There are ways to make magnesium very hard to burn. NeXT did it to the cases on
their computers. https://simson.net/ref/1993/cubefire.html
I assume that laptop computers with magnesium cases use similar alloys.
Mongoose BMX bicycles back in the 80's did a sneaky thing for their factory
team. Their production wheels were die cast aluminum. But in the dead of night
they cast and machined a run in pure magnesium. Quite tricky to not end up with
their wheel casting plant and machine shop on fire. Didn't bother getting
inspection or permits etc for working with molten magnesium because it was a
one off to make wheels for company use.
On Sunday, July 5, 2020, 7:08:36 AM MDT, Gene Heskett
<ghesk...@shentel.net> wrote:
On Sunday 05 July 2020 06:30:13 andy pugh wrote:
> On Sun, 5 Jul 2020 at 07:05, Gene Heskett <ghesk...@shentel.net> wrote:
> > quicker because alox is the 2nd hardest abrasive we have.
>
> No, that's CBN, second after diamond.
>
> > That, and if
> > cutting dry, the heat of oxidation of the chip coming off is 98% of
> > the heat generated.
>
> [citation needed]
>
> You say this a lot, but I have never heard anyone else say it. What is
> your source?
Almost any src discussing the properties of alu. It is a very active
metal, oxidizing (burning IOW) in microseconds behind the passage of a
cutting edge that exposes the bare metal to the oxygen in our air. This
process continues at a rapid rate until a layer of oxide has been made
that protects it by covering the surface with an oxide coat that must be
cut by the next oncoming tool edge. The rate of burn slows until the
oxide, which is also a perfect insulator, has reached a thickness to
withstand around 50 volts, I've read about a millisecond by which time
it takes additional chemical help to get to its best withstand of about
400 volts. Coloring of this oxide coat, commonly called anodizing, takes
place at this time also.
Getting something, almost anything, to coat that bare alu as the cutting
edge passes, slows this burn rate and prolongs the life of the cutting
tool by many times as it reduces the oxide the tool has to cut again
with the next passing edge.
Because its colorfull as it burns, and can be colored by contaminates,
its powdered form is commonly used in fireworks made for aerial
displays. The fireworks delayed explosives are used as an igniter. That
and magnesium which generally are the brighter whiter ones. The trick
for the fireworks experts is to have it all burned before it gets to the
ground and starts a real fire.
Back in the middle 50's, in Iowa City, we burned up a mercury outboard
motor block, on purpose as part of a welding class I took, doing it on
some very poor condition sidewalk 50 feet away from the welding shop on
the front of a vacant lot. The shop owner had a string of military
welding certs in his wallet, and first showed us that mag can be welded
with a smith wrench, aka acetylene torch, and put the stuff knocked out
of that big 6 block back in place that an errant con rod had knocked
out. And once we had looked at the work, he said "and this is what
happens if you aren't carefull" and lit that block up. Took it about 20
minutes to burn and made to good sized pit in the ground doing it. But
the local fire dept had to be restrained for dousing it with water when
they arrived like the 7nth cavalry, which the magnesium would have
loved, creating a much larger pit from the explosion. So they did the
next best thing and wrote him up. But he'd planned that show in advance
and by the time the court date rolled around, the pit had been filled
and a brand new sidewalk the length of that block had been graded and
poured, pix of which got the cite laughed out of court, the city was
glad to get that 40 yo sidewalk fixed at no cost to them. That was my
clue that I was never going to light a smith wrench anywhere near mag.
The smoke is not healthy to start with.
_______________________________________________
Emc-users mailing list
Emc-users@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/emc-users
