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Why do only some magnets stick to stainless steel??

I guess it is to do with the strength of the magnet. Most stainless steels are pretty much non magnetic, and so a weak magnet will not be able to cling. Some magnets however are quite strong, and so will stick to even 'poor' magnetic materials, such as stainless steel.

A simple question maybe, but the answer implies a considerable knowledge of metallurgy, and the physics of magnetic permeability. When I engineered equipment for the bomb disposal squads, I had to be very proficient in this area.

That is my guess anyway Tim. Sorry for the technical dissertation! Some clever person will now show that I am completely off target and there is an extremely simple explanation  :D

Think you've pretty much got it Derek.  My experience is removal fo metal from food and to get stainless steel I have to sue very strong rare-eartjh magnets.

So would think it is all down to power for although stainless is to all intents non-magnetic the action of working it will generally impart a weel magnetism to it plus it is often not pure.

You've basically got it there Icy. However, although magnetic capability (described as permeability) is regarded as either there or not, in reality it is a variable, so different materials have different 'permeabilities'. Even aluminium, regarded as non magnetic, has a low level, which was a problem in my bomb disposal work. These properties arise mainly from the trace elements present in the alloys. Stainless steel actually, encompasses a whole range of different ferrous alloys, with differing permeabilities for each grade. Brass, bronze and copper are all fairly safe, ie zero permeability, unless they are used to pass an electrical current, which itself will generate a magnetic field!

I never really enjoyed the bomb disposal work, whilst it was extremely interesting technically, I knew that if I had made an error in my work, it could cost a man his life. Somehow I managed to sleep at night . . .
Pondering on that issue, when I worked on the missile launch systems, I knew that my equipment WOULD result in loss of life. Given me a heavy heart that has. My apologies for sharing that.

What did I say the other day about the expertise on tap here?

Well done for your 'bit', Derek - my Mother used to 'sodder' (as they termed it) Spitfire radiators at Cowley. And thought of me flying them!!

Magnets - it's so surprising - the butch 'horseshoe' one & its neighbour won't hold, but all the others do. Is there any connection with shape?


And apart from that, the ......fridge, a replacement for the first one which didn't work, doesn't work!!

Thank you for the compliment Tim, from you that is real recognition.

The shape of the magnet does have an effect yes, but not one that can be altered. Poor quality magnets can quite easily lose their power, because the steel cannot retain the strength.

I would suggest that if you are finding problems with your fridge magnets, see if you can salvage some tiny speaker magnets, these are normally high quality.

And where might I find such things, Derek?

We're very paysanne out here!

In speakers  ;D

Exactly RC. Any old radio speakers or similar Tim, normally someone is throwing stuff like that away. Being the sort of squirrel that I am, I normally never find things like that a problem, but you havent seen my house!  :D If and when you get one, you can cut them to size with a hacksaw, but dont hit them.

A friend used a fridge magnet on his computer processor casing to hold notes on.
It took him a long time to figure out that this was what caused his computer to malfunction hahaha.
So, not a good idea. I wouldn't have known that.

Yes have you noticed that these 'commercial' stickies are not magnets but simple gluey pads . . .

i think derek has it, but just to add something else, dont know if it has any truth but could it be to do with electricity and charge.

when iron has a current put through it, it becomes a magnet, how they make motors.... so maybe a small amount of charge on some stainless steel, causes a weak magnetic force, that can then stick magnets. other stainless steel has no charge so they wont stick to it.

Doubt theres charge running through the door- that could kill you if power surged (maybe if you were dieting :-\ - make a good deterrant) and fridges contain very little electronics actually- just the fan motor for the ceramic compressor and the thermostat i suppose.

Microwave ovens contain very strong magnets, so if you can find a dead one, gut it. I was at the Leeds Flower Show this weekend, and there was a stand selling magnetic gadgets claiming to cure all sorts of Ill's. One claim was that placing a plant on a magnetic coaster they were selling promoted growth! In addition they sold a magnet that clamped onto a water pipe, and claimed the water was in some way magnetised and plants watered with it grew healthier. All very strange, and expensive too, especially the bracelets that you wear on your wrist to magnetise your blood. I didn't buy anything, but the magnet under a plant could easily be done as an experiment. They also claim that a jug of water left on the magnetic coaster took on magnetism, and plants grew better when watered with this. Another easy one to try out. I don't believe it, so I'll see if my experiment reflects my negative attitude, are there any believers out there to try an experiment?

Brian

Brilliant idea on the microwave, I wish I had thought of that! One word of warning, NEVER operate a microwave device unless it is in its proper shielded case. The resulting radiation could well prove fatal.
I think that the magnets and water, is based upon ionising the water, although it is also possible that some of the trace elements dissolved in the water do actually become magnetised. This is a marginally researched area, and not a lot is actually understood.

On the fridge front, I can verify that there should be no charge on the fridge enclosure, unless it is faulty, as the equipment will be earthed.

Adam, you have described two different types of magnets - permanent magnets and electromagnets. Permanent magnets CAN be made from electromagnets if the material properties are suitable. It all comes back to the correct material for a strong magnet. You are confusing electrical charge and electrical current. It is the electrical current which causes the magnetic field, not the charge. They are interesting ideas though.

Tim, I hope you are finding this topic fascinating, guess you never envisaged so much interest?

The experiment begins! I have a small but very strong magnet about 15mm. diam. and 6mm. thick that I have taped to my elbow, which has been painfull for a week or two. Yes I know I should go see the quack, but why not in the interest of science try this first. I will let you know if the pain subsides. Off to bed, hope it stays in place.
My next plan is to get my microwave magnet and sit a plant on it, with another close by as a control.

Brian.

Derek - yes, indeed.

One thing I do know - the water softening gimmick does nothing.

24 hours of magnetic therapy before it dropped off!. The magnet, not my elbow. I am not sure what to think, as the pain in my elbow was less, so is something happening?.
I will get a better system of sticking plaster attachment, and try again. Not got around to sitting a plant on a magnet yet.
Tim, did you try the water treatment magnet then? What did you do? Are you looking for some magnets, I buy them from a craft shop in Leeds, you can share a pack with me next time I buy some if you like.

Brian

Well, I stuck it back in place, and have had it there until this morning, my elbow still hurts, so I put some Oruvail gel on instead. I may try again but I'm not convinced it's worth it.
I will try the magnet under the plant though.
Will report any results.
Brian

Gardenantics.  You could place the magnet in tubigrip bandage to keep it in place.  My dad has one of those magnet bracelets (pound shop I think) and he has noticed a miniscule improvement.