# My Iron-Melting Furnace



## greentwin (Jun 23, 2022)

I got interested in making a foundry and casting some aluminum, after seeing a few articles about it in the model engine magazines.
When I decided to build the green twin, I did not initially consider trying to cast any parts in gray iron because I did not think it was possible in a backyard setting.

I did an internet search, and there was an individual who was melting iron with an oil-fired burner, and so that is when I decided I had to learn how to do that, with the confidence that it could be done, and was being done in a backyard setting.


			Melting iron with waste oil
		


I am told that he is certainly not the first to melt iron on a hobby level, but this was the first time I had seen it anywhere online.
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## greentwin (Jun 23, 2022)

I use new diesel to fire my furnace.
Some use waste oil, but I won't use it due to concerns about heavy metals being in it.

I starting reading up on oil burners, and my first experiment with an oil burner was a $20.00 paint sprayer from Harbor Frieght, and a can of kerosene.
I would (carefully with a full face shield and gloves) light off the kerosene spray, and create some very impressive flames.
It was apparent I needed a paint sprayer in a long tube, for a foundry burner, and so that is what I ended up building.

My first furnace was just a circular stack of hard fire bricks, and a welded steel crucible, with a propane burner.

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## greentwin (Jun 23, 2022)

A few safety notes for those who may consider building a furnace.
You want to avoid any refractory dust, ceramic fiber airborne particles, metal fumes, toxic metals, etc.
Do your safety homework before you attempt to build a furnace.

Ditto when you attempt to operate a furnace or burner.
Operating a furnace and burner is not a casual affair, and like driving a car in busy traffic, you have to be well versed at it to avoid mishaps or injury.
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## greentwin (Jun 23, 2022)

I build my first "cast refractory" furnace using two sonotubes, and a massive amount of refractory (perhaps 8 bags at 70 lb each).
While my first iron furnace did work, it is very slow to reach pour temperature due to its high mass.
I ended up building a second furnace, with the intent of keeping the mass as low as possible, and so this thread is about my 2nd iron furnace.
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## greentwin (Jun 23, 2022)

For my 2nd iron furnace, I used a total of two 70 lb bags of refractory, and it functions far better than the first furnace, with much shorter melt times.
Below are photos of how I did it.

I am constantly learning new things about foundries and furnaces, and if I had to build another iron furnace, I would probably do things slightly differently, but this furnace is highly functional, and I am very pleased with how consistently it operates.

These are the dimensions of my furnace, and the intent was to be able to use a range of crucible sizes, by varying the plinth height.
The plinth is the support that the crucible sits on top of.


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## greentwin (Jun 23, 2022)

The idea is to have the burner tube opening (called the tuyere) enter the furnace tangential to the furnace body, to create a swirl of hot gasses that do not impinge on the crucible.
The centerline of the tuyere is generally at the bottom of the crucible.

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## greentwin (Jun 23, 2022)

I used an online program to get a template to use for the tuyere opening, and bought some sonotube (tm) from the hardware store.
I also purchased some insulating fire brick and ceramic blanket.


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## greentwin (Jun 23, 2022)

I bought a used stainless beer keg, and sliced it up.
Those things will spring open, so use caution if you cut the shell.

This turned out to be a minor blunder, since my furnace turned out to be the diameter of a 55 gallon drum, and I could have just purchased a stainless 55 gallon drum, and saved myself a lot of welding.


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## greentwin (Jun 23, 2022)

Here is the spray nozzle that I used for the burner.
This nozzle is commonly used in oil-fired heating units, and so is a proven design.
You don't want to leave the burner tube in the furnace after you turn it off though, else you will melt the o-ring in the nozzle.

I actually ended up redesigning this nozzle to eliminate the o-ring, but that is another story.
I never melted an o-ring, but I did not want to worry about that.

This nozzle uses atomized air through the center, combined with fuel fed in through the hole in the side of the adapter, to atomize the fuel.
The very tip of the nozzle has small angled slots in it, which help mix the atomized fuel with combustion air.

I use a variable speed Toro leaf blower to provide combustion air to the furnace.


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## greentwin (Jun 23, 2022)

I made a circle cutting jig for the rounder, and cut some round forms for the inside of the sonotube, to keep it from collapsing from the weight of the refractory.


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## greentwin (Jun 23, 2022)

I made the exterior form in sections, which turned out to be not really necessary.
I cut and glued the sonotube to get the diameter I needed for the exterior tube.

The sonotube has to be waterproofed, else it will absorb the water from the refractory, and collapse.


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## greentwin (Jun 23, 2022)

I decided to cast this "hot face" (hot face being the dense refractory that lines the interior of the furnace) inverted, and monolithically, which I have never seen anyone else do.

The refractory was mixed similar to concrete, and then rammed into the space between the formers in 4" layers, ramming with a 1/2" dowel rod to be sure the space was fully filled.  The difference between concrete and refractory is that concrete will expolde if used as a furnace refractory, and you only use a tiny amount of water when mixing refractory, which makes it very difficult to mix.
Adding more than the recommended amount of water to refractory will weaken it, so don't do that.

The hot face turned out well, and while I was at it, I cast a few plinths for the crucible to sit on.

Many use ceramic blanket only when building a furnace.
I wanted the durability of a hot face, and so I used cast refractory (Mizzou), but tried to keep it as light as possible.
This hot face was a good compromise on mass and durability, and Mizzou is known to work well at iron temperatures, with a high resistance to iron slag.

There are followingers in some casting circles who insiste that refractory MUST be vibrated into place.
I disagree with that, and did not use a vibrator.
As you can see, there were only minor defects in this hot face.  I was careful to ram each 4" layer with a 1/2" wood dowl rod, to drive out any major air bubbles.
I have seen major defects with folks using vibrated refractory, and I did not want any settling of the refractory aggregate, which can happen if you over-vibrate it.


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## greentwin (Jun 23, 2022)

I cast the tuyere on this furnace, and am not entirely pleased with how this turned out, although it does function well.

The fact is that the tuywere and burner tube (if your burner is operating correctly) operate almost cool to the touch, and so there is really no need for high temperature refractory extending out from the furnace.

If I had to do over, I fould have used soft fire bricks at the tuyere, with the flat part of the bricks resting on the furnace base.
You can drill soft fire bricks with a hole saw, and I would have made a jig to be able to drill the bricks at an angle.

Note that the burner tube should be supported independently of the tuyere.
My tuywere broke away from the furnace, but I patched it without problems.

Also note that the end of the burner tube should not extend into the furnace, else it will overheat and start melting off.


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## greentwin (Jun 23, 2022)

I had a couple of false starts on the lid, and originally cast a flat one.
A flat lid can be problematic, although many commercial furnaces to use that design.

All refractory will crack over time, and that is not a problem, since you can easily patch refractory with high temperature patching compound.
But if the lid refractory cracks, you could potentiall have if fall into the furnace, which would be very bad if you had a crucible full of molten iron in the furnace.

I ended up using Mizzou to cast a domed lid.
The forms were a bit tricky to make, and I was not able to ram the top of the refractory, but the bubbles on the top of the lid refractory are cosmetic, and don't affect the performance of the furnace.

I have since discovered "plastic refractory", which is a refractory that comes in a solid block, and is flexible like stiff putty, and can be formed.
Plastic refractory would make furnace lid construction simple, since you would only need one form, and could just pack an inch of plastic refractory onto it.

This lid turned out to be very functional, and withstands iron temperatures well.
If the refractory cracks, the lid will be self-supporting due to the arch.

I use a short chimney, since that seems to help keep some heat in the furnace, and directs the vented hot gasses upward and away from the casting area.

This lid is 1" thick Mizzou refractory.


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## greentwin (Jun 23, 2022)

I could have used two layers of 1" ceramic blanket on top of the lid, but I wanted some sort of insulating hard surface over the ceramic blanket, to prevent the ceramic fibers from fraying and becoming airboard.
My solution was to cut insulating fire bricks (2,600 F rated) on an angle, and then use a 1" layer of ceramic blanket under them.

This approach actually works quite well, although you could also use a sheet metal cap over two layers of 1" ceramic blanket.

As I mentioned early on, don't inhale any refractory dust or fibers when you cut them.

My angular cuts on the insulating fire bricks were not exact, but I got it done, and made this lid cover in about an hour.


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## greentwin (Jun 23, 2022)

I initially thought I would use a lightweight sheetmetal cover over the base frame, and thus all the angular support members.
I ended up using a steel plate to cover it all, and could have dispensed with much of the framework under the plate.

I used metal wheels, having learned with the first furnace that any plastic or rubber within about 10 feet of an open iron furnace will begin to deteriorate relatively quickly.


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## greentwin (Jun 23, 2022)

I was torn between using two layers of ceramic blanket on the outside of the hot face, or using 2,600 F insulating fire brick.
I went with both; ie: one layer of insulating fire brick, and then two layers of ceramic blanket wrapped around the brick.

I used angle grinder and 4.5" disk to dress the inside of the bricks to give them a round shape for a good fit against the outside of the hot face.
Wear a good commercial dust mask if you do this.

The aluminum pan was discarded, and I used the steel baseplate shown in the previous post.

I used one layer of insulating fire bricks under the hot face, with some ceramic blanket strips.
I wanted the hot face to be fairly rigidly supported, and using a 1" layer of ceramic blanket under it woud cause the blanket to compress, and cause the hot face to settle and perhaps rock around.

The idea behind the soft fire bricks was to provide some level of rigid support behind the hot face.
The stainless steel band that I installed at the top of the hot face was a mistake, and caused the hot face to have excessive cracking (which was repaired; more on that later).
Don't put a band at the top of the hot face.

I also originally intended the lid to notch down into the insulating fire bricks, and that did not work.
The insulating fire bricks should come up flush with the top of the hot face (more on that later also).


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## greentwin (Jun 23, 2022)

This is the lid lifter design I came up with for this furnace.
It allows the lid to rock slightly so that it will seat completely on the top of the furnace without any gaps.

I learned to never support a furnace lid from the refractory (on my first furnace build), and so this lid and vertical support shaft are supported independent of the furnace body.
This arrangement also makes it easy to disassemble the furnace to transport it, and makes it easy to dissable the furnace to work on it, since this is a modular design, and the various components are independent, and not adhered to each other.

The vertical lift shaft sits on a ball bearing, made from a caster wheel.

My latest lid design is a better one than this, and it is just a wrist joint to lean the lid up and back, with a bearing under it for horizontal rotation.
This lid lifter works well, so I will keep it, but the wrist-lift-pivot is a much better design.


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## greentwin (Jun 23, 2022)

It was finally time to fire up the furnace.
I think I dried the hot face for about an hour with low propane heat.

The valve tree was a temporary arrangement that I made so that I could quickly determine what the best fuel flow was.
I could change the fuel flow in increments of 1 gal/hr.
At the time I built this furnace, I was still unsure exactly what fuel flow rate was best for melting iron.

You can see in the first photo how modular the furnace is.

The lid with the large opening was a temporary arrangement, and was replaced with the domed lid with chimney.


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## greentwin (Jun 23, 2022)

I could not find anywhere online an exact concensus about what fuel and combustion air flows produced the hottest furnace interior.
I set up the new furnace with a temporary lid with extra large opening, and ran the burner at night, to better observe how hot it was getting.

I used a PVC valve to control the combustion air flow from the Toro leaf blower, and a valve tree to adjust the diesel fuel flow.

By trial and error, I discovered that a fuel flow of between 2.5 and 2.7 gallons per hour produced the highest furnace temperature, judging temperature by the intensity of the red glow inside the furnace.

The combustion air is adjusted during startup to give about 4 inches of yellow flame out the lid opening, to produce a reducing flame, which creates an slightly rich burn inside the furnace, thus minimizing oxidation of the iron.

Reducing the combustion air flow to the point where no flames come out the lid opening creates an oxidizing burn, which tends to oxidize the iron and create excessive slag on top of the melt.

This was a big deal for me to figure out the correct fuel/air flow rate that would minimize melt times for iron.
I had incorrectly assumed that more fuel would produce a hotter furnace interior, but that turned out to be a false assumption.

What is happening is that the interior of any given furnace can only completely combust a fixed amount of fuel using the opimum amount of combustion air, based on the area of the interior of the furnace.
Using any more or any less fuel and appropriate amount of combustion air will cause the temperature inside the furnace to drop.

The idea is to reach pour temperature, which is about 2,400-2,500 F, in as short a period of time as possible.
Typical time to pour with this furnace, using a #10 crucible, is about 1 hour.

I don't have an immersion iron pyrometer to measure the iron temperature, but I can generally tell when I reach pour temperature, because small sparks begin to fly out of the melt.


View attachment TEST-NEW-FURNACE-01.mp4


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## greentwin (Jun 24, 2022)

Here is the adapter I made for the leaf blower, and the stand I made to support the blower.
For the most part, I had to make up designs for the various equipment as I went.

I run the Toro blower on the lowest setting, and can fine tune the combustion air flow into the furnace with the PVC valve.
As it turns out, the Toro on the LOW setting is the exact amount of combustion air that my furnace needs to combust 2.7 gallons of diesel per hour, when the PVC valve is closed (all the blower air goes into the furnace with the PVC valve closed).


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## greentwin (Jun 24, 2022)

Next I had to find some scrap gray iron to melt.
Motor end bells turned out to be excellent and consistent iron scrap, and I had a buddy who ran a motor-rewind shop, so he let me dumpster-dive.

You can generally tell if scrap iron is usable by breaking it with a sledge hammer, and looking for a nice uniform even break, with no inclusions or white (hard) spots in it.

One common myth that many in the backyard community seem to adhere to is that scrap iron must be clean and free of any corrosion or paint.
You do not have to clean the corrosion off of iron, even if it is heavy, and you don't have to clean off paint either.
I did not believe this to be true until a buddy of mine demonstrated a perfect iron pour with flawless castings, using iron that looked like it had been on the bottom of the ocean for 100 years.
I stopped cleaning my scrap after that, and I get perfect casting results every time, so myth busted.


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## Just for fun (Jun 24, 2022)

Man,  Nice write upon the Furness!  Thanks for sharing.


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## greentwin (Jun 24, 2022)

I dried out the hot face for about an hour the first time I used it, using a propane burner.
The plinths also have to be dried.
The trick is to use enough heat so that the hot face begins to steam, but not so much heat that the steam explodes the refractory.

Over about an hour, the propane burner is gradually increased in output, being careful not to overheat the refractory while it is still steaming.
Finally the steaming will stop, and the propane burner is turned to full output for about 5 minutes.
This is the only dryout method that I use.
Others use very long dry-out schedules, but I don't.

The blue flame hue was with my oil burner, and it was caused I think by the stainless needles that I added to my refractory.
I initially thought that stainless needles would help keep the refractory together, but they have no strength at red hot temperatures, and so they really don't do anything.
The needles to produce a beautiful blue flame though.


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## greentwin (Jun 24, 2022)

Just for fun said:


> Man,  Nice write upon the Furnace!  Thanks for sharing.


Thanks,

I studied several iron furnace designs that various folks had posted online, and paid careful attention to what worked, and what failed.
This furnace design is sort of a hybrid of things I saw online, with my own spin added to the mix.

I sort of stumbled through this furnace build, but I had seen others having good success with melting iron, and so I knew it was just a matter of using high-quality materials, and then figuring out how to operate the burner to achieve maximum heat.

.


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## greentwin (Jun 24, 2022)

I made my first iron pour with the new furnace, and everything well pretty well.
I looked closely for degredation of the interior and crucible, and all things considered, everything held up well.

Mizzou is noted for being a tough refractory, expecially with iron.

A few minor cracks appeared at the top of the hot face, and some slag degredation on the exterior of the crucible.
I got a nice clean iron pour, which broke cleanly with a nice even gray break.

I had to adjust the lid a bit.

Note that I originally did not use the insulating fire bricks around the exterior of the hot face, and the lid actually recessed down past the top of the hot face top edge.
All lids leak some hot gasses, and this lid design directed the leaking hot gasses down beside the outside of the hot face, heating up the stainless shell.
I ended up removing the lip from the lid (filled the lip with plastic refractory to make a flat surface), and made the lid/hot face joint flat and horizontal, with directs any leaking hot gas out horizontally.
This fix solved the lid problem.


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## greentwin (Jun 24, 2022)

As luck would have it, my camera battery died just before pour time, so I missed getting the pour on camera.

I was still in trial mode, and so lots of clutter around the furnace, which should be avoided.

I also installed some thermocouples on the outside of the hot face, to see how hot it got.
The outside of the hot face gets very hot, and the thermocouples all burned up.  Luckily they were inexpensive.

The outside stainless shell of the furnace remains cool to the touch will the furnace is running (after I added the insulating fire brick layer).
The burner tube also runs cool to the touch except right up close to the furnace.


View attachment Pour-01.mp4


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## greentwin (Jun 24, 2022)

I made four iron pours using the new furnace, testing out some new sand, and demonstrating its operation to several friends and family members.
I was asked to do a demonstration for a local art-iron group in town, and so I disassembled the furnace so that I could move it.

The hot face had become cracked during the four iron melts, and when I picked it up to put it in the van, it fell into 4 pieces.
I was not sure what to do, but I was due at the show in 30 minutes, and so I transported everything to the iron festival.

As I was walking around the iron festival, someone was patching the cupola that they use at the show with a white putty-looking material, packing it into the interior of the furnace by hand.
A light bulb went on in my head, and I asked if I could borrow some of that material, which turned out to be 3,800 F plastic refractory.
I was not even aware of such a refractory at the time.

I was able to patch my hot face, reassemble my furnace, and make a demonstration iron pour, which seemed to be well liked by the art-iron crowd that was at the festive.

It was dark by the time I was scheduled to do the demonstration pour, but I am use to doing pours at night, and much perfer that since it is much cooler, and easier to see what is going on in and around the furnace as far as heat, temperature, and such.

The pour went well, and the patched furnace worked well.

Below is the furnace rebuild, which I had to do at the festival.


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## greentwin (Jun 24, 2022)

Discovering plastic refractory was a stroke of luck, and occurred by chance at the iron festival.

There were a few who said "You furnace is ruined; you can just throw it in a dumpster".
At first glance I thought they were right, but after patching the furnace with plastic refractory, I realized that a cracked hot face is no big deal.
All hot faces seem to crack.

But the Mizzou was still solid as granite, and the plastic refractory is the toughest material I have ever seen, and so the furnace has continued to work flawlessly after the cracking problem.
I removed all of the metal bands from the outside of the hot face, and have had only slight cracking in subsequent iron melts.

I touch up any cracking with plastic refractory, but have had only small cosmetic cracks at the top of the hot face since the festival.

It was just sheer luck that I discovered plastic refractory, which made me realize that Mizzou can easily be repaired indefinitely.


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## greentwin (Jun 24, 2022)

This was a 3D pattern that I made for the iron festival.
I have an iron casting of it somewhere that I need to find.
If you ever have a chance to attend an art-iron cupola pour, I highly recommend it.

I changed filament colors in mid-print just by snipping off the green filament, and then feeding in yellow filament until the feeder grabbed it.


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## greentwin (Jun 24, 2022)

A few photos of the art-iron pour.


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## wachuko (Jun 24, 2022)

Amazed at the amount of work required to make a furnace…

Thank you for sharing the process with us!!

Very, very cool!!  I mean hot,  but cool


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## SLK001 (Jun 24, 2022)

Great write-up.  About the art show, I was appalled by the pouring/spilling of molten iron onto the ground.  A little water in the soil underneath and the art show becomes a fireworks show.  As for your pour, you should always pour over a sand bed.  That way, when your crucible fails one day with a full charge, it won't become much of an issue with molten metal on the ground


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## greentwin (Jun 24, 2022)

wachuko said:


> Amazed at the amount of work required to make a furnace…
> 
> Thank you for sharing the process with us!!
> 
> Very, very cool!!  I mean hot,  but cool


Thanks,

You can make a furnace using ceramic blanket, but they do not last as long as a furnace with a cast refractory hot face.
The ceramic blanket needs to be coated with material that will prevent the fibers from becoming airborn and inhaled.

I went with the long lasting approach, which is more build time on the front end, but almost no maintenance after that.

In spite of the cracking that occurred in my hot face, it was easily repaired, and continues to work like a champ.
All hot faces crack.  As long as they don't crumble then cracks are patched easily enough.
.


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## greentwin (Jun 24, 2022)

SLK001 said:


> Great write-up.  About the art show, I was appalled by the pouring/spilling of molten iron onto the ground.  A little water in the soil underneath and the art show becomes a fireworks show.  As for your pour, you should always pour over a sand bed.  That way, when your crucible fails one day with a full charge, it won't become much of an issue with molten metal on the ground


Thanks, I am glad folks are enjoying the photos.  I love attending these art-iron shows, although most have shut down for the last 3 years or so.
I can't wait to see them start back up again.

They water the grass in the weeks before the show, and then water it again after the show, and it grows back quickly.
Grass is a renewable resource, so not a problem.
It was really dry that day, and so there was more grass burn than you would normally see at an iron pour.

They actually have art-iron shows where the sling buckets up moten iron up into the air into the most fantastic display.
Iron is not really as dangerous as some would make it, but I do have some hand burn photos I will post, and one does have to be very cautious when handling molten iron.

I have heard a number of folks mention the sand bed, but I have never used one, and have spilled both molten iron and molten aluminum onto concrete, with no effect at all.  My concrete is a bit old.  For new concrete that has high strength, I have seen a spill spald out a spot.  I would not pour over new concrete, but my driveway needs replacing anyway.

There is danger of moisture being in sand on the ground and causing an explosion during a spill, so sand is not really as safe as you may think.
I use high quality crucibles, and they are not known for failure, but one never knows.
I did have a crucible fall out of my early pouring shank (poor design), and it dumped a #10 full of molten iron on the concrete, but no problem, and no damage even to my driveway, but again, my driveway concrete is pretty weak stuff.

Everybody has to come up with the methods and materials they feel safe and comfortable with.
Many backyard casters do use a sand bed.  I don't, and I know another guy in Australia who does a lot of iron, and he pours exclusively over concrete, and has done so for 20 (+) years without problems, even with spills.

Edit:
I showed my iron pour videos to one fellow, and he noted "There is not a single fire extinguisher in sight".
LOL, it did not even occur to me that I needed a fire extinguisher, and I generally don't set one out, but having an extinguisher on hand is not a bad idea.
I generally don't put anything flamable or anything with moisture within about 20 feet of the furnace.
My main concern is preventing molten iron from contacting my skin.  That is pretty much all I worry about.

The worst furnace fire I have seen is when someone melted the fuel line going to the furnace, and started a large puddle fire.
I don't operate my furnace near the house, just for this reason.  And in the future, I am going to cover my fuel line, probably with flexible metal conduit sheathing, so a spill does not open up the fuel line.

Diesel is very reluctant to burn unless it is vaporized, and even then it is very tame (I will post a video).
Kerosene is much more volatile, and I don't use kerosene, mainly because it is very expensive in this area, but also for safety reasons.
You can drop lit matches into a container full of room-temperature diesel, and you cannot light it.  Basically there are no vapors to light with diesel.

.


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## greentwin (Jun 24, 2022)

My first pouring shank design was not a good one.
The retainer did not work well due to variations in the exact size of crucibles, and so just as I began pouring a full #10 of iron, the crucible slipped out of the pouring shank.

This is the reason you wear leather boots when you pour, and a leather jacket, leather chaps, etc.
And your pants legs go over the top of the boots (nothing worse than molten iron running into your boot).

There was a big splash of iron everywhere, and most of it ran harmlessly off of my leather, but a few tiny droplets ran down inside my gloves.
By the time I got my gloves off, the damage was done.

Luckily molten iron vaporizes nerve endings, and so there was no pain.
It took a while for the scar tissue to fill in the spots.

I generally wear a full face shield and safety glasses, to give two layers of protection.

And I redesigned my pouring shank, so that the crucible is retained regardless of what height it has, or how it sits in the shank supports.

There is no sign of these burns on my hands now, but definitely a lesson learned.
Use very good equipment, and high quality crucibles.
Don't use thin or worn out crucibles.
Keep your poor area as clean and uncluttered as possible.


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## Lo-Fi (Jun 24, 2022)

Thanks for taking time to post so much detail. This is super interesting!


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## greentwin (Jun 24, 2022)

I have a variety of crucibles.
My favorite, and the only type I use these days for iron is the "Morgan Salamander Super".

The Salamander Super can be used for any metal (not for melting steel though), but it is "ferrous-metal-rated", and also rated for iron temperatures at 2,900 F.

Many crucibles are not "ferrous-metal-rated", and not rated for iron temperatures, and so I have seen crucibles fold up like wet cardboard when people try to use them to melt iron.

And you have to place two layers of cardboard under the crucible, on top of the plinth, otherwise the crucible will adhere to the plinth.

The red crucible is a great crucible for for aluminum, but not rated for ferrous metals or iron temperatures.
And the "Salamander" name is unfortunately used on several crucible types.

A "Salamander Hi-Melt" is not ferrous-metal rated, and not rated for iron temperatures.
For iron, it has to be the "Slamander-Super", so be aware.

It should be noted that a rough approximation of the capacity of an A-shaped crucible is that a #10 will hold 30 lbs of gray iron.
The charts typically list the "brim-full" capacity of the crucible, and brim-full is too full to be poured without spilling.
A realistic capacity for an A10 crucible is between 20-25 lbs of iron.

Using the same A10 for aluminum, your volume of melted metal will be the same, but the total melt metal weight will be about 1/3 that of iron.

And it is not a good idea to use once crucible for multiple metal types, ie: don't use a crucible to melt aluminum, and then use that same crucible to melt iron.


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## greentwin (Jun 24, 2022)

Lo-Fi said:


> Thanks for taking time to post so much detail. This is super interesting!


You are welcome.
I would like to see more folks get into iron casting.

Perhaps even start an iron casting club, with regional iron-casting festivals/events and such.

The art-iron festivals that I have attended have been instrumental in teaching me how to consistently and successfully cast gray iron, and I am very grateful to those folks for showing me how to do it correctly.

.


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## greentwin (Jun 24, 2022)

Here are the lifting tongs that I fabricated.
Some folks use combination lift and pour tongs, but since iron is so heavy, I have never found lift-and-pour tongs to be functional.

I use a mechanical stop on my tongs so at to not apply excessive force to the somewhat fragile clay-graphite crucible.

The crucible is suppose to be lifted by the lower part, and never by the upper part or upper lip.

These tongs work well.  They could have been made not quite as wide (if I were only using a #10 crucible), but I think I can use them for the next larger size crucible.


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## rwm (Jun 24, 2022)

Very nice. Great to see you having success with iron.


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## wachuko (Jun 24, 2022)

greentwin said:


> You are welcome.
> I would like to see more folks get into iron casting.
> 
> Perhaps even start an iron casting club, with regional iron-casting festivals/events and such.
> ...


In the past, I had looked at the sets they have in Amazon... but now looking at what you did, the stuff in Amazon seems like it will be good to make something the size of coins.... lol


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## greentwin (Jun 24, 2022)

Some folks cast things on a jewelry scale, and some I know pour with a #70 that contains almost 200 lbs of iron.

They do make small tabletop electric furnaces, mainly used in the jewelry business.
A buddy of mine purchased one, and he expressed concerns about how long it would last (not sure if he meant how long the furnace elements would last, or how long the crucible will last).

It is basically whatever suits your budget and expectations.
If in doubt, begin with a minimal and inexpensive setup, and find out if you really want to be in the casting hobby.
Some folks pour a few ingots, and are done with casting in general, and there is nothing wrong with that.

.


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## greentwin (Jun 24, 2022)

This is my pouring shank.
I have seen a wide variety of pouring shanks, and they vary from a good design to an almost worthless design.

The intent of my shank is as follows:

1. Protect the lifting hand from the radiant heat of the crucible, which is extremely high with iron pours.
2. Provide very good control of the pour rate, when the crucible is in the pouring position, and thus the handle on my pouring shank facing downwards.
3. Positively lock the crucible into the shank with no possibility of the crucible slipping out of the shank, regardless of irregularities between various crucibles of the same size, and regardless of exactly how the crucible rests in the shank.

One of the critical keys to making good castings is to avoid interrupting the pour as you are filling the mold.
If you are struggling to hold the pouring shank, and your wrists and arms are in an awkward and strained position, most likely you will be spilling metal all over, and interrupting the pour.


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## wachuko (Jun 24, 2022)

greentwin said:


> Some folks cast things on a jewelry scale, and some I know pour with a #70 that contains almost 200 lbs of iron.
> 
> They do make small tabletop electric furnaces, mainly used in the jewelry business.
> A buddy of mine purchased one, and he expressed concerns about how long it would last (not sure if he meant how long the furnace elements would last, or how long the crucible will last).
> ...


I was just thinking of something small but big enough to make material that I can turn in the lathe or milling machine...  I just wanted to give it a try.

I will revisit and get something in a few years... after we finally move to the new house... right now we are in between houses... this going back and forth is wearing me out...


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## greentwin (Jun 24, 2022)

These are my charging tongs.
I purchased them, but should have just fabricated my own.
I do not like these tongs, and they tend to bend and let the scrap metal slip out of the jaws.

I am going to make some new tongs with more rigid handles, and jaws with small teeth.

Charging tongs are used both for adding scrap metal to the furnace while it is operating, and also to hold scrap above the opening in the lid to drive off residual moisture that is on all metal.
The resitual moisture that is on scrap metal is not apparent, but if you drop a piece of scrap into a pool of molten metal without drying the metal for about 20 seconds in the exhaust stream, you may have an explosion, with all of the molten metal ejected from the crucible and furnace.


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## greentwin (Jun 24, 2022)

Here is a BIG art-iron pour held at Carrie.
Due to the pandemic, I have not made it to an iron pour at Carrie, but it is definitely on my list of things to do.









						Carrie Blast Furnaces National Historic Landmark
					

A remnant of the U.S. Steel Homestead Works, the Carrie Blast Furnaces are a vestige of Pittsburgh’s 20th-century domination of the steel industry.




					riversofsteel.com
				




Sloss is another big iron pour that is on my bucket list to attend, and I plan to bring my furnace and make iron there too !


And unfortunately I don't recall who sent me these photos, and so I can credit them correctly (they are not my photos).

 That is a pretty hefty ladle isn't it ?

Notice lots and lots of leather, and full face shields and hardhats.


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## greentwin (Jun 24, 2022)

Here is an art-iron show I attended at Tannehill Alabama a few years ago.


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## greentwin (Jun 24, 2022)

I am actually a member of the Sloss group, but due to the pandemic, I have not been able to get involved.
I do plan on taking my furnace to Sloss the next time they have an art-iron pour.









						Sloss Furnaces National Historic Landmark - Birmingham, Alabama
					

Sloss Furnaces is a National Historic Landmark and industrial museum in Birmingham, AL. Visits at this time are by appointment only.




					www.slossfurnaces.com


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## greentwin (Jun 24, 2022)

The Soule Museum in Merridian MS also has several iron pours every year.
Soule still has their original massive cupola-style furnace.

Soule is where all of the Speedy-Twin steam engines were made, and the assembly area is still intact at the museum, with partially finished Speedy Twin engines on the tables.


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## wachuko (Jun 24, 2022)

I want to do stuff like this...






And look at how small is the setup he is using!  I might just play with this sooner than I thought... 

I was just thinking of making stock to machine... he made a part that just needs finishing for use!


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## rwm (Jun 24, 2022)

I am assuming that is pewter or other low melting point metal. Aluminum is not too bad. When you get to brass, the radiant heat is impressive. The crucible is orange and it will ignite wood a foot away. I'm ascared of iron!


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## greentwin (Jun 24, 2022)

wachuko said:


> I want to do stuff like this...
> 
> 
> 
> ...


I suspect rwm is correct, that is probably a pewter-type metal.

I won't deceive anyone, metal casting can be difficult.
The sand he is using looks like petroleum-based greensand, often called by the trademarke name "Petrobond".

You have to maintain petrobond, and add a bit of alcohol to it from time to time.
I started with Petrobond, and had trouble with maintaining it, since it gets too dry, and you can ruin it if you add too much oil (some say add 90% alcohol only).

I gave up on petrobond, and tried greensand, which is a water-based sand and clay molding mixture.
The surface finish with greensand was terrible.
Greensand also has to be maintained, and mixed in a machine called a "muller".

I tried sand (commercial foundry sand called OK85), bound with sodium silicate, hardened with CO2, and that worked pretty well.

Then I discovered resin-bound sand, which is what I use with the OK85 now, and it is a mix-on-demand product.
You have to wear a commercial chemical-rated respirator when mixing resin-bound sand, and it is not reusable.
For iron work, resin-bound sand with a sprayed-on ceramic slurry produces commercial grade casting results, assuming you have your sprue/runners/gates/risers correct.

I have tried low temperature non-lead material, similar to lead-free solder, and I could not get the mold to fill completely.
I don't recommend low temperature metals.

I tried Zamak, since it has a lower melting point than aluminum, and was not pleased with how that material drilled (the metal melts in front of the drill bit).

The metal that most backyard casters use is alloy 356 aluminum, which is designed for casting.
Aluminum that does not make good castings is extruded aluminum, and aluminum cans.
Aluminum alloy auto rims seem to be a good alloy to cast, but those can be troublesome to cut up, and many are painted, which may have to be removed prior to melting.

Melting 356 aluminum is easy, and no more difficult than melting zamak (a propane burner can be used).
Finding good mold sand, and making a good mold is not easy.
It is the sand molding that really limits most backyard casting folks.

This fellow is rather outspoken, perhaps too outspoken for some, but he tells it like it is.
And I respect his opinion because he makes commercial-grade aluminum castings.
I basically agree with everything he says in this video, and I also have John Campbell's casting book.


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## rwm (Jun 24, 2022)

I would be shocked if he really did that casting in a home foundry. It has no detectable porosity and the machined surfaces are perfect. It is obviously heat treated to machine like that. Try machining your raw aluminum castings and you will never get that finish.


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## greentwin (Jun 24, 2022)

rwm said:


> I am assuming that is pewter or other low melting point metal. Aluminum is not too bad. When you get to brass, the radiant heat is impressive. The crucible is orange and it will ignite wood a foot away. I'm ascared of iron!


Melting aluminum is quite a mild mannered affair.
It melts easily with a simple propane burner, and pours at 1,350 F.

Melting brass/bronze is a lot hotter than aluminum.
I forget the pour temperature of bronze, but perhaps between 1,900 F and 2,100 F.

As the temperature goes up, the problem is radiant heat, in the form of infrared radiation.
This is why you wear heavy leathers, and have a heat shield on the pouring shank.

There is also a tremendous amount of heat that comes out of a hot furnace when the lid is open.
Most lids open sideways, but some flip backwards.
The backwards lids put their hot surface facing you directly, and that gets REALLY HOT.

I had melted a bit of brass and bronze before I attempted to melt gray iron, and recall being terrified of the iron temperatures, to the point where my hands would be shaking during the lift and pour sequence.

The charging tongs and skimmer have to have long handles with iron, because the will start to overheat your glove in seconds.
I am going to add a heat shield to my skimmer handle to help with that.

My daughter was using a video camera 10 feet away during an iron pour, and as I was pouring, I noticed her camera was starting to smell like melting plastic.  The infrared will be absorbed by any dark surface, or really most non-reflective surfaces.

It took me about 6 iron pours before I could relax and not get nervous before an iron pour.
Now iron pours for me are almost as routine as aluminum pours, but as I mentioned, use a lot of heat shield and protective leather with iron, and so it is a matter of being prepared and having the right equipment.

Pouring iron is sort of like driving on the expressway at 80 mph.
The first time you do it, it seems very dangerous, but if you do it every day, it becomes routine, and you become good at it, and can do it with relative safety.

.


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## greentwin (Jun 24, 2022)

rwm said:


> I would be shocked if he really did that casting in a home foundry. It has no detectable porosity and the machined surfaces are perfect. It is obviously heat treated to machine like that. Try machining your raw aluminum castings and you will never get that finish.


He basically operates a professional foundry on a small scale.
Check out this casting.











or these runway light housings






Olfoundryman is what I call one of the BOB's, ie: Best of the Best with aluminum castings.
.


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## rwm (Jun 25, 2022)

I stand corrected! Yes I know who he is. That is amazing work, and really not hobby level.


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## greentwin (Jun 26, 2022)

I found a short bio on olfoundryman, and his casting success is not accident.
He was a metalurist, worked in foudries, and ran his own commercial foundry, so he has a lot of depth, and that shows in his work.

He also uses professional materials such as the mold coating, release agent, degassing agent, etc., and that makes the difference between a rough casting and a professional grade casting.

He is very aware of the need to be careful not to entrain air and other things into the casting.

I don't agree with everything he says, but I agree with about 95% of it.
He has a ton of experience.

.


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