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Stainless Steel

Do magnets stick to stainless steel?  Like all good magnet questions, the answer is both simple and complex.  Let’s find some answers.

Quick Answer

Are these steels (ferro)magnetic?

Will a magnet stick to stainless steel?  It depends on what type of stainless you’re using.  Some steels are only weakly magnetic, and some are not magnetic at all.  Austenitic stainless steels like 304 or 316 stainless are good examples of this.

A ferritic stainless like 430 stainless steel, on the other hand, is ferromagnetic.  Magnets stick to it.  You might see magnetic forces that are 5-20% weaker compared to low carbon steel.

Exactly how much weaker?

To go into more detail, we’ve shared some our investigation into the magnetic properties of stainless steel in the video below:

Highlights

Many questions are answered in that video, so let’s use this space for follow up questions.  If you have any questions about magnets and stainless steel we haven’t included, please email us!

How much weaker is stainless steel?

Screenshots of just a few of the many studies considered.

We tested a few different thicknesses of steel vs. 430 stainless steel.  We simulated a lot more.  We considered disc magnets of various diameters and thicknesses.  The steel it sticks to was always much larger than the magnet diameter, but we varied the thickness.  The results varied, yet in all of these scenarios the pull force to stainless ranged from 82% to 99% of the pull force to regular steel.

As a general rule of thumb, we saw more strength where the stainless steel didn’t get saturated, i.e. little magnet to big steel.  If the magnet was large and the steel was thin, that’s where we saw the bigger performance hits.

 

Results of pull force simulations of many magnets to 1/16" thick steel

In the graph shown, we simulated a variety of magnet sizes to a 1/16" steel plate.  Though the results varied quite a lot depending on the exact geometry, all pull force values were within 82% to 99% of the pull force to a piece of regular low carbon steel.

Is all stainless steel magnetic (ferromagnetic)?  Will magnets stick to it?

No.  It varies depending on the exact stainless steel.  We only covered a few in this article.  We found:

  • 430 Ferritic Stainless Steel – Magnetic
  • 304 Austenitic Stainless Steel – Not magnetic, or a little magnetic after cold work (bending, deforming, etc.)
  • 316 Austenitic Stainless Steel – Not magnetic.

How do I know if my stainless steel is magnetic?

Try it!  Finding good magnetic data on all the kinds of steel out there turns out to be surprisingly hard.  We picked these three (304, 316, & 430) because they’re so common.  For some less common varieties, the magnetic specification information can be hard to find, and harder to know if it's trustworthy.

If you’re using an odd variety of steel, don’t make too many assumptions.  Prototype and test!

Will stainless steel act as a magnetic shield?

Magnetic “shields” don’t block magnetic fields, they redirect it.  See our earlier article on Shielding Materials.

All metals that act as good shields are also attractive to magnets.  If you’re using a stainless steel like 316 that isn’t ferromagnetic, it’s not blocking any fields, at least not any more than an air gap.

Will paint reduce the pull force of a magnet to a piece of stainless steel?

Yes.  The magnet is farther away from the steel, by the small distance that’s the thickness of the paint.  This is true for any ferromagnetic steel, not just stainless steel.