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Re: (Steel for) Magnet De

Subject: 
        Re: (Steel for) Magnet De
  Date: 
        Sun, 16 Mar 1997 14:26:44 -0500 (EST)
  From: 
        richard hull <rhull-at-richmond.infi-dot-net>
    To: 
        Tesla List <tesla-at-pupman-dot-com>


>
>T>I thought silicon (transformer) steel was used for magnetic structures
>these
>T>days.
>
>T>John Freau
>
>
>        Eh, yo!  Planet earth calling. Earth to Mars, come in --
>
>        We are talking about:
>
>                - Like Electromagnets, not transformers.
>
>                - Like continuous (or modulated) =dc= power.
>
>                - Like no eddy currents  (after initial turn-on)
>
>                - Like no core losses.
>
>                - Like no hysteresis.
>
>                - Like silicon steel is very hard to purchase in
>                        mass (as opposed to in sheets for making
>                        xfmr. laminations)
>
>                - Like silicon steel is damn-near =impossible=
>                        to machine (especially in comparison to
>                        soft iron; especially if the silicon
>                        steel is in the form of laminations)
>
>                        Like the silicon in it chews up tooling
>                        like you wouldn't believe.
>
>                        Like in cyclotron work (remember?) the
>                        poles will =have= to be machined.
>
>                        Like in cyclotron work, quite likely a lot.
>
>                - Like iron is cheaper than silicon steel.  Like
>                        a =whole lot= cheaper.
>
>        Reality check over, earth out.
>
>                                - - - - - - -
>
>        Honestly Mr. Freau - we're briefly disappointed in you.  As
>        a recognized  (and esteemed) worker in the field we know you
>        know better.  (A little ozone poisoning, perhaps?)
>
>                                        "Steeling" for a living,
>
>                                        Robert Michaels -
>                                        Tough Enough to Live in Detroit
>                                                                USA
>
>
All,

I have noted that the magnet bit is still goin'

Silicon steel would be much better, the best in fact. 

 Iron dies and has a mu of air at about 13-14 Kgauss.  Wrought iron can
go
to about 18K gauss before it equals air.  Cast steel, still very soft,
still
has permeability near 100 at 20k gauss.  The bottom line is that at the
"stated" flux level needed in the original post, way the hell back
there,
most all metals will have flux going into the surrounding air due to
saturation.

A cyclotron magnet doesn't need all that many Kilogauss.  Above 20
kilogauss, the best magnet structure is just copper wire in air.  Some
Ne-Fe-B magnets now being produced in research allow 100 megaguass
oersted
energy products and can stroke most electrical coil structures to the
limit
of any metal's ability to path the stuff over air.

For those not in the know,  once the MU of the metal is unity, as in
saturation, the mag field just ambles on out into space rather that ride
in
the iron, steel cobalt, nickel, gadolinium or whatever ferromagnetic you
might have.  Above 20kG no material is going to contain the mag field
very
well.  At 30KG you are airborne and air cored, like it or not

Richard Hull, TCBOR