哪种不锈钢不带磁性？

哪种不锈钢不带磁性

When testing a piece of stainless steel with a magnet, it sticks. While testing another piece, it doesn’t. Both are labeled “stainless steel.”

So which one is actually non-magnetic? Does it matter for the project?

In medical equipment, MRI-adjacent components, sensors, food processing, and precision instruments — using the wrong grade can cause equipment malfunction, regulatory failure, or outright product rejection.

In short, austenitic stainless steels — primarily grades 304, 316, 321, 310, and 904L, are non-magnetic in their annealed state. Ferritic and martensitic grades (409, 430, 410) are magnetic.

However, the changes after cold working will surprise most buyers.

目录 折叠
1 Why Some Stainless Steels Are Magnetic and Others Aren't
2 哪种不锈钢不带磁性？
3 Magnetic vs Non-Magnetic Stainless Steels
4 Which Non-Magnetic Grade Is Right for Your Application?

Why Some Stainless Steels Are Magnetic and Others Aren't

Magnetism in steel is determined by its “crystal microstructure”, not simply its composition.

Stainless steel can be classified into five structural families:

FamilyMagneticCommon Grades
AusteniticNon-magnetic (annealed)304, 316, 321, 310, 347, 904L
FerriticMagnetic409, 430, 439
MartensiticMagnetic410, 420, 440C
DuplexWeakly magnetic2205, 2507
Precipitation-HardenedSlightly magnetic17-4 PH

The key is the “austenite phase”: a face-centered cubic (FCC) lattice structure that does not align with magnetic fields. Austenite is stabilized by nickel, which is why 300-series stainless steels (with 8–12% Ni) are the preferred non-magnetic choice.

哪种不锈钢不带磁性？

Grade 304 – The Most Common Non-Magnetic Stainless Steel

  • Composition: 18% Cr, 8% Ni
  • Permeability (µr): 1.02–1.08 (effectively non-magnetic)
  • Suit for: General fabrication, kitchenware, architectural components, chemical containers

Cold working (bending, drawing, rolling) can transform some austenite to martensite, introducing slight magnetism. Annealed 304 is reliably non-magnetic.

Grade 316 – Best Non-Magnetic Grade for Corrosive Environments

  • Composition: 16% Cr, 10% Ni, 2% Mo
  • Permeability (µr): 1.02–1.05 (more stable than 304 under cold work)
  • Suit for: Marine, pharmaceutical, food processing, chemical piping


Why it’s preferred for EMI-sensitive applications: The added molybdenum and higher nickel content make the austenite more stable, reducing risk of magnetism after fabrication.

Grade 321 – Non-Magnetic with High-Temperature Stability

  • Composition: 18% Cr, 9% Ni, stabilized with Titanium
  • Suit for: High-temperature exhaust systems, heat exchangers, aerospace components
  • Magnetic: Non-magnetic and stable up to 800–900°C

Grade 310/310S – Non-Magnetic at Extreme Temperatures

  • Composition: 25% Cr, 20% Ni
  • Suit for: Furnaces, kilns, heat treatment equipment
  • Very high nickel content ensures robust austenite stability — remains non-magnetic even after heavy forming.

Grade 904L – Premium Non-Magnetic Austenitic Steel

  • Composition: 20% Cr, 25% Ni, 4.5% Mo, Cu
  • Suit for: Sulfuric acid environments, offshore, luxury watchmaking

Near-zero magnetic permeability even after cold work; used in luxury timepieces for its non-magnetic and corrosion-resistant properties.

Other Austenitic Grades That Are Non-Magnetic

  • Grade 347

Niobium-stabilized; non-magnetic, good for welded structures;

  • Grade 253MA

High-temperature, rare earth additions; non-magnetic

The Cold-Working: When Non-Magnetic Becomes Magnetic

304不锈钢 that has been cold-worked (pipe bending, swaging, deep drawing) can become measurably magnetic. This is because cold deformation converts austenite to martensite – a magnetic phase.

How to detect: Use a Feritscope or magnetic permeability gauge (not just a handheld magnet — too imprecise).

How to fix: Solution annealing (heating to 1050–1120°C and rapid quenching) restores the austenite phase and non-magnetic properties.

Note please: For critical non-magnetic applications, always specify: “solution annealed and water quenched” in order. 

Magnetic vs Non-Magnetic Stainless Steels

GradeMagneticTypical µrCommon Use
304Non-magnetic (annealed)1.02–1.08General use
304 (cold-worked)Slightly magneticUp to 1.5+Depends on forming
316Non-magnetic1.02–1.05Marine/chemical
321Non-magnetic-1.02High temp
310Non-magnetic-1.01Extreme heat
904LNon-magnetic-1.001Premium/precision
430Magnetic400–600Automotive trim
410Magnetic700–1200Cutlery, shafts
409Magnetic200–400Exhaust systems
2205 (Duplex)Weakly magnetic5–10High-strength piping

 

Which Non-Magnetic Grade Is Right for Your Application?

If you need non-magnetic stainless steel pipe or tube:

Choose 316L seamless tube (annealed) for most industrial uses; 304L for budget-sensitive projects.

For MRI rooms and medical imaging environments:

Use 316L or 304L, solution-annealed, with verified µr < 1.005. Require mill test certificates (MTC) and third-party permeability testing.

For offshore and subsea piping:

316L or 904L — both non-magnetic and highly resistant to chloride corrosion.

For food and beverage processing:

304 or 316 — both meet food contact standards and are reliably non-magnetic.

For precision instruments or sensors:

Choose 316L or 904L, cold-drawn and annealed. Avoid 304 if the part undergoes any cold forming.

For high-temperature furnace components:

310S or 321 — austenite stable under thermal cycling.

We supply austenitic stainless steel pipe and tube in grades 304, 304L, 316, 316L, 321, 310S, and 904L — all produced in solution-annealed condition with full mill test certificates.

  • Material traceability from melt to delivery (EN 10204 3.1 / 3.2 MTCs)
  • Magnetic permeability testing available on request
  • Seamless and welded options, OD range 6mm–1200mm
  • Export experience to 40+ countries

常见问题解答

Is 304不锈钢 magnetic?

Grade 304不锈钢 is non-magnetic in its annealed state. However, cold working (bending, drawing, stamping) can induce a slight magnetic response by converting austenite to martensite. For applications requiring guaranteed non-magnetic properties, specify solution-annealed 304 or upgrade to 316L.

316级是一种奥氏体不锈钢，在退火状态下不具磁性。由于其镍和钼含量较高，与304相比，它对冷加工产生的感应磁性具有更强的抗性。.

A simple magnet test can detect strong magnetism (ferritic/martensitic grades). For precise measurement, use a Feritscope or permeability meter. Non-magnetic austenitic grades should have µr < 1.01.

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410不锈钢

410和304不锈钢有什么区别？

304和410不锈钢都是常见的、具有一定耐腐蚀性和耐热性的不锈钢材料。在本篇博客中，让我们来探讨410不锈钢与304不锈钢之间的主要区别。.

differences between 316 and 317 stainless steel

316和317不锈钢有什么区别？

317 is a higher chromium, nickel and molybdenum version of 316 stainless designed principally for increased strength and corrosion resistance when compared to 316.The main characteristic of 317 stainless steel is its higher molybdenum (Mo) content (typically 3.0% to 4.0%), resulting in superior corrosion resistance compared to 316 stainless steel (typically containing 2.0% to 3.0% Mo), especially in resisting pitting corrosion, crevice corrosion, and corrosion in chloride-containing and other highly corrosive chemical environments.

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