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Crucible steels with propane burner/foundry build

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So the TL:DR version, has anyone had any experience making crucible steel with propane burners

I've been toying with the idea of building a foundry, and i have had a pretty niffty oppotunity come up. My workplace where I am an apprentice fitter and turner for a high end fabrication company, they have some 335mm (~13") (australian, sorry) with 10mm (13/32) wall thickness, which to me is already starting to look like a foundry to me. 

I also am able to use all the tools materials and resources my shop has available, which is alot, so I should be able to make as great a foundry as possible. All the times any of you guys have imagined. 


That being said I do have some design constraints,  or at least some preferences. 

First and foremost I do want to on, occasion be able to get the forge hot enough to make (good) crucible steel, which I understand is a tall order as is but i would like to try and do it with 3 venturi propane jet burners, or at least a forced air that runs off of an air compressor or something similar. Or mayb e a combination of, (2 ventri, 1 forced, etc). 

I am not set on anything by any means, Just a l was launching pad. So if I need 1, 2, 4 or 10 burners for example let me know what you think. 


The next major consideration is i will be storing it on my parents farm, and they are a bit sensitive about space so i would like to make this as small as possible, height and foot print. I dont so much mind how heavy it is. 

My initial thoughts on this, I would like to stack the burners vertically. I have access to a CNC lazer cutter, accurate to 1/1000th That I'm keen to use to locate my burner holes, and shape the to accommodate the parralax, set my tangent angles. Etc. 

I'd like to know how much of the length of the burners I can have submerged in the insulation. Or more accurately what's the minimum amount pertuding out I can have, I will be able to machine any specific specs so the only parameter is performance and type. I have a bit of chemical engineering history behind me so if you want to give me the numbers for nerds, go for it

Also want some suggestions on lid mechanisms I'd like it to be handleable  by one person. I've seen some cam/lever mechanisms that seem nice, offer patial opening (hieght) to adjust temperature and back pressure, but also takes up space so... ? 

Let's hear your favourites.


As far as insulation, pretty straight foward 2 or 3 inch layers, 1/2-1" castable refractory, and i was going to put a coat or two of "Mathew's reactor wash", closest thing to a film wash available down here. 

I'd take suggestions on the specifics on floor and lid, I'm not so well versed there. My gut would say similar but thicker refractory layer(?) 

I have alot to address here and I'm sorry I know I could have found all this information In existing posts but all of a sudden I have been given some time pressure. I simply won't keep up on my own, I'll continue to try. Everyone if you have anything to offer here I'll definitley appreciate it. 


I've got some plans and diagrams coming that I didn't have ready (need the help in a hurry) to show you what I have in mind so far. 

Hopefully things comes out really well, and love to keep everyone up on the progress. 

Thanks in advance! 


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Ditch the air compressor; WRONG TOOL!  You will want quite a bit of air at a fairly low pressure rather than a little air at a high pressure.  Think of it as filling a swimming pool: which is better a small high pressure hose or a large low pressure hose?

Also low pressure systems are cheaper and usually need less maintenance than putting a lot of hours on your compressor.

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Hot enough burners are no problem. Your questions, while helpful, show that you are mostly on the wrong track, as to what you need to overcome, in steel casting. Start with the crucible size and type. Then we can discuss the proper furnace design. Otherwise, my own time is too valuable to waste.

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1 hour ago, Mikey98118 said:

 Start with the crucible size and type. 

I'm hoping to be able to use approx 6*5" cup style carbon bonded sillica carbide, graphite (marketed as 6kg) classic cup shape, not totally ideal but Evan if it is on a disposable basis. (But encourage suggestions)

Also I am absolutely prioritising effectiveness over capacity, for what ever difference that makes.

Also availability over here will be an issue especially for a relaible product, so any recommendations are also welcome

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Attached are some PDFs of the working plan so far.

the current plan for insulation is around the walls 3 1' rigidised blankets of ceramic fiber, followed by a 1/2 layer of castible refractory, (Satanite 55 is what i have available, 3200F rated) and a kilm wash.
1/2" castable on the surface that mates with the lid,
and as for the floor I am unsure of what to use but I would like to do about 4" of material and finish with castable, at this stage

This leave me with a 5 25/32" diameter chamber, also 5 25/32 deep as I read here a relatively equal height to width is generally advantageous.
The final volume is approx 153 cubic inches.

In the plans I have used 3, 1/2" naturally aspirated T burners based on @Frosty design mounted vertically, with a 2 degree upwards angle to assist with creating a vortex.
I expect with that volume 3 burners, even half inch, is overkill. The addition of that third burner (And very possibly the 2nd) will be under the point of diminishing returns for effort, however if I could get a couple of hundred degrees out of each of the 2nd and 3rd that would be ideal. Based on my current forge and melting experience and plenty of reading (yet I'm still sure not enough) I'm hopeful that will give me the temps I need to make crucible steels, with out having to tip over into the greatly less convenient options of blowers or solid fuels, as I said in the original post, I am space poor, and poor poor.

I also intend on plumbing the burners so that each is individually isolate-able for lower temp metals, and can run off of multiple fuel sources, to eliminate pressure drop concerns at the end of bottles, pump more pressure in for really high heats and minimize temperature loss during bottle exchanges.

Also in the design, my lid. 3" deep. I currently have my exhaust hole at 4.5" diameter. I honestly had no idea for this one, other then lots of pressure involved with three burners.

The mechanism for the lid is just a place holder, something simple and similar will be nice but I can probably cross that bridge later. Similarly to the stand.

With tall that said I do have some more specific questions,

How should I insulate the floor, space fill with brick/blanket then castable, all castable, bit of all three? And should i do walls first then fill the bottom, or floor first and build the walls off of it

What size exhaust am I looking for? Can always partially obstruct with brick but cant make bigger.

When building the burners for something with so much insulating thickness, how far in do I mount them, the tube length as per Frosty's recommendations  would be 4" (8*burner diameter) should those 4" explicitly start out side the forge, or close to the holes into the chamber. In my diagram I have split the difference as i was unsure. Also, how should I flare the end, if necessary, in relation to this question.

And lastly, I'm almost scared to ask, can I get away with the T burners, I know completely well that they are not ideal, but if I am able to really push them and get the temperatures up there I'd be much happier and comfortable using them, even if I swallow gas far too quickly and have to replace my castable every time I do steel (which wont be too often) if it is possible I'd like to try and make this work. But you guys have the knowledge, hence why I ask.

If I cant get that to work I might need to give up on crucible steel this build, just to paint the position I'm in.

And I doubt it but while here, can I get away with 2? Thoughts?

I know the diagrams are a bit of a headache but I just wanted something up, will answer any questions if you'd like.


foundry initial 12-06-2020.pdf img20200612_17181938.pdf


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