Is Stainless Steel Magnetic? YES or NO – Know the Answer!

Stainless steel is a popular material due to its specific properties. Among those, its lightweight and rust resistance are top characteristics. However, many applications require the material to be magnetic. This raises the question: Is stainless steel magnetic or not? Interestingly, this question is very confusing, and no one-word answer exists.

 

The reason is that stainless steel has multiple types that vary in terms of their microstructures. As this material is 70% iron, people expect it to be magnetic, as this material itself is magnetic. However, the reality may not be as per your expectations. In this article, we will debunk the magnetic behavior of stainless steel. So, let’s begin!

 

Overview of Stainless Steel Materials & Magnetism

Before diving into magnetism, let’s first have a bird overview of stainless steel itself.

 

Stainless steel is an alloy consisting of many alloying elements. Those include iron, chromium, nickel, carbon and manganese. However, iron and chromium comprise 80 to 85% of the composition in most stainless steel grades. This material is majorly popular due to its corrosion resistance. 

 

Here is the chemical composition of stainless steel material: 

 

Element	Typical Composition (%)
Iron (Fe)	65–75%
Chromium (Cr)	10.5–20%
Nickel (Ni)	0–14%
Carbon (C)	≤ 1.2%
Manganese (Mn)	0–2%
Molybdenum (Mo)	0–3%
Silicon (Si)	0–1%

 

The proportion of each alloy element varies from one stainless steel grade to another. However, its chromium (10.5%) content makes it stand out. This material creates a chromium oxide layer when it comes in contact with air or moisture. This oxide layer is very beneficial in making this material corrosion-resistant.

 

Have you got the basics of stainless steel? Let’s talk about the magnetic behavior of materials.

Magnetism is the behavior of material through which it either repels or attracts magnetism. In simple words, it is the force of attraction. This behavior is caused by the spin of electrons, which create magnetic moments. Each moment of an individual electron adds to create a magnetic field. As a result, the material exhibits magnetic behavior.

 

For example, copper is non-magnetic, and cast iron is magnetic in pure form. Magnetic materials stick to magnets. On the flip side, non-magicians don’t love magnets. Regarding stainless steel, some types are magnetic, while others are non-magnetic. We will discuss stainless steel’s behavior in the upcoming portion.

 

Is Stainless Steel Magnetic?

There is no Yes or No answer. Stainless steel has different types that vary in terms of their microstructure. Some of those types are magnetic, while others are non-magnetic. Austenitic is non-magnetic, while ferritic and martensitic are magnetic.

 

Let’s discuss the mechanism of magnetism. As you know, the atom has electrons in its orbitals. These electrons can be either paired or unpaired, depending on the materials. These electrons have their spin, which produces magnetic moments. In an orbital, if two electrons are present, the spin of both electrons will be opposite to each other. 

 

The spin of one electron can be upward, while the second electron’s spin will be downward. If an orbital has paired electrons, their spin cancels out due to their opposite direction. So, the net spin gets zero, and no magnetic moment is produced. On the opposite side, the orbital has an unpaired electron; its spin does not get canceled out. 

 

As a result, the magnetic moment is produced. However, this magnetic moment has to align in the same direction to induce magnetism in the material. Some stainless steel has FCC (Face-Centered Cubic) structure, and atoms are tightly held together. There is no space or magnetic domain where magnetic moments could align. 

 

This type of stainless steel is not magnetic. Conversely, some stainless steel types don’t have tight-held atoms. Spaces remain between atoms. These spaces are called magnetic domains, where magnetic moments align. The alignment of magnetic moments induces magnetism in the material.

 

Types of Stainless Steel & Their Magnetic Behavior

 

As I said earlier, there are multiple types of stainless steel materials. Each of those types differs from each other in terms of their microstructures. Remember, microstructure indicates how strong or weak the atoms are bonded together. Let’s discuss those types and their magnetic behavior:

 

1- Austenitic Stainless Steel

This type of stainless steel is very popular and considered premium. It makes 70% of all types and grades of stainless steel. It has FCC (Face-Centered Cubic) atomic geometry, which means that its atoms are tightly held together. In other words, atoms are packed together in the attic. 

 

There is no gap or space between those atoms. As there is no space, so no magnetic domain is produced. Remember, this stainless steel also has unpaired electrons. However, their magnetic moment does not align in one direction with the magnetic domains. As a result, no magnetism is induced in these types of stainless steel. 

 

2- Ferritic Stainless Steel

 

Stainless steel grades 409 and 430 are examples of the ferritic category. These stainless steels have BCC (Body-Centered Cubic) structures. This atomic arrangement is strong, but the spaces between atoms remain the same. 

 

These spaces give rise to the magnetic domain. Remember, this type of stainless steel has some unpaired electrons. The spin of these unpaired electrons produces magnetic moments. This magnetic moment aligns with the magnetic domain in one direction. As a result, magnetism is induced in these ferritic stainless steel. 

 

3- Martensitic Stainless Steel

 

This stainless steel type has chromium content. Due to this, its corrosion resistance is excellent. Regarding microstructure, it has BCT (Body-Centered Tetragonal) geometry. The overall position of atoms is similar in both BCT and BCC. It means the spaces between atoms remain there, which creates magnetic domains. 

 

Remember, martensitic stainless steel has unpaired electrons that produce magnetic moments. This magnetic-moment production is similar in ferritic and martensitic stainless steels. The small magnet moment produced by each unpaired electron aligns in one direction in the magnetic domain. This results in magnetism in these materials. 

 

4- Duplex Stainless Steel

 

The magnetic behavior of stainless steel can be very confusing, especially to newbies. It exhibits 50% ferritic and 50% austenitic characteristics. It has both FCC (Face-Centered Cubic) and BCC (Body-Centered Cubic) geometry. Some portions of these stainless steel have magnetic domains. 

 

This domain arises due to small gaps between atoms. Conversely, some portions have atoms tightly packed together and have no magnetic domain. This portion does not allow magnetic moments to align and produce magnetism. Its magnetic behavior is between ferritic and austenitic stainless steel.  

 

Does Stainless Steel Stick to Magnet?

 

Yes and No! Stainless steel has multiple types, as discussed above. Each exhibits different magnetic behavior. Stainless steel that is magnetic will stick to a magnet. If it is not magnetic, it won’t. 

 

As discussed earlier, stainless steel has four basic types. Those include austenitic, ferritic, martensitic, and duplex stainless steel. This austenitic stainless is non-magnetic and does not stick to the magnet. The reason is that it has FCC (Face-Centered Cubic) atomic arrangement. Atoms are tightly packed together. 

 

As a result, there are no magnetic domains that could allow the magnetic moment of an electron to align. So, it remains non-magnetic and doesn’t stick to the magnet when it comes close to it. In the case of ferritic and martensitic, both show magnetic properties. This is due to their loose atomic arrangement. 

 

There are gaps between the atoms. As a result, magnetic domains are present in these materials. These domains allow the alignment of magnetic moments. So, these materials are magnetic and stick to the magnet. The duplex stainless steel may stick to the magnet because it has magnetic and non-magnetic properties.

 

304 vs 316 Stainless Steel Magnetism

 

Interestingly, both grades 304 and 316 stainless steel are non-magnetic. They are austenitic and have FCC (Face-Centered Cubic) atomic arrangements. Atoms are tightly packed, and no magnetic domains are present. As a result, they are non-magnetic. However, the 316 stainless steel has a slightly higher proportion of molybdenum (Mo). 

 

When both grades undergo stress or cold working, their atomic structures change. There is a transition from austenite to martensitic or ferritic phases. So, the 304, having little to no molybdenum, temporarily becomes magnetic. It is very weakly magnetic and shows very little attraction towards the magnet. 

 

However, grade 316, when undergoing cold working, does not show any magnetism. This is due to its higher molybdenum proportion. Remember, grade 304 will also be very weakly magnetic, but still, it becomes magnetic. This is how both of these stainless grades differ from each other.

 

Frequently Asked Questions

 

Is 100% stainless steel magnetic?

 

No, there is no 100% stainless steel. Remember, it is an alloy consisting of many alloy elements. Moreover, stainless steel can be both magnetic and non-magnetic, depending on which type you have.

 

Does the magnetism affect the stainless steel CNC machining?

 

No, the magnetic behavior of stainless steel has nothing to do with its CNC machining. Remember, the CNC-based machine cuts the shape and drills the materials. So they can cut the stainless steel, whether it is magnetic or not.

 

What factors affect the magnetism of stainless steel?

 

The magnetism of stainless steel material depends on many factors. Some of those are as follows:

• Heat Treatment
• Crystal Structure
• Alloy Composition
• Mechanical stress through cold working

 

Conclusion

 

Stainless steel is a handy material used across various industries. Its corrosion resistance and low prices make it an ideal option for manufacturing industries. However, many seem to be confused about its magnetism. 

 

The primary reason behind this confusion is that stainless steel has many types. The magnetic behavior of each type varies from the other. In this article, I’ve discussed everything regarding the magnetism of stainless steel. In summary, the austenitic stainless steel is non-magnetic. All other types exhibit non-magnetic behavior.