When choosing the right stainless steel fasteners for your project—especially in sensitive or high-precision environments—magnetism can become an unexpected but critical factor. While austenitic stainless steel fasteners are widely known for being non-magnetic, the reality is a bit more nuanced.
In this guide, we’ll explore how magnetism affects austenitic stainless steel bolts and screws, when it becomes a concern, and how to make the right choice for your application.
What Are Austenitic Stainless Steel Fasteners?
Austenitic stainless steels are the most commonly used class of stainless steel due to their exceptional corrosion resistance, formability, and durability. They are ideal for environments requiring strength and resistance to chemical or saline exposure.
Popular austenitic stainless steel fastener grades include:
304 (A2) – The industry-standard for general-purpose corrosion resistance
316 (A4) – Ideal for marine environments due to superior chloride resistance
310 – Suitable for high-temperature and heat-intensive applications
These fasteners are widely used across industries such as:
Marine and offshore engineering
Food and beverage processing plants
Pharmaceutical and medical equipment manufacturing
Chemical processing industries
Are Austenitic Stainless Steel Fasteners Magnetic?
Non-Magnetic in the Annealed State
In their annealed condition, austenitic stainless steels have a face-centered cubic (FCC) crystal structure, which prevents magnetic alignment. This makes fresh, factory-processed non-magnetic stainless steel bolts and nuts ideal for:
MRI rooms and hospitals
Sensitive electronics assemblies
Scientific and laboratory instruments
Magnetism After Cold Working
However, things change during fabrication. When austenitic stainless fasteners undergo cold working—such as machining, forming, or thread rolling—the material can partially transform into martensite, a phase that exhibits magnetic properties.
This is most noticeable around:
Threaded areas
Head and shank junctions
Bent or formed sections
Thus, cold worked stainless steel fasteners may exhibit slight magnetism, even though they originated as non-magnetic.
Why Magnetism Matters in Fastener Selection
Magnetic properties in stainless steel fasteners may not be an issue in everyday construction, but in precision or electronic environments, it can create real problems:
In MRI suites, even trace magnetism poses safety hazards
In measurement instruments, magnetic interference can distort data
In RF electronics, magnetic fields can cause electromagnetic disruption
Understanding the application sensitivity helps determine whether slightly magnetic fasteners are acceptable or if certified non-magnetic stainless steel bolts are necessary.
How to Minimize Magnetism in Austenitic Fasteners
If your project demands non-magnetic performance, here are proven methods to reduce or eliminate residual magnetism:
✅ Use annealed fasteners – Request solution-annealed stainless steel bolts from your supplier
✅ Choose specialty grades – Opt for low-carbon versions like 316L, or medical-grade 316LVM, which are engineered to reduce magnetism
✅ Request magnetic testing – Ask your supplier for magnetism certification or test results
✅ Demagnetize if needed – Post-processing demagnetization can help eliminate residual magnetic fields caused by fabrication
Quick Comparison Table
| Feature | Austenitic Stainless Steel Fasteners |
|---|---|
| Magnetic in Annealed State | No |
| Magnetic After Cold Working | Slightly |
| Common Grades | 304, 316, 310 |
| Corrosion Resistance | Excellent |
| Best For | Marine, food, chemical, non-magnetic environments |
Final Thoughts
So, are austenitic stainless steel fasteners magnetic? In their natural annealed state, they are not. But after processes like cold working or machining, some slight magnetism may appear.
For general-purpose applications, this minor magnetism typically doesn’t matter. However, in sensitive environments—such as MRI rooms, aerospace systems, or precision sensors—you should choose the right non-magnetic stainless steel fasteners and verify their properties.
For critical projects, always consult with your supplier and request certified non-magnetic stainless bolts and nuts tailored to your application.
