Crucible oven for cast iron

In the topic "its too hot " I prommissed to post the drawings of the crucible 0ven I made and used several years ago
I found some drawings of a smaller one but it can be upgraded without problems
It is a very simple oven made of a castable refractory 1700 dgr C
The oven is poured upside down
As a core I took a pvc tube sawn in 2 pieces lenghtwise and reassambled with some ducktape Thats done to make it easyer to remove afterwards
Then I filled the core with sand and made a hole in it to become the raiser for the crucible Then placed the sheetmetal lining over it
Also made a core for the burner, a bit bigger than the tube of the burner
I waxed that core to make it easyer to remove afterwards
Then poured the refractory as instructed by the fabricator
Follow that instructions as good as possible because it is critical
Take special care when vibrating because when the refractory is to wet and vibrated for too long the haevy parts all move to the bottem
A vibrator is easy made with some shockabsorvers and a electric motor very much in unbalance, for example by grinding off a big piece of a poely placed on the motor
After drying, the bottem is welded on,so all of the oil stays in the oven
For that reason also keep the downside of the burner about 1 or 1,5 cm above the bottem of the oven
The burner is nothing more than a piece of pipe sticking in the oven and a oilinlet welded on top of it, with a tap to regulate the flow Nothing critical about it Even the trouth isn`t neccesary The size matches the size of the fanoutlet or a bit smaller. I started using 1 vacuumcleaner, lateron 2 of them. Finaly I had a industrial fan,which made less noise
Only thing is, you need about the same pressure as the blowside of a vacuumcleaner,so the air can take along the oil When using a hoover,have a spare by hand because they break down when you least want it
Furthermore don`t trottle a hoover They are not made for it. Amps go up that way not down as with a normal ventilator If you want to controle the flow have a part of the air blowing in the open
Fuel is waste oil which is hanging in a cannister about 1,8mtr above the burner Fuel flows through a gardenhose in the burner just by gravity and is taken along by the passing airflow By making the oilinlet and the hose big enough the use of thicker oil is also possible I used simple machineoil which was used by cnc machines (Less PCB`s I hoped)
But everything that burns and you can get through the hole works, even coaldust or sawdust
Make sure there is no air trapped in the fuelhose For that reasson use a transparent hose
In the beginning I started up by starting a woodfire in the oven and some air applied to it
Then I graduatly added the oil
Lateron I started up with gas Just simple ad it to the airflow and ignate it with some petrol
On top of the oven I placed a refractory tile having the outlet on the side I think that works better than in the middle but I may be wrong
The crucible inside is as big as possible Just keep some space to lift it with a tong for the smaller ones The bigger onces need a special tong which grabs the crucible on both sides Google a bit around or use your imagination
But I had less than 2 cm space around the crucible
When ignating the oven for the first time don`t place the crucible inside as long ther is comming moisture out of the refractory
And follow the instruction of the supplier of the refractory as good as possible
In this oven it is hard to have a oxidizing flame because it is so small I think. You can check it by holding a cold pice of steel in the flame for some seconds When it is blach taken out, the flame is reducing Thats hard on your crucible By making the oven higher it can be improved I think, but thats complicating things and I wanted a simple oven
In this oven you can melt aluminium, brass, bronze and cast iron
And BELIEVE IT OR NOT THE SIMLEST MATERIAL TO CAST IS CAST IRON
It may take some more time to heat up but it has little metalurgical problems And a crucible oven improves the quality of the iron a lott so the material to melt has to be simple grey soft cast iron That has the lowest melting point
Don`t use small chips to melt but keep your pieces of scrapp as big as possible I used to make pieces just big enough to lay on top of the crucible with just a little bit of overhang That way they were heated directly by the flames Lateron I placed a refractory funnel on top of the oven where I put the scrapp in That way the scrapp is directly heated by the flames and when it melts it drops in the crucible But beware it isn`t the only opening where the flames can get through When the iron melts and clogges the opening flames need another way out
It happened to me ones and molten iron was flying a meter high
Well I can go on and on telling about casting (did it for about 20 years as a hobby) butI hope this may help the people who asked for it to get started
Some action foto`s




Two more things
When you can get hold of any Exothermic Materials (powders and preformed shapes that ignite on contact with molten metal to provide a heat source, thus extending solidification time. Most exothermic materials act as an insulator once spent)They work great to prevent shrinkage
The easyist to obtain material to cast in is simple sand with about 12 % cement and a little moisture
Specialy on cast iron it works great even for cores


Peter

Wow, that is awesome. My vision of my future shop includes a good metal casting operation. Hobby only, of course.

Ryan

Very nice furnace, Did I see a plastic container of liquid nearby, not fuel or water I hope. The only casting I ever did was in HS shop, I was the king of Shoe shaped accelerator pedals. That work area looks dangerous, liquids and is that concrete block floor. FWIW

These pictures are taken years ago
Normally we kept a layer of sand on the concrete
Perhaps we cleaned it up for the picture
But besides some small burns we never had an accident We also gave a lot of casting demonstrations on modelsteam shows in the Netherlands and Belgium

Regarding the construction of crucible furnaces....
Should coriolis affect be considered in the construction?
http://en.wikipedia.org/wiki/Coriolis_effect

If so...which side of center should the blow pipe be installed?

I'm thinking like a toilet....and therefore on the right hand side looking down from the top. That is..if you are viewing this website in the northern latitudes.

Thank you Peter, I've long wanted to cast Iron, have been waiting 'til I have the time to build a cupola. You've inspired me to buy a new silicon carbide crucuble and give it a try.

Bob

Navigator
Coriolis affect,I have heard of it but I think it has no effect on this oven But you are free to investigate

Bob
I build a cupola too for about 30 kg of cast iron
Works great but it needs more experience to operate Right way to fire it up,right time to apply the coal, cast iron and limestone, right time to open up the cupola etc
I have had the iron both to hot and to cold
And fireing up the cupola 4 or 5 times a year does not give you enough experience
But Bob keep us informed of your results

Ryan ,any results to show for





And for

Thanks Peter

in the old casthouses the floor was invariably brick on edge, old refractory bricks usually have one good side, use trowellong refractory cement like sairset, thin joints about 1/8th inch makes anice looking floor, found sand a bit dogey, can look dry on surface and hide moisture just where you dont want it, under a molten splash, result bang, it seems odd sticking water on top of molten steel dosent cause a problem except for the steam cloud, i put a hosepipe on top af molten steel at 1445 degrees this morning, in continuous casting its called 'capping off' and is a normal practice all over the world, but i must admit it is a little frightening.