Subject: Re: thermite for molten iron casting???

From: [email-masked] (Bruce Winterbon)
Date: Fri, 30 Dec 1994 13:50:03 GMT

In a previous posting, Mark Y. deLevie ([email-masked]) writes:
> Hi, all.
> 
> I know this sounds crazy, but with all the talk about charcoal foundries,
> I started to wonder if thermite could be used to produce molten iron for
> use in a sand foundry.  (thermite is a highly energetic reaction between
> aluminum and iron oxide, yielding molten iron, aluminum oxide, heat, and
> light)
> 
> I know that thermite is used for welding railroad tracks together.  I was
> thinking that a small thermite reaction could provide a stream of hot 
> molten iron that would melt a larger supply of iron, then the whole mess
> would pour down into the sprue of a mold.  This would partially cool the
> hot reaction product (someone told me ~3000 degrees F!  Yowee!).
> 
> Net wisdom requested and appreciated.

After reading about someone's earlier adventures with a charcoal forge,
thermite sounds _really_ exciting. Will someone raise the ante?
A backyard nuclear reactor, perhaps? :-)
--
Bruce Winterbon, Deep River, Ont.

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From: [email-masked] (Mark Y. deLevie)
Date: 30 Dec 1994 05:42:02 GMT

Hi, all.

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From: [email-masked] (David Hoopes)
Date: Fri, 30 Dec 1994 16:36:44 GMT

>Net wisdom requested and appreciated.

A couple of months ago I took a bronze casting class at the local Junior
College.  The instructor was really good.  I ask about casting iron.  He
said that he and someone else had been doing it by using thermite to melt
the iron.  He showed us the big chunks of iron that had welded themselves
to verious things around the shop, the one time it had not worked right.

They where casting art type castings.  He said that the thermite method
worked ok for that, but would not work well for useful casting.

Except for that class, I have not done any casting since Jr. high shop
class.  Most of my metalworking is done in blacksmith mode.  However, I am
trying to get the stuff together to start casting at home. 

Recently I built a propane forge.  But, I built it so that I could turn it
up on end and use it for a furnace.  I havn't tried it as a furnace yet,
but as a forge it will heat iron up to a bright yellow, (about 2000
degrees).  It will not get hot enough to burn the steel (about 2300)
degrees.  I have seen other propane forges built along the same lines that
would reach the higher tempatures.  What I did differant is that I made
the forge/furnace encloser much larger then the ones I had seen.  The
opening in the ones I have seen where about 6in in dia. and about 15
inches long.  The one I built has a 10in opening and is about 24in deep.

The propane burner was pretty easy to make.  It is made from the following
pieces of iron pipe and sundries:

	2 - 2in dia x 12in long threaded on one end
	1 - 2in elbow
	1 - 1/2in x 6in long threaded on both ends
	1 - Valve to fit on 1/2 iron pipe on one end, and attach to flexable
	    propane line on the other end.
	1 - 1 1/2 in dia by 2 in long
	1 - 1 in dia by 2 in long
        ? - steel or iron wedges (big nails will work)
	1 - flexable propane line
	1 - high pressure propane regulator.  (available at most RV
	    service centers.
	1 - blower.  ( I have seen old vacume cleaners used as blowers for
            these things.

Screw the two pieces of 2 in pipe into the elbow.

Attach blower to one end.
Drill and tap a hole in the elbow near the blower end of the elbow (just
above where the threads of the straight piece stop)

Screw in the 1/2 in pipe.  Attach valve, propane line, and regulator.

on the business end, insert the 1 1/2 in piece.  Use three wedges to hold
it in place so that it is centered inside the end of the 2in pipe.  Hammer
these in good. If you have a welder, you might weld these in.  ( I didn't,
and I havn't had any problems, but I always over do it if I can). 
 
Put the 1 in piece inside the 1 1/2 in piece and wedge it in the same way.

Stick it through the hole in the side of the forge/furnace.  Use large
amounts of bailing wire to hold everything in place.

Make sure that you turn on the blower first, then turn on the propane.  I
always wad up a piece of newspaper, light it through it into the forge,
and then turn everything on.

Hope someone finds this useful :-)

-- 
David Hoopes                              Exabyte Corp.
[email-masked]                       11100 W 82nd St.          
Voice: (913) 492-6002 x3323               Lenexa, Ks  66214

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From: Mike Schechter <[email-masked]>
Date: 30 Dec 1994 19:17:12 GMT

>A backyard nuclear reactor, perhaps? :-)
I guess now's the time to relate my own experience. I didn't build a 
Gingery-tyep furnace, but instead, built one out of 1x4.5x9 firebrick.
I started by welding a frame out of 3/4x3/4 angle iron, which would
hold the firbrick to form a cube 9x9x9. The bottom and top were open.
The bottom was covered in expanded metal, 1/2x1/2 grid.
The top had a removable firbrick cover.
The whole thing sat on a 4' high enclosed stand, with a 20" window box fan
underneath it blowing up thru the bottom grid.
I'd start a bunch of charcoal in a grill, and when the coals were hot,
move them into the furnace, filling it half-way. I used a cast-iron
pouring ladle as a crucible (holds about 3 lbs)
With the high volume of air (~900CFM), it took about 15min to melt brass.
 Aluminum would melt very fast, a couple of minutes tops.
The main problem was heat loss thru the firebrick, (I should used
2 or 4 inch thick) and heat loss thru the seams/cracks between bricks.
However, my friends have a few night pictures they took with pretty
impressive flames shooting from all the cracks. Except for the
high rate of charcoal consumption, it worked pretty well, except of
course for when the ladle turned over once and brass hit the fan.
The interesting thing was that there was virtually no spatter on
the inside of the fan-stand - The brass went right thru the spinning plastic
fan blades and motor housing into the coils with no deflection from
the blades!
  oh well! After that I started Mark II, which was three times the size,
with a side mounted fan, steel-over-refractory cement housing, fuel feed
chute and removable tops and heat concentrators (long&narrow vs round etc)
Never did finish it, though.. still out in the garage.
-Mike
Mike Schechter                  | [email-masked]
Systems Engineer                | [email-masked]
Institute for Sensory Research  | (315)443-9742

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From: [email-masked] (Ron Ginger)
Date: Fri, 30 Dec 1994 14:54:55

In article <[email-masked]> [email-masked] (Mark Y. deLevie) writes:
>From: [email-masked] (Mark Y. deLevie)
>Subject: thermite for molten iron casting???
>Date: 30 Dec 1994 05:42:02 GMT

>Net wisdom requested and appreciated.

I see no reason it wouldnt work, but the resulting casting would be of an 
alloy of very strange properties. I suspect it would be terrible to machine. 
And I wouldnt trust it for anything but simple model parts, like maybe a base 
plate.

There is a plan to build a large steel hull square rig sailboat in Maine. The 
keel is to be something like a 2'x3' section 60 or 80 feet long. Iti is to be 
thermite welded together, since such long lengths cant be shipped to the 
building site.  I hope they get to build it, I really want to see the weld!

Ron Ginger
my signature is http://www.ultranet.com/~ginger

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From: [email-masked] (David Hoopes)
Date: Tue, 3 Jan 1995 17:47:37 GMT

>A backyard nuclear reactor, perhaps? :-)

It was discussed at that last ABANA Conference.

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From: [email-masked] (Barry Workman)
Date: Wed, 4 Jan 1995 01:53:36 GMT

>Net wisdom requested and appreciated.

I think I have it figured out.  First, I'm going to use some clay
flower pots with extra refractory packed between them.  I'm going
to plug the hole with a piece of iron cut to fit.  Now fill the 
pots with the iron.  Build a frame that will hold the pots by
their lip.  Position the whole thing over the mold, thermite the
top.  When the iron melts the plug, the metal pours into the mold.

The mass of metal must equal the casting plus sprue and riser.  Execss
metal will continue to pour.  Use water displacement to determine the
volume of metal to pour.  The clay used in flower pots should handle
the 3000F+ heat.

-- 
    - Barry Workman

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From: [email-masked] (william thomas powers)
Date: 4 Jan 1995 09:35:56 -0500

>volume of metal to pour.  The clay used in flower pots should handle
 
Danger! Danger!   Warning! Warning!    Dr Smith!   Dr. Smith!
 
I wouldn't bet on the clay flowerpots handling 3000F heat!
I once tried to use one in my forge to make an enameling oven.
It *melted* when I was not even at a good welding temperature.

A local potter told me that most flower pots are made from low temp
clays and will not handle high temps; stands to reason or else why would
we all be forking out money for high temp refractories?

Thomas Powers
Columbus, Ohio

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From: [email-masked] (Bruce Holder)
Date: Wed, 4 Jan 1995 16:41:57 GMT

David Hoopes ([email-masked]) wrote:
: [email-masked] (Bruce Winterbon) writes:
: >After reading about someone's earlier adventures with a charcoal forge,
: >thermite sounds _really_ exciting. Will someone raise the ante?
: It was discussed at that last ABANA Conference.

  So where can we get copies of the proceedings?