Tale of a smallish foundry furnace

My main hobby for a number of years has been machining, anyone doing machining as a hobby is familiar with what large pieces of aluminum cost, and that there is a limit to how much budget you can sneak past the wife.

One day perusing youtube, I came across a fellow casting scrap aluminum into a soup can to make large turning stock....the light bulb came on at full wattage, and I rounded up an old stainless chore bucket and an old waste oil burner project. It was admittedly sketchy, but it melted aluminum...and aluminium too!



And the slug made a useful fixture. One wonders if this is perhaps how a great many hobbies get started lol.



With ideas in full swing, the junk pile was examined for usable materials, some research done and my dad consulted,(Dad had been casting since the '90s) and more advice sought/questions asked on the AA forum.

A small budget was agreed to with SWMBO, things took shape, and a little furnace emerged. The plan was to use one of my old waste oil burner projects for heat, so the tuyere was sized for 1 1/2" pipe, and internal dimensions would just handle an A8 crucible. I ended up purchasing 2800F refractory. Dad used this in his furnace along with a coating of ITC100. Seeing as his had done numerous iron melts at this point without suffering unduly, it seemed like a good way to go. I did do something different, and will get into that shortly.





During my research at AA, I came across a couple "new to me" ideas. One was the use of foam bead or saw dust mixed into the refractory which after firing and burning out the "filler", would leave an insulating layer. The other idea was a "hot face", which was a solid layer of refractory used to offer some protection to more fragile outer layers...ie insulation.

Believing I had plenty of heat on hand, I was not overly interested in adding insulation, but the idea of replacing refractory material with dirt cheap foam bead appealed to my budget. The more I thought about it, the more it REALLY appealed...so this was done. 3 parts foam bead to 1 part refractory was tried as a plinth block and found to be acceptable after firing...very crumbly if you hit hit but it didn't fall apart on its own.



There wasn't much left over, but one bag of refractory made one furnace and a few plinth blocks, so the people rejoiced.



Assembled and prior to first firing. The burner configured this way did not work well at all. Lesson one grasshopper...a foundry furnace is a different animal, go back to square one.



But it worked before....



NO! Square one I said!

Okkkkaaayyy...let's take another kick at this cat... (no cats were harmed in the making of this furnace)



After some research and re-thinking, we're pretty much up to current date. Still playing with the siphon nozzle, and have decided to stop fighting it and add a blower (picking up fittings later today )

Also tinkering with a propane burner. With the tuyere being larg-ish, I built a large-ish propane burner based on Frosty's T burner... 1 1/4", which is also the size dad used (Wenig/Monster burner) in his furnace. Still playing with that one too, and contemplating the slightly over complicated (JMO) burner designed by Michael Porter (Mikey burner). With machine tools at hand, it should be a reasonably easy build, and I do like how adjustable it is, it's also supposed to be more efficient which couldn't hurt.

Who knows what the future holds, tales of woe for certain as learning involves failure, but hopefully somewhere not too far down the road some tales of success, fire and hot metal poured into interesting and/or useful shapes.

Current status of the furnace/burners can be seen on Youtube.

https://www.youtube.com/user/Gippetos/videos

Regards,

Al

 

My first furnace was fire bricks stacked in a circle, and I was able to melt aluminum with it.
My first oil burner test was with a paint sprayer using kerosene.
It takes a while to get a feel for it all, and sometimes you have to start simple and work up.

You furnace looks pretty slick.
Nice clean design.
I have never been able to get completely away from the Frakenfurnace look on my furnaces, but the latest one does work well.

Adding a blower to a siphon nozzle burner will really bring it to life, and you will get a good test of just how well things will work (and maybe not work) with a siphon nozzle running with a blower at 3 gal/hr.
But with 2,800 F refractory, melting iron is definitely in the cards, assuming you have a good clay-graphite crucible.

So what are your plans for things you are going to cast?

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Thanks guys.

The siphon nozzle was a completely different animal when I fed it a little extra air, I expect the blower will put some serious "pep" into things. It's going to be educational at any rate.

I don't have a clay-graphite crucible at this time. Will see how things go, iron is indeed a useful material, but aluminum satisfies my wants for now and might do the odd thing with za12 as there's some sitting around.

Stock for machining is high on the list of things to do, but there are some parts for an air rifle I'd like to try casting with lost foam. Would save the bar stock and possibly a good deal of setup/machine time. Have been binge-ing on Kellys threads the last couple days with that in mind. Have the cad files for the parts and a small cnc engraver (3018) that should handle foam just fine...only one way to find out though.

Wheels for the furnace would be nice, and a fellow might want to do a "myfordboy" to that little engraver, maybe some custom fittings to match the blower up to the siphon burner, could also use some...uh-oh....seems I might be teetering on the edge of something....lol

Regards,
Al

 

Had a little play time this afternoon and assembled the fittings I picked up yesterday. Fits and appears like it might work. Can slide the nozzle assembly to the rear if needed (position fixed with a grub screw) and aim it (which I see could use more attention lol) using the three cap screws I installed into the T fitting. Height doesn't quite match up, but I can work with it.

Still need to make something to adapt the pipe elbow to the pipe from the blower and round up a router speed control, then I can start testing it.




Al

 

Yes it is. Have an idea?

Al

 

Believe this one has the motor cooling air separate, but wise to check and will keep an eye on temps.

Thanks,

Al

 

I think you will be surprised at the output of this burner with combustion air.

 

Al

 

Well Pat, you were right. I'm quite surprised by the heat output this thing is capable of...I think it's way too hot for what I need! I need to do some more calculated testing, but the first burn and melt are out of the way so we're off to the races so to speak.

This test lasted about 6 minutes, at which time the fuel was shut off, the loaded crucible placed in and the furnace re-lit.



About two minutes after re-lighting with the crucible in the furnace.



Not 100% sure what's going on down there, looks as though it's boiling....or maybe that's turbulence from the swirling flame acting causing the melt to swirl?? At any rate, I had poked the melt and found a lump in it, less than a minute later this was happening. Furnace lining was yellow when opened. This was approx 6 minutes after re-lighting with the crucible in the furnace.



Up next is to install a ball valve after the needle valve (in the fuel line) and determine what the fuel flow is. Then try to turn it down some.

Regards,
Al

 

Alright buddy... Good job on the melt.

Now we have to introduce you to https://shotcut.org/
It's a SUPER easy FREE editor that even I can use. There is tons of youtube tutorials on running it. Pretty much, you create a video timeline on the bottom, open your videos up in shotcut and drag them to your timeline. Add an audio timeline under the video and add some snazzy music. Congrats, you are a real youtuber! You will need to export your creation out of shotcut and there is a setting for youtube videos. Jeff or myself will be happy to help you with shotcut for the usual small fee of 10% of your future youtube earnings.

Hey if you are going to shoot with a cell phone, turn the phone to landscape instead of portrait. Your videos will look sooo much better.

 

Youtuber LMAO...not I. It's more like if a picture is worth 1000 words, a video really gets the point across. Hard to give good feedback if you don't really know what's going on right?
Had used Windows movie maker many (MANY) years back to shorten things up, will have a look at the one you posted. Nobody likes two minutes of shaking/shoddy phone cam footage lol.

Thanks though,

Al

 

I am very glad to hear that the burner is working well.

The only problem with using an oil burner to melt aluminum is that it may melt the metal too quickly.
I did do several aluminum melts with my siphon nozzle burner running flat out, and generally speaking the books recommend melting metal as fast as possible to minimize gas absorption.
I was basically getting 20 lbs of aluminum to pour temperature in 12 minutes flat from a cold start, and that was using an extremely high-mass furnace.

So with a lower mass furnace, it would be super easy to overheat an aluminum melt with full burner output.
The first time I tried it, I assumed the melt time would be longer, and when I looked into the furnace, the aluminum was about to boil right out of the crucible, and was extremely overheated.

The good thing is that if you are ready for it, and have the molds ready, you can melt and pour a whole lot of molds in an hour.
Remember that the melt time on the second consecutive melt (when the furnace is already hot) is at least half of what it is for a cold start, so you could pour 20 lbs of aluminum every 6 minutes or so.

An oil burner running at 2.5 or 3 gal/hr (they seem to run hotter at this flow rate than any other flow rate, for our furnace sizes) it truly a beast.
Anything in or on the furnace that is not rated close to 3,000 F will melt quickly into a puddle.

3 gal/hr = 415,500 Btu/hr (121.77 kW), so if you were running an electric kiln/furnace at 240 volt single phase at this same output, then you would be drawing 507 amps from your home electrical panelboard, which would melt the transformer that feeds your house (actually the transformer fuse would blow, but you get the idea).

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Weighed the ingots I poured from that melt this morning. Came in right at 7lbs. I popped one of the small pucks in the lath and found what looks like a lot of gas pockets (hydrogen), so looks like I'll be exploring a degassing lance in the near future too. I keep bottled nitrogen on hand for the airguns so will be using that with the lance.

 

Before you go to the trouble of degassing, try turning the fuel down. You're running rich which causes the porosity.
An ounce of prevention is worth a pound of cure.

 

The only time I have had porosity like that is when I overheated a melt with an oil burner.
The next time I melted aluminum with an oil burner, I watched it really closely, measured it with a pyrometer, and poured right when it reached 1350f, and had no more porosity issues.

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I will see what I can do as far as leaning it out and reducing output then try remelting it. I was chatting with another fellow and got the impression that the hydrogen does not come out on its own when the metal is re-melted...something like a cumulative effect where it just continues to build up.

Its also quite possible I misunderstood what I was being told....

I do have a 1200C digital thermometer that I'll try out...if I remember lol.

Thanks,
Al