PM
A universal question from both industry leaders and consumers is, is stainless steel magnetic? Stainless steel is found all throughout industry and everyday life, and yet, there is still confusion about its magnetic properties. Stainless steel is made of iron, and therefore, it might be reasonable to assume that stainless steel is always magnetic. This makes one ask the questions - is all stainless steel magnetic? The honest answer is no, there is not a clear yes or no. "Stainless steel" consists of over 57 standard alloy designs (modifications), with very different compositions and arrangements of atoms, which could relate to all physical properties including magnetism, also including fabrication, welding performance, and electrical properties, etc. Therefore, knowing which grades are magnetic is important in the sourcing of products for construction, infrastructure, and industrial manufacturing.
What is Stainless Steel?
Stainless steel is an iron alloy representing chromium and carbon. To be considered stainless steel, steel must contain 10.5 % chromium, and have a carbon content that does not exceed 1.2 %. The typical critical elements in stainless steel include iron, chromium, nickel, molybdenum, silicon, nitrogen, and manganese. For example, grade 304 contains roughly 73 % iron, 18-20 % chromium, and 8-10 % nickle, whereas grade 316 is 71 % iron, 16-18.5 % chromium, 10-14 % nickel, and 2-3 % molybdenum. Chromium reacts with oxygen to create an oxide-layer that heals itself providing corrosion protection. Nickel and molybdenum provide toughness and can also allow resistance to certain environments. Because of its strength and resistance to corrosion, stainless steel is widely used in heavy industry, infrastructure, fabrication, architecture, and engineering.
Magnetic vs. Non‑Magnetic: What’s the Difference?
Before we explore the comparative data, it is helpful to summarize the main variables that influence an individual alloy's behavior as either a magnetic, or a non-magnetic stainless steel. The main factors are the series of the alloy (i.e., its microstructure), its nickel content and the condition of the metal (i.e., had it been cold-worked or hardened). The following table summarizes these variables across the most common types of stainless steel to provide readers with a quick understanding of why some grades of stainless steel are inherently non-magnetic in their annealed conditions, while for other stainless steel alloys the answer is yes, stainless steel is magnetic, and how processing may affect material behavior.
|
Series / category |
Magnetic in annealed state? |
Nickel content & composition |
Effect of cold work / hardening |
Common grades |
|---|---|---|---|---|
|
300‑series (Austenitic) |
Very weak or non‑magnetic |
High nickel (around 8–10 %), e.g., grade 304 contains about 18 % chromium and 8 % nickel |
Cold working or hardening can induce magnetism as some austenite transforms to martensite |
303, 304 (“18‑8”), 316 |
|
400‑series (Magnetic stainless steel grades) |
Strongly magnetic |
Low or no nickel; ferrite or martensite is the dominant phase |
Already magnetic in the annealed state; hardening increases strength but doesn’t significantly change magnetism |
Ferritic: 409, 430; Martensitic: 410, 420, 440 |
|
Precipitation‑hardened (PH) |
Magnetic |
Contains some nickel (e.g., ~4 % in 17‑4 PH) but overall composition and heat treatment lead to a martensitic structure |
Remains magnetic; heat treatment increases strength rather than changing magnetism |
17‑4 PH |
Types of Stainless Steel Explained
- Austenitic stainless steels (non‑magnetic): These alloys, including grades 304, 316 and low‑carbon 316L, are a type of non-magnetic stainless steel. They contain high chromium and nickel; nickel stabilises the austenitic structure, making the steel non‑magnetic. Grade 304 typically has 18–20 % chromium and 8–10 % nickel, while grade 316 includes additional molybdenum for improved resistance to chlorides. Cold working can cause a slight magnetic response. They are used in structural components, hygienic process equipment and chemical tanks where non‑magnetic behaviour is important.
- Ferritic stainless steels (magnetic): Grades 409, 430 and 439 have little or no nickel and 16–18 % chromium; iron makes up around 83 % of grade 430. Their ferrite structure is ferromagnetic. Ferritic alloys offer moderate corrosion resistance and are common in indoor applications, ducting, automotive exhausts and cladding.
- Martensitic stainless steels (magnetic and hardenable): Grades 410, 420 and 440 contain higher carbon levels and can be heat‑treated. The martensitic structure is ferromagnetic because iron is the dominant phase. These steels are used for cutting tools, knives, surgical instruments and fasteners where strength and wear resistance are essential.
- Duplex stainless steels (partially magnetic): Duplex grades combine roughly equal amounts of austenitic and ferritic phases, providing high strength and excellent resistance to pitting and stress corrosion while retaining partial magnetism. They are favoured in offshore platforms, chemical processing and heavy‑duty structural applications.
A Closer Look: Ferritic vs Austenitic Stainless Steel
|
Property |
304 |
316 |
430 |
|---|---|---|---|
|
Magnetism |
Non‑magnetic |
Non‑magnetic |
Magnetic |
|
Metallurgical family |
Austenitic |
Austenitic |
Ferritic |
|
Corrosion & pitting resistance |
Good |
Good |
Reduced |
|
Maximum intermittent service temperature |
870 °C |
870 °C |
870 °C |
|
Iron (approx.) |
~73 % (balance) |
~71 % (balance) |
~83 % (balance) |
|
Chromium |
18–20 % |
16–18.5 % |
16–18 % |
|
Nickel |
8–10 % |
10–14 % |
– |
|
Molybdenum |
– |
2–3 % |
– |
|
Carbon |
<0.08 % |
<0.08 % |
<0.012 % |
This table highlights how the three common grades differ in magnetism, composition and performance. Grades 304 and 316 are both austenitic and non‑magnetic; 316 offers slightly higher nickel and molybdenum content, improving its resistance to chlorides. Grade 430 is ferritic, magnetic and contains no nickel, which lowers its corrosion resistance but increases its magnetic response.
Why Magnetism Matters in Stainless Steel Applications
There can be circumstances in which magnetic fields can affect the performance of stainless steel when making or servicing steel components. In welding applications, magnets can disrupt the welding arcs, creating disorganized weld beads; magnets can also affect electric currents in fabricated parts. On occasion, the designer may purposely specify magnetic stainless steel grades (like 430 or 420) when they want the component to have or respond to a magnetic field; and there are other situations, when made out of non-magnetic stainless steel (like 304 and 316) is critical, as with medical imaging equipment (MRI), and precision instrumentation where there can be no magnetic interference. Therefore, the application determines whether to select magnetic or non-magnetic stainless steel.
Conclusion
In conclusion, the answer to the question 'is stainless steel magnetic?' is that the magnetic behavior is variable and contingent on stainless steel's alloy structure - said structures include ferritic, martensitic or austenitic. Stainless steel with austenitic grades, including 304, 316 and 316L, are generally non-magnetic but may give a small magnetic form after cold work or deformation. Ferritic steels including 430, which is made up of approximately 83% iron and 16-18% chromium, and martensitic steels including 410 and 420 exhibited strong magnetism, confirming that in many cases, stainless steel is magnetic, which should not be perceived as "coercive magnetism." Duplex steels did contain both austenitic and ferritic steels with excellent strength, corrosion resistance and moderate magnetism - it should be noted that although magnetic welding processes, metal plating and electrical behaviour may be impeded by magnetic fields, engineers would need to identify the appropriate grade for the finished product on whether magnetism was important or must be avoided.
Amardeep Steel Centre hold stocks of a vast wide supply network of austenitic, ferritic, martensitic and duplex stainless steels as well. They can advise you on non-magnetic grades, including 316, when dealing with electromagnetic interference or magnetic grades, including 430, when an induced magnetic response is assumed. Their collective experience will allow their customers to balance corrosion resistant materials to mechanical strength to magnetic performance of industrial projects.