Home Foundry

[GreenTwin]

Once you get set up for iron, the process is not much more difficult than casting aluminum.

Getting set up for iron requires some meticulous preparation though, and it is not a casual thing.
Skipping a few steps to save time or money generally leads to failure with iron.

Furnace:
Many backyard casting folks use a thin hot face (1" thick or so) made from poured high-temperature commercial refractory, such as what I used (Mizzou).
Mizzou is 3,000 F rated, very high slag resistance. Iron furnaces splatter a lot of slag on the walls of the furnace when they run.
Behind the hot face can be either insulating fire bricks, and ceramic blanket, or just multiple layers of ceramic blanket.
The lid interior needs to be a cast dome, using Mizzou or equal material.
If you try to use materials rated less than 3,000 F, they will not last long at iron temperatures.

Ironman uses a coated ceramic blanket, I think with a material called Zircon, which I have not been able to find.
Some use a product called satanite to coat their ceramic blanket, and operate at iron temperatures.
I prefer a Mizzou hot face for long term reliability and easy repair.

Crucible:
The crucible needs to be a Morgan "Salamander Super", clay-graphite, 2,900 F rated.
This is a ferrous-metal-rated crucible, and works well with iron.
Never put borax on a crucible for any reason; else you will severely damage the crucible.
Ignore any recommendation of using borax for iron work.

Plinth:
The crucible sits on a pedastal inside the furnace, which is called a plinth.
Make the plinth from Mizzou.
Use two layers of cardboard on top of the plinth, so the crucible does not stick to the plinth.
Don't spill slag down the side of the crucible, else you will cause the crucible to stick to the plinth.

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[GreenTwin]

Burner:
Ironman uses a drip-style oil burner, running on a mix of diesel and waste oil, perhaps 20% diesel (perhaps only the diesel mix in cold weather).
I have never been able to get a drip style burner to have any decent controllability, and so I use a Delavan siphon-nozzle burner running on 100% diesel.
You need an inline automotive filter right before the fuel line enters the burner, else you may clog the nozzle.
You need a ball valve for fast shut-off of the diesel, and a second needle valve for fine flow control, in series with the ball valve.

Most videos on building Delavan siphon-nozzle burners show a propane connection too.
With diesel, you can omit the propane; it is not required since diesel lights easily even in cold weather with a siphon-nozzle.

My burner operates at about 2.7 gallons per hour, which produces about 112 KW.

Lifting Tongs and Pouring Shank:
Some folks on youtube detail "better mousetrap" devices such as combination lifting tongs and pouring shank, for use with aluminum pours.
Don't screw around with gizmos with iron and iron temperatures.
Use standard foundry lifting tongs with an adjustable stop in the closed position, and a separate pouring shank with a good functional crucible retainer. Both of these devices can be fabricated at home if you can weld.

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[GreenTwin]

Propane can be used to melt iron, but due to tank cooling, I find it very problematic, and with cooler outside temperatures, the tank cooling becomes worse.

I highly recommend using an oil burner to melt iron, and not propane.
I prefer using diesel, since waste oil can contain heavy metals, or other contaminates that can cause an uneven and unpredictable burn.

Melt times for a #10 crucible of aluminum is 12 minutes with an oil burner.
Melt time for a #10 crucible of gray iron is about 1 hour for my setup.

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[GreenTwin]

Sand:
Many use what is called greensand when casting iron.
Greensand is sand mixed with a special clay, water, and generally some fine materilal like coal.
Greensand is reusable, but you have to mix it in a mixer that is called a "muller" to fluff it up.
You have to control the water content of greensand somewhat exactly, else you can have a steam explosion.

I tried greensand and got very poor results.
Ironman said it took him a long time to perfect his greensand.

Petrobond can be used with iron, but is prone to errosion problems, which can cause sand inclusions (voids in the casting).
Be aware that if you open a petrobond mold while the casting is still hot, the smoke can explode in a large ball of fire (don't ask me how I know this, just take my word for it).

I sidestepped the entire greensand issue by using resin-bound commercial foundry sand called OK85, which is what the art-iron folks use for their iron pours.
Resin-bound sand is used commercially for iron and steel castings, and is a proven molding material for iron and steel.
I additionally spray two coats of an alcohol-based ceramic mold coat on the interior of each mold, burning off each coat after I spray it.
The ceramic mold coat prevents any burn-on of the sand onto the iron, and gives a perfectly clean shiny finish to iron castings right out of the mold.

Resin-bound sand is not easy to find, and not reusable, but it produces excellent castings with very repeatable quality control.

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[GreenTwin]

Melt Process:

The burner should be adjusted for a reducing burner, which is a slightly rich burn, and with about 4" of yellow flame coming out the furnace lid.
This prevents much of the oxidation that can otherwise occur if you run an oxidizing tune on the burner, which is slightly lean.
If you don't run a reducing burn, you will have excessive metal loss due to a large amount of slag generated.

I fill the crucible with broken scrap iron pieces, being sure they are not jammed, since they expand when heated and can crack the crucible.
If you use garbage iron, you will have garbage castings.
Don't every use sash weights; they are made from discarded trash metal.
I use electric motor end bells only for iron scrap.

I let the initial iron charge melt and create a puddle in the bottom of the crucible.
I hold each piece of additional scrap added over the exhaust stream for about 30 seconds to completely drive off any residual moisture, and then drop the scrap through the lid opening into the crucible. Driving off residual moisture is critical if you don't want a crucible/iron explosion in the furnace.

As each additional piece of scrap is added, a piece of rebar is used to push the scrap through the surface slag, and completely under the surface of the molten pool. This process of pushing the scrap through the slag on top the melt really helps minimize slag, and keeps a hard slag cap from forming on top of the melt during the melting process.

Keep adding scrap pieces one or two at a time, until you have the desired amount of iron in the crucible.

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[GreenTwin]

Radiant Heat:
The radiant heat coming off of the walls of the furnace (when the lid is open), and/or the crucible is extreme.

Any skimmer handles, or pouring shank need a sheet metal hand/glove guard, else you will overheat your glove in seconds if you are within 30" or less of the furnace or crucible.
Use a skimmer with a long handle.

Full leathers and leather boots, or spats must be worn.
I wear a hard hat with face shield, and safety glasses under the face shield.
My safety glasses are cutting-torch tinted.
Without tinted glasses, the infrared rays will quickly burn your eyes (like sunburn in the eyes).

Anything plastic, rubber, or other combustible material must be more than 10 feet from the furnace (like 20 feet away).
The rubber fuel lines should be protected with something that won't easily burn, like a welding blanket.

Don't use any water or moisture anywhere near the furnace.
Don't use water to put out a furnace fire.
If you use sand around your pour area (I don't), try to make sure it is dry sand.

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[GreenTwin]

Pour Temperature:
When the iron reaches pour temperature, I open the furnace with the burner running, skim off the slag, add a slight amount of 75% dry ferrosilicon, stir slightly with a piece of rebar, lift the crucible and set it on an external plinth and onto the end of the pouring shank, secure the crucible retainer, lift, and pour the iron into the sprue.
The iron should basically pour with the consistency of ice tea if you are at pour temperature.
A good iron pour temperature is about 2,500 F.
Iron pyrometers are extremely expensive, and so most don't measure their iron temperature, but just judge by the color and fluidity of the melt.

If you are not wearing sufficient leathers, you will not be able to open the furnace with the burner running and skim the slag.

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[GreenTwin]

I don't use lost foam due to the toxic fumes, and I have seen horrible quality if used with iron.
I have seen some very bad quality when the lost-foam process is used with aluminum too.
The backyard lost-foam method is not the same as a commerical foundry lost foam method, so don't confuse the two.
Commercial lost foam castings are excellent in any metal, and they use polystyrene beads expanded in a permanent metal mold.

Backyard foam castings often use foam that is too dense, or coatings that are not permeable, and so the results can be very bad, or sometimes surprisingly good. I have not seen backyard lost foam castings that approached the real commercial lost-foam method though.

I don't use lost wax or lost PLA, but I have seen it used with iron, and the results were superb.

The slurry material I think most use is called Suspendaslurry.
It has a finite shelf life, and you cannot let it freeze.
The process as I undersand it is to make a pattern in either wax, or 3D printed, dip the pattern into the slurry, shake on dry sand, and then repeat the dip and sand application multiple times.
The coated pattern is then inverted and the wax or filament is burned out in a high-temperature kiln, which also dries the slurry coatings.

The burned out shell is then poured with metal.
I typically see folks pour the shell while it is still very hot, and the shell is typically imbedded in dry sand prior to the pour.

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[GreenTwin]

Melting gray iron is highly problematic if you don't follow the above items religiously.

If you have a good iron setup/equipment, pouring iron is not much worse than melting alumium, but with a lot more radiant heat.

Don't lean over the opening in an iron furnace lid while it is running, else you will melt your faceshield in a few second.
I use an old glass refrigerator shelf in front of my faceshield, to be able to get a look at what is happening inside the furnace during a melt.

I must admit I was terrified when I started trying to melt and pour iron, and to took quite a few pours to get comfortable with the method and equipment.
Iron pours now for me seem as routine as aluminum pours, but with much more leather protection.

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[GreenTwin]

Look at post #5 of this thread, and you can see my furnace running, and the results of some iron pours.

I use a Toro variable speed leaf blower for combustion air, and I put the full blower output into the furnace while the blower is on its slowest speed.

I start the burner with the leaf blower off, to prevent blowing out the burner.

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[ajoeiam]

snip

I fill the crucible with broken scrap iron pieces, being sure they are not jammed, since they expand when heated and can crack the crucible.
If you use garbage iron, you will have garbage castings.
Don't every use sash weights; they are made from discarded trash metal.
I use electric motor end bells only for iron scrap.

snip

Hmmmmmmm - - - - wondering - - - how does one acquire said electric motor end bells?

Are there other sources of material?

 

[Richard Hed]

Another item that I consider a myth is the need for a pouring basin.
Many folks, even very experienced casting folks, will insist that a pouring basin must be used in order to get good castings.

But if you look at what happens when you pour any liquid, including liquid metal, into a basin, you should realize that this process churns air, bifilms, slag, sand, and other unwanted material into the melt, and does far more damage than any perceived good that it is suppose to deliver.

Here is a video of a liquid pouring simulation:




Some will point out that they use a pouring basin, and they get great castings.
For hobby work, and non-structural work in aluminum, few things are critical.
If you do more critical aluminum work, you should consider eliminating the pour basin.

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Hold on here. This vid has some probs for pours: viz: there is no liquide draining at the bottom like a casting would have, and also, if one could, wouldn't one pour directly into the hole in the bottom of tshe bowl, if one could? Lastly, this demonstration is dropping the liquid directly downward which never happens with a real pour--a real pour comes from the side and has some sideways momentum. What then?

Thanx for that "thin skin" discussion on aluminum. I've seen than on alum but not on iron. What about brass? does brass have it? I don't remember seeing it on brass.

 

[Richard Hed]

I generally use a 3" diameter short length of steel pipe (perhaps 1" long) at the sprue, just to catch any initial spill from when the pour starts.

This is intriguing to me, but It is not completely clear (thimpfks I understand), can you show a photo? Ah, just viewed luckygen1001's vid. It shows a "bowl like" round as you describe. I thimpfks, however, that a cone shape would be better. What do yuou thimpfK?

While watching luckygen1001 I waS amazed at his setup. I was thimpfking how is he going to pour that without help? Then he trukt the whole thing out to his shed door.

 

[Richard Hed]

Home foundry guy shows his sprues and explains the "basin/bowl"

 

[GreenTwin]

Hmmmmmmm - - - - wondering - - - how does one acquire said electric motor end bells?

Are there other sources of material?

Cast iron was commonly used for machines, engine blocks, and all sorts of other things.
You can find it at most scrap yards.
If you strike steel with a sledge hammer, it bends.
If you strike gray iron with a sledge hammer, it will break, leaving a rough edge.

Wear a face shield when breaking up iron.
Some will cut it on one side with an angle grinder, to weaken it.

And some use disk brake rotors, but I think they are on the hard side, and I don't use them.

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[GreenTwin]

Hold on here. This vid has some probs for pours: viz: there is no liquide draining at the bottom like a casting would have, and also, if one could, wouldn't one pour directly into the hole in the bottom of tshe bowl, if one could? Lastly, this demonstration is dropping the liquid directly downward which never happens with a real pour--a real pour comes from the side and has some sideways momentum. What then?

Thanx for that "thin skin" discussion on aluminum. I've seen than on alum but not on iron. What about brass? does brass have it? I don't remember seeing it on brass.

I had a link to an actual pour basin simulation but lost it.
But the metal acted much like this video, with lots of splashing and other undesirable effects.

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[GreenTwin]

This is the small basin I use over the spure.

The molds have to be weighted on top, else the hydraulic lifting force will lift the top of the mold (the cope) off of the bottom of the mold (the drag), causing a "runout", where the top half of the mold drains out onto the ground.

 

[GreenTwin]

Home foundry guy shows his sprues and explains the "basin/bowl"

Effectively he is doing the same thing I am doing, ie: he has a small basin over or near the top of the sprue.
His basin is very small, and if you use a basin, make it as small as possible.

I still think pouring straight down the sprue is better, but as I mentioned, I use a ring to sort of catch any misguided initial metal.

I think olfoundryman also sometimes uses a basin just like mine.
I will look for that video of his.

Probably the most critical think from his video though is that the lip of the ladle is very close to the sprue opening, and he fills the sprue very fast, and keeps the sprue full during the mold filling.

Here is a video where he uses a pouring cup, which is basically what I am doing with my metal cup.
The cup basically catches and directs the initial flow of metal at the start of the pour, so you don't slosh metal all over when you start pouring.
See 10:58.

The pouring cup also gives you a slight amount of elevation, so that molten metal can run out of the vent holes and ensure a complete mold fill.

 

[GreenTwin]

For this pour, I stopped pouring a little late, and so had some overrun.

 

[GreenTwin]

For this pour, there is very little splillage, and the metal rose in the mold just to the point where the vent became full.
This is a good clean pour.