Do you know why some stainless steels are magnetic while others are not? You are in luck. This article explains the science behind magnetic steel. Today, you will learn how composition and atomic structure determine whether your steel will attract a magnet or not.
Basic Magnetism & How It Applies to Stainless Steel
Below you will understand how the crystal structure of your stainless steel alloy affects magnetism.
Types of magnetism:
Ferromagnetism, paramagnetism, and diamagnetism are the three main categories for describing magnetism in metals.
Ferromagnets, such as iron, nickel, and cobalt, exhibit a strong magnetic attraction. Paramagnetic metals, in comparison, exhibit a weak magnetic response. Meanwhile, diamagnetic metals such as gold and copper repel the magnet slightly.
Influence of microstructure and alloy composition
Martensitic stainless steels, high in iron, are magnetic. This is because iron possesses a body-centered tetragonal (BCT) crystal structure that aligns with magnetic domains. However, the addition of non-magnetic metals may reduce your alloy’s magnetism slightly.
For instance, there are steels like 310 and 303 that don’t stick to magnets. These alloys possess a lower iron content. Then, there are duplex stainless steels that are partially magnetic. All these depend on their composition and grades.
Role of iron, chromium, nickel, and other alloying elements
As you have learnt, the crystal structure of alloying elements determines the magnetic properties of your steel. Therefore, high-iron SS alloys are magnetic. While SS alloys with more chromium or nickel have diminished magnetism.
Why Don’t Magnets Stick to Some Stainless Steels?
When a magnet doesn’t stick to stainless steel, it doesn’t mean it is fake. The reason usually lies in the type of stainless steel and its thermal processing history.
Austenitic Stainless Steels and their Non-Magnetic Character
Austenitic stainless steels have a face-centered cubic crystal structure, which gives them weak magnetic properties. They are used in making kitchen utensils, sinks, pressure vessels, cryogenic equipment, and handrails.
Cold Working, Deformation, Welding Effects
When you cold-work stainless steel, some of the metal can transform into martensite. For instance, during welding or machining, the heat can create small magnetic domains in austenitic stainless steels.
Coatings, Surface Layers, Gap
Oftentimes, metal alloys are anodized or polished to form an extra layer of protection against corrosion. These layers may contain non-magnetic elements, preventing a magnet from sticking to the surface of your stainless steel.
Magnetic vs Non-Magnetic Stainless Steel Grades
Stainless steels are categorized into:
- Austenitic steels – Non-magnetic because of their crystal structure, but can become slightly magnetic when worked or welded.
- Ferritic steels – Strongly magnetic since they have a structure rich in iron that easily aligns with magnetic fields.
- Duplex steels – These are partly magnetic.
- Precipitation-hardened steels – Magnetic after heat treatment, which changes their structure to make them stronger and responsive to magnets.
Is 304 austenite stainless steel magnetic?
Not exactly. 304 stainless steel is not magnetic. When you bend, weld, stretch, or roll the metal, some parts become martensite, which temporarily makes them magnetic.
Is 316 austenite stainless steel magnetic?
316 austenite stainless steel is not magnetic. The major difference is that 316 contains molybdenum, which helps it fight corrosion better.
Is 430 ferrite stainless steel magnetic?
Yes, it is. 430 contains high concentrations of iron. Even after anodizing or welding, 430 remains magnetic.
Other magnetic grades (e.g., 410, 420, 2205 duplex)
Some other grades of stainless steel and their magnetic properties are
- 410 martensite steel: These martensite steels have high magnetic properties because of the BCT structure.
- 2205 duplex: Duplex steels contain a mix of ferrite and austenite, so they are partially magnetic.
- 17-4: Precipitation-hardened steels like 17-4 have a strong magnetic response due to their underlying martensite crystal lattice.
Comparison Table: Magnetism by Stainless Steel Grade
| Stainless Steel Grade/Type | Crystal Structure / Phase | Typical Magnetic Behavior | Notes & Exceptions |
| 304,316 (Austenitic) | Face-Centered Cubic (FCC) austenite | Not magnetic (but can be a little magnetic if bent or rolled) | Used for sinks and cooking pots. 316 has extra molybdenum to stop rust. |
| 430 (Ferritic) | Body-Centered Cubic (BCC) ferrite | Magnetic | Stays magnetic even after shining or welding. Found in fridges and appliances. |
| 410, 420, 440 (Martensitic) | Body-Centered Tetragonal (BCT) / martensite | Strongly magnetic | Hard. Used for knives, blades, and tools. |
| Duplex stainless steels (e.g., 2205) | Mixed austenite + ferrite | A little magnetic | Strong and used in ships and pipes. |
| Precipitation-hardened stainless (e.g., 17-4 PH) | Martensitic/transformable structure | Magnetic and very strong | Used in airplanes, turbines, and bolts. |
Common Use Cases: Magnets & Stainless Steel in Appliances & Cookware
Magnets and stainless steel interact differently in the kitchen. Sometimes magnets stick; other times, they don’t. Here are common questions about magnets and cookware.
Will magnets stick to a stainless steel refrigerator?
It depends on your refrigerator model. Many refrigerators use type 304 stainless steel panels. Thus, not all magnets might stick to them. At the same time, many older refrigerators and some to date use Type 430 stainless steel, which is ferromagnetic.
Can magnets stick to a stainless steel fridge?
This is another question where the answer depends on your specific fridge model. Most stainless steel fridges attract regular magnets, but neodymium can stick to even non-magnetic austenite.
Do magnets stick to stainless steel pans?
It depends. If a magnet is weak, it won’t stick to austenitic steels. Rather, magnets stick to induction cookware, which is the broad name for cookware with a magnetic base. So if a magnet sticks to the bottom of your pan, that’s a clear sign that it’s induction-ready.
Magnetic surface options for a stainless steel fridge
If your fridge doesn’t hold magnets, attach magnetic sheets or adhesive films to the door. These surface options let you display notes, photos, or decorations without damaging the surface.
Choosing & Testing Magnets for Stainless Steel
You can easily understand steel type and quality by testing for magnetism. You don’t need complex tools to start. Just a few simple magnets and a careful approach.
How to check stainless steel quality
You can check the grade of your stainless steel using a small bar or fridge magnet. Hold the magnet close to your item. If it sticks, then the stainless steel is either ferritic or martensitic. But if it exhibits a weak attraction, your steel is likely an austenitic grade like 304 stainless steel.
Advanced lab techniques
In laboratories, you can check for magnetism using precision instruments. One method is to use magnetic permeability measurements, which indicate how easily a magnetic field passes through the metal. For more details, check the guide on permeability.
Another is magnetic induction testing, which can detect subtle changes in the steel’s structure. Engineers can also study magnetic pair behavior on how a metal reacts to positive and negative poles. This helps confirm if the magnetism is strong, weak, or surface-limited.
Limitations of magnet tests
Magnet tests can be limited by false positives or false negatives. In a false positive, the magnet sticks to a surface due to iron dust or a coating, rather than the steel itself. To remove this effect, thoroughly clean the stainless steel.
In false negatives, a magnet may not stick if the steel has a non-magnetic finish or protective layer. It might also not stick if the magnet is too weak. Hence, magnet tests are useful for quick observation, but not for a detailed understanding of your steel’s composition.
How to Make Stainless Steel Magnetic (or More Magnetic)
Here are the main ways to make stainless steel respond to magnets:
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Cold working/plastic deformation to induce martensite
When cold-working austenitic steel, the internal structure can change. This process can turn some austenite into strain-induced martensite.
Martensite is magnetic, so the steel becomes more magnetic in the areas you’ve coldworked. Cold working increases magnetism easily, but also hardens the steel and reduces its corrosion resistance.
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Heat treatment, annealing, sensitization
Magnetism of stainless steel is significantly enhanced by heat treatment. It typically occurs when heating and then quenching martensitic or precipitation-hardened steels.
Annealing reverses this magnetism and also makes the stainless steel austenitic again. This leads to sensitization and improves how the steel fights corrosion. It also makes the steel easier to work on.
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Applying magnetic coatings or magnetic underlayers
You can apply a magnetic coating to stainless steel to improve its magnetism. These coatings can be magnetic sheets or adhesive films. These coatings make magnets stick easily.
It also keeps the base steel unchanged and maintains the quality of the stainless steel. However, these coatings can wear off, chip, or dull the finish over time.
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Feasibility, limitations, trade-offs
Every method for making steel magnetic has its limitations. Cold working helps to improve magnetism, but it also makes the stainless steel more prone to corrosion.
Over time, the heat treatment can even turn austenite into martensite and cause warping. But note that the coatings are safe, but they don’t last long.
You can make stainless steel magnetic. But it might not work with every stainless steel. If you work in engineering or the industrial sector, cold working and heat treatment are more effective.
Do Magnets Damage Stainless Steel?
Magnets can damage the outer layer of your stainless steel. Here’s what to watch out for when using them:
Risk of scratching or surface abrasion
Regular magnets can scratch stainless steel, especially on polished or brushed finishes. Furthermore, strong neodymium magnets may leave scratches when they snap into place.
Many particles on the magnet’s surface can also drag across the steel, causing fine scratches on the surface. To prevent damage, move magnets gently and avoid sliding them across the surface.
Effects on coatings or protective layers (corrosion risk)
Scratches and coating damage expose the bare metal underneath. Moisture or saltwater from the air can collect in these spots, causing rust. So, wiping the area clean and dry after removing the magnets reduces the risk.
Best practices when using magnets on stainless steel surfaces
- First, always clean both the magnet and the surface before contact.
- Next, use soft or rubber-coated magnets to avoid scratches.
- Third, avoid sliding magnets. Lift them instead.
- Additionally, if you frequently use strong magnets, apply a thin protective film to the steel surface.
Conclusion
Grade and atomic phase play a huge role in how stainless steel responds to magnetic steel. Austenitic types of stainless steels, such as 304 and 316, aren’t magnetic. Meanwhile, the ferritic and martensitic types, such as 430 and 410, are magnetic.
FAQs
Does a magnet stick to a stainless steel fridge/refrigerator?
Some do. Older fridges with Type 430 steel attract magnets, but newer ones with Type 304 don’t. Most magnets stick better to the sides or back of objects.
Are LG stainless steel refrigerators magnetic?
Many LG fridges use 304 steel, so magnets slide off. Older 430 steel models hold magnets.
What are the best magnets for a stainless steel fridge?
If your fridge is based on austenitic steel, it is best to use a neodymium magnet. This type of magnet is strong enough to adhere to trace amounts of martensite in non-magnetic SS alloys. Otherwise, you can use a regular magnet.
How to test a stainless steel magnetism
Place a standard magnet on your steel’s surface.
- If it sticks firmly, it is likely Type 410 or 430 (magnetic).
- If it slides off or makes a weak attraction, it is probably Type 304 or 316 (non-magnetic).
Do magnets ruin or scratch stainless steel?
Yes, strong magnets can scratch polished finishes. This is why it is ideal to use rubber-coated magnets and to regularly clean the surface of your steel.
How to make stainless steel magnetic?
You can cold work, quench, or coat your steel with iron or nickel to increase its magnetic properties.
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