When people think of steel, they often imagine a strong and magnetic metal. However, not all steels are magnetic. In fact, certain types of steel—especially specific grades of stainless steel—are known for being nonmagnetic or only slightly magnetic. Understanding what makes some steels nonmagnetic is essential for engineers, designers, and manufacturers working in industries such as food processing, medical equipment, marine applications, and electronics.
In this article, we’ll explore which types of steel are nonmagnetic, why they behave that way, and where they are commonly used. As a trusted supplier of premium stainless steels, SAKYSTEEL provides in-depth technical expertise and high-quality materials for all nonmagnetic steel requirements.
Nonmagnetic steel refers to alloys that do not exhibit strong magnetic attraction. In scientific terms, they are classified as austenitic steels because of their specific crystal structure, known as face-centered cubic (FCC). This structure does not allow for the alignment of magnetic domains, which makes the steel essentially nonmagnetic.
However, it’s important to note that some steels may become slightly magnetic after cold working or welding, but they still retain much weaker magnetism compared to ferritic or martensitic steels.
Magnetism in steel depends largely on its microstructure. There are three main types of stainless steel microstructures:
Austenitic (Nonmagnetic) – Face-centered cubic structure; contains high amounts of nickel and chromium; nonmagnetic in annealed condition.
Ferritic (Magnetic) – Body-centered cubic structure; contains chromium but little to no nickel; strongly magnetic.
Martensitic (Magnetic) – High carbon and chromium content; magnetic and hardenable by heat treatment.
Austenitic stainless steels owe their nonmagnetic properties to nickel, which stabilizes the FCC structure and prevents the formation of magnetic ferrite or martensite phases.
These are the most widely used nonmagnetic steels. Key grades include:
304 Stainless Steel (UNS S30400)
Known as the most common stainless steel, 304 contains 18% chromium and 8% nickel. It is nonmagnetic in the annealed condition but can become slightly magnetic after heavy cold work.
316 Stainless Steel (UNS S31600)
Contains molybdenum for improved corrosion resistance, especially in marine and chemical environments. It is preferred where both corrosion resistance and nonmagnetic behavior are needed.
310 and 321 Stainless Steels
These grades are also nonmagnetic and are designed for high-temperature or oxidation-resistant applications.
904L Stainless Steel (UNS N08904)
A super austenitic grade with high nickel (24–26%) and molybdenum (4–5%), making it nonmagnetic even after fabrication.
Nonmagnetic steels serve critical roles in industries where magnetic interference, corrosion, and hygiene are key concerns. The benefits include:
Low Magnetic Permeability: Prevents magnetic interference in sensitive electronic or measuring equipment.
Excellent Corrosion Resistance: Ideal for marine, chemical, and medical applications.
Cleanability: Smooth, nonporous surface prevents bacterial buildup—perfect for food and pharmaceutical industries.
Durability and Strength: Maintains high toughness even at cryogenic temperatures.
Because of their unique combination of properties, nonmagnetic steels are used in:
Nonmagnetic stainless steels are used for surgical tools, MRI scanner components, and hospital furniture because they don’t interfere with magnetic fields.
316 and 904L stainless steels are widely used for ship components, propeller shafts, and offshore platforms, offering resistance to seawater corrosion and minimal magnetism.
Austenitic grades such as 304 and 316 ensure cleanliness, hygiene, and resistance to acids and salts found in food processing.
Nonmagnetic properties are crucial in instrumentation housings and aircraft components, where magnetic interference could affect performance.
Austenitic steels maintain stability in extreme cold and do not disturb magnetic sensors, making them ideal for cryogenic storage tanks and precision devices.
Even nonmagnetic steels can develop slight magnetism due to:
Cold Working (Forming, Bending, or Rolling): Mechanical stress may induce partial transformation to martensite, increasing magnetism slightly.
Welding: Heat-affected zones can introduce ferrite, leading to local magnetism.
Composition Variations: Lower nickel content may reduce austenitic stability, increasing the risk of magnetic response.
To maintain nonmagnetic properties, manufacturers must carefully control alloy composition and processing conditions.
A simple way to test is by using a small magnet. Place it near the steel surface:
If there’s no attraction, it’s nonmagnetic (austenitic).
If it sticks slightly, it may have some ferritic or martensitic phases due to cold work.
If it sticks strongly, it’s magnetic (ferritic or martensitic).
Professional laboratories can measure magnetic permeability more precisely using specialized instruments.
| Property | Magnetic Steels (Ferritic/Martensitic) | Nonmagnetic Steels (Austenitic) |
|---|---|---|
| Magnetic Behavior | Strongly magnetic | Nonmagnetic or weakly magnetic |
| Structure | BCC or BCT | FCC |
| Nickel Content | Low or none | High (8–25%) |
| Corrosion Resistance | Moderate to good | Excellent |
| Work Hardening | Low | High |
| Common Grades | 409, 430, 420 | 304, 316, 310, 321, 904L |
This table highlights the major differences between the two steel families, making it easier to select the right grade for each application.
SAKYSTEEL is a professional manufacturer and global supplier of stainless steel materials, offering high-quality austenitic grades suitable for nonmagnetic applications.
Our product range includes:
Stainless Steel 304 / 304L Bars, Plates, and Tubes
Stainless Steel 316 / 316L Marine Grade Materials
Super Austenitic 904L Sheets and Pipes
Custom Sizes and Finishes for Nonmagnetic Components
All materials are supplied with EN 10204 3.1/3.2 certificates and meet ASTM, ASME, and ISO standards. We also provide customized solutions based on customer requirements for strength, corrosion resistance, and magnetic performance.
Not all steels are magnetic—especially those in the austenitic stainless steel family. Grades like 304, 316, and 904L are excellent examples of nonmagnetic steels that offer outstanding corrosion resistance, strength, and durability. These materials are indispensable in industries where magnetic neutrality and reliability are critical.
Whether you need nonmagnetic stainless steel for marine, medical, or industrial use, choosing a trusted supplier ensures quality and performance. SAKYSTEEL stands ready to provide top-tier stainless steel products, technical support, and fast global delivery for your next project.