Steel Permanent Magnet

Neodymium Magnets 03/29/2021

steel permanent magnet

5 MATERIALS FOR PERMANENT MAGNET

Permanent Magnet Steels. Although iron-carbon alloys were used earlier for permanent magnets, the first im- proved material was developed in about 1910.

The permanent magnet materials of this chapter are among the few magnetic materials that do not operate in an electromagnetic manner.

Thus, no windings are used to create the magnetic field in the material.

Most of the rest of the magnetic materials in this book do operate electromagnetically.

Sometimes, the current user is DC, but mainly it is ac of various frequencies.

As a result, the next chapter will deal with the electromagnetic usage of magnetic materials at DC and low frequencies for power applications.

Keywords

Permanent Magnet Coercive Force Barium Ferrite Strontium Ferrite Demagnetization Curve

These keywords were added by machine and not by the authors.

This process is experimental and the keywords may be updated as the learning algorithm improves.

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Steel Discs Magnets

They can be used to create catches, latches, and box closures. These are not magnets. For best results: Steel size should exceed magnet size.

These steel discs offer a highly attractive target for magnets to attach to.

They can be used to create catches, latches, and box closures. These are not magnets.

For best results: Steel size should exceed magnet size.

What’s the deal with magnetic stainless steel?

The theory of the “magnet test,” is sort of this rumor going around in which you’re supposed to test the quality of the stainless steel with a magnet.

But really what this tests for, is whether or not the steel is austenitic, or made of a metal alloy that contains chromium and nickel.

There are three main types of structures in stainless steel—austenite, ferrite, and martensite.

When you see stainless steel labeled as 18/8 or 18/10 this is telling you how much chromium and nickel is in the steel.

The first number indicates 18% chromium, and the second 8% or 10% nickel.

The nickel is the key to forming austenite stainless steel.

Both the 18/8 and 18/10 are therefore austenitic.

So the “magnet test” is to take a magnet to your stainless steel cookware, and if it sticks, it’s “safe”—indicating no nickel present—but if it doesn’t stick, then it’s not safe, and contains nickel (which is austenite steel).

It is true that if a magnet were to stick to the steel, that it would not be a nickel (austenite) alloy.

There’s a problem with this theory, however.

For one thing, there are no stainless steel pans that are magnetic on both the outside AND the inside.

Someone, please correct me if I’m wrong, but I have searched and searched and searched, and have yet to come across a fully-magnetic piece of stainless steel cookware.

And there is a good reason for this—austenitic, or nickel-containing, non-magnetic stainless steel, is highly resistant to corrosion, which is super important if you’re cooking directly on it.

If the piece was fully magnetic stainless steel, it would corrode and not last very long without the nickel to stabilize the metal.

Even though it would be nickel-free, I don’t think I would even want a magnetic, 18/0 stainless steel pan for this reason!

You will find magnetic stainless steel in the layer on the outside of some quality pieces of stainless steel.

This is to make it compatible with induction stovetops, which involve the use of a rapidly changing electromagnetic field to heat the cookware.

High-quality stainless steel, good quality manufacturers use three layers of metal—the austenite layer of steel on the inside, ferrite steel on the outside, and a layer of aluminum sandwiched between the two for optimal heat conductivity (steel alone does not conduct heat evenly).

Lesser-quality stainless steel is usually just one layer of austenitic stainless steel.

But there is still a difference in quality between the types of austenitic, or non-magnetic, stainless steel.

You’ll sometimes find that austenitic stainless steel is weakly magnetized, and that’s because of the manufacturing process.

You can actually form ferrite and martensite by “cold-working” the steel, which does make it more prone to corrosion and leaching.

The formulation of austenite in high-end, quality stainless steel cookware is created with a process that is careful to avoid this.

It leads to an austenite alloy which is very stable and resistant to corrosion and leaching of metals.

I’m no metallurgist, but in my opinion, a carefully-formed and highly-stable, non-corrosive, nickel-containing stainless steel is safer than a purely magnetic stainless steel which could break down and corrode over time.

(And which doesn’t even exist on the market, anyway!)

If you know anyone who has had good quality stainless steel cookware for a number of years, you can tell just by looking at it compared with cheap stainless steel, that it is indeed very resistant to corrosion and holds up well over time.

But, to answer your original question,

How do you know if your stainless is high quality?

Well, unless you’re a metals expert and go inspect the factory where the steel is made to see whether or not their manufacturing process creates pure austenite without corrosive materials formed, you’re not going to know for sure whether or not the craftsmanship of your stainless is of the highest quality.

I think your best bet is to simply buy high-quality stainless steel from the start, from a brand with a reputation for good quality.

But, I think I have figured out one way that you can determine if the stainless cookware you already have is potentially reactive.

The Vinegar Test

I read that you can test the quality (or more accurately, the reactivity) of the steel by boiling some water with a tablespoon of baking soda in the pan for a few minutes.

If the water has a metallic taste, then the steel is reactive and of lesser-quality.

But from what I’ve learned about stainless steel, my understanding was that it’s the acidic foods you have to worry about when it comes to any leaching from stainless steel.

And baking soda is alkaline.

So, I decided to do a little science experiment and try a different test!

Here’s what I did:

I poured a couple of tablespoons of plain white vinegar (which is of course, quite acidic) into two spoons — a good quality spoon, and another generic stainless steel spoon I had lying around.

I also put some of the vinegar into a glass cup as a control.

After a few minutes, I taste-tested the vinegar from each. The good-quality spoon`s vinegar tasted exactly like the vinegar in the glass cup.

But the vinegar in the cheap, generic stainless pan tasted like metal.

Blech.

The taste is still in my mouth as I type!

I’m pretty convinced my vinegar test is a decent way to determine the reactivity of your stainless steel.

Try it out on yours and see if it passes! But if it doesn’t, I wouldn’t freak out over this.

Just be mindful about cooking with very acidic things like tomato-based sauces and stuff, and avoid storing these foods in your stainless steel.

My magnets don't stick to my new stainless steel refrigerator.

What am I going to do with the stuff that hung on my old one?

We feel your pain and also your consternation if you're one of the many people who have stainless steel backsplashes or other surfaces that hold magnets just fine.

What gives?

The reason your refrigerator doesn't hold a magnet, according to Peter Eng, a physicist at the University of Chicago, is that different stainless steels contain different proportions of nickel (added to help keep steel from cracking and to allow the addition of more carbon, for strength).

More than two percent nickel interferes with what Eng calls iron atoms' "magnetic moments." It seems your gorgeous new refrigerator has sacrificed its magnetism for the greater good.

Now to the pressing problem of where to hang your refrigerator art.

One thought is to buy a piece of galvanized steel and screw it to a wall in your kitchen, pantry, or wherever you like, and use it as a magnet board.

Jim Brunetti, the owner of Avenue Metal Manufacturing Company (1640 W. Ogden Ave., 312-243-3483), will cut you a four-by-five-foot piece of light-gauge metal for about $45.

He will punch screw holes in it and hem it, too, if you like.

He even had a cool idea: "You could glue fabric to it, like felt." Call before you go.

Boyle's cool idea was to use a piece of metal with a baked enamel finish (he has three colors on hand).

Boyle is devoted to recycling and he may have a piece of exactly what you're looking for, or a piece of what you didn't know you were looking for, somewhere in the back.

Again, call before you go.

Another thought is to paint a wall in your kitchen with magnetic paint.

Apply two to four coats and then cover it with your own paint color.

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