Casting Furnaces
The size and temperature capability of your furnace should
meet your needs. Most of my is done in aluminum which melts at
F. My small
Flower Pot Furnace will have aluminum ready to pour in about 20
minutes, were as my
large 15 pound furnace will take hours before it's ready.
Finally I needed a furnace that could reach F so I could pour
Brass and Iron.
So think about the projects you plan to do. All three of these
furnaces are documented below.
Brass and Iron Furnace - F
For the hotter metals like NiBrAl at F to Iron at F must
use a clay or silicon carbide crucible. So your foundry gets built
around the crucible. An A30 crucible is about 8 5/8" diameter
and 11 1/2" tall and can hold 66 pounds of brass, 21 pounds of aluminum.
The #35 crucibles we got from Legend;
www.lmine.com are even larger at
9 1/2" diameter and 12.5" tall. So we'll be sure to have
enough metal to cast our propeller blades and most everything else you
find on a boat.
Kay and I visited our local
Canfield & Joseph
foundry supplier and spoke with Jeff Trenholm. who was an excellent
resource for investment and furnace supplies. We came home with $400
worth of materials to build a furnace that is light enough that we
can take it on the boat. The trick to light weight is ceramic
cloth and insulating firebrick or IFB. Jeff also supplied us with
design plans for a larger crucible furnace. My original plan was
based on designs from the metal casting forums that used 1" of
castable refractory for a hot face with 2" of ceramic cloth behind
that. The professional recommendation from Jeff was a more
like 6 inch walls at least 4 inches of castable refractory, but
after I explained that light weight was critical, Jeff ran the
thermal figures on insulated firebrick or IFB with a couple of
inches of ceramic fiber behind it. The lid be only ceramic
fiber. The thermal numbers put the outside skin temperature at
about 500 degrees. The down side is that this design will not
do well for routinely casting iron at F but it will easily do
brass and NiBrAl at F in the furnace in order to get the melt to
about F.
Professional furnace plans.
Oil Drum Furnace
A 55 gallon Oil Drum will be the outer shell and even with a 9.5"
diameter crucible it will have enough room for 5" of firebrick and
ceramic fiber, with a couple of inches for the tongs to reach in a
grab the crucible.
Materials List:
2 - 55 gallon Oil Drums
1 - 55 lb bag MetalKast 70 castable refactory.
Instructions for using
MetalKast 70
1 - 55 lb pail Sairset refractory mortar (Only need 1/2)
1 box Ceramic Fiber Blanket - Cerablanket, 2 x 150 x 24", 25 sqft, 8
lb/cuft
40 - F Insulated Firebricks, measuring: 2.5 x 4.5 x 9"
4 - TIG welding stainless steel filler rods or 12 ft of 1/8"
diameter stainless steel wire.
Store Sairset in a cool location. The shelf life is 12
months and it must be tightly sealed if you plan to keep what you do
not use. Mix thoroughly and use thin brick joints for best results.
Each joint should be completely filled with mortar.
Cut and oil drum to about 21" depending on the
size of the firebricks you get.
We used a masonry saw to cut the fire brick but a
hand saw will do the trick. Don't breath the
dust!
Insulating Fire Brick or IFB cut to fit the bottom
of the oil drum.
Cover the bung holes and trowel in some Sairset
and start laying in the bricks.
Lay the IFB with thin joints. ..and work fast
because it dries fast.
Cerablanket Ceramic Fiber Insulation cuts easily
with a serrated blade and is fit against the inside
of the oil drum
Set the Cerablanket in place.
With a block under one side of the fire brick it's
easy to cut them into a wedge shape for the walls
of the furnace. I had a 40 mph wind, but this
is
when you should use a respriator.
A couple of 12" round boards are used as jigs.
Cut the last brick once the others are in place as
the mortar adds about 3/4".
The lid was made from 4 inches of the bottom of
the barrel because the bottom has no bungs. A 5"
hole was cut though the metal, 4" of
Cerablanket
was fit inside and a ring of sheet metal welded on
in order to hold the Cerablanket in place.
4" was cut off the bottom of a second 55 gallon
oil drum and that was welded to the bottom of the
furnace after 4" of Cerablanket was placed inside.
Stainless steel TIG welding filler rods are welded
to the bottom of the lid and bent so they lap over
the Cerablanket around the furnace vent hole.
Metal flashing is used to make a form for
Metalcast-70 castable refractory. This will
prevent damage to the Cerablanket when adding
metal and also protect the stainless wire.
Castable refractory covers the exposed
Cerablanket around the top of the furnace.
The remaining bag of castable refractory sealed
around the burner hole and make assorted plinths
which will support the crucibles.
The fire bricks were trimmed level with the
refractory.
A hinge for the lid and lifting handles were added.
If you want to learn more, please visit our website lead melting furnace solution.
First Melt
It's an exciting day when you get to try out your new furnace
with a real part. Especially when that part will save you $3,400.
It will pay for the $ furnace and new $ metal lathe.
We are using a clay graphite crucible from
Legend
Foundry Tools
In the back are the crucible lifting tongs used to
lift the crucible out of the furnace and onto a
plinth where it is lifted by two people using the
pouring shank in front. The piece of square tube
on the pouring shank slides over the top lip of the
crucible to keep it from falling out when it's
tilted
over.
In the photo to the right are tongs for
adding metal to the crucible, a fluxing tool which
is just an end cap on a metal stick that pushed flux
to the bottom of the crucible.
Next is a skimmer to skim off the dross that floats
to the top of the melt, and finally a plate to push
any remaining dross or cover flux away from the
edge of the crucible when pouring the metal.
Degree Propane/Diesel/Oil Burner
To reach degrees, you will need more that just a propane
burner. Fortunately Super Dave; not his real name, who lives
just 100 miles away in Oklahoma City has worked out the details of a
great propane and waste oil, forced air burner. Super Dave's
background is in asphalt plants so burners is something he know a
lot about, so and I finally pried him into building me a copy of his
burner. :)
The burner pipe needs to be at least 2 inches ID, but larger will
work too. And it's 16 inches long, but it can be longer or
shorter as needed. And it will work without the tabulator, or
you can fabricate your own from sheet metal, there is no magic to
it.
Suppliers:
www.patriot-supply.com
Burner Parts:
Siphon Type SNA Air Atomizing Nozzle, .75 gal/hr, Hago Delavan Part
Number: -8 $25
Adapter for Nozzle: Hago Delavan Part Number: $24
Large Aluminum Furnace -F
My foundry started from reading several of the very good web
sites available on the topic. See the links at the bottom of this
page.
I wanted to melt upwards to 15 pounds of aluminum so I started
with a crucible (the actual melting pot) that is a little bigger
than a standard #10 crucible. My crucible is made from a 6 inch by
1/4 inch thick steel pipe with a 1/2 inch plate of steel welded onto
the bottom. After a trip to the local junk dealer, the metal scrap
yard, and a foundry supplier I had all of the parts. I made a
simple burner using parts from the turkey fryer burner I picked up
and used to melt lead. A couple of of 30 gallon oil drums ($4 each)
from the local junk dealer would form the body, and Mizzou Castable
Refractory from a local supplier provides the heat resistant
insulation.
I had been working mainly with with aluminum up to this point.
Cutting steel with my Dewalt cut-off saw wore out to $90 blade is
short order. Since it cost $40 to sharpen I had an excuse to buy an
acetylene touch but I decided to first try a cutoff blade in my
grinder first. Harbor Freight sells a box of 25 - 7 inch metal
cutting disk for $14, and a cheep angel grinder will cost $20 to
$30. Surprisingly the cut-off blades worked great.
(1) One of the 30 gallon drums was cut off at 18 inches to make
the bottom of the furnace. Angle iron was added for 4 legs and to
support a pipe that would be the hinge for the lid. The oil drums
are 14 inches in diameter which is just right for my 6+ in wide
crucible + 1 inch of space between the crucible and the refractory
so that the refractory is about 2 1/2 inches thick.
(2) The lid is 2 1/2 inches cut off of another barrel. These
barrels have lids like paint cans, so instead of trying to weld on a
lid I just used another $4 barrel. Others have used pressure
storage tanks used by household water well systems and except that
these are rounded on the top, I think they are a better solution;
unless you are good at welding on the thin metal that the 30 gallon
barrels are make from. I am not.
(1) Angle iron frame around a
30 gallon drum.
(2) Pipe frame welded to the top
of the oil drum lid with rods to
reinforce the Mizzou and a bottle
to form the vent.
(3) Mizzou Castable Refractory
poured in and vibrated by the
table saw underneath.
(4) Mizzou poured 3 inches
deep into the bottom, with a hole
left to drain the metal should the
crucible fail.
(5) Inside form made by
wrapping flashing around wood
furring strips that are glued to the
steel crucible.
(6) Steel pipe for the burner. It is
shaped to fit up against the inside
form around the crucible.
(7) With the burner pipe in place,
Mizzou is added and vibrated.
(8) Leftover Mizzou is used to
make a flower pot furnace and
plinths.
(9) Curing the Mizzouz is done
by slowing increasing the heat
over several nights.
Mizzou Castable Refractory
Refractory is the material you use to insolate your
foundry. You can make your own refractory but I was having
problems finding the materials, so I went the lazy route and
purchased Mizzou Castable Refractory. As much as this stuff looks
like concrete, it is not concrete, it also has a 30 day self life,
which is your ticket to a low price.
When I went to return a couple of unused bags of
Mizzou I saw they had a complete pallet of the stuff sitting out in
the rain because it had gone over its 30 expiration date, they would
have let me use that for free. I asked why they had so much of it on
hand, and it turns out they make crematorium pans, which are the
slabs that go under the body when it is placed into the furnace.
The employee then pointed to a metal building on the other side of
the loading yard with 2 large stacks belching smoke and explained
that they also run a crematorium.
Read the instructions! Mizzou is mainly alumina,
which is aluminum oxide. Wear a respirator, gloves and wash up
after using it. It took 4, 55 lb bags at $27 each to complete my
furnace.
You only use 5 pints of water for each 55 lb bag so
it looks like very dry concrete. The trick is to vibrate this
stuff, and if you have an old table saw then you have the perfect
vibrator. Just lower the blade, cover it with plastic, turn it on,
and let it vibrate your refractory.
(3) I poured the lid first so I could see how it
worked on a small part. You can see the small steel bars welded in
to reinforce the refractory . This is only done in the lid, so that
the refractory is supported when it eventually cracks. A butane
torch with a piece of cardboard wrapped around it sticks through a
hole in the lid. This will form the site hole and vent in the top.
(4) The bottom is poured next, it is 3 inches thick. A 3/4 inch PVC
pipe sticks down through a hole in the center to act as a drain
should the crucible fail. Small channels were also formed into the
refractory to help channel molten metal to the center drain.
(5) While the bottom was drying I made a crucible or
melting pot, from a 6 inch steel pipe with 1/2 inch plate steel
welded on the bottom. The crucible was then used to make the center
form for the refractory. Wooded strips 1 inch wide were glued to the
crucible with dabs of Liquid Nails and then those were wrapped with
aluminum flashing. The flashing was cut and folded over to close off
the top in order to make it easier to shovel in the refectory
without have to try and miss the opening to the center form.
(6) (7) With the bottom dried, the center form was
set in place along with the burner inlet pipe which is a 2 inch
steel pipe shaped to fit the curve of the center form. It is held
in place with Liquid Nails and a piece of metal that is inserted in
the pipe and pierces the center form.
(8) I had enough leftovers to make several plinths
and a flower pot furnace. Plinths are small blocks that support the
crucible above the bottom of the furnace. The flower pot furnace is
so named because it is simply a couple of flower pots lined with
Mizzou. The flower pot furnace is great for small jobs because is
heats up in about 10 minutes.
(9) Curing will be many hours spent gradually
heating up the furnace. The Mizzou Refactory came with a very
specific set of instructions but I did it over multiple evenings,
using heat lamps the first couple of nights, then the next night I
started with the burner. About 5 or so hours with the burner pulled
back out of the burner pipe, turned down low and only partially
venting through the pipe. In order to achieve 250 degrees F, then
higher temperatures on 4 consecutive nights until we were melting
aluminum. After the first 3 hours above 250, steam was escaping
from my porous welding job, so I would not recommend any faster
curing than several days.
Propane
Burner
(10) My burner is made from an aluminum 2 inch to
3/4 inch reducing bell turned on my lathe, but that is just because
I could not find an 1 1/2 x 3/4 inch reducing bell at one of the
local plumbing supply houses and I wanted to play on the lathe. The
center is an 8 inch long 3/4 inch nipple, and the flare is a 1 inch
by 3/4 inch reducer. I cut the threads out of the 1 inch side of
this bell on the lathe, but I doubt that was necessary. I just
borrowed the 5 PSI regulator hose and orifice from my bargain turkey
fryer I picked up for melting lead. You can also dispense with
the regulator. You will get more gas when you want it, but you will
have to control the
flame with the valve on the tank and that is not
easy to do.
(11) I welded a small cross piece in the large end
of the aluminum bell, then drilled an tapped a hole in the center
that would fit the gas hose. I made a butterfly valve to regulate
the air entering the bell, but it turned out to not be needed.
(10) Burner make from 3/4 inch
pipe, a 1 inch by 3/4 reducer on
one end and a bell turned from
aluminum on the other. A brace
is welded into the bell and that is
drilled and threaded for the gas
hose.
(11) Bell end of the burner.
(12) Harbor Freight Propane
"Fires of Hell" Torch -$30.
(13) Tool used to lift the crucible
out of the foundry.
(14) Hooks on a swivel latch
onto ears on the crucible to lift it
from the foundry.
(15) Tilting arm that is welded to
the handle is rotated down to tilt
the crucible for pouring.
(16) Crucible tilted for pouring.
(17) Wheels added, and a lid
keeps the rain out so it can be
stored outside.
I also welded 6 small bits of flat steel onto the 8
inch nipple. This keeps the burner centered in the burner pipe
which allows for additional air flow around the outside of the
burner. One of the tabs of steel is notched to prevent the burner
from sliding too far into the burner pipe. Make sure to keep the
gas turned up enough to keep the flame burning only at the flared
end of the burner. If too low the flame will burn back through the
3/4 inch pipe and start burning inside the intake bell. This will
cause the gas hose fitting to over heat and it would soon melt of
and catch fire. The propane tank would be next and after that blows
up you would not need to worry any more.
I tested the foundry with a small melt and it worked
great. I takes 30 minutes to melt a couple of pounds and over an
hour for about 8 pounds. Larger burners will do the job in 15
minutes and that seems important to many people, but there is always
something else to do other that watch the water boil. Also you
really do not want the aluminum to get much hotter that it's melting
point of degrees. I tried adding a blower taken from a
discarded dryer, in order to force more air thought the burner and
increase the efficiency, but just a small amount of additional air
caused the burner to blow out.
(12) I recently purchased a propane torch from
Harbor Freight;
www.harborfreight.com, for $30. It has a knob that can
adjust the flame and no regulator. This thing is like is the
fires of Hell compared to my old burner. Go get one and see
what the preacher has been talking about!
Crucible Tool
(13) The
design is a hybrid of a couple of others I saw. It has 2 hooks that
can reach down into the furnace and catch 3/4" studs welded onto the
top outside edges of the crucible. The hooks are welded to a 7"
piece of pipe that swivels on the tools handle. (14) (15) Once the
crucible is lifted out of the furnace the handle is rotated allowing
the hooks to swivel and the tilting arm which is welded to the
handle to rotate down and catch the bottom of the crucible. (16) The
crucible can now be tilted for the pour. The photos are only a
demonstration, I'd be wearing gloves if this was real, and the spots
on the crucible are just ash from the Liquid Nails that was used to
hold the wood furring strips in place when the crucible was being
use as part of the from to cast the furnace.
If I had to do this again I might build my furnace
so that the lid included about 3 inches of the side of the furnace.
This would increase the weigh of the lid, but the crucible tool
would be much simpler. I could then cut holes in the side of your
crucible and just slide end of the tool through the holes. You would
want some notches in the tool to help keep the crucible from sliding
off but you eliminate the need for the swivel, the hooks, and the
the studs on the crucible.
(17) It's been over a year and I finally got tired of dragging the
foundry around while stepping over the engine stand laying in my
drive way, and 15 minutes latter the rest of the engine stand is in
the scrap pile and its wheels are welded onto the foundry. What a
wonderful improvement. Just tilt her back and roll it out of the
way. The original oil drum lid is to help keep some of the rain out.
Flower Pot Furnace - Aluminum F
(1) Months ago, when I was building my large foundry
I had some left over Mizzou Castable Refractory and so I made some
plinths and a flower pot furnace. The flower pots were just normal
clay pots borrowed from a pile the neighbor had beside his house.
Ok, I stole them.
(1) Two flower pots lined with
Mizzou Castable Refractory.
(2) The clay was removed and
holes drilled of the burner and
vent.
(3) Using the same propane
burner that heats the big furnace.
heats
(4) A gas cylinder cap is used for
a crucible.
(5) A rod passes through holes
near the top of the crucible.
(6) A tilting arm on the handle is
rotated down to pour.
(2) Well today I finally needed just a small amount of melt and
so I finished making the Flower Pot Foundry which still needed a
burner hole and a sight/vent hole. I used a standard 1/2 masonry
drill bit and drilled several holes to make a crude hole about 1 1/2
inches wide for the burner and several more in the the top for a
vent.
(3) The burner is only resting on steel and the flame directed
through the burner hole. (4) The crucible is made from a gas
cylinder cap I found on the high way, and a couple of bits of steel
have been welded in to close off the holes on it's sides. Another
couple of bits of angle have been welded to the bottom to support it
off the bottom of the furnace. (5) Finally two new 1/2 inch holes
have been drilled at the upper lip, which allow the crucible to be
lifted with a custom crucible tool. (6) The crucible tool is a jack
handle with a 3/8 inch bolt welded onto the end and then the bolts
head was cut down so that it became a slight hook in order to
prevent the crucible from sliding off. An couple of pieces of flat
bar are also welded to the handle so that when the tool is rotated
they catch the bottom of the crucible in order to tilt it for
pouring.
I didn't have to remove the clay flower pot from the castable
refractory; just heating it up once for about 4 minutes to help cure
the refractory did that for me. This refractory had been sitting in
a dry spot for months so curing was not much of an issue, otherwise
the refractory comes with very specific instructions for curing.
(3) This is the same burner I use in my larger foundry with is
converted from a turkey fryer. The details for the larger foundry
and burner are described above. The large furnace is great for
melting up to 15 pounds but takes almost 2 hours and unfortunately
it also takes about 30 minutes to melt just a couple of pounds
because it takes a while to heat up all that refractory. On the
other hand the Flower Pot Foundry melts a couple of pounds in just
15 minutes. There are always plenty of things to do around the
shop, so it's not that I am in a rush, but I am cheep and the
quicker melt time saves on propane. Not only that but handling the
small crucible is much, much easier so pouring funnels are not
necessary.
Flux and Degassing
N400 for Brass and N600 for Aluminum (pdf)
Links
http://www.lmine.com Legend - #
35 Budget Graphite Crucible $60
http://manufacturing.stanford.edu
"How Everyday Things Are
Made" (Covers Casting)
www.backyardmetalcasting.com Back Yard Metal Casting
http://metalcast.boorman.us Brians Metal Casting Project (Well
documented plans)
www.budgetcastingsupply.com Budget Casting
Supply Links
www.buildyouridea.com/foundry/lost_foam_howto/lost_foam_howto.html
Lost Foam How To
www.dansworkshop.com Hot Wire Lathe and Foundry
Suppliers:
Gypsum Solutions
www.gypsumsolutions.com Local Distributor: Independent
Materials, 34 N Owasso Ave. Tulsa, OK 918-582-
- Casting Plaster and Molding Plaster (Plaster of Paris) $20/100
lbs
Ryder Brick, S Memorial Dr, PO Box 550, Bixby, OK
918-366- - Firebrick 9x4.5x2 $1.10 each
Canfield & Joseph Inc, E 42nd Tulsa, OK 918-663-
Petrobond Pre-Mix .60/lb (50lb box). Warehoused in Kansas City
100lbs Petrobond Pre-Mix is $60 + $34.64 shipping + 5.11 tax =
$99.75 (May )
Bryant Industrial, S 65th West Ave, Tulsa, OK 918
446- - Mazzo Refactory Mix 55# 26.95
www.creativepackagingok.com Polystyrene Foam 4' x 8' x 40" (Bun)
for $179.20
Budget Casting Supply
http://budgetcastingsupply.com Petrobond Pre-Mix 100lb box is $124 (May )
For more pb melting furnaceinformation, please contact us. We will provide professional answers.
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