Home Foundry

[GreenTwin]

I used a domed lid, so that if the refractory cracked, it would not fall into the furnace (self-supporting Roman-arch thing), and I had inner and outer domed forms to create the 1" shape with Mizzou.

I used a chimney on top of the lid to try and retain the heat in the furnace just a bit longer.

The formwork for this lid did work and it turned out nicely, but it was all far more complex than it needed to be ( used an upper and lower domed form).

If I had to do over, I would have made the outer shell, found a dome of some type (generally the end of some air compressor tank or any domed shape of any material), and just packed 1" of plastic refractory on it, which would only take about 15 minutes, instead of the days it took me to make this lid.

It is best to work smarter, not harder, when building foundry equipment, and I often find myself using the "harder" methods, when I look back in retrospect.

 

[GreenTwin]

I carefully rammed the refractory before I added the upper domed form, but there was no way to ram the top of the refractory (the upper form was just pushed down into place on top of the refractory).

So there are few air bubbles inside the lid, which is good, but a number of air bubbles on the top of the lid refractory.
The air bubbles on the top of the lid refractory are cosmetic, and are covered by insulating fire bricks or ceramic blanket anyway.

Some folks obsess about air bubbles in their refractory, and get upset at the slightest sign of a void in the hot face.
I did carefully ram my hot face refractory in 4" layers, to get rid of the air bubbles, and got a good surface finish.

There is one school of thought that says cast refractory should be vibrated into place.
I do not prescribe to vibrating refractory, and prefer to hand pack it, because you can settle out the aggregate particles from the fine particles when you vibrate it, which is not what you want. And the cast refractory instructions specifically mention to not trowel the refractory, which I think also separates out the aggregate.

If the air bubbles bother you, just patch them with plastic refractory.
After a few iron pours, the bubbles in the refractory will be the least of your concerns.

 

[GreenTwin]

I added a layer of 1" ceramic blanket on top of the lid refractory, and then added a layer of insulating fire bricks on top of the ceramic blanket.
Seemed like a good idea at the time, but if I had to do over again, I would just use four 1" layers of ceramic blanket, with a thin sheet metal cover over it.

I often do like others when building furnaces, and tend to over-design things, when there are much simpler and cheaper/easier methods.
Live and learn I guess.

One very successful professional foundry person told me a very wise adage about foundry equipment, which was in so many words "Less is More".
These have proven over and over again to be golden words in my experience.
I try to only build complex enough to get the consistent performance I want, and no more.

It is very easy to over-design and over-thing furnaces and burners.
I have seen numerous videos online of highly complex and many times poorly designed burners that don't last any time at all due to overheating, and people melt iron with them, and use them as proof that they are good (the best !) burner designs.
People compete for the title of "best burner", and often get into heated debates online, while never casting anything of any significance.

If you want to make good iron castings, focus on the end product (defect-free castings that are easy to machine), and use materials and a burner that
work consistently ever single time. Consistency of equipment operation is paramount to making good iron castings.
If you constantly have to stop in mid-melt and work on the burner, or constantly have to adjust the burner during a melt, then you will probably not be get good consistent castings.

The worst burner design in the world can often melt iron, but an overheated burner tube or burner component will fail relatively quickly.
The burner tube should be cool to the touch at every point except perhaps where it enters the tuyere.
You should never have to rebuild a burner, and there should not be any flame impingement on a burner tube (opinions differ on this, but my burner tubes last forever, and others of different designs often don't).

Occasionally you have to remove a little residue from the end of a siphon-nozzle tip, but using clean diesel and an inline-fuel filter, I have never clogged a siphon nozzle tip, and never had to rebuild a siphon nozzle burner.

 

[GreenTwin]

Here is a good example of what happens when you don't preheat your ingot mold to perhaps 500F or so before you pour molten metal into it.
Even though the ingot molds may look dry, they have slight residual moisture on their surface, and that tiny amount of moisture will flash and pop the molten metal right into your face shield (you should wear eye protection and a full face shield).

I had this happen (before I found this video) and the iron splattered on my leather jacket and small beads ran into my gloves.
I had a few 3rd degree burns on the hands.

Also don't wear anything synthetic like clothing, shoes, etc., since it can catch fire an burn easily.
I use a leather apron, leather boots, leather welding jacket, leather gloves, head cover, etc.

 

[GreenTwin]

And a good example of many mistakes when pour iron, which is why he posted this video, to save you from making the same mistakes.
And needless to say, you should not be anywhere near an iron pour without a full face shield, and shaded glassed for IR protection.

Water and molten metal to not mix at all, and most of the accidents I see involve water either in the scrap, in the sand mold, in the ingot mold, etc.

And I would say as a rule, never operate a foundry indoors.
One guy operated a furnace about a year ago, got dizzy, walked outside and passed out.
The rushed him to the hospital, and his blood oxygen was so low that they said they were not sure why he survived.
He was very lucky, and had just been operating his furnace for 15 minutes indoors, with the doors and windows open.

 

[GreenTwin]

And check out this video at 0:15 and also at 7:06, the guy in the center has his face mask up when the molten cast iron errupts
from the damp moulding sand.
A near miss, and very close to being a blinded casting guy.

These are art-iron folks, operating a cupula, using coke as fuel. Coke is coal heated in the absence of oxygen.

 

[GreenTwin]

Another blunder I made is using a pouring shank that did not retain the crucible well enough (the retainer was not a good fit at the top of the crucible).
I starting pouring iron, and as I rotated the pouring shank, the entire crucible fell out of the shank.
Needless to say, molten iron flew everywhere.

Making good functional reliable foundry equipment is essential for safety.

I have seen some spill molten metal on their rubber/plastic fuel lines.
Don't do this.

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[dazz]

I have seen some spill molten metal on their rubber/plastic fuel lines.

What could possibly go wrong??

 

[dazz]

All great advice. I wish I could follow it all. Using a 55gal stainless steel drum for a shell is a great idea. It would save a lot of work. Where I live, none are available. If it is available, anything specialised for foundry work is hideously expensive.

I think the advice about safety gear is really important. I know leather gear is very common but animal skin is probably not ideal.
Nomex and Kevlar are modern alternatives.

I found a US supplier of heat resistant material PPE & Flame Resistant Clothing: Best Work Safety Gear . I don't know if they do foundry type products or the prices but the material looks like it has good properties.

I see face shields being worn. Many wear helmets. I don't see flaps down the back of the helmet to stop metal droplets falling down the inside back of overalls.

I have seen terrible footwear. I think industrial boots with spats should be worn.

Dazz

 

[GreenTwin]

I have attended several art-iron shows, and these folks have great talent, both from the aspect of operating cupolas and creating fabulous artwork in iron.
Looking at my photos, I see a few synthetic jackets/outfits, but generally they wear leather.

I guess I am old school. I prefer a leather jacket, apron, gloves, etc.
I have never tried the synthetic material, and so I am not sure if I would like it or not.
I do have a good feel for how leather protects, and how long I can expose a leather glove to heat before it overheats my hand.

If you begin to overheat a leather glove, it will start to smoke, and that is a good warning signal that you better find a cooler place for your hand quickly.

Here are a few photos from one of the local art-iron shows.
These folks spill iron all over the place during an iron tap, and walk around in burning grass with impunity.
The have been a valuable resource when it comes to making resin-bound molds, safety, and all sorts of other things like mold coat.

The person tapping the cupola below is a person who works at the art-iron museum, and she is fearless.
She has been an excellent mentor and friend.
The iron pours have been shut down for the last two years, and I really miss those shows.
It is a tight knit group of really nice folks.

All the flying molten metal, flame etc. is like a walk in the park for these folks.
The do take safety extremely seriously, and have regular safety meetings, and well planned out events, were everyone has a task, and you watch each other's backs.
Everything is carefully choreographed beforehand.

 

[dazz]

Hi
I have a set of naval anti-flash gear. It is made of Kevlar which chars when burnt. It is soft, breathable and light. My daughter used to manufacture custom Nomex auto-race suits. Neither the military or motorsports use the skin of dead cows for flame protection. Leather is cheap and readily available and has been used for a long time.

I found reference to a set of European standards:

• CE EN470-1 Welder use
• CE EN366 Radiant heat
• CE EN532 Flame resistant
• CE EN373 Molten metal splash
• CE EN367 Convective heat

It would be interesting to know if leather meets these, or similar standards of protection.

Dazz

 

[Rocket Man]

Before I retired we use to buy firebrick from Boiler Supply. They come in several ratings as you mentioned we use 2500° rated bricks. Our furnaces were fired with natural gas. Bricks are almost as light weight as Styrofoam and easy to cut like Styrofoam by hand with a hacksaw blade. If we did a good job shaping the bricks we did not need to use furnace cement. We always built an outer metal case with 1/4" steel welded together to hold the bricks in place. Bricks hold up good as new for 20 years. We bought factory made gas burners from boiler supply too they come in several BTU ratings. BTU rating is nothing more than a different size fuel orifice. If you have 200,000. BTU and you want 500K or 750K BTU all you do is change the fuel orifice. Gas burners have a fan and a controller to throttle up the air with the gas for the perfect burn. Burners are not expensive about $600 they have a small controller it is all 120 volts AC. We used Fuji temperature controllers with a thermocouple. We turned off all 11 furnaces every weekend, Monday morning flip the switch furnace is up to full temperature in 45 minutes and 2000 lbs of metal is melted quick. Zinc & bronze are easy we never did cast iron. It looks like you have it all figured out and working good.

 

[GreenTwin]

It would be interesting to know if leather meets these, or similar standards of protection.

I would say the one area that could be improved over leather is the refectivity.
If you can reflect the heat, I think you would stay cooler.
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[GreenTwin]

Before I retired we use to buy firebrick from Boiler Supply. They come in several ratings as you mentioned we use 2500° rated bricks. Our furnaces were fired with natural gas. Bricks are almost as light weight as Styrofoam and easy to cut like Styrofoam by hand with a hacksaw blade. If we did a good job shaping the bricks we did not need to use furnace cement. We always built an outer metal case with 1/4" steel welded together to hold the bricks in place. Bricks hold up good as new for 20 years. We bought factory made gas burners from boiler supply too they come in several BTU ratings. BTU rating is nothing more than a different size fuel orifice. If you have 200,000. BTU and you want 500K or 750K BTU all you do is change the fuel orifice. Gas burners have a fan and a controller to throttle up the air with the gas for the perfect burn. Burners are not expensive about $600 they have a small controller it is all 120 volts AC. We used Fuji temperature controllers with a thermocouple. We turned off all 11 furnaces every weekend, Monday morning flip the switch furnace it up to full temperature in 45 minutes and 2000 lbs of metal is melted quick. Zinc & bronze are easy we never did cast iron. It looks like you have it all figured out and working good.

I learned the hard way about 2,600 F fire bricks.
I build a great smaller furnace from them, and was so proud of that furnace (I will look for photos; I try to forget that furnace).
And like many things I tried, this small furnace was an abject failure, since it crumbled into dust the first time I tried to melt iron in it.
Live and learn I guess.
The main thing is safety though; you can always get more bricks.
I should have used a 3,000 F hot face over the insulating fire bricks on this little furnace.
It was a very sad sight indeed to open my new little furnace and see dust; LOL, I am still broke up about that.
RIP little furnace (sniff, sniff).

I have seen an aluminum making person use thermocouples and a feedback loop for burner control, but at iron temperatures, the thermocouples melt.
Perhaps if the thermocoulple were mounted not directly in the hot area.
I don't need burner control; I just run it a 2.6 gal/hr, which is pretty hot.

Here is a chart I found on BTU output of oil burners:

3412 BTU/hr = 1 KW

Oil Burner Approximate Values:

1 gal/hr = 138,500 Btu/hr (40.59 kW)
2 gal/hr = 277,000 Btu/hr (81.18 kW)
3 gal/hr = 415,500 Btu/hr (121.77 kW)
4 gal/hr = 554,000 Btu/hr (162.36 kW)

5 gal/hr = 692,500 Btu/hr (202.96 kW)
6 gal/hr = 831,000 Btu/hr (243.55 kW)
7 gal/hr = 969,500 Btu/hr (284.14 kW)
8 gal/hr = 1,108,000 Btu/hr (324.73 kW)

9 gal/hr = 1,246,500 Btu/hr (365.32 kW)
10 gal/hr = 1,385,000 Btu/hr (405.92 kW)
11 gal/hr = 1,523,500 Btu/hr (446.51 kW)
12 gal/hr = 1,662,000 Btu/hr (487.10 kW)


Heat Value of Materials:

#2 Diesel = 138,500 BTU/gal

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[mnay]

This is how the pattern was assembled.

View attachment 126954


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View attachment 126958

Great idea!!!!

 

[GreenTwin]

Great idea!!!!

Thanks.
It seemed sort of like a crazy idea at the time, and I really wasn't expecting it to work very well, but it actually worked quite well, and it did not take me very long at all to make the pattern.
I was surprised at how well the casting turned out.
I had a bit of shrinkage on the rim, but that can easily be corrected with a few strategically placed risers.

The reason that I hand-carved the spoke is because I could not figure out how to model an accurate compound curve in Solidworks.
I have not tried to make a compound curved spoke in SW lately, but my approach these days would be to use a lofted shape along a curved path.

3D printing saves a lot of time if your printer works well, and if you can model the part in 3D.

Another approach I have seen from 100 years ago is to make one pie-shaped section of the hub, 1 spoke, and rim.
The pie shaped pattern/core box (which may be for a 12 foot diameter flywheel) was laid on the floor, and one section of the mold was rammed at a time.
If you look at old large flywheels, you can often see the joints around the rim where this method was used.
So a pie-shaped section of the rim/spoke/hub could be 3D printed, and then the entire pattern or part could be molded from this.

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[awake]

And a good example of many mistakes when pour iron, which is why he posted this video, to save you from making the same mistakes.
And needless to say, you should not be anywhere near an iron pour without a full face shield, and shaded glassed for IR protection.

Water and molten metal to not mix at all, and most of the accidents I see involve water either in the scrap, in the sand mold, in the ingot mold, etc.

And I would say as a rule, never operate a foundry indoors.
One guy operated a furnace about a year ago, got dizzy, walked outside and passed out.
The rushed him to the hospital, and his blood oxygen was so low that they said they were not sure why he survived.
He was very lucky, and had just been operating his furnace for 15 minutes indoors, with the doors and windows open.

That was a terrifying video. The camera-man on the right in open sandals ... and the helper helpfully locked into position by being on his knees ... and doing all of this on a concrete floor ... oh, my.

 

[GreenTwin]

That was a terrifying video. The camera-man on the right in open sandals ... and the helper helpfully locked into position by being on his knees ... and doing all of this on a concrete floor ... oh, my.

It was mentioned in the video description that this video was meant to be a learning experience, so others can avoid the errors shown.
Sometimes you can learn a lot more when things go wrong, especially from a safety standpoint, and I pay close attention to my failures and those of others, and try to anticipate safety issues in advance, so that they can be safely handled.

I cringe at some of my early videos too. My first iron pour was in lace-up leather shoes with no spats, but we all live and learn.
If there were a foundry school that I could attend, I would have gladly signed up for that.

In India, there are many videos of very large iron foundries, where all of the workers generally wear short sleeve shirts, sometimes shorts, often open sandals, no face protection, no infrared eye protection (shaded glasses), no dust protection, etc, and yet they work under these conditions all day every day, and think nothing about it.
Generally speaking, splashing minor amounts of molten iron on your person is not that big of a deal, since the iron usually does not remain in contact long enough to do any damage.
UV damage to the eyes is another thing altogether, and that may be permanent damage.

Edit:
Some things I intend to do to make my setup a little safer include installing the fuel line in a flexible metal conduit to prevent any spilled metal from melting it.
I often see people using a 20 lb propane bottle or oil tank near the furnace, and I always remote my fuel tank at least 10 feet away from the furnace, or more.
Having a supply of sand with a shovel on hand is a good idea, since dumping sand on top of a molten iron problem will stop a fire.
The sand should be dry though, as wet sand could cause an explosion.
A good dry-type fire extinguisher is definitely wise.

I have heard the warning about not pouring on concrete, but I have always poured on concrete, and have spilled on concrete.
My concrete driveway is not very high quality, and so it has never exploded.
High grade concrete seems to be worse about exploding, but I don't think it is the danger that people make it out to be.
Generally you may get some spalding of the concrete, which is more about creating bad spots on the driveway than about safety.

I know a guy in Australia who has poured iron over concrete for 20 (+) years, and spilled on it many times.
Not that concrete won't pop if you spill iron on it, but its just not that big of a deal.

Some people make furnaces using concrete instead of refractory, or they don't dry their refractory slowly after casting it, and these situations will cause a massive explosion, and are extremely hazardous (video of a concrete furnace exploding is online).

My rule No.01 is to not use the furnace or have the fuel tank anywhere near the house (or near anything else flamable), and so if things go wrong, all I have to do is step back, and be sure the fuel tank is clear and turned off.

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[dazz]

Hi
The reason I am aiming to use a fuel pump with a constant output pressure, and a nozzle with a fixed flow rate is because the data indicates that nozzles have a relatively narrow fuel pressure range to produce a good atomized spray. Combustion would only be adjusted with the air flow. So if I find that I need to change the fuel flow rate, I would change out the nozzle for one with a different rate.

I did consider making a spinning disk and cup atomizer to allow for control of fuel flow rate but they are too complicated.

Dazz

 

[GreenTwin]

The reason I am aiming to use a fuel pump with a constant output pressure, and a nozzle with a fixed flow rate is because the data indicates that nozzles have a relatively narrow fuel pressure range to produce a good atomized spray. Combustion would only be adjusted with the air flow. So if I find that I need to change the fuel flow rate, I would change out the nozzle for one with a different rate.

I did consider making a spinning disk and cup atomizer to allow for control of fuel flow rate but they are too complicated.

I have seen one person using a fuel pump with a what I think is a siphon-nozzle burner, but I think they also use compressed air.
With enough fuel pressure, perhaps the fuel pump would work with a siphon nozzle without compressed air, but perhaps that would require a pressure nozzle?

The fuel flow rate for a siphon nozzle I think is determined by the compressed air pressure (check me on that).
The fuel flow rate for a pressure nozzle is controlled by the rate of fuel that you return to the fuel tank (for a given pump presure such as 100 psi constant).
Can the fuel flow be modified by changing the nozzle for one of a different rate? I am not sure about that; you will have to research that.
The flow rates on siphon nozzles I think are all pegged at a given compressed air pressure, and the flow rate on the pressure nozzles I think depend on pressure delivered by the gear pump, assuming no return to the fuel tank.

There is a noticeable difference in the size of the hole in the end of a siphon nozzle tip, between a 1 gal/hr nominal rated, and the smaller flow nozzles.
I have used a 1 gal/hr siphon nozzle at 10 gal/hr, by increasing the fuel tank pressure slightly, and using a little more compressed air.
Note that a 10 gal/hr fuel flow rate is far more than most home foundries would use, but it can be done, and a siphon nozzle and pressure nozzle are easily rated for a 4:1 flow ratio, and can be pushed much heigher with perhaps some sacrifice in atomization.

The siphon nozzle has one fuel line from the fuel tank to the burner.
The pressure nozzle has two fuel lines from the fuel tank, a supply and a return.

The is a spinning disk burner build out there, and it has tons of views, but I have never seen it actually work; it was just a lot of experimentation, but never a functional burner.

Not that a spin type burner would not or could not work, but many of the comments the builder got was "it is too complex for a home foundry".
That being said, if it was proven that a spin disk burner worked better than anything else, I would consider using one.
Making a new burner type is very common on the net.
Demonstrating that a new burner type will reliably melt iron with no degradation over time, and no adjustments during a melt, is a rare thing.

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