Date:         Wed, 23 Nov 2005 21:48:48 +1300
Reply-To:     Andrew Grebneff <andrew.grebneff@STONEBOW.OTAGO.AC.NZ>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Andrew Grebneff <andrew.grebneff@STONEBOW.OTAGO.AC.NZ>
Subject:      Re: Exhaust Pipe Rust Prevention
In-Reply-To:  <20051122.210250.-506559.13.KAYAKJR@juno.com>
Content-type: text/plain; format=flowed; charset=us-ascii

>  You can take a piece of 304(usually not> ferromagnetic) and beat the
>crap out of it with a hammer and it'll
>  > become > ferromagnetic because you've changed the structure

I think you'll find that a metal (or iron-bearing rock) is magnetic
when the charged grains (crystals, when speaking about metals) are
aligned so that the magnetic fields of each particle are aligned and
in the same orientation. The more particles so-aligned, the more
magnetic the whole appear. It's not that "nonmagnetic" stainless
isn't magnetic... it's just that the particles' fields are random in
orientation, so no overall field is displayed. Malleating or intense
heating can alter the orientation of particles so that they increase
in alignment; heat will do so by melting the metal, and the particles
will tend to realign themselves while molten (this is how ocean-floor
magnetism creates strips of like-charged basaltic rock on either side
of the midoceanic ridge system, which can be poicked up by
magnetometers). Malleating (pouning metal in sucha  way as to cause
it to effectively flow (yes, solids DO flow under sufficient
pressure, as can be seen in the Earth's mantle) probably realigns the
field by causing the particles' fields to be altered in direction,
rather than the particles themselves reorienting; after all, the
particles themselves cannot align when being mashed.
--
Andrew Grebneff
Dunedin
New Zealand
Fossil preparator
<andrew.grebneff@stonebow.otago.ac.nz>
Seashell, Macintosh, VW/Toyota van nut

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