iron cores; how important is iron vs other magnetic ore

[mcorrade]

I can't seem to find iron anywhere for my coil cores. How important is iron vs steel or some other magnetic ore?

[triffid]

Try coat hangers for a cheap source of iron.

[poopypantallons]

Thats is a great question!

Let me piggyback on it....

More importantly, what is the best metal/alloy to use that works great as an elctromagnet in a coil but does not retain its magnetism when powered off?

I recall someone indicating that a concrete anchor bushing of some sort had great properties. However, no material make or metal type was identified, that I recall. It hink it was hoptoad who said it. Wish I could find some here in California.

Thanks

[solinear]

What you want to do is think of magnetism as a circuit, just like electricity.... but one that *IS* going to close the circle, no matter what you do.  Think of permeability as conductance.  Air/space has a permeability rating of 1 (very bad).  Steel has a permeability rating of 700... in other words, it conducts magnetism around 700 times better than air does.  To put this in better terms, the impact upon 1cm of air will be the same as having around 200 cm of steel to run that magnetic field through.  As long as you can get something well over 100 permeability rating, it won't much matter what material you use.  Thinking of a 1cm electromagnet with 1cm of air gap between the poles with steel as a core, the steel core would contribute approximately 1/800th of the coercivity (inconsequential).  Going from that steel to some of the insane levels of permeability materials (alloys with up to 1,000,000 permeability rating), you would go from 100.12 coercivity rating to a 100.0001 total coercivity rating.  Basically no difference at all, but you just spent a crapload of money getting the 'perfect' core material.  Shortening the air gap would have a much larger effect than changing your core once you get something over a 100 permeability rating.

As for finding something that won't retain it's magnetic properties, it's based upon the material and how strong of a field that you're putting on it.  2000 gauss is quite a bit.  Wikipedia can give you a bit of good information about permeability (how much magnetism likes a material), paramagnetism (materials that won't keep a magnetic field) and so forth.

[The Observer]

MC...

You may be interested in knowing how and why magnets/ electromagnets work.

Something, I am afraid to say... most here do not see as I see.

      Sol says permeability has to do with how well magnetism is conducted.

     This makes no sense since the ferromagnetic materials become magnetic by way of already existing dipoles turning from contrasting positions to similar positions in terms of direction.

A piece of iron has 'tons'  of magnetism in it before any other magnetic field comes close to it.

When a magnetic field does come close to it...the dipoles in the iron turn (line up direction) and ADD...

     yes I said ADD...

             to the external magnetic field !

the formula for a coil solenoid is this...

B = (μ0 * μr * N * i) / l

Explanation of this and more is contained in an explorative posting I made last summer entitled.

      Magnetic Permeability.. I can't find anyone talking about this !!!!!

         http://www.overunity.com/index.php?topic=4831.0;wap2

Here you will find more information about how magnets work than anywhere else on this site.

( I say this because you have to be talking about magnetic permeability if you are talking about how magnets work. And quite frankly, I am about the only one !)

If anyone else is more interested at this point... Let's explore this !

Good Tidings to All,
                                The Observer