---
title: "Is Stainless Steel Magnetic? Grade by Grade"
source: "https://www.laxconsteels.com/is-stainless-steel-magnetic/"
description: "Ferritic, martensitic, duplex and PH stainless steels are magnetic; annealed austenitic 304 and 316 are not, and turn weakly magnetic after cold work."
---
# Is Stainless Steel Magnetic? The Answer, Grade by Grade

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Published 11 September 2026 8 min read

Stainless steel is magnetic or non-magnetic according to its crystal structure, not according to whether it is stainless. The ferritic grades (430, 409), the martensitic grades (410, 420, 431), the duplex grades (2205, 2507) and the martensitic precipitation hardening grades (17-4 PH, 15-5 PH) are ferromagnetic: a magnet holds to them as it holds to carbon steel. The austenitic grades (304, 316, 321, 310) are not magnetic in the annealed condition, and they account for most stainless steel in service, which is why the material has the reputation of being non-magnetic. The same austenitic grades become weakly magnetic after cold work: a cold drawn 304 bright bar attracts a magnet slightly, while the annealed hot rolled bar it was drawn from does not. Magnetic response is therefore a property of the grade and its condition, and a magnet is a rough guide to which family a piece belongs to, not a test of quality or of corrosion resistance.

## Why some stainless steels are magnetic and others are not

Iron is ferromagnetic because its atoms sit in a body-centred cubic lattice, called ferrite, in which the magnetic moments of neighbouring atoms line up. Any steel that keeps this lattice at room temperature is magnetic, whatever else is alloyed into it. Chromium, the element that makes a steel stainless, is itself a ferrite former: a plain iron-chromium alloy with 11 to 30 percent chromium and little carbon stays body-centred cubic from the melt to room temperature, and that is the ferritic family. Add enough carbon and the same lattice can be hardened by quenching into body-centred tetragonal martensite, which is also ferromagnetic: the martensitic family.

Nickel changes the lattice. Around 8 percent nickel with 18 percent chromium, the composition of 304, stabilises the face-centred cubic lattice, called austenite, all the way down to room temperature. In austenite the atomic moments do not align, so the steel is paramagnetic: it is drawn toward a strong magnet only very slightly, and an ordinary hand magnet does not hold to it. Manganese and nitrogen stabilise austenite in the same way, which is how the 200 series grades reach the same structure with less nickel. The duplex grades are deliberately half ferrite and half austenite, and the ferrite half is enough to make them magnetic.

## Magnetic response by grade

*Stainless steel grades, their crystal structure and their magnetic response*

| Grade | Family | Structure at room temperature | Magnetic response |
| --- | --- | --- | --- |
| [304](https://www.laxconsteels.com/grades/aisi-304/), 304L | Austenitic | Face-centred cubic | Non-magnetic annealed; weakly magnetic after cold work |
| [316](https://www.laxconsteels.com/grades/aisi-316/), 316L | Austenitic | Face-centred cubic | Non-magnetic annealed; less magnetic than 304 after the same cold work |
| [321](https://www.laxconsteels.com/grades/aisi-321/), 347 | Austenitic | Face-centred cubic | Non-magnetic annealed; weakly magnetic after cold work |
| [310S](https://www.laxconsteels.com/grades/aisi-310s/) | Austenitic | Face-centred cubic, highly stable | Non-magnetic in every condition |
| [303](https://www.laxconsteels.com/grades/aisi-303/) | Austenitic | Face-centred cubic | Non-magnetic annealed; weakly magnetic after machining or cold work |
| 201, 202 | Austenitic (manganese) | Face-centred cubic, less stable than 304 | Non-magnetic annealed; noticeably magnetic after cold work |
| [430](https://www.laxconsteels.com/grades/aisi-430/), 409 | Ferritic | Body-centred cubic | Magnetic |
| [410](https://www.laxconsteels.com/grades/aisi-410/), [420](https://www.laxconsteels.com/grades/aisi-420/), [431](https://www.laxconsteels.com/grades/aisi-431/), [416](https://www.laxconsteels.com/grades/aisi-416/) | Martensitic | Body-centred cubic or tetragonal | Magnetic, annealed or hardened |
| [2205](https://www.laxconsteels.com/grades/duplex-2205/), [2507](https://www.laxconsteels.com/grades/super-duplex-2507/) | Duplex | About half ferrite, half austenite | Magnetic |
| [17-4 PH](https://www.laxconsteels.com/grades/17-4-ph/), [15-5 PH](https://www.laxconsteels.com/grades/15-5-ph/) | Precipitation hardening, martensitic | Martensitic | Magnetic, solution treated or aged |
| A-286 | Precipitation hardening, austenitic | Face-centred cubic | Non-magnetic in every condition |

Precipitation hardening is a hardening mechanism rather than a structure, so the family divides on magnetic response like any other. The martensitic types, 17-4 PH and 15-5 PH, are magnetic; the austenitic types, of which A-286 is the common one, are not, and the [precipitation hardening article](https://www.laxconsteels.com/understanding-precipitation-hardening-stainless-steel-process-types-and-benefits/) sets out both.

The magnetic grades are ferromagnetic to a degree that varies with composition. Ferritic 430 has a relative permeability of several hundred to over a thousand, comparable with mild steel. Martensitic grades are somewhat lower in the hardened condition. Duplex grades are magnetic but less strongly than a ferritic grade of the same chromium content, because only about half the volume is ferrite. Annealed austenitic grades have a relative permeability very close to 1, typically 1.003 to 1.02, which is the figure specified when a part must be non-magnetic.

## Why cold work makes 304 magnetic

The austenite in 304 is stable at room temperature only while the steel is left alone. Plastic deformation supplies the energy to transform some of it into martensite, called strain-induced or deformation martensite, and martensite is ferromagnetic. Cold drawing a bar through a die, cold rolling a sheet, bending, deep drawing, machining with a heavy cut and even the grip of a chuck all produce it. The amount depends on the strain, the temperature (colder working produces more) and on how stable the austenite of that particular heat is, which is set by its nickel, carbon and nitrogen content within the grade window. A 304 bright bar drawn with a 10 to 20 percent reduction in area typically shows a relative permeability of 1.1 to 2, enough for a magnet to hold weakly at the surface. The same bar in the hot rolled, annealed and pickled condition reads close to 1 and shows no attraction at all.

Grades with more nickel, or with molybdenum and nitrogen, have more stable austenite and form less martensite for the same strain. 316 after cold drawing is measurably less magnetic than 304; 310S, with 19 to 22 percent nickel, forms essentially none. The 200 series, with less nickel and more manganese, transforms more readily than 304 and is often distinctly magnetic after forming. A full solution anneal at 1,010 to 1,120 degrees Celsius followed by a rapid cool dissolves the martensite and returns the steel to the non-magnetic condition.

The finishing route therefore decides the magnetic response of a bar of one grade, and the [bright bar and black bar comparison](https://www.laxconsteels.com/bright-bar-vs-black-bar/) sets those routes out: peeling removes the rolled skin without much strain and leaves the bar close to non-magnetic, cold drawing strains the whole section and leaves it weakly magnetic, and centreless grinding after either changes only the surface. None of this changes the composition of the grade, and the loss of corrosion resistance from cold work alone is small. Structure does count elsewhere: sensitisation at the grain boundaries and heat tint beside a weld both lower corrosion resistance while the analysis on the certificate stays the same, as the article on [corrosion of stainless steel](https://www.laxconsteels.com/corrosion-of-stainless-steel/) describes.

## The magnet test and its limits

A hand magnet is a common first check of an unmarked piece of stainless steel. What it can establish is the family: a magnet that holds firmly indicates a ferritic, martensitic, duplex or martensitic precipitation hardening grade; a magnet that does not hold, or holds only weakly at a cold worked surface, indicates an austenitic grade, including the austenitic precipitation hardening grades. What it cannot establish is the grade within the family. It does not separate 304 from 316, both non-magnetic when annealed, nor 430 from 410, both magnetic. It does not measure corrosion resistance: a magnetic 2205 duplex bar resists chlorides far better than a non-magnetic 304. And it can mislead in the other direction, because a heavily cold worked 304 part and a 201 part both hold a magnet weakly.

Grade identification that can be relied on comes from the mill certificate, and where the certificate is missing, from a chemical analysis: optical emission spectrometry on a prepared surface, or a handheld X-ray fluorescence analyser, which reads chromium, nickel and molybdenum directly. The composition tables in the [grade reference](https://www.laxconsteels.com/grades/) give the windows each grade must sit inside.

## Where non-magnetic stainless steel is specified

Some applications require a steel with a relative permeability close to 1 and specify it, usually as a maximum permeability after fabrication. Magnetic resonance imaging suites and their fittings, electrical and instrument housings that must not disturb a field, minesweeper and naval components, particle physics apparatus and some medical implants are the usual cases. For these the austenitic grades are chosen, the more stable ones (316L, 316LN, 310S) preferred over 304 where cold work cannot be avoided, and a final solution anneal is specified after forming so that any strain-induced martensite is removed. The specification names the permeability test, commonly a low-mu permeability indicator against a set of reference inserts, as well as the grade.

Where magnetic response is wanted, as in solenoid cores, magnetic clutches and the drive components of pumps with magnetic couplings, the ferritic and martensitic grades are used, and 430F and 416 are the free-machining versions specified for those parts. Cutlery and cookware are indifferent to magnetism except in one respect: an induction hob needs a magnetic base, which is why 18/0 ferritic steel or a bonded ferritic disc is used under an austenitic pan.

## Both structures as bar

Laxcon Steels melts and rolls austenitic, martensitic, ferritic, duplex and precipitation hardening grades as long products. [Hot rolled round bar](https://www.laxconsteels.com/products/hot-rolled-round-bars/) is supplied from 16 to 125 mm in the annealed and pickled condition, in which an austenitic bar is non-magnetic; [bright bar](https://www.laxconsteels.com/products/bright-bars/) from 5 to 115 mm is cold drawn, peeled or ground, and a cold drawn austenitic bar carries the slight magnetic response described above. [Duplex bar](https://www.laxconsteels.com/products/duplex-steel/) is magnetic in every condition supplied, as is [precipitation hardening bar](https://www.laxconsteels.com/products/precipitation-hardening-steels/) in the martensitic types. The heat analysis on the certificate places each bar inside its grade window whatever its condition.

## Frequently asked questions

### Is 304 stainless steel magnetic?

Not in the annealed condition, in which it is austenitic and a hand magnet does not hold to it. After cold work such as drawing, bending or rolling, part of the austenite transforms to martensite and the steel becomes weakly magnetic. A solution anneal restores the non-magnetic condition.

### Is 316 stainless steel magnetic?

No, when annealed. Its higher nickel and its molybdenum make the austenite more stable than that of 304, so 316 stays closer to non-magnetic after the same amount of cold work. It is the usual choice where a low permeability is required after forming.

### Does a magnet sticking mean the steel is not stainless?

No. Ferritic 430, martensitic 410 and 420, duplex 2205 and the martensitic precipitation hardening grade 17-4 PH are all stainless steels and all magnetic. A magnet identifies the family, not whether the steel is stainless, and it says nothing about the corrosion resistance of the piece.

### Why does a bright bar of 304 attract a magnet when the black bar did not?

Cold drawing strains the whole cross-section of the bar and converts some austenite to strain-induced martensite, which is ferromagnetic. The hot rolled black bar was annealed and had none. The composition and the corrosion resistance of the two bars are the same.

## Sources

- ASTM A276/A276M, Standard Specification for Stainless Steel Bars and Shapes.
- EN 10088-1, Stainless steels, list of stainless steels.
- ASTM A342/A342M, Standard Test Methods for Permeability of Weakly Magnetic Materials.
- Nickel Institute, Magnetic properties of stainless steels (technical guide).
- Atlas Steels, Technical Handbook of Stainless Steels: magnetic response of the stainless families.

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